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alphagamma · Oct 22, 2009, 11:35 AM

My existing Honeywell wiring is like so,
4 wires coming in:

W
R
G
Y

My problem is that Y is also connected to a terminal labeled 1.
I am about to replace this w/ new programmable thermostat.
What the heel do I do about the "Y to 1" connection?

Thanks.

hvac1000 · Oct 22, 2009, 01:14 PM

First of all what is the exact model of your old thermostat?

alphagamma · Oct 22, 2009, 02:50 PM

My house was built in 1999, it's an old honeywell.
I will see if I can find where the model number is labeled tonight.
I was hoping that this configuration was frequent enough that there was a general explanation for why this is?
More importantly if I can just hook it up to my new thermostat R>RC/RH, (w/ jumper conecting RC/RH) Y>Y, W>W, G>G like my instincts are telling me too.
What are the repercussions if I attempt this and it is wrong?
By the way, thanks for your fast resposne!

hvac1000 · Oct 22, 2009, 04:05 PM

What the heel do I do about the "Y to 1" connection?

The 1 connection is why I asked for the exact model number.

If you have a standard gas/oil furnace with A/C then the below should work.

R>RC/RH, (w/ jumper conecting RC/RH) Y>Y, W>W, G>G like my instincts are telling me too.

alphagamma · Oct 23, 2009, 01:23 PM

Where do I look on my existing thermostat for the serial number?
Also, I have a terminal that reads Y1 on my new thermostat, does that sound like a comparable choice?

Existing thermostat: yellow wire coming in to Y terminal, then a jumper form "Y" to "1".
New thermostat: Yellow wire directly into terminal labeled Y1.

I know it's difficult to give advice w/ out knowing serial number, but is this making sense?

letmetellu · Oct 23, 2009, 02:20 PM

Try the way you said you thought was right. About the only thing that can happen is you may blow a fuse on the low voltage line, it can be replaced very easily.

hvac1000 · Oct 23, 2009, 04:49 PM

What is your existing system? Heat pump? Gas furnace?

alphagamma · Oct 25, 2009, 01:26 PM

Electric AC, Gas heat.

Here are the numbers I've seen from the existing THERMOSTAT:

LP1620
9943
T8034C1481 >2

Let me know what you think?

Thanks again man! You've had some sound advice so far!

hvac1000 · Oct 25, 2009, 01:56 PM

here is the original Honeywell wiring diagram

http://www.air-n-water.com/manuals/t8034nmanual.pdf

To replace the old with thew new just follow the wiring diagram from the old and transpose to the new. BTW Y1 is the first stage of cooling and Y1= plain Y. They usually only mark thermostats with Y1 if there are more stages of cooling control available on your new stat.