[zlessley]

Hey, I'm replacing some thermostats (double pole,20A circuit) the ones connected now are mechanical ones (aka no batteries) but are getting old and not working so well. I tried connecting a ritetemp one that required two AA batteries, I hooked up everything just as the other one was hooked up: top(two wires to one) to top, bottom to bottom(one wire to one) and reversed sides because on the old one, the line was on the right and on the new one it's on the left. As soon as I flipped the breaker back on, it shorted, well.. exploded is a better term but not as helpful...

What in bloody heck did I do wrong?? L1 on each side got the double wire, L2 got the single, I hooked it up according to how the old one said where the line and load were.

Any tips?

[rtw_travel]

You must have directly connected one live wire to another.

WHich model do you have?

[KISS]

What are the terminal designations on the new stat or the answer to what rtw_travel asked?

[tkrussell]

Here is a simple wiring diagram for a heat circuit. If you connected the Line to the two wires one one side of the stat, instead of the top Line, and ditto on the other, you can see that once the stat is turned on, you have created a dead short.

[zlessley]

Just designated line on the left, load on the right, and L1 on the top and L2 on the bottom on both sides. On each side there is a connection that is 2 wires twisted together rather than one, should that go in L1 or L2?

I made sure line was on the left and load on the right (I disconnected one side at a time from the thermostat)

Oh, I ended up blowing up all three I had (good job.. ) and just put the old one back on and it still works... well.. it's still off temperature wise but it doesn't blow up and it turns the heater on.

[tkrussell]

Just to be sure you are looking at the diagram properly, the t'stat is lying down, and both Line terminals are at the left, and the two Load terminals are on the right.

If this is what you did and still having a problem, is it possible that your not sure which wires in the stat box are Line and Load?

[zlessley]

Hmmm.. could be, I'm reading your diagram right, but when I connect it up to the old thermostat with line and load going to the right area, it still works... Any idea why there is a connection on both the line and the load that connects to two wired twisted together from the wall?

Could there be a problem with going from a mechanical thermostat to a battery operated one?

[tkrussell]

Please explain:

Any idea why there is a connection on both the line and the load that connects to two wired twisted together from the wall?

Is the new stat rated 120 volts or 240 volts?

Do you know which wires are Line and Load?

[zlessley]

Don't know, I was thinking that yesterday, I chucked them all so I don't know anymore, but the circuit is 240. Yes, I know which is the line and load (if I had them flipped would the old thermostat still work?)

[KISS]

Yep, the old t-tat would still work.

There is one thing ODD about these mechanical stats. One side (Switch) is closed at all temperatures except when the knob is turned to off. The other side (switch) opens on temperature rise. This provides isolation when the control is set to the off position.

Line and load is easily identified with a digital voltmeter.

Two 120 V test lamps in series will act as a 240 test lamp.

[EPMiller]

zlessley, Are you certain that the new tstat has the terminals in the same positions as the old tstat? I have done plenty of line voltage tstats and I know that the terminals are in different combinations from different manufacturers. Lines in on the top 2 and out on the bottom 2 is very common but I've seen in on one side and out on the other also. Terminals can be marked very cryptically too. Like L1 and L2 actually referring to the LOAD not LINE as I would expect. That tstat had a little sine wave symbol on the inputs.

[zlessley]

Sorry, I don't have one or know how to operate it...
EP, yeah.. both have line and load written out, I'm thinking the old one was hooked up backwards...
But I'm still curious as to the two wires twisted into one on the line and load... what are those?

[stanfortyman]

If you know which wires are line and which are load, and you can read instructions, you should be able to do this.
DO NOT go by the old t-stat as the others have said. You NEED to read the instructions of the new one to see how it is hooked up.

Although I must say, someone working on ANY electrical, without even owning or knowing how to use a tester, is a pretty scary thought. :rolleyes:

[KISS]

The two twisted together. What colors are they, not that it matters much, but it could help.

The number of cables and the colors of the wires in the cables. I'm suspecting 3 cables, with a white black and bare not properly marked. The whites should probably be taped red.

If you have 2 whites attached to the stat and 2 blacks attached to the stat then there are two possibilities: 1) 2 heaters controlled by the same stat e.g. the load terminal or 2) Somebody piggybacked off another 240 V circuit e.g the LINE terminals.

Don't do this on a regular basis, but take one of the wires going to the tstat ( a dual black or a dual white) and temporarily connect the lowest wattage lamp you can find from these terminals and the metal box with the tstat off. The set that lights (double or single wire) will be the line terminals.

[zlessley]

Ha.. KISS, they're all white... I think the dumbass who installed them switched line and load.. And stanfortyman, just very basic electrics, I know how circuits and such work (a year of College physics.. not much) all I do it just flip the breaker.

[KISS]

In 240 circuits there are two lines, lets call them L1 and L2, so they both must be switched off when part of a disconnect. If L1 was switched, the heater would be off, BUT if L2 came in contact with ground, L2 would meet sparky. That's also why the poles of a 240 V breaker are mechanically linked.

So, now you know the importance of taping the wires the proper colors. e.g. taping the whites Red and Black.

[zlessley]

Yup yup, I understand taping colors, I didn't wire the place, and until I figure out what's what I'm going to leave them white

The ground seems to be something completely separate inside.. I saw it in the back... Do you all understand that on each side there are a total of 3 wires, two come twisted together... does that make sense?

[KISS]

Get a voltmeter or a 120 V test light. The test light will cost a few bucks.

Take ALL the wires off the terminals. Leave the twisted wires twisted.

Connect the test light to the ground of the box. If it lights it's line. If it doesn't, it's load.
You can mix up the relative sides, but you can't mix up line and load for a non-mechanical stat.

Are their multiple heaters that you can see?

Does the breaker feeding this circuit feed something else?

If you don't know these answers, get a test light or a voltmeter.

Edit: 2/17; Leave wires twisted