Any HVAC techs on here to ask a question?

[767Jockey]

This is my first winter in this house. It's a two story house, with two different gas fired forced hot air heating units (Carrier) and two separate A/C systems, one for each floor. When I run the heat for downstairs, the A/C compressor outside (the unit for downstairs) runs as well. Is this normal? I've never had forced air heat before, so I don;t know what normal ops is supposed to look like. The air that comes out of the register is pretty warm, but not hot. It's a White Rodgers digital thermostat if that matters. If anyone has any advice or troubleshooting I can do on this I'd appreciate it. Thanks!
Doug

[FWB]

Originally Posted by 767Jockey

This is my first winter in this house. It's a two story house, with two different gas fired forced hot air heating units (Carrier) and two separate A/C systems, one for each floor. When I run the heat for downstairs, the A/C compressor outside (the unit for downstairs) runs as well. Is this normal? I've never had forced air heat before, so I don;t know what normal ops is supposed to look like. The air that comes out of the register is pretty warm, but not hot. It's a White Rodgers digital thermostat if that matters. If anyone has any advice or troubleshooting I can do on this I'd appreciate it. Thanks!
Doug

doug, had a heat pump system in another house and the compressor does cycle when you call for heat. i'm not a HVAC tech but i did stay at a holiday inn once.......

[Z-linkCobra]

Gas fired furnace should not run the compressor or outside unit when in the heat mode. You have a wiring problem with you t-stat. I would have to look at a wiring diagram to know for sure. But if i remember correctly there is a jumper wire that has to be removed for electric or gas heat as oppsed to heat pump.

The only time your outside unit should run when in the heat mode is if you have a heat pump.

Have someone check it out for you, at this point your electric bill is going to go through the roof. Your trying to chill and heat the air at the same time.

[767Jockey]

Originally Posted by Z-linkCobra

Gas fired furnace should not run the compressor or outside unit when in the heat mode. You have a wiring problem with you t-stat. I would have to look at a wiring diagram to know for sure. But if i remember correctly there is a jumper wire that has to be removed for electric or gas heat as oppsed to heat pump.

The only time your outside unit should run when in the heat mode is if you have a heat pump.

Have someone check it out for you, at this point your electric bill is going to go through the roof. Your trying to chill and heat the air at the same time.

Yeah, I didn't think that they should run together. Burning gas and spinning the meter at the same time is not good........anyone know how a neophyte like me can troubleshoot this thing? No budget right now to call a guy in......

[Z-linkCobra]

How old are the units? For a really simple fix....on the outside unit there is are two wire going to it. Little bitty wires that control the low voltage side of the contactor for the compressor. They will probably be together in like a brown outer insulator. They should run right along the refrigeration lines running out to the unit. Its the ones that always get cut with the weedeater in the summer time...lol.

Pull the cover off the unit and find where they are wire nutted to the wires coing from the unit. youll see the connection with two little white or blue wire nuts most times. If you take one of the wires loose and put the wire nut back on thw wire coming from the house...the outside unit wont run no matter what mode its in. That operates the contactor for the unit outside.

Its low voltage 24v so it wont hurt you if you touch it. try not to let touch ground...kind hard on transformers.

Thats the easiest cheapest way to fix it right now.

[Excaliber]

Well done Z-Link, you covered that nicely. Another possible easy solution may be to simply turn off the breaker for the AC unit(s). There should be one fairly close the unit itself, typically mounted outside the house.

It does sound like a T-Stat wiring problem and it is likely at some point you will have to call in a professional. I'm retired, so that leaves me out!

[gunn427]

Thermostat connections are R W Y1 G which are usually Red White Yellow and Green. These will run to identically labeled terminals on the furnace. A two wire will run from the furnace at Y and C to the outdoor condenser. Good luck

[Tommy]

Doug,
I seem to recall you were in Houston at one time. That is prime heat pump country. Are you certain your downstairs unit is a gas fired furnace? In other words, have you seen the pilot light and burning gas when the unit is running? I'd hate to see you trying to troubleshoot something that is working normally.

[Gatorac]

It sounds like you have what's called a "hybrid" system. A heat pump with a gas furnace. A heat pump will cost less to run then a gas furnace down to about 40 degrees outside temperature. The system has an outdoor thermostat that will run the heat pump until it gets too cold for it to be effective and then lets the furnace take over. The previous owners were smart and made a wise investment that you get to take advantage of.

I'm only an air conditioning contractor with about 22 years in the business so I may be wrong. Give me the model numbers of the equipment and I might be a little more confident.;-)

[olddog]

I second Tommy.

You definitely want to know if it is a heat pump or not. Heat pumps both heat and cool. They are typically physically larger than an air conditioner for a similar sized house.

Here in Ohio it is very common on new installations to put a heat pump in and use it with a gas furnace. You get the best economy that way. If it is mildly cool outside the heat pump is more efficient. Under those conditions the heat pump will run and the burner in the gas furnace will not light.

[86Sebring]

Doug, if you still live in LI, chances are you don't have a heatpump, so it sounds like cooling and heating is running at the same time.
But if you live in Texas, that could very well be a hp, the compressor runs in heating and cooling mode and there won't be as high a discharge temp as with a gas fired unit.
First I think you need to find out if you have a hp or not.
good luck

[767Jockey]

Guys,
I'm in Houston, TX. I had to light the pilot light on the downstairs furnace up in the attic last night, so I know it's a gas unit. That was interesting trying to figure out how to do that. Anyway, the downstairs compressor unit is made by a company named "Payne". I never heard of them, it's probably junk, but I didn't choose it, it was already installed when I bought the house. The "Product" number is PH13NR036000ACAA, the Model number is PH13NR036-C, and the serial number is 2007X66156. Anything at all that you guys can tell me about this unit would be appreciated. I don't know if it's A/C, a heat pump, if it's good stuff or cheap junk, how old it is, efficiency, etc. I know nothing about it.
As for the compressor for upstairs, that's a bigger mystery, as all brand identifying labels are gone from it, although it appears visually to be a newer unit than the larger downstairs unit. This unit does NOT run when the upstairs heat runs. The only numbers I see on it are Model number TCGD36S21S2A, and serial number W0G8083973. Same questions as above for this unit as well.

The thermostat for the downstairs is a digital Carrier thermostat (I was mistaken when I said White Rogers earlier, that's the old mechanical one for for upstairs). It has two terminal blocks inside, the top one has only an orange wire going to a terminal labeled "O/W2*", and the following terminals on the upper block are unused - S2, S1, Y1, B

The bottom of the two terminal blocks inside the Carrier thermostat have the following connections:
Red wire to R terminal, Yellow wire to Y/Y2, green wire to G, Brown wire to C, and white wire to W/W1. Is this all hooked up correctly? If so can it just be a faulty thermostat? The A/C worked fine all summer, last night was the first night I used the heat. How can I tell if the thermostat is good or faulty?

Any advice you guys can give would be greatly appreciated.
Luckily I have felt good yesterday and today so I can try to get this thing going. Thanks so much, guys.
Doug

[Tommy]

You may want to wait until Jim Pomroy gives you a definitive answer, but my Google search of your model number PH13NR036-C, shows it to be a heat pump. If your system also includes a gas furnace, it sounds like the hybrid system he mentioned. I suggest you not rush into fixing anything. It may be working normally.

[undy]

dual fuel, heat pump w/gas back-up. I installed 15 of those system this past year and have one in my house too. You'll have some sort of outside temperature sensing, either via a sensor through the thermostat or a temp switch at the heat pump. For instance; anything above 35 degF runs in the heat pump mode and outside temps below 35 degF runs the gas furnace. The systems are usually accompanied by "condensing" gas furnaces, using schd 40 PVC as the flue...

[767Jockey]

Thanks for all the help, guys. Here's the text of a PM I just sent to Gene (Z-Link Cobra). It pretty much sums up where I'm at with this so far. If anyone has any further ideas on this please feel free to pass them along. I can't believe I'm confused by my HVAC system.

I think I got it sorted out. Look like I have a "hybrid" heating system - Apparently from what I have been able to learn the heat pump is the primary source of heat, with the gas furnace to kick in as back up at lower outside temps where the heat pump is not so effective. I'm thinking that the main source of my confusion now is with the thermostat that's in there. I was able to download the installation and setup guide, as well as the owners operation guide, from the internet. To say that the documentation is poorly written would be an understatement. I'm still trying to sort out some of the details of how to operate this darn setup. The T'stat is a Carrier non programmable digital, looks like mid to late 1990's vintage. Hopefully I get it all sorted out soon. I think it's working ok now. It's hasn't been very cool outside. I need to figure out what temp that the gas furnace is supposed to kick in at. The thermostat has a button sequence that you can press to get the outside temp displayed at the moment. This module is optional. One of the display functions is to display dashes if this module is not installed when you try to call up the outside temp. My thermostat shows the dashes instead of the outside temperature, which tells me that the sensor is not installed in my system. How in the world does this crazy system know when to turn on the gas furnace as backup, and how do I find out what that temp is and adjust it if necessary? Boy, I miss the simplicity of my old system in NY. Is the heat pump that much more efficient than a gas furnace to put in a wacky system like this? I'm paying about $0.13 per KWH for electric, so the juice isn't super cheap down here.

[undy]

There's also typically a temperature switch inside the control panel on the outside heat pump. It should have a dial and a screw to adjust the transition temp on it, 30 degF to 35 degF settings are customary.

[Tommy]

Originally Posted by 767Jockey

Is the heat pump that much more efficient than a gas furnace to put in a wacky system like this? I'm paying about $0.13 per KWH for electric, so the juice isn't super cheap down here.

If you haven't studied thermodynamics, you may have to take my word for this one. But yes, within a certain temperature range, a heat pump is more efficient and cost effective than a furnace. Here's my attempt at an explanation. Energy is energy whether it is in the form of watts of electricity, cubic feet of natural gas, or a volume of warm air flowing into your house. Any form of energy can be expressed in standard units such as BTUs. It turns out that if you burn a volume of natural gas containing 1,000 BTUs of energy, you'll get a volume of warm air containing about 1,000 BTUs of heat. (There is some loss of energy due to inefficiencies such as hot exhaust going up the flue.) But a heat pump is different. A heat pump uses a refrigeration cycle to move energy from one place to another. In its heating mode, the heat pump extracts heat energy from the outside air and carries that heat inside where it is used to heat the air blowing through your house. (Yes, even when it's cold outside there is enough heat energy in the outside air to take some to heat your house). Even with all the inefficiencies of operating pumps and moving heat over a distance, when the outside air temperature is above 35 degrees or so, it can transfer more heat energy to your house than it uses in electrical energy to do the job. For example, your system might use 50 BTUs of electical energy to transfer 100 BTUs of heat to your house. So the bottom line is that in the south where outside air temps don't stay too cold, a heat pump is usually more cost effective. But they don't work as well as the outside temperature gets colder.

[Gatorac]

Yes, a heat pump will cost less to heat then gas. At least down to a certain outdoor temperature.

Payne is a Carrier with a different sticker on it.

My suggestion is to not mess with any of the settings unless it's not keeping your home comfortable. You have the best of both worlds with that system.