honeywell 8230A programmable thermostats


Old 04-25-07, 10:58 AM
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honeywell 8230A programmable thermostats

I have a vacation home 4 hours from where I am now posting to you all. There are 9 thermostats & 9 baseboard heaters in the entire home. This home had old Mears Controls Inc. model # M21DP non-programmable thermostats operating these baseboard heaters. The temperature adjusting knob broke in my hand a few months ago rendering the thermostat inoperable. I decided to look into replacing all the thermostats due to this incident. I brought the old Mears thermostat to show an A/C & Heating expert the type I had and he ordered me 9 honeywell 8230A programmable thermostats.

I unscrewed the Mears thermostat & noted the following installation: The Mears thermostat had 4 wires (2 red line wires & 2 black load wires). I noted 1 load & 1 line wire capped together. I noted the other load wire attached to a black wire in the wall box & the other line wire attached to a black wire in the wall box. There were 2 white wires capped together in the wall box.

I tried to match the original wiring hookup of the Mears to the new Honeywells to no avail, the display worked but there was no heat produced in the heater itself. What am I doing wrong and are these compatible? It seems that the Mears was a double pole and that the Honeywell is a double pole so what could be wrong?

Please understand I am not an electrician but I thought it would be a matter of a straight swap. I have a voltage continuity tester.

Thanks for your help.

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Old 04-25-07, 11:18 AM
Join Date: Sep 2003
Location: Central New York State
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Is this a 120 volt heater or a 240 volt heater?

One (or more) of several things is happening:

The 240 volt thermostats are not compatible with a 120 volt system. What does the instruction manual say about this?

You reversed the line and load wires in the wall. A programmable thermostat needs power to run. A traditional thermostat does not. Did you figure out which wires in the wall are line and which are load?

The thermostat is broken. This is unlikely, but it could be the case.

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