HVAC Questions? Ask an HVAC Expert for Answers ASAP
Hello, my name is XXXXX XXXXX I will assist you today
Your old thermostar has an Rc and Rh or Rc and R ?
Oops Rc and R
What was hooked up was W,Y,G,Rc, R and C
Okay, you should have a wire that fed the R or the Rc with a jumper across. Is that correct?
uh no jumper. two separate wires. The Red from AC went to Rc, The red from heat went to R
That indicates you have a 2 transformer system which is rare. Most a/c units don't have a transformer
You may not be able to have a 2 transformer system with this t stat, but you can convert it to a 1 transformer system.
Let me look at your new stat wiring diagram. just a minute please.
hmm. i had a c wire run because i was using a battery operated tstat prior.
it worked with the old honeywell. there is no power to the venstar now
are you saying Rc is a 24Volt input?
Rc is 24 volt input for cooling
so should i hook that up to the c on the venstar?
The C is the 24 volt common or neutral and will be needed for the stat to funtion
I would put the wire going to Rc on the R terminal and tape off the wire that was going to the R terminal on the old stat.
If you accidently shorted the Rc wire or the R wire, you may have blown a fuse at the furnace circuit board
can you jumper the Rc to the G and see if the blower comes on?
i dont think so. let me quickly hook up the old one. ill get back to you in 5
ok. back. both ac and heat come on now
so the old one works
you have the R and Rc connected?
Does your heat work also?
seems to be
I see you said it did, sorry.
Can you access the heat ? And what type heat do you have?
thats ok. i had a nest tstat. wouldnt work until i hooked up a c. when i did it worked fine for a while until the baseplate blew out.
never get a nest.
i have gas hot water heat
We can try to convert this to a 1 transformer system if you would like.
i dont think anything is working now. ill get back to you in a few
The only problem I have with this is we don't know the size of your transformers.
the heat works. the blower motor for the ac does not turn on now. prolly blew the fuse in it
does the a/c and the heat use the same blower?
gas hot water heat, rheem electric ac
two separate systems
I understand. So the thermostat controls the fan on the a/c only?
the tstat call for cooling but nothing happens
the tstat controls the blower which then passes on the call for cooling to the compressor
but the fan doesnt come on at all now. the blower unit is dead
Does the a/c unit run?
my understanding is the fan should come on if i switch it on at the tstat even if i dont want cooling, correct?
that is correct
the compressor never turns on.
the fan and compressor are on the same transformer
i think the call to the compressor is relayed through the blower unit. yes i beleive they are
so im basically stuck until i get the blower unit up again
Typ, the Rc is the hot and on a call for cooling, it energizes the Y and the G terminal with the Y being cooling and G being the fan
i shouldve just watched football :-)
Sorry for your troubles.
Where do you live?
is it warm there now?
its not a big deal. i will have my HVAC guy fix the fuse. my setup with my old honeywell tstat was easy. venstar should give you better instructions,
its about 72 out
Here is what I would do
jumper the rc to the c?
You have a 2 transformer system and trying to make it work on a 1 transformer t-stat.
Rc to C would be a direct short
R and Rc are both hot wires.
C is a common/neutral
I would have the a/c guy change you over to a 1 transformer system
hm ok where does my c go to now?
We could do that now, but I don't know if the transformers are large enough
the C still goes to the C terminal
its not going to help now since i blew that fuse, correct?
and why was it ok with my old tstat?
well, if the transformer for the heat were large enough, it would. But we don't know
Because the old stat had a place for 2 hot wires. One to rhe R and the other to the Rc
i dont want to mess with my heating unot. its a new traingle tube with microprocessors etc. i was told not to mess with the transformer on that one,.
understood. so when i switched from heat to cool it just used the RC wire rather thab the r, correct?
It can still be changed over to single transformer.
yes, that is correct
R is hot wire for heat and Rc is hot wire for cool
gotcha so how would i do that?
keep the transformer for the heat
the R wire?
BUT, instead of the hot going through the thermostat, it would go through a set of relay contacts.
correct, the R
then, use the wire going to the Rc terminal and put it on the R terminal on the stat.
would be normal operation for cooling. But when it calls for heat, it would energize the relay which in turn closes the contacts bringing the boiler on
right now, it turns the boiler on without the relay
we need the relay to seperate the 2 transformers.
give me a little bit and I will draw this out for you if you would like
sounds complicated. ok. great
your HVAC tech should know how to do it
I will show your boiler as energizing a gas valve as I don't know what all controlls you have on it.
yes he should. just pisses me off that venstar doesnt clarify this. as i said its a fairly standard installation around here,
They could have put a Rh for heat and Rc for cool
exactly. thats what the Nest Tstat had. but thats a crap product,
give me a bit and I will draw up your existing and the way it will need to be done.
will be a rough sketch
I will attach it here as a picture
okay, going to scan these, then I will post.
This may not be exact, your cooling transformer may be in the cooling unit and not the blower. Just the location of wiring would change.
thanks. looks simple enough. ill rate you so you get paid. thanks again. if you would like to know how it turns out send me your email adress. imXXX@XXXXXX.XXX
we can't give out our email, but you can come back to this question and let me know. I would appreciate that.
ok. how would i do that?
your email shows as just x to me
I will put you down for a follow up in a couple days. you will get an email
how about this? tmatwellatgmaildotcom
ok great thanks again for your help
Thank you and good luck. This will work for you