Electrical Service upgrade from 200 amp to 320/400 amp? (apartment, house)

[HoustonTexasEngineer]

Im looking to make the transition to all electrical Mini Split heat pumps with this transition we will need to upgrade our current service to 320/400 amp. what all is involved in this? can the current underground wire/conductors supply this amperage or will CMP need to be called to run a new line? this is an underground line so i imagine CMP would charge a fortune for this?

[Northern Maine Land Man]

Your electrician can tell you the gauge and amperage of your wire. Most underground wires are set up so you can run your big welder while the electric clothes dryer and well pump are both running.

Your entrance breaker box is another matter. Do not change breaker boxes. Leave you present breaker box in place and add a second box if necessary for your new project

[OutdoorLover]

I would imagine that you will need a new service line and service meter too. If a buried service line is sitting inside some kind of protective pipe, then they may be able to just use the existing cable to pull a larger cable through (as opposed to digging everything up).

[vaughanwilliams]

Will a heat pump without backup heat work in Maine? I thought they were pretty inefficient for temps below zero.

In my experience (electrician for 30+ years), the homeowners contractor installs the service from the pole to the meter, at least where I am. Then the power company does the final hook up at the pole. May be different in Maine, though.

[399083453]

If I remember correctly, you had boiler problems. Is this going to replace your boiler?

[OutdoorLover]

Originally Posted by vaughanwilliams

Will a heat pump without backup heat work in Maine? I thought they were pretty inefficient for temps below zero.

In my experience (electrician for 30+ years), the homeowners contractor installs the service from the pole to the meter, at least where I am. Then the power company does the final hook up at the pole. May be different in Maine, though.

Recently, Fujitsu and Mitsubishi have introduced some special low temperature models (not the whole line) that still work well down to -10, -15F. Now you're still suggested to have a backup system if you can reach or exceed those temperatures, but if you're adding to an existing home, then the existing system can be the backup.

P.S. One thing to recognize about these ductless mini-split systems though, is that you don't have heat distribution units in every room like you would with central forced air or hot water/steam system... so they tend to work best in homes that are fairly well insulated, otherwise a lot of the heat will be lost before it gets to the rooms lacking a distribution unit, if you expect the even temperatures throughout the house that you actually get with a properly designed forced air or radiator system.

[joesig]

Why do you have to add over 100 amps of service for a heat pump? Is your breaker box full and no option for half sized breakers?

My house is 25 years old with an equally aged heat pump and 200A has been fine. Defrost mode, drying clothes, taking a shower while baking cookies was never a problem.

My cousin in NY added a new mini split heat pump to his 50YO house and and his 100A service was fine. It was just a little bit of a trick finding room in the box.

I'd take the gamble of new breakers for your current box and see how it goes before shelling out for a new box and all of the labor to install it, etc. Worst case, your new breakers should be usable in the new box (with the presumption you'll want matching boxes for interchangeability.)

[mtnbiker65]

I'm kind of surprised as to what's being asked of the OP. First of all, a 320 amp or a 400 amp is kind of unheard of for what I presume is a single family dwelling. A small apartment house? Yeah, I can believe that.

I don't know the age of the OP's home, either. Back prior to about the late 70's, many homes were wired with a 60 amp entrance. Newer homes starting in the late 70's were outfitted with 100 amp entrances. Today, it's not that uncommon to see 200 amp entrances.

The first thing the OP needs to do is to find out what size entrance he has. That's easily determined by looking at the breaker. The OP can also go here and review section 901:
https://www.cmpco.com/MediaLibrary/3...s/handbook.pdf

If, and I mean, if the OP does have to go up to a 400 amp entrance, there's an extremely good chance he'll have to dig everything up. He likely also will be replacing the meter and socket as well. The amount of work to be done with the cabling will all depend on the size of his service entrance to begin with.

If it were me, I'd be asking the question as to why I need to jump up to a 400 amp service for a heat pump. Do heat pumps really consume that much power? What is the actual power consumption of the heat pump in question? If the power consumption truly is that high, I'd be seeking alternative forms of heat as the electric bill would kill you.

If the real issue is having a newer 200 amp panel with no more open spaces, that's an easy resolution. Just pop out an existing two pole breaker, then wire in a sub-panel in a suitable location. You would then need to move that two pole breaker and associated cabling over to the sub-panel. It's a little extra work, but considerably less work and far cheaper than upgrading a service entrance.

[mensaguy]

You really need to hire an electrician to tell you what you need. Nobody on a forum can tell you. What needs to be done depends no only on the size of the wires between the pole and the meter, but also the size of the conduit. It's possible that you would need to increase the size of the conduit, use larger wires, and install a larger capacity meter base in order to accommodate capacity above 200A An electrician should be able to accurately answer those questions after a brief examination of your existing installation.

He can also advise you about heat pumps, their installation and their electrical consumption.

[The Villages Guy]

Originally Posted by vaughanwilliams

Will a heat pump without backup heat work in Maine? I thought they were pretty inefficient for temps below zero.

In my experience (electrician for 30+ years), the homeowners contractor installs the service from the pole to the meter, at least where I am. Then the power company does the final hook up at the pole. May be different in Maine, though.

I was wondering that, too. We have problems heating our home in Florida once it is in the 20's. Can't imagine below zero, unless there is something different in ones up there. That's a lot of amps.