CBHvac wrote:
Hi all,
I had to run an additional wire to supply 24vac which I ran from the 24vac
t ransformer on the side of the furnace to RH and C. I then ran the original
wires to W1 and C through a 24vac isolation coil. The system seems to be
working well.
Rich
: "Rich" wrote in message
: om...
: I have a new 3-wire programmable thermostat but only two wires coming
: up through the wall. The thermostat calls for wires to Rh, C and W.
: I can pull a new three wire thermostat cable but am not sure how to
: wire it to the oil burner. The system is oil-fired hot water and the
: thermostat that I want to replace is the primary zone with no zone
: valve as far as I can see. I tried hooking up the the red wire to Rh
: terminal and and the white wire to C terminal and got power to the
: thermostat but when the thermostat calls for heat there is none.
:
: Thanks for your help,
: Richard

: First, do you have a 18VAC or 24VAC transformer in the furnace?
: No..not the 10,000VAC burner transformer, but the control transformer...


: IF and ONLY if its a 24VAC, you are still going to need a common....and you
: dont have that on a 2 wire...

: Not being able to see what you have is another issue, but, it sounds like
: you have a common required stat, (hate em) and since all you have is the
: loop for heat..well...it would be wise to have someone that can see your
: situation wire in a new one, but the red wire is NORMALLY 24VAC, and the
: white is NORMALLY your heat call, meaning it goes to the W terminal, and the
: common you dont have, can go to a couple of places, and will go the C
: terminal.



--
Ciao,
Rich

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Richard Mandel | E-mail address:
Boston Univ. School of Medicine | Phone No. 617-638-4512
Boston, MA 02118 | Fax No. 617-638-4085
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