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Heat Mat - Frequently Asked Questions

Click on the drop down links below to read a frequently asked question:

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How long will it take for the underfloor heating system to warm up?

The warm up time of an electric underfloor heating system will be dictated by the insulation used beneath it and the output of the system. In general, the better insulated the sub-floor the faster the system will warm up, with Heat Mat Underfloor Insulation boards facilitating a very speedy warm up time of as little as 15 minutes, and un-insulated concrete floors causing the slowest warm up time. Using a 200W system beneath ceramic/stone tiles provides a faster warm up time than 150W or 160W systems. We recommend using Thermal Underfloor Insulation boards wherever practical when installing our systems onto concrete floors.

How much will it cost to run an electric underfloor heating system?

The cost of running your system is based around many different factors so it is hard to generalise. When our systems are used in well insulated internal rooms we would expect them to cost up to £6.48/€14.68 to run per square meter per annum, and in conservatories up to £9.44/€21.32 per annum. This should be more efficient than any other electric form of heating and will often be cheaper than a radiator system.

These costs are based on a unit price of electricity of 8p in the UK and 18.2 € cents in Ireland. Both examples assume rooms insulated up to the current building regulations, that the systems are laid directly onto suitable insulation and controlled by our NGT thermostat set to 20 degrees. The first example assumes a 200W/sqm system heating the room for 135 days per annum, ten hours a day and supplying power 30% of the time. The conservatory example assumes a 200W/sqm system heating the room for 210 days a year, eight hours a day and supplying power 35% of the time.

The only things which significantly affect the cost of running one system compared to another are the insulation used beneath the system, the output of the system and the use of an intelligent thermostat. In general, the better the insulation used beneath it, and the higher output of the system, the cheaper it will be to run as long as it is used with an intelligent thermostat like Heat Mat's NGT thermostat/timer.

Some suppliers offer electric underfloor heating which they claim to be 30-50% more efficient than 'normal' electric underfloor heating systems. Are they?

The truth is very simple, with any mains voltage electric heating system one kilowatt of electricity will produce one kilowatt of heat, whether it is a 3mm or 7mm cable, heating mats or heating ribbons. With a low voltage system there is a small amount of wasted energy in the form of heat and noise within the transformer. The only things which significantly affect the cost of running one system compared to another are the insulation used beneath the system, the output of the system and the use of an intelligent thermostat. In general, the better the insulation used beneath it, and the higher output of the system, the cheaper it will be to run as long as it is used with an intelligent thermostat like Heat Mat's NGT thermostat/timer.

I want to replace one of my old underfloor heating thermostats with a Heat Mat NGT thermostat. Is this possible without taking up my floor to install a new floor sensor?

Yes, our 4th generation thermostat is designed to be a straight swap with older thermostats, even those produced by other companies. Each brands floor sensor operates on a different Ohm rating, but our NGT thermostat is designed to take this into account. If you call our Technical Support Team and explain to them the type of thermostat you want to replace they will let you know if it is possible, and how to set up the new thermostat to work with your old floor sensor.

What does a BEAB or VDE system approval mean?

Unlike CE marking, which is a non-independent self-certificate, BEAB and VDE system approvals are completely independent. A system approval, such as Heat Mat have on their heating mats, means that BEAB and VDE have independently verified and tested the heating mats with Heat Mat's thermostats and they have confirmed that the system is safe and suitable for use as underfloor heating and that it complies with all necessary legislation. At the time of writing Heat Mat are the only manufacturer with this approval, and all of our heating mats, cables and thermostats are manufactured in BEAB approved factories.

Which is more expensive to run, 160W or 200W heating mats?

If the system is used with the thermostats adaptive function switched on then the 200W system will be slightly cheaper to use than the 160W system. This is due to the warm up time of the 200W system being slightly faster.

Turn my heating on the day it is laid?

If you have installed your heating beneath tile adhesive, levelling compound or a screed you must allow this to dry out before turning on your system for the first time. If the system is turned on too early it will force the moisture out of the covering which may lead it to crack. We would recommend speaking to the manufacturer of your flexible tile adhesive, grout or screed to confirm the drying time required.

Are the heating systems connected in parallel or series?

The heating systems are always connected in parallel at the thermostat or in a connection box.

How do I install more than 14/16 Amps of underfloor heating?

If your chosen system exceeds the maximum Amp rating of your thermostat, you should consult your electrician who will be able to advise you on using a contactor to control the system.

Does each room require its own thermostat?

We would recommend that each room has its own heating system controlled by its own thermostat. This will allow for simpler and more accurate temperature control of each room and will avoid heating rooms which do not require it.

Can the heating cable be shortened?

The heating cable cannot be shortened because each heating element has an adaptive resistance suitable for only one length of cable. If you shorten the cable it will not operate correctly. The only types of heating cables that can be shortened are self limiting cables.

I am uncertain of my final floor covering, what system should I install?

If you install 160W/sqm heating mats or 3mm cable beneath a levelling compound, or 7mm cable at 160W/m2 beneath a screed, virtually any floor covering can be laid on top.

Can I tile straight onto heating mats and 3mm cables?

You can tile straight onto heating mats and 3mm cables as long as you use a flexible tile adhesive and ensure that all of the heating cables are thoroughly covered. If installing a system in this way, the tiler should take particular care not to damage the heating cable when cleaning out grout lines.

If I damage a heating element can it be repaired?

Although the heating systems are very robust, accidents do happen! Luckily, it is very simple to repair all of our heating elements (with the exception of our underlaminate system eleiment) if the damage is found before they are covered. If a heating element is damaged please contact your supplier to arrange for a repair kit and easy to follow instructions to be sent to you.

Can the heating system be repaired if it stops working, without taking the whole floor up?

On the very rare occasion that a system stops working once it has been covered all is not lost. Usually the problem is related to the electrical wiring or thermostat connections and if you speak to Heat Mat's Technical Team they should be able to assist you in locating and correcting the error. If the fault appears to be located beneath a tiled floor or levelling compound, Heat Mat can provide the services of an independent engineer who specialises in locating and repairing damaged heating systems. The damaged area is located by using a thermal imaging camera and usually can be pinpointed to an area roughly the size of a ten pence piece. The engineer can then repair the cable beneath the floor by removing the minimum amount of tiles or compound. There is a charge for this service if the damage is found to have been caused subsequent to Heat Mat supplying the product.

If I need to drill a hole in the floor after my system has been laid, how do I miss the cables?

Although we do not recommend installing underfloor heating beneath areas where you will later need to drill into the floor, it does happen! Often a door stop needs to be installed or a pedestal requires screwing down and in these cases Heat Mat can supply Cable Trace film. Cable Trace film can locate 3mm heating cables and heating mats if they have been laid directly beneath tiled floors. You simply place the film on the cold floor and then turn the heating on, and the image of the cables will show up on the film. Cable trace can be obtained from your Heat Mat retailer and is reusable and also works with Heat Mat's underlaminate system.

What is a thermal block?

A thermal block is any layer of insulating material that is placed on top of an underfloor heating system that prevents the heat from leaving the floor. Thermal blocks include obvious items such as large beanbag furniture or a futon with no air gap beneath it but also include less obvious items such as rubber backed rugs or even a pile of newspapers. By preventing the heat from escaping the thermal block causes the floor beneath it to keep on heating up above it’s normal temperature and, unless the floor temperature sensor happens to be located beneath the thermal block, the heating system will not realise the heat is building up and will keep heating the floor. In extreme circumstances this can lead to the floor covering being damaged. In-screed heating systems and cables covered in levelling compound or tiles do not suffer seriously from thermal blocks as the heat is conducted away from the area by the covering. Heat Mat’s underlaminate system is designed to help the heat work it’s way around the block through the aluminium heat dissipation layer however carbon films and heating ribbons can suffer very seriously with thermal blocks and with these systems it is vital to ensure you do not place anything on top of your floor that could prevent the heat from escaping.

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