Pest Control Heat Treatment Systems

Kill Bed Bugs & Termites Without Pesticides

The call from consumers today has changed in recent years. Today’s pest customers have been educated by the ongoing news of bedbugs in the media and the benefits of using pest control heat treatment systems or ‘Thermal Treatment  as the most efficient method to the eradication of  infestations

They specifically request to have heat instead of chemical insecticide treatments.

Heat does not have many limitations with respect to the number of items treated and the area to be treated. There are no chemical residues to consider and, compared to gas fumigation of areas, margins for safety are considerably greater.

With Flexiheat UK’s E18SH high temperature electric heater or our M range warm Air heater you don’t just enjoy the best return on investment in the industry, you get the original developers and a team that truly cares and is passionate about this technology as an alternate to insecticides to eradicate indoor insects.

Pesticide-based indoor bed bug control methods raise concern over the safety of occupants. Our affordable heat treatment systems offer you the ability to perform bed bug control work without relying on toxic chemical residues.

Heat is a proven technology. Our state-of–the-art tested technology developed and perfected by Kroll Energy means our equipment is designed to be a complete Pest Control Heat Treatment System without sacrificing quality or capability.

Basic Guidelines To Bed Bug Heat Treatments


Pest Control Heat Treatment Systems


Every Living Organism Has A Thermal Death Point
Bed bugs exposed to 45°C will die if they receive constant exposure to that temperature for 90 minutes or more. However, they will die within 20 minutes if exposed to 48°C. Interestingly, bed bug eggs must be exposed to 48°C for 90 minutes to reach 100% mortality.
The same process for treating bed bugs will also kill, and in some cases, completely eradicate other organisms.

Regardless of the heat source, temperatures and run times must be achieved throughout the structure to achieve the eradication of the pest !

Let’s Compare the two pest control heat treatment systems

Electric Vs Propane,
What heat system you employ affects heat treatment run times and methodology

Pest Control Heat Treatment Systems

  • Electric heat is a closed system. It operates from within the structure being treated with heat. Electric heat is slower in the beginning of the heating process than propane.
    With Flexiheat’s electric E18SH heater, starting room temperatures raise by approximately 5˚C for every hour. However, the ambient room air temperature will increase at a faster and faster rate as the room temperature rises and recycles itself. It is the multiplying effect of air turnover with a closed system.
    Electric heat requires power sources. Adding more electric heaters, will be more productive to your heat treatments. However, the power source becomes a growing challenge.Check your available amperes.

Pest Control Heat Treatment Systems



  • Propane heat is an open system. The unit stays outside the structure and the heat is ducted into the building. It produces positive air pressure. The units require a source of propane to operate. for more information on our range of indirect fired mobile heater – click here
    Intense and immediate heating of the space. Higher air output, higher volume of heated air, high productivity capabilities as compared to electric systems. Propane can be divided with splitting the heat ducting to cover more area, rooms or even another unit.
    Propane results in more thorough penetration and distribution of the heated air.

Factors to consider –

  • Square feet: large or small space. The larger the area the longer heating time for all areas to reach lethal temperatures.
  • Building materials: cement, steel, dry wall, etc. will affect the heating times. Cement floors and walls will take as much as 3 times the time due to the fact that cement acts as an insulator and can maintain cool temperatures with slowly changing thus requiring more heat time.
  • Furnishings: lots of furniture will require more run time due to the amount of objects surface area needing to get to temperature and the obstacle of more furnishing for the heated air to travel through and around.
  • Clutter: Piles of clothing and blankets are very important to move around and mix. The room air temperatures can be 55˚C and under the pile of clothing it could be 27˚C which is not lethal. No clutter, is recommended.
  • Weather: heating in a desert or in high altitude with snow. Is it warm or hot when starting? Humidity and cold will take adjustments and more heat time.
  • Degree of infestation: Identifying infestations early is key to control and is much easier to get a 100% kill. If the infestation is large and mature, basically way over due for treatment, you will need to take time to move objects, furniture, open all draws and closets and spend extra time preparing and allowing more time for longer heat penetration of the structure and furnishings.
  • Starting temperature: Similar to weather but room temperature. Is the treatment beginning temperature at, for example: 25˚C or 5˚C?

All efforts should be taken to preheat a structure prior or during set-up of heat treatment equipment. Starting with a pre-heated room achieves faster arrival times for lethal temperature resulting in less treatment time, and higher productivity.


For more information on pest control heat treatment systems,  please click on our products page here .  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here

Warm Air Heating – Introduction & Benefits

Why is warm air heating consistently popular for large spaces?

Of the various options that are available for heating spaces such as factories, warehouses and retail ‘sheds’, warm air heating has been the most popular for decades. So why is this?

The reason is that not only does warm air heating offer a number of significant benefits for the majority of these buildings, it has also proven those benefits time and again, in many different applications. Consequently, it’s worth considering just what those benefits are.

 Energy efficient

Standard indirect-fired non-condensing warm air heaters are able to deliver minimum net efficiencies of 91% and the latest condensing models provide even higher efficiencies with a minimum 101% (net) at both full and part load, in compliance with the latest EU regulations.

A further significant benefit is that the heat input can be closely tailored to meet the building’s heating requirements. Configured with optional high/low or modulating heat outputs, the heater(s) automatically reduce output once the building environment conditions have been attained, offering a comfortable environment without significant swings in temperature.

With warm air heating, system output can usually be matched to the building load requirements. The same is not always true of alternatives such as radiant where heat input is sometimes compromised to provide adequate coverage of the heated zone. This is typical for modern well insulated buildings.

Depending on the application, warm air heating systems may be combined with destratification fans for even greater efficiency. The Carbon Trust estimates that the use of destratification fans in industrial buildings with high ceilings that are operating a warm air heating system can reduce energy consumption by 20%.

Even distribution

Warm air space heating systems use a fan to draw air in from the space being heated, pass it across a heat exchanger, and distribute the warmed air evenly throughout the space. This even distribution by warm air heating systems is in contrast to heating technologies such as radiant heating that only warms objects that are in ‘direct line of sight’. This means they are vulnerable to ‘shading’ issues that leads to uneven heat distribution.

Versatile positioning

Warm air heaters offer considerable flexibility in terms of their location, ensuring the layout of the heating system is optimised for the configuration of the space being heated. They can be suspended above the space, mounted on walls or they can stand on the floor. Models are available with discharge heads or louvres for direct warming of the air; alternatively heaters can be specified for connection to ductwork for distribution across a wider area.

Warm Air Heating

Air movement

A feature of warm air heaters is that they also offer flexibility in terms of air movement. Most systems re-circulate warm air within the building; however they can also be used to provide air movement in the summer by operating ‘fan only’. In addition heaters can be equipped with fresh air intakes – particularly useful for dusty environments or where fresh air is considered beneficial.

If a building has a process with extract ventilation then it is often a good idea to bring the replacement air in via a fresh air input to the heater. In that way, the input air is warmed and tempered preventing cold uncomfortable draughts.

 Flexible heat sources

Warm air heating offers a choice of heat sources to best suit the application and current energy costs. Warm air heaters are typically operated on natural gas and LPG  – see our SG product range,   light fuel oil see our SO product range or even waste oil see our SZ product range

Warm Air Heating


Warm air heaters are also highly controllable, enabling their operation to be closely aligned to the requirements within the space – thus avoiding wasted energy. For example, if there are some areas of the space that are only used occasionally it may be beneficial to zone the heating system so that these spaces are not heated to the same temperature as areas where people are working all day.

There will also be benefits to optimum start and stop control to minimise energy consumption.


For more information on our range of warm air heating solutions, please click on our main products page here .  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here


Permanently Condensing Boilers – A Perfect Energy Saving Solution

In times of rising fuel costs , we need to start thinking about utilising the technology now available.  Flexiheat UK are a firm believing in this. That is why we are at the forefront of energy saving technology.  We offer an ideal solution to achieving the goal of saving money and energy in the shape of our BK Permanently Condensing Boilers

BK Permanently condensing boilers

 Condensing Boilers – The History

Condensing boilers are water heaters fuelled by gas or oil. They achieve high efficiency (typically greater than 90% on the higher heating value) by condensing water vapour in the exhaust gases and so recovering its latent heat of vaporisation, which would otherwise have been wasted. The efficiency of a typical non-condensing boiler is around 75%,

Traditional condensing boilers, are really – SEMI CONDENSING BOILERS –As they are reliant on the return water being under 57°C for Gas and 47°C for Oil- Otherwise the physics of the heat transfer will not work !!!!

A Condensing Boiler

Permanently Condensing Boilers

The concept for BK Permanently Condensing Boiler is both ingenious and simple:  Fuel and flue gas temperatures are reduced to a minimum, ensuring the boiler operates in a condensing mode at all times.


BK Operation Animation



Permanently Condensing – How It Works -Step by Step 

  1. The flue gas is cooled down to approx. 70°C by the flue gas passes which are surrounded by the boiler water
  2. The water is heated up from at least 55°C to maximum 80°C, going upwards in a counter flow configuration
  3. The flue gas enters the secondary  heat exchanger made of plastic and cools down below its dew point temperature (48°C for Oil or 57 C for Gas )
  4. The flue gas leaves the system with less than 48°C (for heating oil), and it has an outlet temperature of about 20°C – 40°C at the end of the chimney
  5. The air ( combustion air ) which is taken from outside is already preheated in the chimney to approx. 30°C
  6. The burner combustion air is preheated to 50°C – 60°C, prior to entering the burner
  7. The preheated combustion air is lead to the burner via a hose and the cycle starts again


Permanently Condensing Boilers – Advantages

  • Heat Exchanger: The secondary heat exchanger had been engineered to resist the high sulphur content associated with burning oil. It is manufactured from A.B.S which is renowned for its resistance to acids.
  • Room Sealed: No additional combustion air is required
  • Fuel: The Kroll range of BK Permanently Condensing Boilers are available in both oil and gas
  • Environmentally Friendly: Because the exhaust flue gases are at such a low temperature, the polluting element of the gas can be neutralised in an environmentally friendly way
  • Efficient: The Kroll Condensing boilers have an efficiency of 106% for oil and 111% for gas

The Kroll condensing system does not need to meet the following additional requirements:

No  low boiler water temperature of 40/30 °C are necessary, therefore no danger of “legionella” when producing domestic hot water and no problems when heating  up the boiler itself –  i.e. Condensation forming in the combustion chamber

No increase of radiator sizes or the undesired subsequent installation of an  under floor heating system in order to be able to work inside the range of condensation..

No split heating / domestic hot water systems are required

* Also, due to the low flue gas temperatures, a low-cost chimney of plastic can be used. This avoids the expense associated with Stainless Steel flue systems

Energy Saving Comparison

For more information on our BK range, please click  here .  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here

Warm Air Heating for Greenhouse Applications

There are three main methods of warm air heating for greenhouse applications;-  firstly warm air unit heaters like our LH range of warm air unit heaters. These can use hot water, via a low, medium or high temperature hot water wet boiler system to heat the greenhouse. The second system is via an indirect warm air heater, such as our S range of cabinet heaters, which can be fuel be either gas,(both natural or LPG) see our SG range  ,Oil (both 35 second or 28 second) – see our SO range  or even vegetable/ or waste oil via our SZ range  and lastly with a direct fired warm air heater like our P range 

We are now going to discuss the third method ,direct warm air heaters in more detail. Firstly we need to explain direct fired – this is where the products of combustion ( sometimes referred to as the flue gases ) are expelled directly into the area being heated. This means CO² is being pumped into the heated area, which is beneficial to plant / crop growth.

A correct temperature and an even air distribution are important factors for the growing environment in both agriculture and horticulture. The PE-series is especially designed to control these factors optimally. The large air flow capacity (2500 – 6650 m³/h) and the special round shape of the heater ensure an optimum air distribution, which guarantees an even heat distribution and consistent climate throughout. The PE heaters have a guaranteed efficiency of 100% as all generated heat is supplied directly in to the room. The burner with it’s stabilised flame provides a clean, complete combustion in combination with a relatively low energy consumption. The PE direct fired warm air heater can be supplied suitable for various fuels:  – natural gas, butane, propane or LPG (please specify at time of order)

The “PE” direct fired warm air heater is a very robust heater as it is completely manufactured from stainless steel. This characteristic ensures a long and maintenance free life cycle

Safety and reliability

The complete PE range is CE approved. Every PE heater is subjected to a final inspection during which electrical safety, correct emission values and general operation are checked. Kroll Energy is ISO 9001 certified, ensuring all over quality and safety are guaranteed, as you would expect from a German manufacturer. The heater is provided with the latest technology for optimum control. The ignition process is fully controlled by a digital circuit board. To limit the risk on failures, the PE carries out a self-check each hour. It is also possibly to switch the PE to ventilation only mode. The PCB control board and associated components are placed in a spray proof casing. The IP rating of the control box is IP X4

So, if you are looking for Warm Air Heating for Greenhouse Applications then Flexiheat have it covered

Warm Air Heating for Greenhouse Applications





Waste/Multi Oil Burner- a great money saving alternative

More and more people are turning to a waste oil heater or boiler as a viable heating alternative. It is a suitable way of heating a commercial property. The waste oil used in the appliance is usually derived from used automotive or vegetable oil. If you have access to a regular supply of waste oil, you will find a waste oil heater or boiler one of the cheapest heating options. That is why Kroll Energy have perfected a perfect solution to this demand –  The KG/UB waste/multi oil burner

Waste/Multi Oil Burner

The advantages of using a Kroll KG/UB waste/multi oil burner on your heater cabinet or boiler speak for themselves

Economical   Heating using waste oil guarantees much lower energy costs over using regular heating oil. New oil prices exceed waste oil costs by far. If using new oil for your heating, you are bound to constantly face high fuel bills. Using waste oil will significantly reduce your energy bills by almost 100 percent. Besides, prices for new oil are constantly rising because of global market factors

Environmental   Using recycled oil in a heater or burner reduces the demand exerted on environmental resources. This helps encourage sustainable resource utilisation. It also reduces the chances of “disposed “waste oil turning up in waterways or landfills. This is because the waste oil is instead reused as a useful energy resource in the heater or boiler which means less environmental pollution. Little odour, smoke or other emissions are produced while during operation. The minimal pollution adds to the environmental benefits of a waste oil heater. If you purchase a quality waste oil heater or boiler and clean it periodically, the efficiency of the system is significantly enhanced. This will ensure that it burns cleanly with minimal pollution to the environment

Durability    Like any piece of equipment, a waste oil heater or boiler requires some degree of maintenance to run at peak performance. All Kroll waste oil products are quite easy to maintain, and for the most part, can be serviced in-house with proper instructions and attention

Made in Germany our range of KG/UB waste / multi oil burners are all manufactured to an exacting high standard at the Kroll factory near Stuttgart, Germany.  An area renowned and synonymous with engineering quality

waste/multi oil burner- saving


The Working Principles of a KG/UB Waste/Multi Oil Burner


  • The fuel is pumped from the storage tank by means of a pump system. This in turn enters a pre-heat tank on the burner which is regulated thanks to a float level switch.


  • A thermostat regulates the oil temperature within the pre heat tank. Typically for waste mineral oils the temperature needs to be set to between 80 °C and 100°C. For rape seed oil it would need to be set between 80 °C and 140°C


  • An additional overheat thermostat prevents overheating and malfunction


  • Then the burner control box checks the procedure.


  • A special waste oil nozzle draws the fuel, by using the passing of compressed air, which serves as primary air for the combustion, and atomizes it.


  • The combustion fan delivers the secondary air that is mixed with the spray mist at the flame ring.


Thereby a perfect combustion and safe operation are guaranteed


main parts of burner


LR5300 Industrial Air Cleaner

Pollutants must be eliminated – particularly where people work and live. Dust, fibres, mould spores or even asbestos fumes can be found in the air and represent a serious health risk. When it comes to professional air purification, the commercial LR5300 Industrial Air Cleaner from Kroll Energy is the perfect solution


Where construction work is performed, there is dust. In most cases actually a lot. Dust not only affects workers and their health at the site but also the general public. Dust containing quartz, mineral fibre, wood, cellulose and asbestos are particularly hazardous because they enter the airways and lead to sustainable health effects. Fine dust, in particular, can enter the respiratory tract and lungs, and as these are enclosed by connective tissue making it practically impossible for the particles to exit again. This is followed by chronic sicknesses for the persons affected, such as the much-feared silicosis. Respirable dust consists of particles that are smaller than five thousandths of a millimetre in size. In order to prevent its entry into the respiratory tract, only one preventative measure does the job: the fine dust has to be filtered from the air in advance. The LR5300 Industrial Air Cleaner from Kroll Energy is especially designed for the raw day-to-day work on busy construction sites.

Additionally, spores, allergens and micro fibres, which can result during building, insulation and mould restoration, should not be underestimated.

Another factor to consider are in places of work; facilities and operating material have to adjust the limit values within the next four years. What use is the most sophisticated process optimisation in production when the goods then get damaged in the warehouse? It is vital to ensure optimal conditions in warehouses and storage facilities and to regularly check these.

A sophisticated combination of our LR5300 Industrial Air Cleaner and Dehumidifiers is all you need to take care of and maintain these sensitive areas. You can find various powerful dehumidifiers among the Flexiheat range. With the LR5300 Industrial Air Cleaner you can protect against any pollutants. Your products can be permanently and safely protected when in storage. Improper storage can result in serious damage to goods. Moist air in warehouses damages packaging and in the worst case mould can even form.  Within just a short time pallets or even an entire inventory can be completely ruined.  In short, what this means is that your goods can no longer be sold. Dust, mould spores and bacteria in the air are also not uncommon in warehouses and this too must also be effectively combatted. Pollutants do not just damage your goods; they can also expose your employees to great risk. From a human point of view this is a disaster. And on top of that work colleagues can easily be affected by allergies, rendering them unable to work, which can of course become quite expensive for your company.

If you combine one of our dehumidifiers with our powerful LR5300 Industrial Air Cleaner you will effectively combat dust and pollutants. These mobile professional devices provide a unique air flow control. In no time at all, dust, mould spores and bacteria in the air are no longer an issue in your warehouse or storage facility.



For more information on the LR5300 Industrial Air Cleaner, please click here  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here



Can I fit a Kroll waste / multi oil burner onto my existing boiler?

A Kroll KG/UB waste / multi oil burner from Flexiheat UK is a great way to significantly reduce your heating costs. With its ability to burn almost any used oils from waste engine oils and hydraulic oils to used vegetables oils and Bio Diesel.  In fact, our range of waste/multi oil burners are so universal that they can also burn 100% rape seed oil and heating oils.  Because of these wonderful advantages, more and more people are looking to replace their existing oil burner with one of our KG/UB burners.

Below, we have set out a variety of questions which should help you decide if a waste / multi oil burner is suitable for your existing appliance.


1. Will the KG/UB burner fit onto my existing boiler? Please check the dimensions, especially the dimensions of the “holes of the burner plate” and the “dimension of the burner tube”. If these dimensions correspond to the dimensions of the burner’s flame tube, the burner flange can be connected. Please check the below paying particular detail to dimensions “E” and “G”. If the burner tube will fit and you can pick up the burner mountings (G) which have a range due to the slotted burner mounting flange

Download technical details of the KG/UB burners


2. The minimum combustion chamber diameter is 180mm The minimum combustion chamber length must be –

KG/UB20P = 300 mm

KG/UB20 = 320 mm

KG/UB55 = 360 mm

KG/UB70 = 360 mm

KG/UB100 = 380 mm

KG/UB150 = 400 mm

KG/UB200 = 400 mm


3.Construction of your Boilers Combustion Chamber;-

We have developed and patented our “ZVP” burner tube. This acts like another combustion chamber, within a combustion chamber, ensuring higher efficiency, better combustion, lower flue gas temperatures and longer maintenance periods

ZVP Tube
The following picture shows one of our 200kW waste / multi oil burners with our ZVP tube attached

Waste / Multi Oil Burner


The ZVP burner tube ,which is attached directly to the burner comes with a ceramic mat for combustion chambers with convex rear as standard or a 500mm x 500mm ceramic fiber board for combustion chambers with a vertical rear panel

 Download drawing of combustion chamber variants


4. The Kroll waste/multi oil burners range require a compressed air supply. This is neither a large amount of air (cfm) nor a high pressure (1.5 Bar Maximum). Kroll produce a whisper quiet compressor, which is extremely quiet and compact (roughly the size of a briefcase), this compressor is controlled by the burner, and is only in use when the burner has a demand. You can utilise your own compressor, as long as it meets the requirements of the burner, and you fit a good quality filter, regulator, water trap prior to the burner.


5. We would recommend that your existing flue system is at least, 4 meters, and includes an open terminal and a draught stabilizer,  required. See below drawing of our recommended flue kit we can supply you if so required

Download recommended flue kit configuration for a waste oil boiler


For more information on our waste / multi  oil burner range, please click here  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking   here
















Many homes and buildings suffer from high humidity and the problems it causes; Damp patches, condensation on walls and windows, mould and increased dust mite populations. A good domestic or commercial dehumidifier will reduce the levels of moisture and help to alleviate these problems.

High humidity is a problem that affects many environments. From homes to building sites, wine cellars to swimming pools.

Newer homes are better sealed with double glazing and often have less ventilation; older homes may have solid walls that allow damp to enter into the home. Common causes of excess moisture are drying clothes inside and poor ventilation

A domestic or commercial dehumidifier from Kroll is an ideal solution for so many applications;-

  • Drying out water or flood damaged buildings, eliminating the need to replace and reconstruct
  • Developing stable environments for exposed metal to prevent corrosion
  • Reducing drying times at construction sites for concrete, insulation, and fireproofing
  • Preparing surfaces and vessels for painting and coating applications
  • Blanketing equipment to protect from humid air
  • Maintaining correct ambient conditions for laying of flooring
  • Prevention of mould and fungus growth

Domestic or Commercial Dehumidifier

So, what is Humidity?

 Relative humidity is a measure of how much water is in the air relative to the amount that air could hold if it was saturated. Relative humidity is expressed as a percentage. When relative humidity reaches 100% it is at the “dew point”. In other words the air is “full” of water and that water will start to condense onto any surface. Warm air holds more water than cool air so as air cools relative humidity rises even though the physical quantity remains constant.

For every fall in temperature of 20°F/10°C the capacity of the air to hold water is halved. For example air at 80°F with a relative humidity of 50% will reach the dew point, 100% RH when it has cooled to 60°F.


Performance of dehumidifiers? How are they calculated?

Most dehumidifier manufacturers quote the capacities of their dehumidifiers based on a temperature of 30°C and 100 % relative humidity i.e the temperatures and humidity levels that you would find in Florida, in the summer. The capacity the units will extract is given in litres per 24 hours. If the temperature is lower, as we often find in the UK, then the performance of the unit is lower. Here is an example;-

                                                                                                          Kroll unit                                                       Kroll unit

Temperature & Relative Humidity                        T20D dual voltage  model                       T40D dual voltage model

At 10°C / 60% Relative Humidity                                                       4.2 litres                                                                 8 litres

At 25°C / 60% Relative Humidity                                                       9.5 litres                                                                 20 litres

At 30°C / 60% Relative Humidity                                                       20 litres                                                                  36 litres

As you can see from the above, the colder the temperature, the less water is extracted. At a temperature of 5°C refrigerant dehumidifiers will stop extracting all together


Domestic or Commercial Dehumidifier

What can I do about this, to get my extraction rate up ?

Quite simple, add a heat source to the area to be dried. The best option is an electrical heater or an indirect ( this means the products of combustion do not enter the area being heated ) oil or gas heater. The hotter the area is, the better the extraction rate you will achieve

Airflow is important – You need to ensure that you are using the right size dehumidifier for the area you want to extract the vapour from. The general rule is –

To keep the room dry, multiply the air volume the unit will do by 2

So, for the Kroll T20D it is 160 M³/h thus a room with a volume of 320 M³

To dry a room, multiply the air volume the unit will do by 1

So,  for the Kroll T20D it is 160 M³/h thus a room with a volume of 160 M³

Here’s a quick reference chart for all our models




Room Volume for

Keeping Dry  / m³

Room Volume for Drying  / m³


What can happen if I put 2 smaller dehumidifiers in one room, for example I want to keep dry a 640 M³ building, with two Kroll T20D dehumidifiers?

This isn’t a problem, although you need to evenly place the units within the area, for even extraction to take place. If one side of the room is wetter than the other, expect to see the closest dehumidifier to have extracted more than the other unit.


I’ve just had a phone call from a customer and he says the unit isn’t working, nothing or very little is water is coming out?

We test every domestic or commercial dehumidifier prior to dispatch – the unit is working, if the green light is on – simple as that

It’s probably one of these reasons, why the the performance is poor

  1. Our Domestic or Commercial Dehumidifier units only work down to 30% Relative humidity – the ideal relative humidity is around 50% or less within a living environment –  check what relative humidity you have with a hydrostat. If it’s under 30% the unit won’t work
  2. What’s the temperature within the room? Is there heating within that area? Please bear in mind night time temperatures, where heating systems have be turned off, a room can easily get down to 5°C in the winter – the unit won’t work at 5°C or below , and the performance drops off dramatically with lower temperatures, as stated previously
  3. Do you have windows / doors etc open that is allowing fresh damp air into the area?
  4. Are you using a direct fired oil or gas heater? if so , then this adds water content, that is given off in the combustion process
  5. Is the unit the correct size for the room – please see the above sizing chart
  6. Do you have more than one domestic or commercial d dehumidifier in the room – are they evenly placed? Is one in the in the wetter area?

Domestic or Commercial Dehumidifier


For more information on our domestic and commercial dehumidifier range, please click on our main products page here .  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here





Waste Oil Boilers

Burning waste oil in order to generate heat is a relatively new way to provide warmth and hot water to households that is becoming increasingly popular among industrial or domestic users. Although, installing a waste oil boiler within one’s home would not be possible, due to its design specifics, it still can be mounted in a garage, shed, workshop or a greenhouse. It is one of the most cost-efficient stand-alone boilers currently available on the market, given that it is using a by-product as a heating source. The price of a waste oil boiler is roughly the same as that of a conventional or gas boiler, but the operational costs are much lower.

A waste oil boiler delivers an efficient way to recycle waste oils as a free fuel source to generate heat and hot water, which can be easily accommodated for a broad range of applications

Waste Oil Boiler

So, what makes a waste oil boiler such a worthwhile investment?

There are a number of advantages to consider

  1. The waste oil boiler can run on any kind of synthetic or mineral oil, being one of the cheapest liquid fuels available on the market at the moment. Listed below are just some of oils you would be able to utilise;-
  • 35 second Heating Oil/Diesel
  • Processed Fuel Oil ( PFO )
  • Rapeseed Oil
  • Linseed Oil
  • Certain Vegetable Oils
  • Used Engine Oil (subject to licensing control)
  • Hydraulic Oil
  • Bio Diesel
  1. A waste oil boiler represents a profitable investment, since all the costs associated with buying and installing the boiler will pay themselves off in a short period, due to considerable savings coming from using the waste oil to run the boiler, which is a very cheap heat source.
  2. An environmentally friendly installation, whereas the boiler does not burn the oil itself but its vapours, which burn without leaving any substantial residual products
  3. A high efficiency rate, which in the case of forced convection can quickly generate a considerable amount of heat that would be enough to warm an area.

Kroll waste oil boilers from Flexiheat UK are your best choice for economical and plentiful hot water and are ideal for so many applications from garages and vehicle workshops to warehouses and distributions centres.

For more information on our waste oil boiler range, please click here  Alternatively, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here



LTHW Air Unit Heaters

LTHW air unit heaters

Many industrial buildings prefer to run their heating from a piped hot water circuit. Where heat is available in this form then the use of LTHW air unit heaters fed with hot water is invariably the most cost-effective method of space heating a room or building. As with electric fan heaters, there are a variety of types and options available and we aim to make choosing the right model as easy as possible. The following guidance is written around our LTHW unit heater extensive range that we call the LH series. They are also referred to as lphw unit heaters – (low pressure hot water).

They are great heating installation solution for large areas such as warehouses, exhibition halls, factories etc.



LTHW air unit heaters

Applications for Water LTHW air unit heaters / lphw unit heaters

There is no doubt that if you have a good source of heated water on a piped circuit then these unit heaters are a very cost-effective way to discharge the heat in to the areas in which it is needed. Each model has a large range of heat output depending on the flow temperature, return temperature, ambient air temperature, and water flow rate. This means that with the addition of a recirculation air / fresh air mixer cabinet and suitable controls, these ranges are an ideal compliment to heat sources that are bit less controllable than straight oil gas or electricity fired systems. For biomass boilers, solar fed thermal stores and wind turbine heated thermal stores it is useful to have not only a quick and effective means of dumping excess heat, but also a system that can deliver heat from quite low temperatures and be easy to integrate with a secondary heating system when water temperature is too low.


If you are using a water fed LTHW air unit heater to space heat an area, the implication is that you are using available surplus heat and this will be the principle heating for the area.  As with any heating requirement the initial stage is to identify the size of the heat output requirement. Please contact us at Flexiheat UK for advice


It is seldom the case that a required heat output for a system of water fed unit heaters can be met neatly with a single heater. In most cases there are a number of configurations using a number of models from a range to achieve the overall space heating requirement for an application. Sometimes there is a choice between a number of unit heaters of a large size or a greater number of unit heaters at a smaller size.

Generally the smaller number of larger unit heaters will be more cost-effective in terms of unit heater cost, control costs and installation cost. But the choice of unit heaters should also take into consideration the shape of the room and air throw of heaters, perhaps using larger unit heaters for larger uniform areas, and using smaller unit heater for smaller dead areas of the main area.

Uses of Fresh Air in Space heating

LTHW air unit heaters

Because a water fed unit heater usually uses a circuit of hot water that is often ‘surplus’ it is quite common that these unit heaters are not merely mounted on wall brackets, in 100% re-circulation mode, but mounted on mixer boxes, which themselves are mounted over a vent in the outside wall, enabling heated air to be a mixture of re-circulated and fresh air.

With the addition of options available such as either manual or motorized dampers , the mixer boxes allows the flow to through the unit heater to be set at any level from 100% fresh to 100% re-circulated and anywhere in between.

Mixer boxes are useful because in addition to being able to take air straight from the room through a grill, the grill can be removed leaving an upstand (spigot) for ducting connection, so that the mixing box can be part of a more complex ducted ventilation system.

The key element to connection to a mixing box where outside air is brought in, is that the heater control system incorporates frost protection functionality, to prevent any chance of water freezing in the coils when the heater coils are not being used for general heating.

As well as mixer box options, there are also filter box options allowing a G3 efficiency filter to be fitted. This fitting is essential if the unit heater are to be used in dusty environments in order that build up of dust on the coils is prevented.


Whilst many will consider conventional boilers to be the heat source of choice for a hot water circuit, they are not necessarily the most flexible source of heat. Water fed unit heaters are not fussy about what heats the water up and will operate perfectly well from a wide range of water feed temperatures. This means that as well as being ideally suited to conventional large boilers, the units can also use relatively low-grade heat produced by chiller/heat pump/ boiler combinations, where the chiller or heat pump preheats water to say 40-50°C  before the boiler adds top temperature to get it to normal heating circuit flow of say 80°C. The benefit of this type of arrangement is that typically the winter heating costs are lower and that in summer the chiller can be used to produce cool water for the heating circuit. Even if you have a heat pump or chiller producing 60°C this is hot enough to be used to feed LTHW air unit heaters, the only difference being that you will get fewer kilowatts out of it than if the flow temperature was higher. The beauty of LTHW air unit heaters is that even for lower temperature flows, they are still a very cost-effective way of discharging heat.

Our LH range of unit heaters from Kroll(A German manufacturer ) offer a wide range sizes and are noted for larger sizes with nominal heat outputs up to 118kw. They are competitively priced and at the bigger end of the range they offer size and output which is beyond the range of most of the other manufactures.

LTHW air unit heaters

The larger Kroll lthw air unit heaters in this range have two fans and at the output at 90/70°C and an ambient air temperature of -15°C the largest LH range heater produces a whopping 203kw. Other useful features in our range are that there are extensive range of options for filter boxes, louvers, and side outlets. There are also options the heaters being supplied with stainless steel casing as an alternative to the standard powder coating. These air unit heaters can also be supplied with explosion proof fan motors, where required.

For more information please visit our  LTHW Unit Heater page , or contact us on 01202 822221  or  visit our website