Terminal Blocks for Radiant Floors

I would contact the manufacturer for what they recommend. They may specify one particular type (theirs, for a small fee) or tell you the warranty is void if others are used.

They have no suggestion, they told me today to get what I was comfortable with and met US code.

A couple questions-

1- What is the size of each mat? 8 watts per SF has to have some level of maximum power

2- What is the voltage of each mat? 2 leads could be 120 VAC- or 208/240/480 single phase. This is a big deal since it will ultimately determine (along with Item 1) the connected amperage. 16 Ga leads implies less than 10 amps per mat, but need to know actual loads.

If up to 12 mats can be connected in parallel, the feeding cable and the terminal blocks need to be rated for 125% of the TOTAL connected amperage load. Your note implies that the thermostat will be line-voltage, so it also must be rated for the peak connected load. By the way- a safer installation (relative to home-owners and installers) would be to use a low voltage (24 VAC) thermostat (powered by an appropriate line voltage transformer) and a contactor to control the power feeds to the mats. This will aslo allow appropriate wiring installation- likely in conduit between power controller and mat connections and between power source and power controller. If you use the low voltage thermostat, the contactor and the terminal strip cam be contained in the same control/junction box.

By the way- if the panels are powered by 120 VAC, you COULD use something like Romex cable between the terminals and a junction box at the mat, but any other level of voltage will require conduit for the power wiring.

You also did not mention any type of grounding connection- this is a cause for concern relative to codes and personel safety. ANY wiring devices outside of the mats must be grounded continuously.

Hope this helps.

We have recently pick up a line of heat mats froma Israeli supplier.

It sounds like you are going to be a reseller of some kind. If this is the case I would insist on getting better technical support than you have received so far. You will be asked to answer the question you just posed by just about every potential customer you have. Nothing turns off a buyer like an uninformed or misinformed sales type.

Well said and totally true.

I concur but.... they are counting on me to apply the US standard.

We are only the third company in the US with thier product, the first two are not even offering what I intend to offer. I am the US tech support for the midwest. They have given me own lead if I want it or not.

I met with their engineer in Lansing MI in Jan, we had a slight language barrier, more pointing and nodding. I should have paid attention in Hebrew class......not.

I must find a safe solution. The thermostats we sell are Non GFI with floor sensors and an ambient temp over-ride, they are made by Honeywell/Aube. We suggest direct feed to a GFI Breaker, is this good choice?

Use of a GFI breaker should not be necessary. These are normally used for conditions where there is a risk of wet hands or standing in wet areas and interaction with electric feeds (like bathrooms, kitchens, basements or corridors where wet mopping is done).

The bigger issue is the need for all power supplies to be grounded to eliminate the risk of accidental short circuits that could cause a fire due to overheating of the feed wires- the ground allows very high rates of power flow which will trip the breaker where a low-grade ungrounded short may allow high power flow but not high enough to trip the breaker.

Since you are looking at marketing this installation, I would suggest that you hire a local licensed electrical consulting engineer to develop a "standard" installation procedure- It should only cost a couple thousand dollars at most- and use this as your template. That way you will be assured that your installations will be fully up to code regardless of who does the installation- especially if you add a disclaimer of any liability or warranty if the installation is not made per your written instructions and diagrams.

Good luck.

Thank you for your input, I am not done here just simply working out of town. When I get back to my home office I will reingage about the heat mats.