Author Topic: geothermal heat pumps  (Read 4271 times)

0 Members and 1 Guest are viewing this topic.

drbob

  • Newbie
  • *
  • Posts: 46
  • Country: us
geothermal heat pumps
« on: August 15, 2014, 06:11:56 PM »
I heat with a earth coupled heat pump aka geothermal heating and have been using it for over 25 years.  I like it

madlabs

  • Hero Member
  • *****
  • Posts: 686
  • Country: us
Re: geothermal heat pumps
« Reply #1 on: August 15, 2014, 07:43:16 PM »
I am going to convert a well drilling rig I built to do 2" holes and do a heat pump. I don't want to be messing with firewood when I'm old.

Can you share more system details?

Jonathan

micropv

  • Newbie
  • *
  • Posts: 27
  • Country: us
Re: geothermal heat pumps
« Reply #2 on: August 15, 2014, 08:14:31 PM »
The school I work at is entirely geothermal, all 67,666 square feet.  It works quite well, but does not have a central  dehumidifier, so on humid days outside, it can often be humid inside.


drbob

  • Newbie
  • *
  • Posts: 46
  • Country: us
Re: geothermal heat pumps
« Reply #3 on: August 15, 2014, 10:43:40 PM »
as a rule of thumb, for a closed loop using vertical boring it takes 200' of borehole to  provide a ton of heat (12,000 btuh) .  Vertical loops are best done by a professional licensed well driller. This is really something that a novice should not  consider, there is a lot more than just drilling holes and placing loops in them.  Proper grouting of the borehole is crucial for the loop to perform properly and avoid cross contamination of aquafers at depth.
I live in an area that is blessed with abundant ground water and I heat with an open loop using well water for my heat source. This was a common practice 25 years ago when I first installed my system but is rare  now.   

madlabs

  • Hero Member
  • *****
  • Posts: 686
  • Country: us
Re: geothermal heat pumps
« Reply #4 on: August 16, 2014, 01:15:07 AM »
I'm not too worried about doing boreholes. I have drilled two water wells myself, sealed them properly etc. Books and the internet can do wonders. And poverty is a heck of a motivator, no way I'm ever going to have the cash to pay someone to drill for me.

But what about your system and experience with it?

Jonathan

drbob

  • Newbie
  • *
  • Posts: 46
  • Country: us
Re: geothermal heat pumps
« Reply #5 on: August 16, 2014, 07:26:18 AM »
my present heat pump is an econar 4.5 ton water to air machine.   It is quiet and very efficient It has been delivering an efficiency of over 400% since I Installed it in 1995.  In 2000 I had a water side heat exchanger freeze rupture causing extensive damage to the machine.  The cause was a defective low temp sensor and the manufacturer warranteed the machine, effectively replacing all refrigeration components, compressor , water side and airside heat exchangers free of charge including shipping back from the factory.  In 2013 I had a refrigerant leak on the water side heat exchanger and the defect was determined to be a manufacturing defect and the heat exchanger has replaced under warranty!!  18 years after I purchased the machine.   This was a parts only warranty but oh well it was a $800 part  and besides that the new one does a lot better job.

My normal heating cost for a northern Wisconsin winter has been in the $400 range for the whole season, as compared to my neighbors who heat with propane who normally heat for closer to $2000.00 annually.    Air conditioning is astoundingly cheap  about 8 bucks a month and I don't scrimp on the air either.   A neighbor with a similar house with a conventional a/c system pays about $80.00 per month for his air conditioning.

I do not participate in any off peak programs and pay the normal electric rates.    I do not have a desuperheater for domestic hot water this would have saved me an additional $250 bucks a year  but I feel they can cause more problems than they are worth.

In operation I change the air filter 4 times a year and the water filter gets changed once a year. 

I figure I have saved $36,000.00 in heating and air conditioning in the last 18 years.

The equipment cost for a new heat pump is about the same as buying a new furnace and air conditioning system. 

The big cost of a geothermal system is the heat exchange ground loop in a closed loop system,  In this area loops cost about $2000.00 a ton or $10,000 for a 5 ton loop.   nothing to sneeze at.  I did not opt for the closed loop system and have driven my heat pump with my well instead.    This is not common anymore but it has been problem free for me.  You really have to have good water for an open loop system and I am fortunate here.  All the water I use is discharged and soaks back in the ground in effect goes back where it came from not wasted, all I took from the water was heat.

My water consumption is 6 g.p.m. in the heating mode and 3 g.p.m. in the cooling mode.    My well is capable of 20 g.p.m. all day long so I have no water shortage issues

Would I do it again?   yup.   I can give you 36,000 reasons why and the reasons are adding up more every day

madlabs

  • Hero Member
  • *****
  • Posts: 686
  • Country: us
Re: geothermal heat pumps
« Reply #6 on: August 16, 2014, 10:18:30 AM »
Here in CA I think that using the well is illegal. While I have a decent water table, that would be too much load on it. So ground loop it is for me. I'll likely go with 60' holes, there is a layer of hard stuff here at that depth. So quite a few holes, but if I'm doing 'em myself not bad cost wise.

Thanks for the details on your system. If it works for you in Wisconson it'll work for me here in Northern CA!

Jonathan


drbob

  • Newbie
  • *
  • Posts: 46
  • Country: us
Re: geothermal heat pumps
« Reply #7 on: August 16, 2014, 10:43:04 AM »
good luck  open loops are not for everyone. If you are handy you can surely install your own heat pump.  Check ebay and there are some bargains to be had on heat pumps. Just avoid heat pumps that operate on r-22 as that go juice is getting spendy.     As for the loop use 3/4" HDPE socket heat fusable pipe.   it is just the best and it will last for generations.

Frank S

  • Hero Member
  • *****
  • Posts: 1901
  • Country: us
  • Home with a view of Double mountain
Re: geothermal heat pumps
« Reply #8 on: August 16, 2014, 05:32:48 PM »
Johnathan; I believe you mentioned that you were going to modify your rig to drill 2" bore holes.
 How would you be able to get your loop down a 2" hole?
 I should think that a 4" bore hole would be about as small as possible to get a looped tubing down it . Even at that there would be a risk of kinking in the bend unless you used heat to form the bend
I live so far outside of the box, when I die they will stretch my carcass over the coffin

Frank S

  • Hero Member
  • *****
  • Posts: 1901
  • Country: us
  • Home with a view of Double mountain
Re: geothermal heat pumps
« Reply #9 on: August 16, 2014, 06:05:43 PM »
 Ideally I would think that if it were possible to have a coil of tubing down the hole. With only a 60' nominal depth if you could get say 400 ft of length going down and the 60 coming back up or vice versa  the coiled length would be in close contact with the bore hole walls for some sympathy heat exchange. should the water table be quite high up then so much the better.
 in that case a 6" or larger diameter might be better still.
I live so far outside of the box, when I die they will stretch my carcass over the coffin

drbob

  • Newbie
  • *
  • Posts: 46
  • Country: us
Re: geothermal heat pumps
« Reply #10 on: August 16, 2014, 06:33:00 PM »
in vertical loops the u bends are pre made and welded onto the pipes using a socket fusion machine.   1 pipe goes down and 1 pipe goes up.   a 4" borehole is common for  3/4" hdpe pipes.   2" is a little small to fit the pipes down