GSHP: Ground Source Heat Pump
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Solar Boosted Ground Source Heat Pump Click Here

First Attempts: GSHP Feasibility and Payback Click Here


I have'nt found no way to economically add this to my eco - adventure at my old house.

I've come up with the ULTIMATE GUIDE TO GSHP

Here's what will make you the ideal GSHP candidate:
New Building:
  • MINIMUM 50 x 100 lot - 75 x 100, 50 x 150 and bigger all better.
  • Low electric rates.
  • No piped natural gas.
  • You WANT air conditioning as much as heat.
  • You DON"T want a forced air central heating and cooling system (such as you don't want to smell dinner, 3 mins after it hits the pan and 2 hrs before it's ready, your little one needs a humidifier, etc.)
  • North of the Mason - Dixie line, the further, the better.
  • South of the Mason - Dixie, if you have high electric rates, which you won't. (Caveat:  If you are a business in the South, you're AC costs are HUGE, and you can join the US Military and drill baby drill - you're own GSHP cooling system and save big bucks)
New or Existing:  Super insulating your building.

Existing Building:

  • Radient floor or low temperature convector heating installed already
  • Forced air system with large air ducts, low pressure delivery, heavily insulated, all joints sealed, all ducts WITHIN conditioned envelope.
  • 500 foot deep well with water table up at 50 feet or closer to surface, with 10 gpm minimum recovery rate.
  • (If you are thinking of a shallow well and pump and dump, you aren't thinking sustainably)
  • Lake over 1 acre and 20 feet deep, within say 100 feet of house.
  • 100 x 100 lot minimum.
  • If you can't say YES to at least 1/2 of these criteria, you may well not be a good candidate.
  • You will also need a highly skilled and reputable installer, with whom you can and do check at least 6 references all over 5 yrs and 2 from the last 12 months who all say great, super, fantastic, never fails, lowest bills ever, property never looked better, on time, on budget!  This is a huge investment, you do not want to take a bath, it's really really hard to fix GSHP's once they are in. 
Caveat, if you have a six figure income - DO IT - even with a 30 yr payback you are helping support an industry that is making the world more sustainable, think of it as charity with a pay back to boot!

Back to my story:

Money, money, no money.  3rd yr of marginal employement.  Went through the mad money, living hand to mouth and thankful I can.  While I continue building out the old family home, it's all energy saving intiatives with 5yr or less paybacks, followed by turning the house into a 21st century rooming house, all suites sans kitchens, so I'll have that to fall back on should even hand to mouth work become impossible to obtain.

Here's where it was before I had to abandon all thought of it:


The recession hasn't stopped me, but it's slowed me down, and made this a DIY project.  So, despite some info I've found out, like the physics of cold water, I've redesigned again to make it as easy as possible to:


        Build it myself

            Build it in phases, with as much functionality at each step and phase of the build


Site Problems INTO Site Opportunities


  • Too much water and all the work it entails
  • Erosion
  • Cleaning ditches
  • Pond cleaning and repairs
  • A spring running through the basement even!
  • It really irks me to see that hose from the spring gushing into the pond all winter, and the heat it represents, when the air temperature dives under 20 and the furnace really ramps up.

Make those pluses by using water flow and pond as the primary heating and cooling supply, eroded ditches for ground source loop, yearly eroded material to increase coverage over ground loops.  Add a insulated cover over the pond, with a 3 season double use as reflecting pool and solar water heater / solar pond - which will also keep leaves and organics from settling into pond.

  • A garden equally maintainence intensive, requiring permanent raised beds and paved walks to be useful and delightful in a fast paced, only here for a weekend world we live in.
  • A growing and outdoor fun season cut short by the extreme micro - climate - being nesled deep in a narrow valley.

Make those pluses burying ground source loops under the paths, dampening seasonal thermal swings in the surrounding soils by using foam sheeting as a base under pavers, which also speeds installation, ensures dead flat conditions, eliminates weeds growing in the cracks.  Later, when the greenhouse is built, dump excess heat into the ground source loop!

  • Money and time dictate a slow paced phased construction with econmy at all turns.
  • High level of construction experience. 

Make those positives by using time to monitor enviornmental conditions, try techniques one by one, small scale before full roll out, always planning for re-use of materials and time spent.

  • An interior distribution system that isn't adaptable for GSHP supply
  • An interior distribution system designed for P/T summer use only, undersized, unsealed, uninsualted, in a crawlspace as low as a few inches.
  • Partial electric heating, or no heating, for those 'summer' rooms not deemed worthy of any ductwork.
  • A family with respitory challanges, various pets (believe it or not, unrelated)
  • An old country house that's been around upwards of a century, with enough "contaminants" to keep a CSI lab busy a year trying to pin down.  Mold, spores, insects and their wastes, vermin and their wastes, a few tons of wood and tobacco smoke probably worked deep in the walls too. 

Which just screams out, install FCU's, BB's or some combo and abandon the existing system.P installer or engineer.


What do the pros say about all this:

  • 99 out of 100 Ground source heat pump installers and engineers will tell you this pond system won't work as it's too small and not deep enough.  
  • 10 out of a hundred will offer trying to run the water through a heat exchanger, with all the clogging, scale, and cleaning that entails.   
  • 1 out of 100 will be surprised , no shocked, that in a micro climate of  6,000 to 7,000 degree days a 5 foot deep pond freezes only a couple of times a winter.  
  • 0 out of 100 will believe the enviornmental stats based on the knowledge gained over 3 generations, that there is year round water flowing through the pond of 5 to 50 gallons a minute, at temps no lower than 37 degrees, with flow heavy in the winter. 


I cannot blame professionals who stand by their work, know what works, and don't want to try something different.  Margins are tight and there are plenty of clients who can use the tried and true systems. 

I thought of mounting the tubing vertically, see following link for changes to this  - The Physics of Cold Water - Click here for more.  Then I thought, not.  Still an interesting subject.


The gory details

Problems and Opportunities

Pond and Spring Temperatures:  
Over the 2009 - 2010 - 2011-2012  winters, temperatures in the pond varied from 37 degrees to 75 degrees.  Low temperatures were measured at very cold periods, with temperatures in the single digits at night, and low 20's tops for the over 2 weeks, during which ice cover remained below 50% (Ice, ironically, is a plus for traditonal pond based system, to cut heat loss to the atmosphere in the winter.  Spring flow temps to the pond ran about a degree higher than the pond in the winter, if the spring line is buried, might be able to increase this a bit more, and raise pond temps another degree or two by covering it with insulation.  The potential is for a flow in excess of 15 gpm at 40 degrees all winter. 

Flow Rate of Existing Springs:  
Two springs drain into the property, averaging over 20 gpm for 2/3 of the year, 5 gal 1/3 the year.  A rule of thumb for Ground Souce Heat Pumps is 3 gal per ton, I'm slated for a five ton system so plenty of water flow.  Currently these springs are a maintenance burden, a BIG one, you ever dig a ditch?  Also, they erode dirt and rock from the hilly portion, it builds up in the flat portion, and you have to continually redress these conditions or you end up with a gully and swamp.   It would be good to make use of the water, turning it from burden to boon.

Well Water Temperatures
Despite the rules of thumb for ground water temperature in the broad geographical area, the micro - climate reaches down into the earth also.  Well water, a good proxy for deep soil temperature,  in the summer, 45 degrees.  Nearly 10 degrees below what it "should" be and in general.  Micro - climate, it goes deep.      

AC - I don't need no Stinkin AC
Which is good, as there's little flowing water in the summer.  Did I mention the micro - climate tends to be cool, 7 - 10 degrees cooler than forecasts for the area, and 10 - 15 degrees less than the adjacent Hudson Valley.  Bad in winter, but in summer, it means when NYC is sweltering at night at 80 degrees, we have 60 degrees, lowering the need for AC drastically - really noon to bedtime would do.

Existing Pond: 

Ponds don't care for themselves either.  Expansion and contraction of walls and soils crack it, small holes in the bottom erode soil out from under it, eroding over time the pond bottom, algae, plauge of frogs (litterall), etc., etc..  120 sacks of gravel mix in 10 yrs.  No small amount of work.  Fill it with dirt and rock, that's $400 - $600 per 16 yd truck, lots of truck loads, and the dozer to grade it, topsoil , settling, filling with more top soil, and, it's a pond because it's in a low wet spot, so I'll end up with a bog anyway.   Drain tiles and pipes, money, work, cleaning.  Instead, I will get heating, a smaller water feature, water for site for irrigation in lieu of pumped water.



Existing forced air is undersized, uninsulated, nearly inaccessible duct work under the building, where insulation would be turned into a vermin hotel anyway, as there is no foundation or rat slab. Forced air is a poor option due to allergies and asthma in the family.  The attic space is quite limited and would require heavily insulated ducts and fan coil units.   I need to replace distribution even if I just opt for a new oil fueld furnace.  Given all this, the ideal distribution is for perimeter low temperature baseboard for heating and partial coverage for Air Conditioning via fan coil units based on where there is room for one.

Initial estimates for the ground loop, heat pump and distribution via fan coil units were upwards of $30,000 or $6,000 a ton.  This is the equivalent of at least 6 years oil, probably 10, especially if you invest the money in CD's, earn some interest.  Add to that the $1,500 or so in electric costs per year, and you end up with a 15 to 20 year payback.  Obviously, this isn't viable.  There has to be a way to reduce costs or GSHP's will remain limited in use.  Currently, loans are used to justify the cost, ie, I'd pay $2,000 a yeaar to the bank, $1,500 to the electric utility, leaving a savings of $500 to $1,500 or more depending on the price of oil, or a 5% or less return on investment.  Not stellar.  You can double it to 10% if you have the cash for a system.  However, it's still a 15 to 20 yr payback then, ouch!
That which is why I can't buy a typical ground source heat pump, new distribution, or for that matter, much of anything, but is why I have time to DIY it (Do It Yourself) and luckily, I'm building savvy and handy.

GSHP: Ground Source HeatPump 

An Experimental  Design 


Instead I'm installing two "experimental" "ground" loops, one in the pond, one in the garden, and a pre-tempering loop for the spring water, to boost it up a bit in the winter, which will be under a greenhouse still to be done.


The Pond / Spring loop.


One is for the pond.  The pond is too small and too shallow, by the rules, but those are for a POND, a still body of water where the primary source of thermal transfer is the earth in the winter and evaporation from the surface in the summer.  My use of a pond is as a tank for a heat exchanger to transfer thermal energy from the spring water flowing through it. 


There is constant water flow and a substantially water proof pool to hold it.  The incoming water is never under 38, or over 75 degrees.  In the heating season, one spring is at least 15 gpm, and a typical flow for both fills a 3 inch piipe, over 50  gpm.  A rule of thumb for a Ground Source Heat Pump system is 3 gpm per ton. 


How sure am I of this, pretty sure.  I've got a brain, did the basic math.  However, I am cautious, so if it will not provide for the whole load, the heat exhanger in the pond will just be a whole bunch of standard tubing used for ground loops.  Then, if it's  miserable failure, it can be resued for a GSHP buried loop.   Win - Win.


Also, I know some of the rules are a bit extreme, like allowing for 4 to 6 feet of water drop in a drought, for evaporation and soaking away into the surrounding soil and only allowing for thermal transfer from the earth and evaporation to the atmosphere.  I suspect  these are hold overs from the early days of alternative energy, the first Arab oil embargo.  Back then HP technology optimized for commercial heat pumps.  I remember the origional design for the SERI facility inlcuded turning the measa top into a huge solar pond heat pumps would tap into.


Eventually I want to try covering the pond with insulation and a shallow 6 inch deep reflecting pool.  It will keep leaves from fouling the "pool" /  thermal storage? underneath, certainly easier to clean, less of a drowning hazard AND it will keep the pool under it cooler in the summer and warmer in the heating season (one GSHP pond rule of thumb is you can get more capacity from it IF IT'S ICE COVERED IN WINTER, the ice is an insulator, foam insulation even better!).  


In the garden I want to try out a ground loop that would work in hard landscaped areas more commonly found in suburban and even urban neighborhoods and if it worked, much more economically feasible, requiring less specialized equipment or skilled labor making GSHP's more accessible to building owners


Like the pond, insulation would thermally isolate the loop from the yearly atmospheric swings.   This is very much as happens in a Frost Protected Shallow Foundation System.  It would also provide a fantastically smooth and even sub base for pavers, much simpler to install and maintain then a sand bed, and impervious to weeds with no frost heaving too!  Lifting, cleaning off accumulated silt and seedlings with a hose, and resetting would be a cinch, cheap to hire the work done, and equally easier for any homeowner to do.  Win - Win.


The pre-tempering element for one spring would be 3 inch PVC pipe looping under the bed edges, holding some 900 gals of water, which will leave it in contact for over an hour, plenty of time for serious thermal transfer.  These pipe runs will double as footings for support posts for the raised garden beds and greenhouse above.  Win - Win.


Fall back, layout tubing all over property, dig a 2 foot wide 6 foot deep trench, slip 2 tubes in from the top, one on each side - no man in trench, use hose from spring to wash dirt over tubing, after a foot or two, use backhoe to back fill.  Open only as much trench as can be backfilled in a day.  Less fuss, less muss, no dangerous trenches open for days, weeks if the GC disappears in the middle of the job.