[AC_Hacker]

Originally Posted by cholcombe

So I think ac_hacker might be the best to answer some of these questions.

Sorry cholcombe, I'm a bit late coming to the party...

Originally Posted by cholcombe

I'm living right outside of Portland now :-).
I had a salesman come to evaluate what a gshp would cost. He kinda blew me away when he said it would be 32K for a 5Ton system.

Actually, in Portland area, $32K for a 5-Ton system is a bit on the low side. If your contract specified that the installer would eat all of the 'extra costs', it would be a competitive price.

Originally Posted by cholcombe

I'm looking online and a fancy two stage gshp is going for 6-8K. So where does the other 24K go? Surely it can't cost that much to dig s trench for the lines.

Earth work is not simple or easy, and it is where the money goes if you want to hire it out.

"Dig a trench" is a considerable understatement. The trench needs to be deep and it needs to be long.

Close to Portland, a 6 ft deep, 4 ft wide slinky trench should be at minimum, 80 feet long per Ton of heating. If your house actually needs 5-Tons of heating, then you will need 5 X 80 ft of trench (minimum). There will be additional trenching required to runs the lines into your house, also. Since a slinky trench is about 4 feet wide, you would be dealing with 4 X 6 X 80 X 5 = 9600 cubic feet of earth. Since wet earth is about 100 lb/cubic ft, (not counting the trenches to get the water lines to your house) you are talking about 960,000 pounds of earth or 480 Tons.

Digging trenches may not be a straight-forward process. There may be many problems.

Living in the Portland area myself, I'm very familiar with the great geological event called, "The Missoula Flood." In truth, it was not a flood, but rather a series of floods that took placed somewhere between 15,000 and 10,000 years ago. The series of floods carried debris, clay, sand, gravel, stones the size of your fist, stones the size of basket ball, stones the sized of cars, and scattered them in each tumult of the flood in successive layers around the Pacific North West, which includes Portland. Each part is different.

This just gives you open earth to lay HDPE.

Then there is the matter of tube sizing, and tube welding, and manifold connection (if you go with an external manifold) and testing.

Then the 480 Tons of dirt and rocks needs to be replaced. All together, you will need to move almost 2,000,000 pounds of wet, heavy dirt.

Then there is the issue of dressing the water lines into your house, and assuring that there are no water leaks, if it comes in to your basement (ideal situation).

Then there is placing your Heat Pump unit, establishing the indoor manifold and valving if you aren't going to use a buries manifold.

Connecting the power legally, setting up the control system.

Flushing all the water lines with a high-power pump to assure no water voids.

Final testing to the customer's satisfaction.

So, I guess cholcombe what I'm trying to say is that there is more to it than, "...digging a trench".

Originally Posted by cholcombe

The salesman also said something odd. I asked him if I could plant fruit trees on top of the area the lines were installed. He said sure it wouldn't be a problem. Is this true?!

From the standpoint of the ground loop, he is correct, the HDPE is incredibly tough and resilient, it can take it.

From the standpoint of the fruit trees, you need to be aware that a GSHP will remove heat from the ground, and that the temperature of the ground will decline during the winter, when your home heating is required. It will warm up during the summer because of the sun.

I don't know how much you know about fruit trees, but they get their signals about when to go into a budding/flowering/fruiting cycle from the temperature of the ground.

The smaller your loop field, the lower the temperature will fall during the winter's use... the larger the field, the less the temperature drop.

So, there will be a delay, hopefully not much.

Originally Posted by cholcombe

They proposed trenching a 60x40ft area 5ft deep. Seems extreme to me.

I agree with you completely... it is extremely small.

If you were going with slinky, your 4 ft wide by 80 ft long trenches should have about 16 ft apart from each other.

So you're talking about:

80 X (4 + 16 + 4 + 16 + 4 + 16 + 4) or 80 ft x 64 ft

These are minimum numbers, a larger loop filed is always to your advantage.

Originally Posted by cholcombe

ac_hacker how big was your system? How much did you end up out of pocket?

My badly broken arm has taken a lot of the steam out of my projects, and my system is not yet finished, but it has been tested.

My design goal was to get enough heat from the ground to keep one highly insulated room warm during the winter.

I have tested my ground loop and I'm confidant that my goal can be realized.

I did several heat loss calculations, using methods similar to Manual-J, each result was reasonable, but not identical. I also logged the electric heat required through some of the worst winter days, an came to the conclusion that all these methods converged on about 2/3-Tons, worst case.

My loop field consisted of 16 bore holes, each was 17 feet deep. It should be bigger.

Originally Posted by cholcombe

How much did you end up out of pocket?

So far I have spent less than $1000, mostly on tools, like welder, and horizontal steel cutting band saw... to make tools. Some of the tools were very valuable, some not so much.

* * *

I learned that even if you totally DIY (construct your own heat pump, etc.) and dig your own loop field, the biggest amount of work is in the earth work. The amount of work in the Heat Pump is less. If you have heavy equipment, the man-hours dedicated to the loop field will be greatly reduced.

Randen did a DIY of the whole thing, with experienced help on the earth work, and he was able to leverage his considerable skill and very powerful machining tools to craft his own heat pump, which is finally working to his great satisfaction, but he certainly had his dark days.

If you want to DIY the whole thing, we will be here to see you through, though it may take a while. A 4-Ton DIY is not trivial. There was a blog that has slid off of the Internet, of a guy who bought a packaged heat pump and did all the earth work and lake-loop (he was using a lake), and hookup. When he got through, it was working to his satisfaction, and he said that he had never undertaken a project that approached the scale of his heat pump project.

There is a reputable organization called the International Ground Source Heat Pump Association (IGSHPA). They have the very best information on the subject. They also have a certification program that I completely trust. If you want to have someone do the work for you, I would seriously advise you to make sure they are IGSHPA certified.

As for advice, there is no one who has replied to this thread whose advice I would trust with out double-checking other sources.

However, if randen weighs in, it changes things for the better.

I would advise you to certainly ask for advise, but to weigh very carefully any advice, including my own, and to see if it held up to other research. I would recommend literature that is supplied by IGSHPA. Their basic manual is a culmination of 60 years of international experience, and is the gold standard of the GSHP world.

Lastly, you're probably gonna go with an existing forced air system. You need to know that to keep that place warm you will need a greater than normal volume of air flow, because it will not be as hot as fossil fuel. So, if your duct work was normal size, the greater volume of air will be audible. If you were doing this as new construction, and used over sized ducts, there would be no air noise.

* * *

In short,

• 3000 ft house is a big house
• 1" of insulation doesn't mean very much
• 5-Tons might be right, but it would indicate a poorly insulated house. In PDX, the rule of thumb is 1-Ton per 1000 sq feet. this ignores infiltration, insulation, solar gain, etc. It certainly is not an Engineered number, but it can be useful as a BS-detector.
• You absolutely need to know what you heat loss really is.
• A properly sized Heat Pump is slightly undersized, not over-sized.
• The loop field you quoted seems too small. It could result in long-term cooling of your ground source.

Best,

-AC