Gigo

"I get what you are saying. Really, I do. But as much as everyone keeps telling me the DSH has absolutely nothing to do with anything related to LT1 lockouts, all I can say is that when I am experiencing lockouts and I turn off the DSH, the lockouts stop."

Your words:
"23 Feb 2015 06:14 AM
Another lockout this morning, 10 minutes after I got in the shower. DSH is off."

Did you even try reversing the system (that is cooling)?

I did try reversing the system the last time around when I was troubleshooting. Twice. Both time, the system went into LT2 lockout within minutes of startup.

An update to this recent round of troubleshooting. The system is still locking out, even with the DSH off, but not as frequently as it had been. What I have observed at the times of these lockouts is that they seem to coincide with large volumes of water usage, namely showers. What Bergey said was something I have been thinking for a while now and seems to fit:

Posted By Bergy on 12 Mar 2015 02:43 PM


ET,
Something in the system must be very marginal so when you "steal" a little heat from the compressor discharge line it tips the balance and locks out.
Bergy

Though even with the DSH off, when something like a shower happens I see water flowing through the DSH. My monitoring system shows the temperature drop on the DSH lines. As an example, the wife jumped in the shower and at 7:08 this morning I see the temperature of the DSH output line drop from 152F to 80F and the DSH input line from 89F to 53F. Coincidence? Maybe, but I don't buy that. If the flow of cold water into the DSH is enough of a drop to "Steal" enough heat from the system, maybe that is enough to trip LT1. If there are other factors like improper antifreeze leves, low refrigerant, etc, maybe those are the source of the problem, but my observations say that something having to do with the DSH is involved somehow. I have seen this behavior on multiple occasions when there is a large water draw. I have looked at the plumbing for the DSH and it appears to be correct according to the install instructions for a two-tank system. What I don't understand, since I don't know the internal mechanics and plumbing of the DSH pipes inside the unit, is why, when the DSH is disabled, does cold water continue to flow into and out of the system. Perhaps, with the DSH off, should I also close the valve that feeds cold water into the DSH to see if that makes any difference?

I know you all must think I am getting hung up on the DSH. I don't believe that it is the source of the problem, but I do believe that it exacerbates it somehow. I don't buy into coincidences. I believe in cause and effect. In the end, i really just want a working system that I don't have to babysit constantly and worry over whether or not it will lock out today, or tomorrow or next week. What I think makes things more difficult for me is that my installer, while trying to help resolve the issue, just doesn't seem to be very good at troubleshooting the problem, they take forever to call me back and they are more interested in their new installation jobs than they are in diagnosing and fixing broken systems. I am about ready to just cut bait with them and look for another service company. But since they installed the system, I have been reluctant to sever this relationship and I tend to try to give people the benefit of the doubt. I shouldn't have to spend hours trying to understand the nuances of heat pumps, refrigeration systems and desuperheater plumbing. Quite honestly, I have better things to do. But since I don't trust that my installer really has a handle on the problem, I come to forums like this to educate myself so that I know what should be done and whether they are feeding me a line of bullshit. At this point, they are scheduled to come out on Monday to replace the TXV. Everyone in the forum here has been quite helpful and I appreciate all the advice. Here's to hoping things get resolved soon.

"should I also close the valve that feeds cold water into the DSH to see if that makes any difference?"

I would close the valve enough to get the water to go down the dip tube in the storage tank rather then the DSH path.

The Pro's would know better if closing the valve completely is bad idea or no problem. I know you don't want the plumbing through the DSH to have air in it.

Chris

"I know you all must think I am getting hung up on the DSH."

Yes you are.

"I don't believe that it is the source of the problem, but I do believe that it exacerbates it somehow. I don't buy into coincidences."

Coincidence? It locks out whether DSH is on or off and that's a coincidence?

Here's a real coincidece; the system behavior is exactly that of a fouled TXV which can sometimes be solved with Re-Nu (additive) or turning the system on cool but never by turning off the DSH. Sometimes the TXV has to be replaced. Which BTW is why the manufacturer stated it needs a new TXV.

Since it appeared to work after the cooling cycle and the mystery additive, myself and Doc suggested if it continued to work that you not have them replace the TXV which is intrusive surgery. If it doesn't continue to work then you have no choice.

Forgive me for sounding snarky, but multiple experts told you it's not the DSH. Multiple experts told you it's a problem with a TXV. Climatemaster and other manufacturers have a service bulletin out about this very problem and your symptoms. The one and only, single, solitary thing you could do that might help is to turn the system to "cool" which is why I suggested you try it again a few times, but play with the DSH if you'd rather.

Oh correction there's one other thing you could do. Disconnect (and cap so it doesn't ground out) Y2 if your weather is mild. Can't swear to it but most of the time the lockouts only occur in second stage. I have done this in a client's home so they weren't running solely on auxiliary til I could get the TXV in.

WARNING: IF YOU DISREGARD everything else I suggest, DO NOT turn off valves to DSH (one or both) unless you drain it. You can't turn DSH off only the circulator, but the system will continue to heat water in the heat exchanger. Heating water in a sealed vessel where the water has no place to go is not a good or safe plan.

Joe, I think maybe you are missing the point. There seems to be agreement that the TXV is faulty. The tech is coming out on Monday to replace it. In the mean time, the system does not run continuously for more than an hour when the DSH is enabled. So in order to keep the system running until they get here to replace the TXV, I have disabled the DSH. Why does that work? I don't know, and at this point I don't really care. It works. The system runs, my house stays warm and my family is comfortable. After they replace the TXV on Monday, I can reevaluate.

And just to be clear about what I tried yesterday, after reading your most recent post, I turned on the DSH and placed the system in cooling mode. It ran for a few minutes and then locked out with an LT2 (Low Air Temperature) fault. I then placed the system back into heating mode and went and took a shower. A minute after I got out of the shower the system locked out. Then, for the next four hours I continued to simply reset the lockout. The system would not run for more than an hour before locking out with an LT1 fault. Most times is was more like 20 minutes. At that point, I decided that was enough, I turned off the DSH and reset the system one more time. It has been running continuously ever since.

TXV replaced today. Immediate result is that system running in stage 2 heat has an LT1 temp of 23F-25F as opposed to the 12F or lower that I was seeing all the time.

good news