Is it possible for a head to be spinning at the same time light bulbs are going on?

Oh, you're in the zone now.

Certainly no lightbulb went on in your installers head. By handing you his pressure drop calculations, he documented part of his screw up.

Posted By jonr on 12 Apr 2013 08:26 PM
This is correct, right?

WtA geo $5.86/MBtu
Nat gas $7.61/MBtu
WtW geo $8.20/MBtu

It seems pretty clear to me that you want the WtW geo removed (a nice simplification) and the WtA geo as primary.

The WtW geo does not have to run at such a bad COP, because it has an internal outdoor reset which can be activated. The control strategy here is bad, it can be much more efficient.

Posted By jonr on 12 Apr 2013 08:26 PM
This is correct, right?

WtA geo $5.86/MBtu
Nat gas $7.61/MBtu
WtW geo $8.20/MBtu

It seems pretty clear to me that you want the WtW geo removed (a nice simplification) and the WtA geo as primary.

The geo numbers assume different COP's for WtW and WtA. I was thinking just pulling the breaker on the WtW would be our best bet, but if the consensus here is the current design won't support this unit ever being efficient even if gas prices rise, then I guess it should come out.

Doc, I'm not ignoring your thoughts about having the WtW be first stage. That's what my husband and I thought we were buying, but somehow the plan was switched and it was not explained to us in a way that we understood (or it wasn't explained to us at all).

Now we have other decisions that have been made that dictate that the WtA be first stage (for example, no radiator in our new kitchen). If the WtW is undersized for the application, doesn't have the needed buffer tank, and the piping is too small to support it, then it seems far easier to pull it out than to continue to have geo re-design and maintenance be such a big part of our lives.

With heating oil being so expensive, is there a secondary market for WtW units? Carrier has a 10 year limited warranty, so maybe our unit would work for someone else. I don't imagine people go on Craig'slist looking for geo units, though....

I understand, but what happened to "We will do whatever it takes to make this right" talking of your contractor? You'll be surprised what sells on craigslist. Your loopfield would support a 5 ton unit just fine, meaning the 5 ton W-A split.

Posted By docjenser on 13 Apr 2013 06:22 PM
I understand, but what happened to "We will do whatever it takes to make this right" talking of your contractor? You'll be surprised what sells on craigslist. Your loopfield would support a 5 ton unit just fine, meaning the 5 ton W-A split.

The installer is still willing to make it right; I am still trying to figure out what that means.

If we don't want a completely redone system, is there an alternative to the 3 pumps we have now that would run more efficiently? I am not sure previous recommendations still hold now that this latest documentation has surfaced.

Also, no one has commented yet on whether the Phoenix boiler is an appropriate buffer tank. Is it?

the Phoenix boiler is an appropriate buffer tank. Is it?

Yes (with your system and a single radiator zone).

Since you have natural gas available, I would consider keeping the 5T WtA geothermal unit for first stage heating and A/C and replacing the 3T WtW geothermal unit with a highly efficient natural gas fired condensing boiler for supplemental heating since your loop field and interconnecting piping appears sufficient for 5T but not 8T and natural gas prices are low now and should be into the foreseeable future. If your contractor is willing to work with you, he should be able to re-sell the 3T WtW unit to someone else at a discount off new and refund that money to you. The 5T WtA unit should be able to handle the load when weather conditions are milder, then the gas unit could kick in when conditions are more extreme.

Could he not keep the 3ton ww unit as first stage and the boiler as second stage if it was programmed correctly? Have outdoor reset. The 3 ton could likely cover 70% of his heat load. He could stage the loop pumps. That could be effective and efficient. No? And give the heat for the new kitchen. Run the wta geo for ac? The existing loops are fine if only running one geo.

Getting the high output boiler to play well with the low output WtW heat pump's outdoor reset would be a real control challenge. Theoretically, it would be more efficient to run with just the two geo units under most conditions and switch to the WtA and the boiler when it's really cold (requiring high output temps that reduce the WtW's $ efficiency to less than the boiler). Running both the WtW geo and the boiler at the same time doesn't make sense to me. Ie, depending on outdoor/output temp, one OR the other is best.

Hard to say what ideal control of the 3 systems would save in operating cost and how it would compare to the cost to build and maintain it. None of your heat sources are really inefficient on a $/btu basis - so as long as something isn't broken (sounds like your ground loop plumbing is broken for two heat pumps), your bills should always be tolerable.

"Also, no one has commented yet on whether the Phoenix boiler is an appropriate buffer tank. Is it?"
No. The purpose of a buffer tank is to seperate the gas fired appliance from the geo. A WTW geo and a gas boiler could run in concert if they are seperated by a buffer but in your design they each exclude the other.
The problem with selling used geo is it does not qualify for the tax credit. Yes it will sell but at a grossly discounted price.
As was mentioned before, reynolds number is important to minimize loopfield, that is a non issue here.
You need to find a real expert.

The goal of a outdoor reset system is to run at steady state flow. At that point, a buffer tank isn't separating anything from anything. For the OP - yes.

The answer to the question "is a phx boiler an appropriate buffer tank?" is no. Are there design strategies where you might not need it? Yes but that wasnt the question. So far this installer seems to have no strategy.

"....The problem with selling used geo is it does not qualify for the tax credit. Yes it will sell but at a grossly discounted price."

Since we got the tax rebate on the project including this piece of equipment, we would expect a grossly discounted price. Unless you're saying that making a used geo part of a new install disqualifies the whole install for the rebate. Then we might need to pay someone to take it off our hands!

docjenser,
Wow, those systems make me jealous, just fantastic.  Search for info on geo and cast iron, mostly you just get a lot of pontificating, yes it will work, no it won't, but almost no one who has actually tried it.  For sure the math says you can do it (so does the 50YEW manual), but very encouraging to see that someone who knows what they're doing has made it work in real life. 

I wish WF made a smaller hi-temp unit.   I've got ~1300 sf of space with calculated 560 sf EDR worth of radiators.  3 tons would be perfect but I'm suspicious of the Carrier hi-temp unit, due to comments from users that even though it can put out 140F, is wasn't designed to do that on a continuous basis and that it's pushing the limits of the R410A refrigerant.  

Anyway, thanks for posting those systems. 

The size of the WF is just fine, keep in mind that the nominal capacity is at 104F entering load temperature. At 150F supply temp is around 5 ton capacity, just about right for most of the older homes. 1300 sqf still need a heatloss calc, how do you know that 3 tons W-W are perfect for you?
high temp WF thread.

http://www.geoexchange.org/forum/geothermal-heat-pump-discussions/5310-7-ton-waterfurnace-502w12-high-temperature-hydronic-heat-pump.html The 7 tom W_W is R134, I have not heard about issues with R410a and the 3 ton carrier unit. R410a runs with high temps in Europe all the time. And who said it wasn't designed to do so on a continuous basis? It has an outdoor reset built in, so no need to run it on high load on a continuous basis anyway.
PS: Tamar might want to get rid of hers.

Posted By jonr on 14 Apr 2013 01:20 AM
Getting the high output boiler to play well with the low output WtW heat pump's outdoor reset would be a real control challenge.

A tekmar 261 which is a 2 stage boiler control, nicely can fire the high temp w-w first, and when that is not enough capacity anymore, have the boiler inject BTUs into the same buffer tank. Her is an example.
http://welserver.com/WEL0267/

Theoretically, it would be more efficient to run with just the two geo units under most conditions and switch to the WtA and the boiler when it's really cold (requiring high output temps that reduce the WtW's $ efficiency to less than the boiler).

Again, the problem is that the current loopfield and pumping design, at least the way we think it is, does not support running both the WtW geo and the boiler at the same time. It is a flow issue, not a length of loop issue.

I am just getting what the Web Energy Logger website is. I am slow to catch on sometimes. I thought you were all posting installs that you had personally done. Now I'm getting that this is a great resource for reviewing what others have done and how well it works.

Posted By tamar on 15 Apr 2013 01:33 AM
Doc, I wish you were in Rochester/Buffalo, MN instead of Rochester/Buffalo, NY! I am wondering how our well-known installer gets away with not creating the type of schematics you and others have posted in this thread.

The schematics are not key, they just look pretty and are a bit PR. But they show us and others what design works well under certain conditions, and how well it works. We just take bit pride in making them look OK. As you discovered, the key is not only to make it work, but to make it work efficiently.
I really hate you to give up the radiant, since I am big fan of it. Find out what your installer is willing to do. We can help him to salvage the situation if he is willing to listen.