Changing thermostat

[CJreef]

I am replacing a wall thermostat with a new model for a hydronic electric baseboard. The wires on the new thermostat are cleary marked load and power. My problem is I don't know which of the lines to the old thermostat is the load and which is the power. Can I assume that the power always comes from the top of the box and the load goes out the bottom? Thanks.

[jimbrown]

NO. If you have a multi meter you can check to see which ones are hot, thats the power, and the other ones should be the load.

[CJreef]

Thanks for replying. I guess I'm out of luck without a meter [img]/forums/images/icons/frown.gif[/img]

[RichZ]

You can buy a cheap multi meter for a job like this. It certainly would be worth it, to hook up the thermostat properly. You can get a cheal one at Harbor Freight for under $10. It'll be good enough for this job.

[eccentricfarmer]

Yes the meter is a good thing around the farm and should be part of a basic homeowner kit. I think the little sensors that tell if there is power in the line are even cheaper if that is an issue. I like using that better if just chasing a line and looking for a break. But then in a pinch i have been known to use a LITE BULB for a tester.

[Pat]

I have several meters, some expensive and the cheapest a Harbor Freight digital pocket sized that cost about $3 which is plenty good enough.

If you disconnect the suspected load wires and have voltage to the other wires then they are the ones getting power from the breaker. Don't test for voltage using your tongue. Get a cheap meter or alternatively get an outlet tester, the kind you plug into an outlet to see if it is powered up and wired correctly. Also get a couple alligator clip leads. Attach one end of each clip lead to one of the prongs on the tester. If you clip the other ends of the clip leads to the wires under test AND there is power a light will light up on the tester.

Maybe one of the SMART GUYS can tell me what difference it makes which way you connect a direct power switching thermostat. Isn't is just a switch that closes to apply power and opens to shut it off?

Pat