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Old 02-24-2010, 10:35 AM   #1
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2-wire system reversed?


Trying to replace a thermostat in my condo that uses a central boiler + hydronic baseboard heaters. I removed the old mercury thermostat that has two black wires. I've discovered that:

When the circuit is open = heat on
When the circuit is closed = heat off

I've tried two different digital thermostats and both cause the system to work in reverse. When I turn the heat up, the heat goes off, and vice versa. Is there anything I can do? I do not have access to the boiler room.

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Old 02-24-2010, 01:22 PM   #2
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2-wire system reversed?


What type of thermostat are you putting in? make/model?

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Old 02-24-2010, 01:39 PM   #3
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2-wire system reversed?


Honeywell PRO 1000.

Manual - http://www.forwardthinking.honeywell...69_1968efs.pdf

Reverse valve jumper mentioned does nothing as its for a heat pump.
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Old 02-24-2010, 03:03 PM   #4
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2-wire system reversed?


Wire it up as a cooling only thermostat. Set it to cool and what temp you want. It will work then.
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Old 02-24-2010, 03:18 PM   #5
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2-wire system reversed?


Hah! I guess that will work although it will confuse the hell out of people. hmm.
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Old 02-24-2010, 03:21 PM   #6
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2-wire system reversed?


Quote:
Originally Posted by n0c7 View Post
Hah! I guess that will work although it will confuse the hell out of people. hmm.
No worse then the old Coleman moble furnace units with A/C.
There was no heat or cooling switch on the stat. You turned a switch in the furnace to heat or cool. And the stat only had 2 wires.

Just leave a note inside the stat, that its connected to a reverse acting control system.
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Old 02-24-2010, 03:31 PM   #7
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2-wire system reversed?


Is this pretty common, and are there any adapters to reverse the control?
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Old 02-24-2010, 03:42 PM   #8
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2-wire system reversed?


Not really common. But was done at large apartment buildings on occasion.
Your may have been a pnematic system at once. And the apartments converted to low voltage, but the boilers control system left as reverse acting.

There probably are some made. I just don't know of any off the top of my head.
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Old 02-24-2010, 03:46 PM   #9
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2-wire system reversed?


This would be by my manual thermostat has only R and Y terminals instead of R and W?

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