Low voltage wiring

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jjhoward

jjhoward

Senior Member
Location
Northern NJ
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Owner TJ Electric
Hello All,
First off, Happy Birthday to the US Marines!
And.. thank you all Veterans, tomorrow is Veterans Day, thank you for your service and sacrifice.

I am working a few Warmfloor installs (radiant floor heat).
This product is a 1 foot wide plastic mesh with flat, braided, tinned 14 awg cables embedded along its edges. To install this stuff:
1) Lay a length of this material on the surface to heat.
2) Expose the embedded the 14 awg flat braided cables at one end of the mat (cut into and remove the plastic).
3) Crimp the 24 volt lines (14 awg or 12 awg cable) from the xformer secondary to braided mat cable.
4) Cover with flooring materials (wood, tile etc.)

These lines are limited to 120VA (5 amps @ 24 volts). The transformers are Class 2 xformers.

Is it code compliant to lay the 24 volt lines from the xformer under the flooring? I am reading through article 725 but I am not seeing an answer to my question.

Thank you all.
 
Hey Org,
424.99 most likely was written to address line voltage heating elements.
This stuff from Warmfloors is low voltage, class 2 circuits.
Can I lay class 2 wiring under the floor?
 
HI Jim,
I am learning more about this stuff. It actually looks pretty good.
The material has a postive temp. coefficient. So, as it gets warmer it consumes less power.
It has been installed in > 100K homes. It can be used as the main heat source not just supplimental heat.

But...can I lay class 2 wires under the floor?
 
Are the class 2 wires supplied with the floor heat? The ones I have done, everything comes with the product, so as long as you install it according to instructions, you should be OK.
 
Hi John,
Good point. Yes the cables are included with the materials from the company (WarmFloors). I am confused on the proper wiring methods for LV cables.
I guess these wires coming off the mats are similar to the 24v cables that are normally tacked to the underside of cabinets.

But in this case, I am concerned with putting them under the floor.
The Warmfloor literature shows running these same cables through walls!

I will discuss with the AHJ.
 
I'm curious to know if this type of heat is economical. Around here electricity rates are rather high so electric heating is not really practical. Does anyone know of a cost comparison between this type of heat and say radiant hydronic heat?
 
Hi Trevor,
I have been reviewing the detials of this heating system with help from the factory. It is definitly more efficient than any fossil fuel fired radiant system.
Here in NJ, our energy costs are very high, $2.50/gallon or more for propane. Electricity is .11/KWH (a few months ago).

This system has the advantage of being maintence free and the comfort level is hyped as being superior to hydronic systems. Fewer cold spots, tighter temp. control in the room. The material in the mat generates less output as it warms up.

I am waiting on some info on a 7500 sq ft home done with this system. (Aspen CO, in 2004). Will be reviewing to directly compare with a new house going up here in NJ.

Let me know if you are interested and I will update you with more info when I get it.

Joe
 
Normally in Illinois we do hot water but I've put it in a couple bathrooms where the customer doesn't like a cold floor getting out of the shower even in the summer when the A/C is on. I'm not sure about efficiency but I would expect it to be about the same as any other radiant heat for its target which is floor first then the air in the room. Since it is so low to the ground the heat should flow upward filling the room... probably better than baseboards which tend to flow up the wall. Although they may be close to 100% efficient the cost of gas vs electric per Btu will probably always favor gas, but for areas where electric heat is the norm I think they'd beat everything but the a heat pump.
 
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The biggest reason a homeowner tells me yhey want something like this is getting out of the shower or bath and having a nice warm floor. I have done ones that have a fancy programable thermostat that you can program so it warms up before you go in in the morning. Have to admit, I live in a basement appartment, and I wouldn't mind having it some morning
 
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