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CharlesT 09-04-2012 12:35 AM

American Standard Heat Pump Issue
Hello all,

I need some advice on my 2006 American Standard 3-ton heat pump. All has been working well, that is until this weekend when it couldn't keep up with cooling.

Upon further investigation, I noticed that if the unit is turned off (via the thermostat) for a short period and then turned back on it works well for about 30 to 45 minutes then the cold air disappears and it feels as though only the fan is running without the compressor working.

The first thing I tested was the thermostat and it's working perfectly. I then checked the unit's control board and the status LED is blinking (just like the literature says it's supposed to (slow steady blinking) and the 1st and 2nd stage cooling LEDs are lit (indicating the thermostat is calling for both stages). Additionally, the fan is running at full speed but if I place my hand above it, the air is not hotter than ambient (usually I can feel much hotter air).

Before I get too far into testing, I thought I would ask the gurus on the site if there is a known problem that's common to these newer American Standard heat pumps...?

I have not checked the high/low pressures yet (my manifold is at my workplace so I'll get it tomorrow), but I'm assuming that if the pressure was too low it would turn itself off and not keep working away as though it thinks that everything is ok...?

I work in an electronics field and we have a constant problem with capacitors (overseas crap that just doesn't cut it). Thus, I started thinking that maybe it's a condenser cap that might be flaky. Does this make sense, or am I barking up the wrong tree?

hvac122 09-04-2012 05:52 AM

Is the outdoor coil clean?

Its A Good Life!

Acomfort 09-04-2012 06:41 AM

Have to ask.... is the furnace filter clean

techpappy 09-04-2012 08:42 AM

could it be on a defrost cycle. I've heard this can happen if coil freezes up due to ?? I'm not an AC tech but, just a SWAG It may be a starting point

CharlesT 09-04-2012 11:22 AM

hvac122 & Acomfort: Sorry I didn't post the basics but should have...

The filter was changed at the beginning of summer and still looks good, but to be 100% certain I swapped it out for a new one when the problem started a few days ago.

The outdoor coil is clean too. Being a package unit up on the roof it doesn't have to contend with pet hair, grass, etc.

tp: Thanks, but the system is in cooling mode, not heating so I doubt the coil is freezing. Also, the outdoor fan is running at full speed and I seem to remember that when it's running through a defrost cycle the outdoor fan turns off (could be wrong on that, but it makes sense, lol).

techpappy 09-04-2012 11:43 AM

I thought the defrost cycle came on.... to defrost AC coil if it freezes up for any reason during cooling..of course that could be for many reasons of which I wouldn't guess..perhaps some of the HVAC pros on here will contribute some ideas

beenthere 09-04-2012 07:56 PM

Compressor may be tripping on internal over load. clean the condenser coil, use a chemical cleaner on it.

CharlesT 09-04-2012 08:15 PM

Here's an update to the problem:

Checked the High and Lo pressures (while it was working before it turned off the compressor) and they are spot on.

While I was putting a stuck panel back on I noticed that when I hit it with my palm the compressor (which was off) kicked on and the outdoor fan started immediately blowing hot air. However, I think the timing was a coincidence (although I have never been able to get the compressor to restart without turning the unit off for a few minutes and restarting).

There is a green CFM led on one of the control boards. I noticed it blinks 7 short blinks when the compressor is on and 10 short blinks when the unit is acting up and turns off the compressor. Does anyone know if this is normal? Any ideas as to the blinking codes?

beenthere 09-04-2012 08:19 PM

Codes should be on the panel.

CharlesT 09-04-2012 10:19 PM

Update #2 - Long...
Thanks beenthere! I looked for them and didn't see anything. Upon closer inspection I found a note that mentioned that the led blinks once per every 100 RPM of the outdoor fan.

High speed is supposed to be around 1050 RPM so the 10 blinks makes perfect sense. Then it hit me that when it was working (when I coincidentally tapped on the panel) it was only running at 700 (or so) RPM, which must mean that the thermostat called only for 1st stage cooling.

Sure enough I manually dropped the 24 volts from Y2 and (after one minute of both contactors open), the red Y1 LED lit solid, contactor1 closed and the smaller compressor kicked on. The fan speed was slower, and the CFM LED was back to blinking 7 times. Additionally, the fan was expelling hot air. Seems like the 1st stage is working correctly!

The bad news:
I then reconnected Y2 and it released contactor1 and waited a minute before the Y1 and Y2 red LEDs lit solid, it closed contactor2, the fan speed was high (and the green CFM led was back to blinking 10 times). However, I did NOT hear the compressor turn on and there was no heat being expelled by the fan (despite cranking away at high speed)!

I checked the voltages through the contactor and all was good. There was not any error/fault LEDs lit and, as far as I could tell, the system (control) thought it had started the 2nd stage compressor.

Since the 2nd stage compressor will usually run (for about 30 to 45 mins) after a break, I disconnected Y2 again, waited about 5 minutes, and then reconnected it to 24 volts. It went through the entire process again, and this time the 2nd stage compressor started.


A couple of other things:
1) The capacitors looked fine, but I dropped power, discharged them and tested them with my Fluke 376 and they were fine.

2) According to the wiring diagram in the service facts paperwork the wires run from the contactor directly to the compressor (I could not verify this as it got dark and I didn't want to disassemble the outdoor section in the dark). However, it appears as though the control board monitors all the safety devices/switches and won't close the contactor if there's a problem. However, the 2nd stage contactor always closes when the problem exists.

3) Just for fun I checked the LPCO switch, but, as expected (it also affects the 1st stage and that appears to be working fine) it was closed.

4) The paperwork says the compressor has an internal thermal shut-off so I'm not certain if I can test it...? However, the outdoor coil is very very clean (bright and shinny and not clogged with any debris.

Where do I go from here?

beenthere 09-05-2012 05:25 AM

Wait till it fails, then turn off power, remove wires from compressor, and ohm it out. If there is no continuity between Common and run, then the internal over load is opening.

And gauges would hve to be put on to see what is happening that it is opening. The nex time it was cooled and ran.

CharlesT 09-05-2012 04:14 PM

Thanks again!

Makes perfect sense, so I'll do exactly that...

Would you agree that, with the exception of the internal overload, all the other cutouts and controls are commonly before the contactor(s) on these types of units? In other words if there's a problem detected by the control board it won't close the contactor(s), right?

beenthere 09-05-2012 04:36 PM

Right. The low pressure and high pressure switches are on the low voltage side, an prevent the contactor from closing.

CharlesT 09-06-2012 09:10 AM

Got it. Since the contactor is closing every time, it means that it can only be the high voltage wiring downstream of the contactor, the 2nd stage run capacitor, or the compressor itself (with integrated overload protection).

However, it appears that ever since I mucked with it two days ago (checking capacitance and all) it hasn't happened again. I was all set yesterday to check for an open between the compressor's common and run as suggested, but it worked perfectly all night and into this morning! I let it run for hours (house was freezing), I turned it on/off (from the thermostat) a half dozen times. I even jumpered the thermostat to only call for 2nd stage cooling (since that is where the problem lies). Nothing, not a single hick-up! Darn.

I'll try again tonight...

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