On Thu, 01 Aug 2003 17:08:19 , "HvacTech2"
wrote:

what is the model number of your thermostat? if it is a honeywell T87?? or
one of several other mechanical models this will cause the A/C to run and it
will cause damage. the relay may have to be wired differently to make it
work.

I'm out of town now so I can't tell you the model number of my thermostat
but I will post that here when I'm back home next week. For now I can
tell you that it is a non-programmable mechanical model. Honeywell, I
think but I'm not positive.

Perhaps I should rephrase my original question to the following:

I want to connect an external normally-open relay to my HVAC system that
will paralel the function of the fan on/auto switch on my thermostat.
When the relay is closed it would be the same as the fan switch being in
the on position and when the relay is open it would be the same as the fan
switch being in the auto position. The relay should control only the fan;
it should not cause the compressor or heating system to run. Those
functions should continue to be controlled only by the thermostat setting.

That being the objective...

1. Is there any way to do this without damaging my HVAC system?

2. If so, to what terminals on the control panel inside my HVAC unit
should I connect the relay?

Peter

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