Outside design temps for Phonix according to Don's program is winter 34� and summer 107�.
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Dumb sounding questions are better than Dumb mistakes

We were right on the verge of making you fix it yourself!

If the duct is bad, and the unit is 30 years old, you may want to go ahead and get a new system. MANY of your problems (uneven cool/heat, ventilation, etc.) will go away with a newer high efficiency system.

If you had no supplemental heat, on nights when the temp gets down to 10-15, your house temp would track downward with the outdoor temp, maintaining a relatively constant delta.

The cycling of heat versus cooling is normal in most stats, because the heat anticipation and cooling anticipation are seperate entities, with seperate circuits and everything. In many stats (I'm pretty sure Chronotherm is one of them) the heating anticipation is adjustable, but cooling is not. Have you ever taken that stat off the wall? The sub-base (brown?) is seperate from the stat itself, and if you pull up and out from the bottom, the stat just pops off. In the back of that stat, there are 2 or 4 screws. Recessed into holes in the back. I don't remember the 'combination' but that is where you set the anticipation and secondary heat source.

When the man comes to fix or replace your unit, be sure and let us know what he decides was wrong with the cycling problem. I'd also be very curious to know if you have/had supplemental heat or not, and (for my own research) I'd love to see a 24 hour plot of the temp swings with the fan on "continous" and a seperate plot of the fan on "cycles with unit." I know how my own house responds, but to have a plot of that data. . .Wow.
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There are no stupid questions. . .just a lot of inquisitive idiots.

Wow! Is that all the colder it gets there? Maybe he doesn't have supp heat after all.

I stuck 10KW in my friends 3 ton Trane, XL1200 heat pump design. Wonder if it's ever been on?
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There are no stupid questions. . .just a lot of inquisitive idiots.

We size the supplemental heat to do the whole house in case of HP problems. Operate them in conjunction with ODT's. The sales people and enginers at GE hated it when we referred to the backup as EMERGENCY HEAT. They insisted it was supplemental heat.
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Dumb sounding questions are better than Dumb mistakes

BamaCracker:

Yes, I understand that 30 years old equipment doesn't work as good as new, or even as good as it was 30 years ago But, here are some considerations:

- I'm pretty tight with this declining market, doubt I can afford it now

- The bill is sustainable - last time it was about $100, the worst I ever got was $278 in August

- There are other problems that have to be fixed first, like nonexistent insulation and bad single-pane windows and patio doors

- The worst problem that haunts me is not insufficient heating or cooling, but unbalanced one.

The new unit has to be at least 4 ton, my guess is preferrably 6 ton (the house is 2,360 sq. ft), and the price for them (to the best of my understanding) is about $1K/ton, so I'm looking at $6-8K, including installation. At the same time, as I mentioned before, the smart A/C system I'm working on can solve all the problems that I have now for under $500.

However, the urgency of fixing the bad duct has been impressed upon me

As for 24 hour plot with the fan on, I guess, it would be just enough to have it on when the heat kicks in - I'll do it tonight and give you the exact start and end time.

I didn't exactly understand your remark about how cold does it get here - the temperatures are in celsius, remember?

And no, I don't think I have supplemental heat
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--vt

If the present unit cooled (cools) the house OK, why would you asume that you need a 6 ton unit. It is not feasable to push 6 tons of A/C through ducts that were designed for 4 tons. Do a load calculation with present window and insulation (or lack of) and compare it to upgraded conditions. You may be amazed. I think your price estimates are very high. Upgrading you home insulating values is like putting money in the bank.
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Dumb sounding questions are better than Dumb mistakes

rayr:

I didn't say it was cooling OK. In the hottest days, it was barely chugging along. But then again, I blame it not on the insufficient cooling capacity, but on the poor insulation.

I will, of course, have the new A/C professionally sized before doing anything, and I couldn't agree more with your remark about insulation - that's what I will do first.
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--vt

Your comment about the fan being on when the heat kicked in was not clear to me. . .what I would like to have is a plot of all those little colored lines with the fan running 24/7. I frequently recommend to customers that they solve their uneven heating and cooling problems by switching the fan to "ON" instead of using the "AUTO" function.

I just remembered something about that. . .I used to have to explain this a lot when I was a service man, but the fan can/does operate seperately from the heat and cool. You can circulate the air in your house (to achieve uniformity) by running the fan all the time. This does not add a huge amount to your power bill, because only the indoor fan is running.

I already have access to the plots of the swings and imbalance when the fan runs with heat, so if you could post the plot of the swings and imbalance (or balance) then I could have physical data to back up my recommendations, (or to prove myself wrong).

I certainly understand the money crunch, having a family and just finished college this past August, but you need to be aware that a 30 year old system is about 10-15 years past it's design intent. So, you have at least been warned.

It's been fun, be sure to let us know how it ends up.
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There are no stupid questions. . .just a lot of inquisitive idiots.

Package units usually cost a lot less to change than a split system. Addition of any insulation will probably lower your need for cooling capacity. You can download a great heat loss and gain calculation from a member of this web site, Don Sleeth. http://www.hvac-calc.com Download the "one house" version, then play around with how much you can save by changing different aspects of the house. (i.e., calculate a load with the house just like it is. then, go back and add insulation, upgrade windows and doors, etc., and see how the load changes) Just some random additional thoughts.
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There are no stupid questions. . .just a lot of inquisitive idiots.

Hey Vermont, take their advice and do that heat load. It costs only $39.00. You won't be sorry. Bama and RAYR know what they are talking about.
I size the emergency heat for the complete heat load too. So far, no call backs.
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" If three or more people say you are a horse's tail...Maybe it's time to wear a saddle."

Charlie

BamaCracker:

(indoor fan) part of the day the ambient temperature is high enough not to cause the heater to turn on, I thought that it doesn't make any difference in respect of the phenomenon being discussed whether the indoor fan is 'on' or 'auto' at this time. But I see what you mean. You'll see it on the graph starting 4:55PM Dec 15 (see archive).

(new unit) advice taken with respect and gratitude. I just have to plan ahead now and prioritize things.

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--vt

Well Vt, I congratulate you. At least you listen and will take precautions. We have a lot of fun on this forum, but we do know what we are talking about.
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" If three or more people say you are a horse's tail...Maybe it's time to wear a saddle."

Charlie

BamaCracker:

Here's the graph with the fan on:

http://freehold.crocodile.org/temp-cut4.gif

The start time of the graph is when it was switched on, the end time is when it was switched back to auto 'cause it annoys the hell out everybody in the house.

Just for the reference:

- red: where the thermostat is; big, southern exposure, patio door
- blue: small, southern, downstairs, computer 24/7
- green: big, southern, upstairs, somewhat better insulated.
- cyan & purple: small, northern, upstairs.

The temperature to hold was temporarily shifted up to 71F and then set back to 69F. The registers were fully open and not moved during this run.

Does this go along well with your expectations of it?

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--vt

Thanks for the follow up Vt. No, it did not show what I expected it too, since the upstairs still tracks substantially higher than the downstairs during the afternoon/early evening.

What my experience has shown me in the past is a much closer track of all plots when the fan runs continous. Maybe the air you are losing on the roof is making the difference, but I had hoped we'd see the maximum difference between the red and any other zone at 3�F or less. Sure as heck didn't get that did we?

Does the blower bother everyone because of the noise or the draft? White noise develops after 72 hours, after which you don't hear it anymore (if exposed constantly, more like 2 weeks if exposed intermittenly) but you never get used to the draft.

Still, you might want to try again after you get the ductwork repaired. Thanks again,
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There are no stupid questions. . .just a lot of inquisitive idiots.

BamaCracker:

The tracks are indeed closer than they are usually, but I'm surprised to see they still diverge in the night, when the outdoor is the coldest.

Blower is a little bit noisy, but the draft is more noticeable, I guess I can call it a primary annoyance.

And the ductwork - I was planning to take care of it today.

I guess, for the practical matters, we can call this case closed, unresolved (the original question being a funny behavior when the ambient gets below the freezing point).

Thanks to everybody involved, I do really appreciate you sharing your knowledge. If I ever find the cause, I'll post it here - I guess it can happen this winter because I'm planning to replace the thermostat with the specialized controller, and then if it ever pulls a stunt like that, the cause will be clear.
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--vt

Is "balance point" the answer to this question?

http://energyoutlet.com/res/heatpump/balancepoint.html

rayr:

You were saying:

quote:

---

Outside design temps for Phoenix according to Don's program is winter 34� and summer 107�.

---

I guess this has to be adjusted - I've seen temperatures as low as 28.5� and as high as 120�. If I understand properly what those numbers are, that is
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--vt

VT;

Design temps are not the maximums you'll ever see, but the temps you design for so that 95% of the conditions you'll ever see are accounted for. i.e. If you have a record high temp every year of 110�F, and that temp usually only sustains for 2-5 hours, then you would want to design for a more frequent high temp, probably about 103-105�. If your average low temps are in the low 20s, with an occasional night dipping into the teens, you want to design for about 25�.

An example; Pensacola Florida once had a record low of 4�F, but it was in 1964, and lasted for 3-4 hours. They occasionally (once every two or three years) have lows in the teens, but average lowest temp for any given year would probably be about 20. Design temp for Pensacola is 25�. Similiarly; ocassionally, every few years, they may see 100�, but usually 97 or 98 is the highest temp each year. Design temp is 95.

Now, about the question which balancepoint might be the answer to; which question is that?
I may not have followed the logic train as closely as I should have, but balance point is the temperature at which your heatpump is able to supply 100% of your home's heating needs without dopping the indoor temp below setpoint, and without kicking on the supplemental heat, which you tell us you do not have.

So, if that does not clear up the questino, post the question again.

BTW, I have a hero who lives in Phoenix. He used to be a customer of mine, but 5 hurricaines in one year forced him and his wife to move to a less stressful climate! He's a retired USMC guy (I think Colonel, but I'm not sure) and he is a GREAT person. I bet if you looked him up and told him I sent you, he'd buy you a beer!
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There are no stupid questions. . .just a lot of inquisitive idiots.

BamaCracker:

The original question was - why does the heat pump gets stuck in heating mode all the time when the temperature drops, and blacks out once in a while. Now that I put it all together, it seems that the behavior I observed is indeed related to it, though I guess the complete answer will still be a mystery

About your friend - you reminded me of mine, he's the former Army guy as well, used to tell funniest stories I've ever heard.

One of them was, he was serving in Germany and got used to the absence of speed limits, then got back, had to drive to Iowa from the East Coast, got pulled for speeding three times in one day, 'course got his license suspended.

The other one was, he was caught speeding 140 on 65 while wearing uniform, the police officer who pulled him over looked at him and said "Son, you can't afford the ticket, so I'll just give you a warning".

As for beer, I don't drink beer, except for virtual. However, I do enjoy a good company

In Iowa, we lived in a mansion of sorts. It took my 11 year old 7 minutes to ride around the property on the bike. It took me 5 hours to mow the damn thing with the tractor. Man, do I miss those times... 5 cars lined up on a driveway looked really small... BBQ was great
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--vt

I have not looked at all charts. But I looked at the last one and saw the drop in the living room as the ambient temp fell. Honey well therms run on set cycles per hour. So as the temp falls outside and less heat is produce by the pump the less heat delivered. This causes the house temp to slowly fall but still maintained at a slightly lower temp. I am not sure I am making my point clear.

Are any dampers closed or adjusted during the time the problem shows up? Have you ever had a blank screen on the stat when problem appears?

What I was think is that the power to the stat is lost from a limit in the 24 volt wiring. This may be due to closing of dampers.

It is probably the stat? Don't care for the honeywells at all. To short of cycles. Try one in my house. Used data logger to track. Therm holding temp within .25 degrees. Humidity was to high do to short cycles. During a set back recovery those stats will actually shut off a/c long before reaching setpoint.

I have been trying to find out how to set up my own data logging system on my computer. I want to collect so temps my self for a little experiment. And possibly proof the set back are junk.

I will try your sites for info on sensors and such.

Will you email me some more info @ lornelambert@charter.net

I don't nmean to throw you guys of your train of thought.

Lorne:

The tstat I have is Honeywell Chronotherm III, it doesn't cycle by the hour, but works on demand.

No dampers were moved, the blank screen never appeared.

Temperature holding within .25 degrees: my guess is that the sensor was in the box with a high temperature inertia. A telltale sign of that would be an absence of a clearly visible gradient change when heating or cooling.

Setback on this thermostat works in a really funny way (though I can understand why having looked at Honeywell patents) - instead of just starting heating/cooling in time to get to the setpoint, the guys just slowly adjust the setpoint so it might cycle 2-3 times throughout that 'anticipation' time. Also, when dropping from, say, 72F to 70F (in heating mode) the rest of the house suffers from the usual problems related to unbalanced house (see the graphs), so I just keep it on hold, otherwise it annoys me.

For more information about the sensors and stuff, see the "DIY zoning" thread.

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--vt