TG hijacked, and I'm an accessory after the fact...

I didn't do it.....
Extraction is suspect here, my other point was I may want someone other than original installer to have a peek since their design is shakey.
Not sure but 20kbtu might be light for first stage even.
j

The new service tech (not from the installer company) was back today to take a closer look. He spent some time on the phone with WaterFurnace tech support discussing the various readings. He also said the compressor is so loud he cringes when it starts. After discussion with WF they suspect that valves in the compressor have failed. The WF tech support person also mentioned that there is a "compressor upgrade" for this unit. So a replacement compressor should be on its way soon. The service tech also said that the new compressor is a scroll compressor rather than the piston type that is currently in the unit. He also mentioned that when he checked the pressure on the loop his pressure guage bounced around quite a bit so he wants to bring his flush cart when he returns with the new compressor and make sure there are no air pockets in the loop. After the new compressor and its associated control board are installed he wants to take readings again to make sure the restrictive ducts aren't causing the head pressure to get too high.

I hope I've conveyed all of that accurately. I'll keep posting as this continues.

Posted By glenn.campbell on 18 Feb 2011 03:54 PM
... After discussion with WF they suspect that valves in the compressor have failed. The WF tech support person also mentioned that there is a "compressor upgrade" for this unit. So a replacement compressor should be on its way soon.  ...

A replacement compressor huh, is this a warranty replacement 7 years after the install? A "compressor upgrade" or compressor 2.0 makes me wonder if there was a design flaw with the original unit. Now about my duct work...

If properly replaced a scroll should offer quieter operation and a 10+% efficiency inprovement over a recip (piston).

That said, recips are tough and long-lasting. If a recip's valves failed, it was subject to an abnormal operating condition such as extremely high head pressure, oil or refigerant slugging. swapping in a scroll without addressing the underlying problem will be a short-lived solution.

Low delta-P across a compressor may be mis-diagnosed as a compressor valve failure when in fact the reversing valve does not completely slide into the required mode. refrigerant will bypass and cause the low delta-P condition. Reversing valves are also tough and reliable devices but they are vulnerable to debris in the system from poor installation or brazing practices (brazing without required inert gas purge).

I don't expect this to make immediate sense to a typical homeowner, but the tech should be asked if he/she has ruled out the reversing valve (and if so, how) before embarking on a compressor swap.

Posted By engineer on 18 Feb 2011 11:03 PM
That said, recips are tough and long-lasting. If a recip's valves failed, it was subject to an abnormal operating condition such as extremely high head pressure, oil or refigerant slugging. swapping in a scroll without addressing the underlying problem will be a short-lived solution.

After the new compressor swap, it would be a good investment to have the new company check the duct install. Duct sizes posted by the OP are very small to support 6 tons of airflow. Piston compressors are very tough and something caused the failure.

The new Copeland scroll compressor and control board were installed 2 days ago and for the first time in years I'm actually warm inside my house with an outside temp in the low 30s. What a nice feeling. I had to work the day it was installed so I wasn't able to look over the shoulder of the service tech as much as I would have liked but he did show me that I'm now getting a 5-6 degree temperature change across my loop rather than the 2 degrees I got with the old Bristol T/S compressor.
For the initial setup he had all of my zones open and the return air duct removed to make sure restricted air flow wouldn't throw off the pressure readings. He stayed on the phone with Waterfurnace tech support while doing this and adding the refrigerant to make sure everything was to their liking. I'm not sure what the pressure readings were during this process. After he reconnected the return air duct I did get a look at the discharge pressure. It looked like it was around 400 or maybe a tad under while the unit was operating in second stage. I hope this is within acceptable limits of the compressor.
The Waterfurnace tech support person also had the service tech disconnect and reconnect a wire on the solenoid of the reversing valve. I don't know if this was some sort of test of the reversing valve or if it was just a typical step in the installation process.

I still have my cheap thermomenters dangling in the return and supply ducts and it looks like I'm now getting around a 20-30 degree temperature increase when the unit is operating in first stage. I haven't yet seen it in second stage (not after the installation was complete anyway) so I don't know what kind of temperature increase I'll get there. I'm not saying that it hasn't been in second stage yet, just that I haven't been standing in front of it when it was.

I'd still like to add some capacity to the return air ducts. I don't think there's much I can do with the supply ducts without tearing into walls and ceilings and such. I'd have to do a little of that to add to the return side but not as much. The supply duct for the first floor zone is in the crawlspace so I could probably do something with that if I needed to.

So far so good. The labor aspect of the parts and labor warranty fell drastically short but as long as I stay warm I'm happy. Until summer and then as long as I stay cool I'll be happy. This has all been fascinating stuff. So much so that I wonder if it is time for a career change.

Posted By glenn.campbell on 11 Mar 2011 04:54 PM
This has all been fascinating stuff. So much so that I wonder if it is time for a career change.

Sure if you are into wealth and chicks.....oh wait, that's Hollywood.
How do you like wrecked knees, sore backs and working in the elements?
We tried to talk Curt out of it
j

You didn't try hard enough...

A properly equipped tech ought to be able to take some of the mystery out of duct issues. Measure airflow out of each supply and static pressure drop across the system.

He / she could also perform an energy balance - temperature changes and flows across air and water side, measure system power use.