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Home > Archive > Heating and air conditioning > July 2005 > Tstat wiring - dual transformer, 1 "R" connection
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Tstat wiring - dual transformer, 1 "R" connection
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I have a dual transformer system - one for heat, one for cool. The
thermostat I'm replacing has an Rc and an Rh connection. The new
thermostat has a single R connection. The transformers are in phase
with each other, however, the heat one puts out 24vac, while the
cooling one is at 26.7vac. Can I connect them both to the R connector
on the new thermostat, or will that not work?
Thanks
John
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| pjm@see_my_sig_for_address.com 2005-07-30, 1:21 pm |
| On Sat, 30 Jul 2005 11:46:14 -0400, John
<apostrophe27@yahooXREMOVEX.com> wrote:
>
>I have a dual transformer system - one for heat, one for cool. The
>thermostat I'm replacing has an Rc and an Rh connection. The new
>thermostat has a single R connection. The transformers are in phase
>with each other, however, the heat one puts out 24vac, while the
>cooling one is at 26.7vac. Can I connect them both to the R connector
>on the new thermostat, or will that not work?
You can ask in alt.home.repair, not here.
Click here every day to feed an animal that needs you today !!!
http://www.theanimalrescuesite.com/
Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'
'With sufficient thrust, pigs fly just fine.'
HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/
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| Oscar_Lives 2005-07-30, 1:21 pm |
|
"John" <apostrophe27@yahooXREMOVEX.com> wrote in message
news:pq7ne15i6lk5hl1enef8jksj2h3i314ang@4ax.com...
>
> I have a dual transformer system - one for heat, one for cool. The
> thermostat I'm replacing has an Rc and an Rh connection. The new
> thermostat has a single R connection. The transformers are in phase
> with each other, however, the heat one puts out 24vac, while the
> cooling one is at 26.7vac. Can I connect them both to the R connector
> on the new thermostat, or will that not work?
>
> Thanks
>
> John
Yes.
You are welcome.
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| TURTLE 2005-07-30, 2:21 pm |
|
"John" <apostrophe27@yahooXREMOVEX.com> wrote in message
news:pq7ne15i6lk5hl1enef8jksj2h3i314ang@4ax.com...
>
> I have a dual transformer system - one for heat, one for cool. The
> thermostat I'm replacing has an Rc and an Rh connection. The new
> thermostat has a single R connection. The transformers are in phase
> with each other, however, the heat one puts out 24vac, while the
> cooling one is at 26.7vac. Can I connect them both to the R connector
> on the new thermostat, or will that not work?
>
> Thanks
>
> John
This is Turtle.
well if the two transformer are really in phase with each other , you can tie
them in together. now if they are not phase together your going to burn one of
them up and the other will take over. Now in some cases you can take both
transformer out.
If you say they are phased together no problem. If not watch out.
TURTLE
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| Carolina Breeze HVAC 2005-07-30, 2:21 pm |
|
<pjm@see_my_sig_for_address.com> wrote in message
news:sk8ne1tlofc460on0dkqdib79tt1crk84b@4ax.com...
> On Sat, 30 Jul 2005 11:46:14 -0400, John
> <apostrophe27@yahooXREMOVEX.com> wrote:
>
>
> You can ask in alt.home.repair, not here.
He did.
I think I am gonna try Terrys suggestion of wiring two transformers of
unknown condition together, and see how long it takes before one smokes.
Any bets?
Should they be the same amp rating, or should we get one 20amp rated unit
and wire it to a 50?
>
>
> Click here every day to feed an animal that needs you today !!!
>
> http://www.theanimalrescuesite.com/
>
> Paul ( pjm @ pobox . com ) - remove spaces to email me
> 'Some days, it's just not worth chewing through the restraints.'
> 'With sufficient thrust, pigs fly just fine.'
> HVAC/R program for Palm PDA's
> Free demo now available online http://pmilligan.net/palm/
> Free Temperature / Pressure charts for 38 Ref's
> http://pmilligan.net/pmtherm/
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| PrecisionMachinisT 2005-07-30, 5:21 pm |
|
"TURTLE" <turtle4aire@bellsouth.net> wrote in message
news:cSNGe.22708$8g5.19153@bignews4.bellsouth.net...
>
> "John" <apostrophe27@yahooXREMOVEX.com> wrote in message
> news:pq7ne15i6lk5hl1enef8jksj2h3i314ang@4ax.com...
>
> This is Turtle.
>
> well if the two transformer are really in phase with each other , you can
tie
> them in together. now if they are not phase together your going to burn
one of
> them up and the other will take over. Now in some cases you can take both
> transformer out.
>
> If you say they are phased together no problem. If not watch out.
>
What exactly is gonna happen to his 2.7V in the case above ???
--
SVL
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| Noon-Air 2005-07-30, 5:21 pm |
|
"John" <apostrophe27@yahooXREMOVEX.com> wrote in message
news:pq7ne15i6lk5hl1enef8jksj2h3i314ang@4ax.com...
>
> I have a dual transformer system - one for heat, one for cool. The
> thermostat I'm replacing has an Rc and an Rh connection. The new
> thermostat has a single R connection. The transformers are in phase
> with each other, however, the heat one puts out 24vac, while the
> cooling one is at 26.7vac. Can I connect them both to the R connector
> on the new thermostat, or will that not work?
>
> Thanks
>
> John
Hmmm.....I didn't think they still made dual transformer systems for
trailers any more.
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| mastertech@techREMOVEmaster.com 2005-07-30, 7:21 pm |
| John wrote:
>
>I have a dual transformer system - one for heat, one for cool. The
>thermostat I'm replacing has an Rc and an Rh connection. The new
>thermostat has a single R connection. The transformers are in phase
>with each other, however, the heat one puts out 24vac, while the
>cooling one is at 26.7vac. Can I connect them both to the R connector
>on the new thermostat, or will that not work?
>
>Thanks
>
>John
Wire the ac transformer to the new thermostat. Wire W1 on the new thermostat to
the coil of an isolation realy, and the other side of the coil to common on the
ac transformer. Connect the heat transformer thru the normally open contacts on
the isolation relay.
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| TURTLE 2005-07-30, 7:21 pm |
|
"PrecisionMachinisT" <precisionmachinist@hotmail.com> wrote in message
news:3YadnTVt9dzwT3bfRVn-vg@scnresearch.com...
>
> "TURTLE" <turtle4aire@bellsouth.net> wrote in message
> news:cSNGe.22708$8g5.19153@bignews4.bellsouth.net...
> tie
> one of
>
> What exactly is gonna happen to his 2.7V in the case above ???
>
> --
>
> SVL
>
This is Turtle.
If Crossed phased the 27 volt will burn the 24 volt.
If NOT Crossed phased the 27 volt and the 24 volt will put up with each other.
The 2.7 volts more is not going to make it no difference. Now the 27 volt will
run most of the power / VA .
Now if there is two circuits he will be running off two transformers. His odds
of not cross phasing is very low and if you have two system running here. He is
going to burn one of the transformer for it's rare to get two system to not
cross phase with each other.
TURTLE
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| TURTLE 2005-07-30, 7:21 pm |
|
"Noon-Air" <Noon-Air@comcast.net> wrote in message
news:jbudnZjHcLpdQHbfRVn-3A@comcast.com...
>
> "John" <apostrophe27@yahooXREMOVEX.com> wrote in message
> news:pq7ne15i6lk5hl1enef8jksj2h3i314ang@4ax.com...
>
> Hmmm.....I didn't think they still made dual transformer systems for trailers
> any more.
>
This is Turtle.
Yea , they have add on air condition by putting package air unit and have the
regular straight heat gas furnace in the hall way. These trailor companys can
install a new thermostat and package unit ouitside and not need licences to
install them. If you install a split system . You will need licences to put in a
evaperator coil and tubing set for the condenser unit. Billy Bob trailor sales
can add cooling and use their people on the trailor lot to install it.
TURTLE
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| PrecisionMachinisT 2005-07-31, 5:21 am |
|
"TURTLE" <turtle4aire@bellsouth.net> wrote in message
news:enSGe.17085$G71.1660@bignews3.bellsouth.net...
>
> "PrecisionMachinisT" <precisionmachinist@hotmail.com> wrote in message
> news:3YadnTVt9dzwT3bfRVn-vg@scnresearch.com...
can[color=darkred]
both[color=darkred]
>
> This is Turtle.
>
> If Crossed phased the 27 volt will burn the 24 volt.
>
> If NOT Crossed phased the 27 volt and the 24 volt will put up with each
other.
> The 2.7 volts more is not going to make it no difference. Now the 27 volt
will
> run most of the power / VA .
>
> Now if there is two circuits he will be running off two transformers. His
odds
> of not cross phasing is very low and if you have two system running here.
He is
> going to burn one of the transformer for it's rare to get two system to
not
> cross phase with each other.
>
man your a real buzz,sometimes........
zzzzzzzzz
--
SVL
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| >>
>
> tie
>
>
> one of
>
>
>
> What exactly is gonna happen to his 2.7V in the case above ???
>
> --
>
> SVL
>
>
I thought about this one a little while, purely from a electrical
standpoint, and wanted to offer my opinion(s):
Provided that the transformer primaries are the same phase (which is
easy to check, and you have a 50 percent chance of being right-or-wrong
on a single phase resi system) parallel outputs from two different
transformers should not cause a problem in itself... even with small
secondary voltage differences.
VA output may be a real problem, though. You are dealing with a
current-limited signaling circuit under the code, and effectively
doubling the circuit VA may be over the top. AT the very least, fuses
and lockout relays might need to be added in various places. There are
also issues of what might happen if one unit is de-energized
independently of the other and backfeeding scenarios occur.
This is just a messy solution, and would require more work to get it
right than just adding the iso relay someone suggested. Simply tying the
two transformers together is not appropriate or correct, IMHO.
Jake
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| TURTLE 2005-07-31, 1:21 pm |
|
"Jake" <jkelleyus@insightbb.com> wrote in message
news:ov5He.227970$xm3.134289@attbi_s21...
>
> I thought about this one a little while, purely from a electrical standpoint,
> and wanted to offer my opinion(s):
>
> Provided that the transformer primaries are the same phase (which is easy to
> check, and you have a 50 percent chance of being right-or-wrong on a single
> phase resi system) parallel outputs from two different transformers should not
> cause a problem in itself... even with small secondary voltage differences.
>
> VA output may be a real problem, though. You are dealing with a
> current-limited signaling circuit under the code, and effectively doubling the
> circuit VA may be over the top. AT the very least, fuses and lockout relays
> might need to be added in various places. There are also issues of what might
> happen if one unit is de-energized independently of the other and backfeeding
> scenarios occur.
>
> This is just a messy solution, and would require more work to get it right
> than just adding the iso relay someone suggested. Simply tying the two
> transformers together is not appropriate or correct, IMHO.
>
> Jake
This is Turtle.
WOW , You got that stuff down.
We / I have been putting 2 -- 40 va transformers together to make a 80 va
transformer all my life. If you want a 40 va , you can put 2 -- 20 va
tramsformers together to get a 40 va. Then if you can't get a 120 va transformer
you can put 3 --- 40 va transformers together to make a 120 va. .
The transformers must be in parallel with each other and then start stacking up
the va to get the bigger va ability transformers.
TURTLE
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