I'm contemplating going to Geo Thermal heat,
I've talked to a couple different installers and they say that I need 400
amp service to do this.
this would be split into 2 200 amp boxes, one for the geo and accessories,
(which qualify for a lower rate) and 1 for the rest of the house.
currently I have 2 meters on the house 1st is a 150 amp service and the
second is an interruptible service meter for my AC unit.
( I am in SE Michigan, use DTE energy)
If I need to go to 400 amp service is it as simple as having both meters
replaced with larger 200 amp units?
or would new wire need to be pulled from the road? a quick call to DTE
resulted in an
"I don't know, We've done geo therm before and never had to put in new
wire, but, I don't know everything"
On Mon, 5 Mar 2007 20:13:18 -0500, "Zephyr" <Someguy@an email
I'd hate to pay your electric bill......
YES, you need larger cable from the pole and all the way to the
breaker box(s). Possibly a new transformer on the pole. Possibly new
meter sockets, and definately new breaker boxes (or at least for the
Are you sure you really need that much power? I live on a farm, and
my whole farm has 400A service. There are two 200A mains. I dont
even use one of those mains. Of course the former owners had some
electric grain bin dryers and those things are big power users. I run
the whole farm on 200A with plenty to spare.
Read the original post! The second breaker box and meter is to isolate the
heating from the rest of the electric load. It is not that uncommon (though
not widely publicized) that you get a discount for electric for heating
purposes. This LOWERS the electric bill. My b-i-l did this a few years ago
and he is saving gobs of money on heating!
Maybe you should look into electic heat since you already have 2 boxes set
up. You could save a bundle on yoru heating bills!
50+50+500. Do the compressor and aux heat ever run at the same time?
If not the load for those 2 is 50A. What is the 50A for hot water - is
that derived from geo or simple resistance heat. Resistance electric hot
water is commonly a 30A circuit. **What circuit rating does the
manufacturer say is required - or max concurrent connected load? As
others are indicating, 200A sounds way high.
Sounds like your house now runs off 150A separate from the existing A/C.
Why increase that to 200A?
i dont know. but: the electricians know your loads for the new pumps.
perhaps your new heating unit has auxilliary electric heat or air
conditioning and needs more electricity.
maybe you also need to consider a natural gas generator for emergency
hookup with an additional panel and auto disconnect.
code determines how many drops per type of dewlling/structure.
and you can't put in a service main panel any larger than the existing
there is a hidden extra cost of each monthly meter charge in buffalo
ny around $16 per month.
as in buffalo, you have winter. in our climate be careful. if you
underestimate for energy efficiency, estimates of btu's required to
quickly reheat your home on a windchill day by many energy efficiency
calculations could be too chilly for too long.
these systems you may want to have control over could use lots of
zoning and temperature sensors if you want to see how the system is
working and to help pinpoint problems.
at the very least i'd want monitoring temperature gauges and indicator
lights for the running pumps. and show me underground water temp in
and out, and home zone temp in and out.
I guess that is the heart of the question I am asking,
how can I tell if the service wires will accommodate the 400 amp service?
does the fact that I have 2 meters right now give any indication to that
On Mon, 5 Mar 2007 17:57:19 -0500, "Zephyr" <an address @ some place
.com> wrote:>Hey group,
Are you going to use the Geo to heat you, or are you goint to heat the
If you need 400 amps, it sounds like the second. Seriously, I'm new
to this, but how could something that needs so much electricity save
you money? Or save the world anything? How many amps are needed for
Sorry, I can't answer your questions.
The question to DTE is irrelevant that it is goethermal. The question to
them is can you upgrade the service to 400 amps without changing the wiring?
They for sure should be able to tell you this.
As an aside, do you think the geothermal system will really save you any
money in the long run? What about when you factor in what sounds like a
sizable hike to your electric bill?
If you do the geothermal, I would be interested to read about your
experiences with it as it is an interesting technology.
DTE offers a 50% reduced rate on electric for people with geo, as for
saving money, the compressor is all that runs really, and so its not that
big of a bill, I've had companies promise me up to 50% savings on a typical
gas bill for a house my size (2100 SF)
check out www.waterfurnace.com for more info
currently it looks like around $16,000 - $20,000 to get in though
the contractors are pushing a 8.5 year payback if the ratio of gas to
less if gas gets more expensive vs electric.
Something is really off. Geothermal should use less energy than a
standard heat pump for both heating and cooling. A 2100 sq foot house
should use about 3 tons (36,000 BTU) in the mid atlantic region, maybe
4 tons in Michigan. A geothermal unit is not dependent on outside
temp since it draws heat from a constant earth temperature. Even if
the electric service is sized for emergency resistance heat the amp
ratings seem very high. Might want to check some geo mfgr websites
Something does not sound right. At the low end up front cost of $16,000 an
8.5 year payback means you would have a savings of $1182 per year or $156
per month. Couple that with a maximum expected savings of "up to 50%" on
gas means that your gas bills now would have to average over $2300 per year
or over $300 per month to make the figures you were given add up. I just
don't see it but maybe I am missing something.
I had a good friend look into geothermal heat for his home but he decided
against it saying it would be too expensive.
You are ignoring rebates. Does your electric company offer any rebated for
geo? Also, there are tax rebates from the federal govt for going geo.
Check with your state also. Your price seems quite high. My son's is only
going to be about $3000.
On Mon, 5 Mar 2007 21:31:54 -0500, "Zephyr" <Someguy@an email
If you're pulling 50 amps for the compressor,
and 50 amps for "aux" heat, then that's 100 amps * 220V
or 22000 watts.
Which would produce 74800 BTUs per hour.
(Or, at 80%, around 60,000 BTUS) if you used it
as straight electric-resistance heating.
What does your heating-load calculation say you actually need?
'cause that seems like it ought to be enough,
all by itself, in which case, what the hell is the
heat pump good for?
I mean, the whole point of geothermal is that it's supposed
to use LESS electricity than electric resistance heating, right?
A 1 story 2100 sqft house that's 28 x 75'
assume 2100 sqft ceiling at R36, (U~60)
1650 sqft of wall (10% window), @ R15 so (U~98)
10 % windows at R=1 so (U~165)
=======Figure 20 below, outside, 72 in = 92 * 323 ~~ 30,000 BTUs/hr
plus 2100 sqft floor, R5 ground temp 0 ~~ 30,000 BTUs...
On Mon, 5 Mar 2007 20:30:10 -0500, "Frank Ketchum"
I only know the basic principals of geo-thermal, but it seems to me
that the whole thing is run with a couple pumps, and I imagine there
are a few blower fans too. I cant see where any of these pumps or fans
would require any more than a well pump or common furnace blower.
A common well pump runs on a 20A breaker, and your could likely run
two furnace blowers on a 15A breaker. IF there's 2 pumps, your max
usage would be 55A. You are obviously disconnecting a standard
furnace, so that will save a few amps. I agree, if this thing really
needs 400A, I cant see the savings at all.
Is this an underground service or overhead? The power companies rate their
conductors differently than what is permitted in the code book. I know that
one power company here in New Jersey has all of their service drops rated
for a minimum of 320 amps. For larger services they would install larger
You didn't say if you plan to do this work yourself or have a contractor do
it. A local electrician should know what is needed. If you are going to do
the work yourself, I suggest that you get the paperwork started with your
power company as soon as possible.
It sounds as though you only need to upgrade one of the services and leave
the existing house service as is.
You are wise to seek advice in this matter. IMHO, a 400 amp electric
service for a 2100 SF house is just ridiculous. An HVAC contractor
should be consulted only to calculate what size geothermal unit that
you need. One should then give the electrical specifications for that
unit to an electrical contractor, preferably one that is not
associated with the HVAC contractor, and have them do an electrical
service calculation, or do it yourself. Many electrical contractors
who work with HVAC contractors are "yes people" and, since the HVAC
contractor is buttering their bread, will install anything that the
HVAC contractor asks for, in this case, a 400 amp electric service.
RUN, don't walk, from anyone who tells you that you need a 400 amp
electric service for a 2100 SF house!
The purpose of using a geothermal unit is to provide a high comfort
level with a low energy cost. Installing a 400 amp service for an
energy saving geothermal unit, IMHO, would be an oxymoron. Think
about it. If one is indeed actually using the lion's share of a 400
amp service, one would probably need to get the place zoned for and
open a restaurant to help pay the electric bill.
If you consult an electrical contractor, or the power co., I think you
may find that installing a panel on the load side of the interruptible
service meter large enough to accommodate the geo and it's accessories
may be an option. I don't think that your "problem" is capacity, but
more of one of physical spaces in the panel for the equipment.
Discontinuing use of your existing heat/AC is going to free up spaces
for the new equipment.
I saw your other posts, and I checked out your link to www.waterfurnace.com,
but without knowing your existing electrical requirements and the
model number of unit that you are considering (hopefully this was
calculated by the HVAC contractors), including what size aux. heat in
kW, one cannot make a electric service load calculation for you.
There are plenty of people in this NG who can make the calculation for
you, but we need more info from you, if you want to take the time:
1...SF of the house, OK, we know that, 2100 SF.
2...which appliances are currently gas and which appliances will
remain gas once everything is said and done.
3...is your water going to be heated by the geothermal unit, and if
so, what size is the backup (in kilowatts), if electric.
4...a list of your current electric equipment, such as whether or not
you have (or going to have) an electric a water heater, disposal,
dishwasher, dryer, washer, pumps, large fans, shop equipment, large
There is an online electric service calculator, but I can't remember
where it's at. Maybe someone can post that link if you want to do it
yourself. If you decide to do that, I would recommend that you get
your calculation checked by a qualified person. There's plenty of
help at: http://www.selfhelpandmore.com/index.htm
Electric services are not sized by adding up the breakers in the
panel, they are based on well established demand factors, and only a
properly made electric service calculation will give you the correct
size electric service that you need. I seriously doubt that the HVAC
contractors who you consulted even made an electric service
calculation. I would also suspect that those same contractors didn't
bother to make a calculation to size the geothermal unit either. One
simply does not ask an electrical contractor to size an AC unit, nor
ask an HVAC contractor to size an electric service, unless, of course,
that person is licensed AND/OR qualified to do both.
A true 400 amp service will not only require larger wire, but most
likely a larger conduit. Things can get expensive in a hurry....all
for something that you most likely don't need.
It may not seem like much of a statement, but is says a lot.
You want to keep the power co. in the loop. You may want to call them
back and ask to speak to someone in the engineering dept. You may
want to ask if they will come to your home and do an energy audit.
You may want to call the geo unit manufacturer and ask them for the
names of contractors in your area who have experience installing their
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