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Old 12-07-2010, 12:32 PM   #1
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


Since having a heat pump system added to my 80% gas furnace 2 summers ago, I've often wondered why no gas fire when the heat pump goes into defrost. Lately I have been reading what I could find on which wires mean what coming from where and I found what I believe to be the DEFROST SIGNAL (24v) coming from the Heat Pump control board, wired back through the gas furnace air handler (without connecting to anything), continuing back to my 1F95-1291 thermostat, and terminating at the W2 terminal.

I think I am right, when I say, that the W2 should be an output from the thermostat to kick on second stage gas fire (which I don't have), rather than an input from the heat pump telling the thermostat I am in defrost. I see no connection on the tstat for that input.

That being said, I wonder if the installer meant to run this wire into the same output post W/E so that this would provide an alternative signal to the gas fire (other than the tstat call) to turn on during defrost? Can it be that to fix my defrost problem - ie no gas heat during defrost - all I have to do is push this wire into the W/E post which already includes a wire going to the gas furnace to turn it on?

My gas fire manual says that when the unit "sees" the compressor signal PLUS the gas fire signal, it knows that a defrost has been initiated and it will do a different firing sequence including NOT turning off the blower. So, it seems to me that if I simply move this signal to the W/E post, then that signal will light the gas fire while at the same time the air handler sees the compressor still on indication.

Alternatively, since this DEFROST signal is currently running into my air handler along with the other wires coming from/going to the outdoor unit, I could simpy snip it and tie it directly to the gas fire on post of the air handler control board, right?

I won't call back the installers, at least NOT THOSE INSTALLERS, because since the installation they've been extremely unhelpful.

Thanks,
Mike

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Old 12-07-2010, 04:41 PM   #2
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


Correct, hook it to w in gas furnace, if it is providing 24v in defrost mode only

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Old 12-07-2010, 05:44 PM   #3
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


Ok, so I should simply disconnect the input on the W2 terminal at the thermostat since it obviously does nothing right now, then go into the air handler and tie the 24v defrost signal to the W terminal on the furnace.

Assuming the installer did incorrectly attach the defrost line to my W2 stat, wouldn't I accomplish the same thing simply by removing this wire from the W2 stat post and pushing it together with the W/E connector (which already goes from the tstat to turn on the furnace)?

It would save me a trip up into the attic to rewire the air handler.

Thanks for your prompt reply.
Mike
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Old 12-07-2010, 05:58 PM   #4
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


yes, you could do that
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Old 12-07-2010, 08:11 PM   #5
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


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Originally Posted by hvactech126
yes, you could do that
I recommend that you change the lock out temp, so your hp does not go into defrost. Some set ups will not allow w2 to break until system reaches desired temp. I live in VA we use dual fuel a lot never do we want gas and hp to run at same time. You may have a charge problem, in our area with humidity and temp we lock out at 40*
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Old 12-07-2010, 08:30 PM   #6
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


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Originally Posted by Hixheat1 View Post
I recommend that you change the lock out temp, so your hp does not go into defrost. Some set ups will not allow w2 to break until system reaches desired temp. I live in VA we use dual fuel a lot never do we want gas and hp to run at same time. You may have a charge problem, in our area with humidity and temp we lock out at 40*
In PA. We set the furnace lock out at the economical balance point. Which is always well under 40. No problem with furnace running while heat pump is in defrost. It won't hurt the heat pump.
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Old 12-07-2010, 08:38 PM   #7
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


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Originally Posted by beenthere

In PA. We set the furnace lock out at the economical balance point. Which is always well under 40. No problem with furnace running while heat pump is in defrost. It won't hurt the heat pump.
True if it is set up properly if the stat is set up to break w2 when it comes out of defrost if not high head pre sure not so good however if odu is controlling it should work. Thank u I learn something every day.
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Old 12-07-2010, 08:57 PM   #8
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Originally Posted by Hixheat1 View Post
True if it is set up properly if the stat is set up to break w2 when it comes out of defrost if not high head pre sure not so good however if odu is controlling it should work. Thank u I learn something every day.
Thermostat has no bearing on defrost, doesn't know the heat pump is in a defrost mode. The defrost board controls defrost.
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Old 12-07-2010, 09:00 PM   #9
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


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Originally Posted by beenthere

Thermostat has no bearing on defrost, doesn't know the heat pump is in a defrost mode. The defrost board controls defrost.
Right on. In the old days we used lock out relays it is what it is
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Old 12-08-2010, 07:16 AM   #10
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


Thanks to all respondents. I've wired the lower unit so that the defrost signal from the outdoor unit goes to W on the furnace. For the attic unit I have connected what the installer had as an output from W2 on the thermostat to W/E on the thermostat since my assumption is he did the same wire job upstairs as downstairs, so that this is actually the same defrost signal - thus it will light up the W to the furnace when the outdoor unit goes into defrost. Temps are up to 49 today so there won't be any defrosts.

Another question - this gas furnace fan has 4 speeds HI, MED HI, MED LO, and LOW. I know the typical setting for heat is a lower, not a higher speed because of the way air feels on the skin, whereas for cooling a high speed is the way to go typically. The two units were setup with heatpump wired to the HI speed and the furnace to MED HI. I have switched them for the winter because the heat pump runs most of the time, and I think its louder than it should be plus with a little less fan the output air is just a bit warmer - just a bit.

Question is, in the summer, should I be too concerned about switching the speeds back so that the air conditioner runs on HI rather than MED HI? My info regarding the gas furnace/air handler is that both units are 80% 80,000btu systems, while the heat pumps are 3ton and 2ton units.

Thanks for all the info,
Mike
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Old 12-08-2010, 01:13 PM   #11
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


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Originally Posted by mgroves
Thanks to all respondents. I've wired the lower unit so that the defrost signal from the outdoor unit goes to W on the furnace. For the attic unit I have connected what the installer had as an output from W2 on the thermostat to W/E on the thermostat since my assumption is he did the same wire job upstairs as downstairs, so that this is actually the same defrost signal - thus it will light up the W to the furnace when the outdoor unit goes into defrost. Temps are up to 49 today so there won't be any defrosts.

Another question - this gas furnace fan has 4 speeds HI, MED HI, MED LO, and LOW. I know the typical setting for heat is a lower, not a higher speed because of the way air feels on the skin, whereas for cooling a high speed is the way to go typically. The two units were setup with heatpump wired to the HI speed and the furnace to MED HI. I have switched them for the winter because the heat pump runs most of the time, and I think its louder than it should be plus with a little less fan the output air is just a bit warmer - just a bit.

Question is, in the summer, should I be too concerned about switching the speeds back so that the air conditioner runs on HI rather than MED HI? My info regarding the gas furnace/air handler is that both units are 80% 80,000btu systems, while the heat pumps are 3ton and 2ton units.

Thanks for all the info,
Mike
Your system was charge in high speed when you lower your fan speed you may effect the performance of the system via high head pressure
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Old 12-08-2010, 04:58 PM   #12
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


That makes sense. Sound wise there seems to be little difference in HI versus MED HI for this Carrier Gas Furnace 58PAV and 58RAV. Is there a resource that I can use online that gives the CFM numbers for each fan speed? Is that how it would be measured? Since one heat pump is a 2ton and the other a 3ton, seems that one is either getting too much air or one is not getting enough in the current configurations given identical air handlers (although one is horizontal and one is an up flow).

Thanks,
Mike
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Old 12-08-2010, 05:11 PM   #13
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


N o one set amount of air for the speed setting alone. You would need to know the static pressure the blower was working against also.
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Old 12-08-2010, 05:33 PM   #14
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


Thanks, ok, that one is over my head. I am considering, with the trouble I've had with the original installers, of looking for very reputable company to come in here and tell me where these guys went wrong. After visiting the attic to take a look at the system, it appears that they used the existing coil (in addition to the lineset which I ok'ed because it was inside the wall) when they replaced my air conditioner outdoor unit with the 2 ton hp.

According to their bid, I paid for 2 indoor coils. The bottom unit had no existing coil as it was never an air conditioner so they "custom crafted" a housing for the new coil which sits a top the upflow furnace. The attic housing appears to be factory created, and that's why I think they simply reused it. I mean, you couldn't have take it apart and put in another coil from Goodman, right, or could they? Anyway, the upstairs unit, the 2 ton, seems to put out hotter air than the downstairs - it just seems to do a better job overall, so maybe I should be happy they reused the factory made coil w/housing...

Anyway, the close I look, the more questionable their work becomes. I know this is too much information. Thanks for your reply regarding the static pressure.

Mike
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Old 12-08-2010, 05:45 PM   #15
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Hybrid Heating System with White Rodgers TSTAT 1F95-1291


They may have been able to install an ADP or Aspen coil in the case.

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