Again, tonnage is relative.

Heatpumps usually operate between 20-120F water temp,, although they work more efficiently between 30-90F. However, they need a certain minimum flow, and they need antifreeze in the loop at temps below 40F. They are rated for heating at 32F loop temperature.

So 40F incoming water from the loop field is not too low, but rather normal in December. The units usually throw an error code and lock out when they detect freezing conditions, usually due to a lack or not enough antifreeze.

The contraction of the pipe between 40F and 30F is minimal, but if you have between single digit and 40+, again, chances are that a heat exchanger froze due to not enough antifreeze.

Chances are that you do not have enough flow if you indeed have only (2) 1" lines in the ground. Not enough antifreeze coupled with a small loop field (2 x 300" bores) and not enough flow due to only (2) x 1" line starts to create the perfect storm.

Verify antifreeze levels, flow, temperatures, lockout code and heat extraction, and post the numbers here.

Likely course of action:

1) Add antifreeze if low.
2) If loop temp is too low (below 25F coming in), you need more loop.
3) If your flow is too low, you might need another loop circuit too, different piping to the boreholes, different (bigger) piping inside, and maybe different pumps. Maybe be all of the above.

A follow-up insulation question. What's the priority in insulating? I am thinking Windows first, then basement walls, then the rest of the house (non-exposed) walls.

The insulation estimates for the walls were $8,000 +, the windows were coming in about $90 a window, total at $12,000.

Any recommendations for insulation in the DC area would be great. Thanks Tanja.

If you already have storm windows the walls are higher priority, including the foundation walls (even if you aren't using the basement as living space.)

But the initial priority isn't on insulation, it's air sealing. They are often done in combination, but it's important to air seal first. Not all air leaks are created equal. The priority locations for air sealing are the foundation walls and attic floor first, since the highest and lowest elevation air leaks are what defines the 24/7 stack-effect drives.

$8K seems on the high side for the walls- what was included in that proposal/quote?

$90 per window sounds on the very cheap side (unless that's a typo), what was included there?

We don't have storms, so that will go first. The $90 was the estimate for a storm window. What else can I do with old Windows? They are old, historic, single pane double hung and casement windows. Do you know a good contractor to work on these in the DC area?

The 8,000 for wall insulation was for blown in cellulose, several year old estimate, no tax credits included. Do you prefer cellulose or fiberglass or foam? Don't like foam for old walls, like cellulose but worry about water. Again, contractors are helpful. Tanja

A better-grade low-E storm window costs about $90-100 just for the storm window, so budget ~$150-200 per window as the installed price for decent grade low-E storms. Even though that's more expensive than a budget clear-glass storm, the higher performance of the low-E coating makes it "pay off" financially much quicker than an un-coated storm window.

http://labhomes.pnnl.gov/documents/PNNL_23355_Lab_Homes_Low-e_Storms.pdf

Alas, I don't have local contractor recommendations for you.

Larson sells low-E storm windows through the big box stores, if that's of any use. Most box stores in my area have contractors they refer for installation of all sorts of their goods, and it's not exactly a rocket-science type of project to hang a storm window correctly.

All Larson storm windows can be ordered with a hard-coat low-E option.

https://www.larsondoors.com/inspiration/larson-spotlight/larson-spotlight/2015/07/01/top-5-reasons-to-buy-storm-windows

The tightest in the industry is the Harvey Tru-channel, which also have a low-E glazing option:

http://www.harveybp.com/storm_windows.aspx

They're a regional player in the northeast- the nearest showroom to you would be in the Phildephia area, but they may still have contractors supporting them in D.C..:

http://www.harveybp.com/locations.aspx?type=cs

Cellulose dense-packed to 3.2lbs per cubic foot would be a good option in your area. If fiberglass, dense-packed to 1.8lbs works. Dense packed fiberglass is slightly higher thermal performance but usually more expensive than dense packed cellulose. The hygric buffering of cellulose is more protective of the structural wood than fiberglass since it shares the diffusion moisture burden, but fiberglass dries quicker from bulk water incursions. In my mind it's a toss up for most house. With bungalows the deeper roof overhangs make bulk incursions less likely, which may tip in favor of cellulose. Even at low density (not dense packed) cellulose is fairly air retardent, and it WILL tighten up your house. With fiberglass it has be dense packed to a minimum of 1.8lbs to be comparable, but a 2.2.lbs it's at least as tight as 3.5lb cellulose. At 1.0lbs (a cheaper yet commonly installed density) fiberglass it's more of an air filter than an air retarder. JM Spider, Owens-Corning L77, and Certainteed Optima are all fairly equivalent fiberglass blowing wools for retrofit dense packing. Spider can be damp-sprayed in open cavities, which can be an advantage in new construction.

Have you considered adding interior storm windows? We also have an old stucco house with steel casement windows, and we have tried a bunch of different types. I like the WindowSavr inserts, which are rigid metal frames holding a strong flexible plastic membrane, with foam around the perimeter that just friction-fits into the window frame. They stop drafts quite effectively and obviously, they don't affect the exterior appearance of the house.

Following up on a post from earlier this year involving my house with 4400 square feet, 7 ton water furnace system in the house, 4 tons in underground loop (big screw-up by contractors who have since gone bankrupt) and our attempts to fix this problem. More details in first post. Thanks everyone for the responses earlier this year.

I have some follow-up questions about the specific fix we're planning to implement. We are going to add insulation and do one of the following two:

1. install 70 gallon bradford dual coil heat exchanger (model s-dc-dw2-70R6SW), connect hot water storage tank to existing boiler to geothermal system for additional heat. connect to existing hot water storage tank to supplement hot water, add a new circulating pump, taco 007

2. install bradford 75 gallon single coil heat exchanger and a 50 gallon water heating tank. Connect the well system to the open side of the water heater tank, connect the heat exchange loop of the water tank to a new heating circuit from the existing hot water boiler, taco 007 circulator pump to control water temp; connect desuper heater circuits to new water tank

Does anyone have thoughts on which of these alternatives is better and potential issues to watch out for? Our primary problem here is in the winter, when the system freezes out. Have issues about fluid temperature, wondering if there are other issues. Thanks Tanja

I'm not completely clear on the details of your two proposed solutions, but before getting into the details of how the heat exchangers are configured, I'd like to discuss your overall plan. In at least one of these options, it sounds like you are planning to add heat to the well loop of your geothermal system from a water heater or boiler. It makes sense to me that you'd consider adding a supplemental heat source, but I don't think that's a good place to add it. If you add heat there, you have to pay twice for the heat you get delivered to the house for space heating--once in the water heater and once in the heat pump. If you delivered that extra heat on the output side of the heat pump, you'd reduce the freeze-up of the loop about the same amount, but you'd only pay for the heat once.

If you've got a desuperheater feeding a water tank now, and really simple step you could take would be to just stop using that, and use whatever other water heating system you have now as a backup.

OK, after re-reading the earlier comments, I see that you have a complete separate natural gas boiler and radiator system installed and presumably still working. If you want to reduce the load on your wells, you can just use that for some of the winter. No new equipment or new configurations needed.

Knowing that, I strongly recommend against any kind of combined system. It will be complicated to implement, will be unlikely to work right, and, most importantly, even if it works right, it will be more expensive to run than just using your boiler system for heating some of the time in the winter. After you get the storm windows and insulation installed, my guess is that you will be fine without doing anything more, but if not, just pick a few weeks in Jan or Feb and run the old system those weeks to allow it to recover.

There are some issues with the radiator system: (1) it did not do a great job heating the house when it last worked and (2) there are no radiators in our addition, and hard to put them in because of lack of space, although possible to put toe-kick radiators under the island that might work.

My thinking on this was to use the distribution system of the geothermal and to add a new heat source. However, there are pros and cons to all of these alternatives. The radiator option would involve at least 4 new radiators.

We are not using the desuperheater now, so that option drops out.

What do you mean by adding an extra heat source on the output side of the pump? What is an example? Thanks. Tanja

If the goal is to remove some load from the geothermal system with a separate, parallel system then there is no need to have radiators everywhere. Just operate both systems at the same time and adjust the balance.

When my new system is pressure-tested, it does not have a problem. Over time, however, it loses a small amount of pressure at a fairly constant rate. In summer, it loses about a gallon (total), in the winter it goes down to zero over a about a month. I live in Maryland, have a 7 ton system with a 4400 square foot house. Temperature in the system is staying relatively constant (50 in winter).

Contractor is suggesting checking the inside connections to see if there is any rusting from an anitfreeze release (he thinks at the slow rate of release he is unlikely to see any dripping; I have not seen any). After that he is suggesting a pressureless flow center. He thinks a leak underground will be difficult/expensive to find.

Any thoughts on this? What is an intelligent way to approach this problem?

How old is your system? What is the warranty on the loop. Such a tiny leak is impossible to find, if it exists at all.

Chances are that with a non pressurized flow center you do not see any indication of leaking anymore.