Would a heat pump or gas furnace help?

Questions on how we spend our money and our time - consumer goods and services, home and vehicle, leisure and recreational activities
Post Reply
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Would a heat pump or gas furnace help?

Post by Archimedes »

We live in a northern climate where typical winter temperatures are in the 20's and 30's. This week, in the arctic chill we got down to -1. Most winters our coldest temperatures are in the single digits. At times, every year or two, when it gets very cold we have a freeze up in one part of our heating system. I am currently looking for a definitive solution to this problem.

Current heating system:
Buderis High Efficiency Condensing Boiler - Gas fired
5,700 square foot home
4 zones of hydroair heat with air handlers and summer A/C compressors
8 zones of radiant heat
hot water storage tank

All of our system works consistently and reliably with the exception of one hydroair zone, which requires the hot water to go up through an outside wall and sloped roof to an air handler in the attic at the farthest part of the house. The hot water for this hydroair zone will freeze up in severe cold. We add antifreeze to the entire system on a regular basis every year or two. However, given the size of the house, the necessary quantity of antifreeze is substantial. The last time we charged up the system it cost us $2000 for many gallons of heating system compatible antifreeze and labor. The system checked out at safe down to -30 at that time. Now, about 1 year later, in the severe cold this week, that zone froze up again. All of our other zones are not at risk of freezing due to being within the envelope of the house, either basement or heated attic.

I am thinking I should change the heating system for that one remote zone to something other than hydroair. That would make this freeze up problem go away forever. I was thinking that I could get a heat pump to work with the air handler that is there. Or I could switch out that one furnace to a gas fired furnace. We have a gas line for the fireplace below that air handler, so there is a gas line not too far away.

I am looking for advice on how we might best solve this problem, whether my thoughts of a gas fired furnace or heat pump might work. Our heating contractor will be here next week, but I am reluctant to repeatedly spend significant sums for anitfreeze when we tried that less than a year ago. I would rather find a more permanent solution. It may cost some money to convert the system, but I don't want to have this expensive, ongoing need to add more antifreeze.
User avatar
Epsilon Delta
Posts: 8090
Joined: Thu Apr 28, 2011 7:00 pm

Re: Would a heat pump or gas furnace help?

Post by Epsilon Delta »

The cheap solution is probably either electrical heat tape on the line that freezes or if access is impossible a small re-circulation pump on that line. Either one controlled by a thermostat so it comes on when the line would freeze.

Insulating the line would help but may not be enough unless a source of heat is added.

Replacing the the system just because of a minor instillation problem looks like overkill.
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

Epsilon Delta wrote: Fri Feb 01, 2019 5:27 pm The cheap solution is probably either electrical heat tape on the line that freezes or if access is impossible a small re-circulation pump on that line. Either one controlled by a thermostat so it comes on when the line would freeze.

Insulating the line would help but may not be enough unless a source of heat is added.

Replacing the the system just because of a minor instillation problem looks like overkill.
Thank you for that suggestion Epsilon Delta.

The hydroair line goes up through a wall and roof that is filled with closed cell foam, so it is likely quite hard to access. But perhaps we could bore out a core of foam next to the tubing for the hydroair line and put an electric heat tape on it with a thermostatic control. I hadn't thought of that.
dknightd
Posts: 2453
Joined: Wed Mar 07, 2018 11:57 am

Re: Would a heat pump or gas furnace help?

Post by dknightd »

I'm not a heating expert. But to me something sounds wrong. An antifreeze mixture rated to -30 should not freeze at -1 one year later.
A recirculating pump for that leg might be an option.
Can the lines be re-routed?
A heat pump is probably not a good solution, they don't work well below 0F
A separate furnace might be an option. But maybe the water lines could be rerouted where the gas line for the fireplace is?
If you value a bird in the hand, pay off the loan. If you are willing to risk getting two birds (or none) from the market, invest the funds. Retired 9/19. Still working on mortgage payoff.
Millennial
Posts: 372
Joined: Tue Mar 25, 2014 4:46 pm

Re: Would a heat pump or gas furnace help?

Post by Millennial »

Something is wrong here... Where is the antifreeze going? In our last house (owned 8 years), we had heat lines go through unconditioned space. Previous owners had added antifreeze, we never added any... Never had a freeze
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

Millennial wrote: Fri Feb 01, 2019 5:59 pm Something is wrong here... Where is the antifreeze going? In our last house (owned 8 years), we had heat lines go through unconditioned space. Previous owners had added antifreeze, we never added any... Never had a freeze
Our old house had a regular gas furnace. This hydroair system is new to me since we moved here 4 years ago. A large quantity of antifreeze was added one year ago and 3 years ago, at considerable expense. I remember the HVAC contractor stating that there is some loss from the system that gets topped off with water and that can dilute the antifreeze over time, but this does seem excessive.
Uniballer
Posts: 318
Joined: Thu Apr 20, 2017 9:55 am

Re: Would a heat pump or gas furnace help?

Post by Uniballer »

One possibility is that you have a leak somewhere in the hydronic system, and that the anti-freeze treated water is gradually being replaced with fresh water by an automatic make-up valve (sometimes called a feeder valve, or a pressure-reducing valve).
Millennial
Posts: 372
Joined: Tue Mar 25, 2014 4:46 pm

Re: Would a heat pump or gas furnace help?

Post by Millennial »

Archimedes wrote: Fri Feb 01, 2019 6:05 pm Our old house had a regular gas furnace. This hydroair system is new to me since we moved here 4 years ago. A large quantity of antifreeze was added one year ago and 3 years ago, at considerable expense. I remember the HVAC contractor stating that there is some loss from the system that gets topped off with water and that can dilute the antifreeze over time, but this does seem excessive.
I guess I still don't get it. I understand the system is hooked up to water for automatic refilling, but that should be water replacing water, right? Seems reasonable that there could be sone water loss thru steam, but I don't see a pathway to lose antifreeze and therefore don't understand why it would get dilluted...
Time2Decumulate
Posts: 35
Joined: Tue Jan 29, 2019 2:41 pm

Re: Would a heat pump or gas furnace help?

Post by Time2Decumulate »

We've got 2 zones of hydro-air fed by a high-efficiency condensing boiler.

Our fan coils (made by Heat Controller) have a freeze protection mode where they will call for heat when the fan coil is less than 42degF.
One is in an un-conditioned attic and we've never had an issue.

Perhaps your HVAC guy could retrofit in something similar?
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

Millennial wrote: Fri Feb 01, 2019 11:07 pm
I guess I still don't get it. I understand the system is hooked up to water for automatic refilling, but that should be water replacing water, right? Seems reasonable that there could be sone water loss thru steam, but I don't see a pathway to lose antifreeze and therefore don't understand why it would get dilluted...
What circulates through the boiler and back to the radiant floors and the hydroair handlers is a mixture of water and antifreeze. This is a semi-closed system, meaning the same mixture continuously circulates. However, if there is a loss of liquid in the system, the water/antifreeze mixture gets topped off with pure water. This would lower the percentage of antifreeze and therefore allow the system to freeze up.

This discussion has been quite helpful. We will ask the HVAC contractor to test the freezing point depression of the mixture of water and antifreeze first. It was good for -30 degrees last time it was tested. If that has changed substantially, that implies that the diagnosis is a leak somewhere in the system.

If that is the case, then we can try to find a leak. Although not so easily done, maybe we can find the leak and permanently fix the problem. The biggest challenge will be finding the leak as the tubing goes all over the house through hard to access places. Are their any tips on how to find such a leak?
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

jwasilko wrote: Sat Feb 02, 2019 12:31 am We've got 2 zones of hydro-air fed by a high-efficiency condensing boiler.

Our fan coils (made by Heat Controller) have a freeze protection mode where they will call for heat when the fan coil is less than 42degF.
One is in an un-conditioned attic and we've never had an issue.

Perhaps your HVAC guy could retrofit in something similar?
Thank you jwasilko, another great idea. Something like that would be much more reasonable than getting a new furnace in that zone. I will ask the contractor about that option.

I love this forum as I am getting so much good advice here.
User avatar
Bammerman
Posts: 400
Joined: Fri Apr 06, 2007 4:58 pm

Re: Would a heat pump or gas furnace help?

Post by Bammerman »

Seems like the first step is establishing whether there is a leak or not. I have no experience or knowledge to contribute there*. I do have electric heat tape (controlled by a thermostat) wrapped around water supply (metal) pipes at one point in my old house, and that simple technology does work to prevent the pipes from freezing. Access to your pipes does sound like it could problematic, but perhaps you wouldn't need to expose the entire surface of the pipe -- maybe just enough surface area to affix the heat tape. In other words, instead of wrapping the heat tape around the pipe, run it along the length of the pipe. Just a thought.

Or you could extend your gas line to the cold part of the house and install a direct-vent gas fireplace/furnace. They're pretty, and put out a heck of a lot of heat, without putting exhaust fumes inside your house. I don't own one of these myself yet but have been doing a lot of research, as I plan to upgrade my vented (ornamental) gas log fireplace set to a direct-vent gas fireplace/furnace, probably in time for next winter.

*although I have heard of a technique that coats the interior of some kinds of pipes with an epoxy coating that eliminates leaks.
User avatar
Epsilon Delta
Posts: 8090
Joined: Thu Apr 28, 2011 7:00 pm

Re: Would a heat pump or gas furnace help?

Post by Epsilon Delta »

I'd suspect that the pipe is freezing in a fairly small section. It might be possible to locate the problem area using a thermal camera (some ordinary cameras can do this with a filter). Look for a hot spot that comes and goes when the heater in question turns on and off (there will be a delay so have patience).

If you can locate the problem you can figure out how to get to it, which probably involves removing small amounts of siding or small areas of drywall or squeezing into uncomfortable places. At that point it may be enough to add insulation and air barriers between the pipe and the outside and remove any insulation between the pipe and the heated space, thus moving the pipe into the heated area.
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

A thermal camera is a good idea. It will help me locate exactly where the PEX tubing runs. I have a good idea where it is in the wall, but there is closed cell foam in the walls. I suspect the freezing is happening where the tubing runs in the roof before it gets into the attic.
BIGal
Posts: 149
Joined: Fri Oct 26, 2012 9:34 pm

Re: Would a heat pump or gas furnace help?

Post by BIGal »

I would suggest that you hire a professional to analyze and recommend what corrective actions could be taken.
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

BIGal wrote: Sat Feb 02, 2019 5:04 pm I would suggest that you hire a professional to analyze and recommend what corrective actions could be taken.
Yes, a highly qualified HVAC company is coming on Monday to assess the situation. However, it seems like a good idea to have questions to ask and some idea about the various approaches to the situation.
dknightd
Posts: 2453
Joined: Wed Mar 07, 2018 11:57 am

Re: Would a heat pump or gas furnace help?

Post by dknightd »

Archimedes wrote: Sat Feb 02, 2019 7:18 pm
BIGal wrote: Sat Feb 02, 2019 5:04 pm I would suggest that you hire a professional to analyze and recommend what corrective actions could be taken.
Yes, a highly qualified HVAC company is coming on Monday to assess the situation. However, it seems like a good idea to have questions to ask and some idea about the various approaches to the situation.
Was it the same company that charged you $2k to add antifreeze last year?
And perhaps the years before that?

My first question would be how did it freeze up at -1 when it was rated to -30 ?

Did the same company also happen to install the system originally?

In any case somebody should be standing behind their work. $2k for antifreeze every year or so is crazy! That is probably getting close to your fuel usage!

I'd play dumb. Let them figure out what the problem is. They are the experts, let them do their job. I imagine anybody with experience with your type of heating system should be able to sort it out. If there is a leak that causes too much replenishment they should be able to find it. Perhaps by pressure testing each zone?

I'm not sure how it was decided to run the pipes in an exterior wall, then through the roof. That seems kind off silly. But perhaps it was the only option. I'd consider abandoning those pipes and try to run ones though heated space. But that still leaves the question, why did the pipes freeze at all with antifreeze in them?

I'd greet your experts with a look of bewilderment and awe. Give them some time to check out the situation. Let them offer solutions. Only then let them know about your ideas on a possible solution. Likely they will have a better solution - they are the experts!

You might want to visit https://heatinghelp.com/ Create an account, post a question. The folks there know way more about heating than bogleheads. At least on average ;)

I'm no help, my house has gas fired single pipe steam for heat (except for one room where we use an air-air heat pump, or electric radiator as required). Cooling is all done by heat pumps.
If you value a bird in the hand, pay off the loan. If you are willing to risk getting two birds (or none) from the market, invest the funds. Retired 9/19. Still working on mortgage payoff.
adamthesmythe
Posts: 3937
Joined: Mon Sep 22, 2014 4:47 pm

Re: Would a heat pump or gas furnace help?

Post by adamthesmythe »

The answer to supplying supplementary heat on very cold days is not a heat pump. It is an electric resistance heater, which is what a heat pump defaults to on very cold days. Expensive to run, though.

It sounds like part of the problem is that the system is big and too complex.

I've had hydronic heat in a similar occasionally rather cold climate. But never had a problem with heating pipes freezing, and never put antifreeze in the system.
TheGreyingDuke
Posts: 1824
Joined: Fri Sep 02, 2011 10:34 am

Re: Would a heat pump or gas furnace help?

Post by TheGreyingDuke »

Cold climate air source heat pumps will provide heat as low as -13F without using resistance heating, although I would concur with the ideas expressed...

Something is not right that should be made right rather than add yet another complexity to what is already a complex arrangement.
"Every time I see an adult on a bicycle, I no longer despair for the future of the human race." H.G. Wells
Topic Author
Archimedes
Posts: 291
Joined: Wed Feb 15, 2017 11:27 am

Re: Would a heat pump or gas furnace help?

Post by Archimedes »

The HVAC company came and tested our system. The liquid in the system came out blue, meaning there is still a lot of antifreeze. It tested out at -1 degree, which is exactly the outdoor temperature at which our system froze up. Last year after charging the system with antifreeze, it tested out, if I remember correctly, at -30 degrees.

The technician said there could be a leak. He wants to speak with the experts at his home office before suggesting the best approach to a fix. He said they could potentially check by pressuring up each zone individually with an in line gauge to determine which zone has a leak. But it may be tricky because it is likely a very slow leak. I am currently waiting to hear back.
Post Reply