Heat Pump Condensing Unit Won't Turn On


  #1  
Old 02-08-14, 01:07 PM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
Heat Pump Condensing Unit Won't Turn On

I don’t believe my heat pump is wired properly and am hoping I can get some advice. The heat pump was installed in summer 2012 and the contactor wired a temporary thermostat that works for cooling but I did not test it for heating until now. (My project is huge and it has taken this long to for my basement finish to be completed, and my heating contractor is no longer around).

Problem: When I call for heat, the condenser unit does not turn on and the 8KW electric kit turns on immediately.

The heat pump is a Carrier 25HCC5, the air handler is a Carrier FV4C, and the thermostat is a PRO1 1AQ model T855. The current terminal connections are shown in the tables below. Logic would suggest that the problem is in the third row of the table, which shows that Heat Pump terminal W2 is connected to air handler terminal W1, and Thermostat terminal W2 is connected to air handler terminal W1. My guess is that the connections should be W2 to W2 in both cases. Is that right?

Name:  heat pump connections.jpg
Views: 2427
Size:  47.3 KB

Thanks in advance for your help.
Randy
 
  #2  
Old 02-08-14, 01:37 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,872
Received 1,480 Votes on 1,368 Posts
I'm not the pro in this forum but I don't think you should be using the W2 terminal on the t'stat.

Even if there was nothing on W2 the heatpump system should still work.

For A/C...... the Y(compressor), the O(reversing valve) and the G(blower) are energized.
For heatpump..... the Y(compressor) and the G(blower) are energized.

It sounds like the t'stat may not be programmed correctly.

The forums pros will stop by later.
 
  #3  
Old 02-10-14, 06:08 PM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
Thanks PJmax.

No pros have yet weighed in, but it would seem that I could do a risk-free test of your theory by disconnecting the W2 connection on the thermostat and see if it works. You agree?

As you can see in the table I included in my first post, the heat pump has a W2 terminal and no W1 terminal. At this link, Thermostat wiring colors and furnace terminal designations repair.

I found this explanation:

(W), (W1), (W2) White, "Heat" (gas burner, oil burner , electric heat, (auxiliary heat on a heat pump including defrost output from the outdoor unit to activate electric heat and turn on the AUX. heat lamp). Note: some thermostats require a jumper from "W" to "Y" for heat pump operation.

The thermostat manual says the W2 connection is for "auxiliary heat relay, third stage of heat" My thermostat manual is here: http://pro1iaq.com/images/800Manuals...anual_T855.pdf

Thanks,
Randy
 
  #4  
Old 02-10-14, 07:25 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
It is wired correctly except you need a jumper between W2 and W/E.
This thermostat must be also configured for heat pump operation.







The factory setting is heat pump Off.
 
  #5  
Old 02-13-14, 08:27 AM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
Thanks Houston204 for your help.

I’ve configured the thermostat to operate a heat pump, but have not jumped W/E and W2, and the outside unit does turn on now. I suspect that the auxiliary heat goes on immediately, however. (How would I know if the auxiliary heat is on?)

In any case, before jumping W/E and W2 on the thermostat, I was hoping to gain some understanding of how the system is supposed to work. Three questions:

1. I gather that the basic operation of the heat pump only requires connections to heat pump terminals Y and O. If that is correct, what does heat pump terminal W2 do?

2. My thermostat manual says W2 is auxiliary heat and W/E is emergency heat. I assume what is called “8KW Electric Kit” on my installation contract is auxiliary heat, not emergency heat. Is that right? If so, why would I need to use the W/E connection on my thermostat?

3. Again, when the air handler is pumping hot air, how can I know whether my auxiliary heat is on or off?

Thanks,
Randy
 
  #6  
Old 02-13-14, 06:53 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
I suspect that the auxiliary heat goes on immediately, however. (How would I know if the auxiliary heat is on?
I use a clamp Fluke 902 meter...


I gather that the basic operation of the heat pump only requires connections to heat pump terminals Y and O. If that is correct, what does heat pump terminal W2 do?


The thermostat closes contacts between R and Y, and G with a first stage heating demand. The stat adds W2 for stage 2. The heat pump energizes W2 when it goes into defrost mode.
(R to O,Y and G is cool mode)


2. My thermostat manual says W2 is auxiliary heat and W/E is emergency heat. I assume what is called “8KW Electric Kit” on my installation contract is auxiliary heat, not emergency heat. Is that right? If so, why would I need to use the W/E connection on my thermostat?
If the outdoor fan motor failed, you picked up a refrigerant leak, or some other problem occurred with the outdoor unit, E allows you to heat your pump with the electric heat strips without running the outdoor unit.

3. Again, when the air handler is pumping hot air, how can I know whether my auxiliary heat is on or off?
You can give the stat a 1 degree heating demand and measure the return air temperature and the supply air temperature to get the rise in temperature.
Increase the heating demand to 3 degrees and take your readings again.
(or buy an amp meter)
 
  #7  
Old 02-23-14, 04:00 PM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
Houston204, a belated thanks for answering my questions.

I believe all is working fine with the thermostat wired as explained in my first post, but with it set up for heat pump (which it was not at the time of my first post). I did buy a clamp meter and confirmed that the second stage heat did activate immediately. But then I noticed in my thermostat manual that the second stage heat will engage whenever the temperature is more than 2X below the set point, where X is the “swing setting.” (See “Note” at the bottom of page 10 of the manual, link given with my first post.) My basement has been unheated, so this was true when I first turn on the unit. I have verified that the auxiliary heat does turn off with the temperature reaches the set temperature less 2X.

BTW, it would seem to me a better rule for the auxiliary heat turning on would be that the system is on but the temperature fails to rise faster than some minimal set amount (say 1 degree every 20 minutes). This would save a lot more energy, as just going from night to daytime settings of the thermostat would normally result in the auxiliary heat engaging unnecessarily. Thoughts?

I have also verified that the thermostat setting for emergency heat works without a jumper between W2 and W/E. I don’t know how it works, because I agree that logically you would think the jumper would be needed.

Thanks again to all.
Randy
 
  #8  
Old 02-23-14, 06:38 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
That's great news. Thanks for posting back with your results.
 
  #9  
Old 06-09-14, 05:40 PM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
This continues a thread that I thought was finalized in February. When I last tested the heating part of my heat pump system in February, it was working fine. IN anticipation of the system being inspected by the County, I tested it today and the AC seems to work fine but the heating system is not working fine. I have set the thermostat several degrees above the current inside temperature (more than twice the swing setting), and the auxiliary heat does not come on. The compressor runs but the air being circulated is not very warm. (The outside temperature has been in the high 70's to mid 80s.)

The only thing that has changed since February is that I moved the thermostat to its permanent location. In doing that, I apparently forgot to turn off the power and I blew a 5 amp fuse in the air handler. I replaced the fuse and the AC works fine.

Any ideas on how to troubleshoot this would be greatly appreciated.
 
  #10  
Old 06-09-14, 07:28 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
Is the large copper pipe by the outdoor unit hot when you are in heat mode?

What is the amp reading at the indoor unit with a 4 degree heating demand?
 
  #11  
Old 06-10-14, 08:21 AM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
I set the temporary heat setting to 76 when the room temperature was 71. 45 minutes later the room temperature was 73 and the outside copper pipe was very hot. The amp reading was 1.2 amps for the entire time.

I discovered my clamp meter has a temperature sensor. So I turned the system back on 15 minutes later and inserted the sensor into one of the radiators. The immediate reading was 83 degrees. 15 minutes later the reading was 87 degrees.

I'm guessing the heat pump is working ok, but my auxiliary heat isn't kicking in for some reason. As I said before, I blew a 5amp fuse when working with the thermostat wires. Is it possible I blew a second fuse somewhere that is preventing communication to the auxiliary heat?

Thanks,
Randy
 
  #12  
Old 06-10-14, 07:24 PM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
Can I jump two connections at the air handler to simulate a call for auxiliary heat? If so, this would allow to rule out that the problem is a discontinuity between the thermostat and the air handler. Thanks.
 
  #13  
Old 06-10-14, 08:17 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
You can jump R to W at the air handler to energize the heat strip.
 
  #14  
Old 06-12-14, 08:29 AM
R
Member
Thread Starter
Join Date: Feb 2013
Location: USA
Posts: 54
Received 0 Votes on 0 Posts
Thanks Houston204. I jumped R and W and the auxiliary heat did go on. I then discovered my white wire had been pinched and partially broken a few inches back from the thermostat. It probably never was connected and I failed to verify that auxiliary heat worked when I changed the thermostat location. Will report back after I rewire the thermostat, probably Sunday.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: