Background: I have a Climatemaster Tranquility 27 4ton. Closed loop with antifreeze. Two zones & a desuperheater. I'm using the climatemaster thermostats (ATP32U03) with 3 stage configuration. It'll go through all 3 stages if we crank up the temp 10 degrees. The JW3 jumper is cut for low temperature operation. The entering water temp is in the 30-40 degreeF range. Problem: On a cold night, the system will run in stage one for ~12 hours without ever going to stage 2 or stage 3. On really cold nights it will freeze itself to death. And then cut over to stage 3 aux electric heat. It'll require a power-cycle before I can get it to use the ground loop again. My theory is that this may be because of the two zones overlapping. Each zone gets satisfied and never drops the air temp much (less than one degree). So stage 2 is never called for nor is stage 3. Maybe it is thermostat configuration? How do people set up multizone systems to avoid this problem if it really is overlap between the zones causing the system to fail?

overlap between zones shouldn't cause system to fail.
I don't know what is meant by "freeze itself to death", but your description of it maintaining temp (on really cold nights) without going into second or third stage suggests inexperienced designer.
Could have sizing, wiring and antifreeze problems.
J

Yes, my HVAC installer company was not the greatest. I'm trying to help resolve the problems. I think I found the fix for this one: the zone controller has a staging timer that one can set to limit the amount of time the system is in stage 1 or 2 to N minutes - regardless of which thermostat is calling. That should fix the problem, by forcing the GSHP in to stage 2 and stage 3. We'll set the N limit to 20 min. That should get the system going in to stage 2 after 20 minutes and then stage 3 twendy minutes after that if required. I called the tech support for my zone controller and they were like "of course, you idiot. that's what the staging timer is there for." So I'm optimistic :-)

Thanks!

Why are you eager to force the system into greater electrical consumption?
What did you mean by freeze out?
j

Posted By joe.ami on 25 Feb 2011 09:14 AM
Why are you eager to force the system into greater electrical consumption?

I agree, especially when it comes to engaging stage 3 (aux heat).  Let the system run without aux as long as the thermostat is not losing ground.  Even then, if you are still comfortable with sweaters, blankets etc., I still wouldn't use aux unless I was uncomfortable.

Of course, I wouldn't go crazy like the mother in "A Christmas Story" who dressed her younger son in so many layers that he could not put his arms down. 

Well, when the system ran in stage 1 for 12 hours straight a few times (I have TED -- "The Energy Detective" -- power monitoring stuff -- really great BTW), it would appear to freeze the compressor. (At least that's what my HVAC company said). It would fault and cut over to aux electric heat. And I'd have to power cycle the system to get it to use the ground loop again... Presumably after the compressor thawed.

The theory I'm working under is: by letting the system get to stage 2 or stage 3 when needed, it'll give the compressor a chance to rest on really cold cold nights. I don't want it to use stage 2 / 3 obviously, but I also don't want to get in to this state where they claim the compress or freezes. And I end up using the stage 3 for days before I notice what has happened.

Did the compressor freeze? Well I don't know. That's what I was told. There were ice crystals on it. And there was a few drops of ground loop fluid (water+glycol) dripping out of the ground loop return connector (to the GSHP).

Suggestions / education welcome! Great forum. Thanks!!

Explain "it would appear to freeze the compressor"

I'm a great fan of TED, but compressors don't "freeze" They run, or they stop.

If the system is underlooped, the loop temperature will drop below a cut-out limit. That should never happen no matter how long the compressor runs in stage 1 which does not tax the loop with design load - only stage 2 should do that.

I'd wanna verify antifreeze in loop but I don't know what the heck your install company is talking about. A heat pump with proper flow should be able to run 7/24/365. How do you know unit is not going to stage 2?
I'm getting more concerned with installer's competence, how big is the supply duct to each zone?
Where are you located?

Geome you misunderstand (Of course, I wouldn't go crazy like the mother in "A Christmas Story" who dressed her younger son in so many layers that he could not put his arms down.) OP mentioned temp staying constant (never falling a full degree) I'm suggesting that the equipment doesn't need to go into stage 2 .
j

Hi, we are located in suburban Boston. We used the large company in the area, but they mostly do solar. Their one accredited GSHP guy left (or was fired) last week. I think I might need to bring in an outside consultant to figure out if my system is not designed properly and if so, how to remedy it.

Zone 1 is fed by a 20x7 rectangular duct. Zone is fed by a 12 inch circular duct. The ducting is from my previous oil-fired furnaces. (I actually had *two* 87K BTU furnaces for a 2400 sq ft 1990's vintage house!! It was incredibly oversized. Frequent cycling, etc.).

If I understand correctly, "Engineer" says that using stage 2 continuously could freeze the loop? So this would seem to imply the use of the staging timer in the zone controller in a multizone system to avoid that freezing. Yes? Otherwise the independent zones might do what my system is doing: use stage 2 for a long enough time overlapping & getting satisfied until the loop freezes. Seems like a good staging control system would factor the loop temp in to the staging decisions... Like if it were about to freeze, go to stage 3 aux heat?

I believe they made the loop 25% propylene glycol. We have two vertical wells 20ft apart and 290 feet deep using a reverse return. Is that the right ratio of water to glycol?

Without setting the zone controller staging timer, on the coldest nights, the system occasionally goes in to stage 2 briefly. But I'd say 90% of the time it is in stage 1. Joe.ami, the TED shows the power draw and the stage 1/2 behavior is very clear. Great monitoring / graphing. It is not perfect because power line noise sometimes interferes with its data logging. (And my ASHP (geospring) water heater is also on that subpanel so I have to factor in its smaller bumps in the power usage graphs).

The Bell Gossett loop circulation pump (NRF-36) that I have has 3 speeds. I have not been able to find the data on how many GPM each speed is. I gather it depends on how much water is in the loop. We had it on speed 2, but have increased it to speed 3. Their theory was that the higher the loop speed, the lower the temperature drop. Basically making the loop work less hard. Is that valid? http://www.bellgossett.com/WhatsNew/LIT27Apr06-Bulletin-112C.pdf

Thank you for any suggestions you can provide!

m9999, there is much confusion on the 25% number... some brands seem to be somewhat 'watered' down, so adding in 25% doesn't really achieve a 25% mixture. There are quite a few post about this confusion. You should get the loop fluid tested to ensure where the freeze point is really at. What is the EWT after running for a hour or so? 30-40 is a 'big' range.

From ClimateMaster FlowController3 flow center installation manual:

http://www.climatemaster.com/downloads/97B0015N01.pdf

Propylene glycol - Nontoxic, non-corrosive, expensive, hard to handle when cold,
poorest heat transfer, has formed “slime-type” coatings inside pipe. Poor heat
transfer has required its removal in some systems. Propylene glycol is acceptable
in systems anticipating loops temperatures no colder than 40°F. These systems
typically use antifreeze because of low ambient conditions (outside plumbing or
cooling tower, etc.). When loop temperatures are below 40°F, the fluid becomes
very difficult to pump and heat transfer characteristics suffer greatly.

Only food grade propylene glycol is recommended to prevent the corrosion
inhibitors (often present in other mixtures) from reacting with local water and
‘coming out’ of solution to form slime type coatings inside heat exchangers
and thus hinder heat transfer. If propylene glycol must be used (e.g. code
requirements), careful consideration of loop Reynolds numbers, pump selection
and pressure drop must be considered.

Thanks for that excellent reference, Looby. I took a look and on the next page, despite their not recommending propylene glycol , they say in Table 4 (page 14) that a 25% solution of propylene glycol is acceptable for min temp of 15 degrees F. They seem to send an inconsistent message. What do you guys recommend? (premixed) methanol? Something else? Gotta check the local codes...

To answer dgbair, the EWT this time of year is about 36 degF after an hour or so. This is approximate; I have a sensor attached the pipe where it re-enters the GSHP. It correlated well with the probe that my installer has the few times we checked. I'll ask them to measure the concentration of the glycol. Excellent point. Gotta figure out how to do that...

Posted By m9999 on 26 Feb 2011 12:59 PM
... despite their not recommending propylene glycol, they say in Table 4
(page 14) that a 25% solution of propylene glycol is acceptable for min
temp of 15 degrees F. They seem to send an inconsistent message.

As I read it, that table simply lists freezing points versus concentrations.
If you choose to consider that an endorsement ...well, it's your system.

Does anyone want to know the fault code?

I don't have the fault codes from the last couple of outages. My now departed HVAC technician's last attempt was to swap out the thermostats. In addition to his belief that this would fix my freezing issue, we were not getting fault codes reported at the t-stats. So he "ran a test": unplugging the blower fan to generate a fault and see if it reported to the thermostat. Well that stopped the system alright! But no fault was reported. He then contacted climatemaster and was told that the fault has to occur 3 times before it'll show up on the thermostat -- or so he says. Anyway, his "test" would have wiped out the previous "real" fault code, I assume.

Anyway after his little test, my desuperheater stopped working!! They are going to replace a sensor they believe was faulty next week. I was looking for fault codes from the desuperheater LED. But the AN1 LED (above the DIP switches) was not even on --- and the DIP switches were set right -- it had been working before the "test" (above). And so there was no fault code from that. The tech said that that AN1 LED does not work. I could swear that I saw that LED on when the HWG was operating. I think he is not telling the truth; that has happened before. He seems to just makes stuff up. Anyone know if the AN1 LED.

--

Previously when they forgot to cut the JW3 jumper, the system froze up with a FP1 fault code #4 :Water coil low temp limit. I don't know what the last couple have been unfortunately.

First piece of advise - find a new tech.

AN1 LED - "When the control is powered and the HWG pump output is not active, the status LED (AN1) will be "On". When the HWG pump output is active for water temperature sampling or HWG operation, the status LED will slowly flash (On 1 second, Off 1 second)." .... on a fault it will flash the fault code.
(My LED works as describe... wonder if the tech fried the board?)

methanol - has very good properties.

Lots of systems work fine with glycol.
You misunderstand Engineer. He is not suggesting the loops should freeze at all, rather if they were going to, it would be more likely in second stage.
It was offered in the context of your earliest post: "Problem: On a cold night, the system will run in stage one for ~12 hours without ever going to stage 2 or stage 3." Now that we know it's going into stage 2 sometimes, I think you need to check your antifreeze.
You definately need a new technician.
Your duct work is not suitable for required airflow in second stage unless both zones are calling.
J

[Joe.ami] > Lots of systems work fine with glycol.

Even below 40 degF (with antifreeze, of course)?

Thanks for the clarification about the stage 2 / freeze thing.

I will definitely request a check of the antifreeze!


[Joe.ami]> You definately need a new technician.

Yes, I know I need a new technician. Right now the company seems willing to attempt to remedy stuff; they just do not have the right people. I'm hoping to get an accredited GSHP person to supervise their work.

[Joe.ami] > Your duct work is not suitable for required airflow in second stage unless both zones are calling.

Can you point me to the spec for that? Are we talking 5% under or 50% undersized? What is the implication of using the system this way? Damage to the system? It would be hard to retrofit the trunks in the house. Only obvious solution would be to remove the zone dampers?

Thank you again for your advice!

You have to go through the trouble shooting list here. We need more precise information on temperatures, pressures and stages running.

1) No loop should ever freeze, under no circumstances. If it does, check antifreeze, flow, and see if there is air in there air-locking part of the loopfield. Do not trust any calculations, only the readings from the spectrometer. No need to give the compressor or the loop a break. Confirm that it freezes up and then goes into lockdown status and emergency heat.
2) Independent from the freeze issue, it should go into 1st, then 2nd and then 3rd stage, if needed. Issues could be mis-wirering, issues with the controller or incorrect programming of the thermostats or the controller. I have seen thermostats being programmed for air source and not ground source heatpumps.

Prop Glycol works even below 40F. It is not the superior antifreeze in my opinion, but some enviro police think it's superior to others if it should leak into the ground.
Duct sizing is done with a combination of ingredients i.e. required CFM, design static pressure etc. ACCA manual D is the design tool many use.
Dump zones, bleeds and bypasses are all ways to assure proper air flow with a zoned system.
J