I am in the process of installing electrical radiant heating under a floor. It's a pretty simple circuit - I have a dedicated 120V 20A circuit connected to a line-voltage, GFI protected thermostat. The thermostat then feeds the radiant mats (there are 6 mats, pulling a total of 13.2A at 120V).

I'm installing these in an Eichler (if you know Eichler's you can probably guess the rest of my question). The house is built on slab with no attic for wire runs. So the circuit runs through conduit on the outside of the house and enters the room directly at the wall where the thermostat is installed.

Here's the problem. Space on the entry wall is very tight. I can only fit one single-gang deep box (11 or 12 cu in if I recall correctly). And there are *lots* of wires to connect from the radiant pads. I'm pretty sure the box is not big enough to safely connect all the wires (mats = 12 X 14AWG, line = 2 X 12 AWG + neutral). And I can't fit a 2 gang box in the space.

I think I have 2 options - try to make it work in the single gang box or install a weatherproof junction box on the outside of the house.

Thanks for any advice or other ideas as to how to safely solve this problem.

I think you have way too much of a mess. Mount a PVC NEMA 3 NEMA 4 and Other NEMA Ratings or NEMA 3x box on the outside. Put an LB pulling elbow on the side.

Page 2 has kind of what I'm looking for minus the hinge. It's a PVC enclosure with a backing plate. http://www.americanonsite.com/american/pdf/lit9904.pdf

Here are terminal blocks Terminal Blocks Products that mount on DIN rail. These guys also have enclosures.

It will give you a nice clean install. You will need:

1. NEMA enclosure for outdoors (Conduit entry)
2. Backing plate allows you to mount stuff on the back
3. DIN Rail
4. Terminal blocks
5. Jumper bars. Basically connect the center bars together
6. End brackets
7. Ground bar
8. End stops

It will give you a large ganged terminals in which you can connnect all your wires together. It will look neat and easy to troubleshoot. Industrial stuff is made this way.

Thanks a ton for the pointers and advice. I'm going with an outdoor box that'll have plenty of room - the terminal blocks will make it much more straightforward as well. I've tried to keep the entire system metal for grounding purposes - are there any issues with putting a PVC box in the middle of the system? I'm not too worried about the extra cost of a metal box but I suspect the PVC boxes may have better systems for the terminal blocks.

Again, thanks for the advice.

Actually, it's the other way around. Metal boxes easily come with base plates. I was trying to figure out a way to go from a PVC LB pulling elbow to a watertight seal in the case. Notice it's difficult to buy 1. Try DigiKey Corp. | Electronic Components Distributor | United States Home Page for some minor selections.

It might be hard to figure out how to use DIN rail, but it's fairly simple. Note that there are a few types and they make a combi block that fits both types. You want the T shaped rail.

It becomes fairly straightforward for you, just two rails ad possibly a ground bar with a jumper bar between each set.

KISS, thanks for the advice, I finished the project last weekend. I used a metal NEMA box, 6X6X4, and mounted a terminal strip inside. I crimped lugs onto the load lead wires and ran the thermo load wires to the terminal strip as well. It's much neater and there's plenty of room.

Great! DIN terminals are neater yet. Next time?