On 9/26/2012 6:01 PM, Pete C. wrote:

dpb wrote:

On 9/26/2012 3:39 PM, wrote:
...

I generally agree that a geothermal system is probably an
advantage to a house. But it also would depend on where
the house is located climate wise and the cost of electricity
there versus alternate fuels. Here in NJ with electric at 18c
it may not look as good compared to nat gas as someplace
where it's 10c.

Well, of course, but the choice here isn't against competing systems for
a new install; it's already in. Unless it was a case of a demo house or
the like one would presume at least some of those considerations went
into the choice.

And the age of the system and the replacement cost. I know
a lot of the big cost is the outside part, but I wonder how much
replacement of just the inside heat pump part costs as compared
to replacing a gas furnace/AC unit?

Well, that's true for any system, whatever the type. Have you priced a
hi-eff gas system recently? You also get "free" A/C w/ the heat
pump--don't forget to add in the cost there in the replacement as well.
And, if the A/C is used, many have the option of using the waste heat
there for water heating that is another input energy cost reducer. In
TN for the entire summer months and much of spring and well into fall
the water heating was essentially free. Obviously that's not as big a
deal as one gets more and more into more temperate climates so I'd not
expect a unit in PA to have it.

I'm not saying it's always going to be the best possible choice or that
even in this case it's a real plus but I'd surely think odds are it's a
positive as opposed to run-of-the-mill furnace you'd find in the average
house on the block for sale.

All in all, though, after my experience, I'm sold on the concept...

--

A few things to keep in mind:

- Heat pumps in general are pretty efficient these days, and of course
provide both heating and cooling.

Possibly, but others have mentioned "a heat pump is a heat pump"...


- In heating mode, an air source heat pump becomes inefficient as the
air temperature nears the freezing point. Ground source heat pumps don't
have this limitation since soil temperatures at the loop depth don't get
that cold.

- In cooling mode, an air source heat pump becomes inefficient when the
air temperature gets above a certain point and the heat pump has
difficulty dumping the heat it's moving into the air. Ground source heat
pumps don't have this limitation since soil temperatures at the loop
depth don't get that warm.

- Early ground source heat pumps relied on deep drilled wells or
vertical loops or sometimes very long horizontal loops. More recent
research has shown that these installation methods are not needed since
the ground has a tremendous thermal mass. The new installation method is
trenched vertical coil, where a large Ditch-Witch type trencher cuts a
trench and the plastic tubing installed in a vertically oriented
overlapping coil configuration. This takes far less installation space
and less expensive installation equipment. Installers that are heavily
invested in other technologies like drill rigs may try to persuade you
to spend more for their method, but the scientific data show there is no
benefit to the older methods.

The current thinking at least in my area is to use wells with loops of
tubing dropped in them because the heat you can get from burying the
tubing in soil isn't enough for a typical installation (normal size
property)


- A loop is a loop is a loop, so in the event the heat pump needs to be
replaced due to failure or to a higher efficiency model, it can be
connected to the existing ground loop and thus have minimal installation
costs. In the event the house is added on to and more capacity is
needed, the existing ground loop may be large enough to accommodate a
larger heat pump, or additional ground loop may be added to the system
without the need to "throw away" the existing loop.

So, in PA, absolutely a ground source heat pump is a positive,
especially if nat gas service is not available in the area and thus
another relatively inexpensive heating option is not available.


I am in PA know a few savvy people who could not get natural gas and ran
the numbers and put in a ground source heat pump.