On Mar 5, 5:57 pm, "Zephyr" an address @ some place .com wrote:
Hey group,

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.

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.


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 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
motors, etc.

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.

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 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.


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"

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
equipment.