How many installers does it take to test electric underfloor heating? Hopefully, just one! But with so many common mistakes made along the way, we thought it was time to share the definitive 3-step guide to testing your electric underfloor heating system the right way.
At ThermoSphere, we’re often asked: What’s the best method for testing electric underfloor heating? So, if you're installing our ThermoSphere underfloor heating systems, this quick 4-minute read will walk you through exactly what to do, step by step. As always, If you're short on time and just need answers fast, feel free to contact one of the team, we’re always happy to help.
First things first, take your brand new ThermoSphere product out of the box. We know how exciting this part is, and how badly you’ll want to get it laid and installed straight away, but before you do anything else, there’s one crucial step: Testing. Grab your multimeter and take a resistance reading before you even think about unrolling it. This test will avoid costing you time and money later—so trust us, it’s worth it.
I could tell you to make sure you connect your crocodile clips to the correct wires and I could tell you that you’re testing the resistance to ensure all the electrical components are functioning correctly—but if you’re reading this article, the chances are you already know the basics. That said, here’s a quick tip: if you don’t have an auto-ranging multimeter, make sure to set your Ohms (Ω) to the correct range. Usually, 2000 or 2K Ohms will give you the most accurate result. If the product passes the test, your reading should fall within our tolerable margin of +10% or -5% of the factory reading, which you’ll find in the manufacturer’s test log or printed on the product’s packaging. This applies to ThermoSphere Ultimate®, Mesh and Foil.
Next, it’s time to grab your megohmmeter—also known as an insulation tester—to check the integrity of the cable’s insulation. It works by sending a high-voltage DC charge into the cable to simulate the kind of stress it’ll be under when it’s live. It will also detect any ‘earth leakage’ that could cause an RCD to trip. Connect your live and neutral wires to one probe and your earth braid to the other. If the meter reads an open circuit, often displayed as 999M or infinite, you’re in the clear. This means there is no path for the voltage to flow between the L/N wires and the earth. A failed test result would be a lower resistance reading, typically below 400M Ohms. If you get a reading like this at any stage it is important to call our tech support team for advice on the best next steps.
Finally, you need to test the temperature probe. Set your multimeter to 20k Ohms and connect one crocodile clip to each of the wires. Generally, a reading of 8k-12k Ohms is acceptable for this test. The manufacturer’s test values can again be found in the test log. You need to ensure the resistance matches this value—if not, your probe won’t work, meaning your temperatures will be way off. Please do not send any voltage from your megohmmeter through your floor probe—unless, of course, you want crazy hair and all your colleagues to laugh at you!
Once these checks are all done and you’ve confirmed that everything’s working as it should, you’re good to move forward. A few minutes of careful testing now can save you a world of frustration later. And if anything feels off or confusing, we’re just a phone call away on 01622 689440. We’re here to help you get it right the first time.
Now, calling this a ‘3-step’ guide is a little bit cheeky, because steps 2 and 3 are simply to repeat the above process two more times: Once after the heating has been cut and laid, and again once the flooring has been installed over the top of it. Whilst this guide isn't exactly groundbreaking stuff, not testing and finding an issue after you’ve laid the floor would mean having to take up all your hard work and that would be… groundbreaking! These checks confirm that nothing has gone wrong during each phase of the install, and they give both you and the homeowner peace of mind that everything’s working exactly as it should.
It is important to make sure all tests are completed properly, and the results are clearly recorded in the manufacturer’s test log. This log isn’t just paperwork—it needs to be passed on to the homeowner, as it is vital in validating the warranty of the product for the customer.
Testing at these key points also helps catch any issues caused during delivery, fitting, or when laying the final floor covering. Keep in mind that the manufacturer’s test conditions are based on a temperature of 20 degrees Celsius. So, if you’re testing in mid-summer or during a cold snap, just be aware that this can affect the readings slightly.
If any of the results don’t look quite right, or if there’s something you’re unsure about that we haven’t covered here, just give us a call on 01622 689440. We’d much rather you check in with us than second-guess it—we’re here to help and always happy to chat things through. After all, making sure everything’s running smoothly now will save everyone time and stress later.
If you have any questions about what’s been covered in this heating blog article, please contact us via the website or give one of the team a call on 01622 689440. If you're unsure as to which electric underfloor heating system is the right one for you, have a read of one of our other blogs here.