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Question DetailsAsked on 1/20/2018

We need a 220 line in the back of our house (no basement/crawling space). Can that be done?

We need to install an additional, small, electric heating/cooling unit at the back of our townhouse. There is no 220 outlet there. We do not have a basement or a crawling space. Can that be done by an electrician?

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Voted Best Answer

Sure - you can do almost anything - just takes more $ sometimes.

What you are looking for might be quite easy, or might get into quite a few bucks, depending on your electrical system layout and on whether your system has the capacity for that added load.

The lack of basement or crawlspace is no problem - the line can be run around the house either buried (a bit higher cost unless you do the ditching), or can be run around the house in exposed metal conduit. Neither will add dramatically to the cost.

Depending on the existing loads and availability of space in the breaker panel for an additional pair of 220/240V breakers, and how far that is from the new heat pump,, he might tap off there and run wiring to the new unit (around the house to avoid tearing into walls or ceilings) or maybe through the garage in exposed conduit on the walls if breaker box is in/near the garage.

Or if the distance is significantly less, or the existing breaker panel or the wiring to it does not have the available power capacity, he might tap off the service connection at the meter panel - in an existing main breaker box there if it has room, or putting in a new small breaker box with both a main breaker for the main breaker panel, and a separate breaker for the new heat pump.

Then, if the incoming service drop and meter panel doers not have the combined amperage capacity for the entire household load including the new heat pump, that might have to be upgraded too.

There are a fair number of previous questions about adding high-amperage circuits, with answers, including discussions and ballpark costs about just adding a circuit, upgrading a panel, upgrading service wires to panels, and upgrading the incoming service drop - see the Home > Electrical link, under Browse Projects, at lower left.

Your cost might, if the existing breaker box has the capacity and is close by, run about $500 plus or minus or possibly even a bit less in the best case - but commonly above $500 total including the circuit and breaker in the breaker box and the breaker or circuit interrupter required near the new het pump. If the existing breaker panel needs upgrading (usually adding a new panel for the new load would be cheaper than a total distribution/breaker panel upgrade) you are usually looking more in the $1000-2000 or occasionally range, and a total system upgrade including upgrading the amperage rating of the the incoming service drop and meter panel will commonly run $2000-3000 range including the new circuit for the heat pump - sometimes more - VERY rough ballpark.

if your system can handle the new heat pump but only if the existing unit (since your said "additional" is not running, I have seen cases like this (where the new unit is serving say an added addition or such, not needed in addition to the existing unit just to keep up with the demand from the house), where an interlock was installed to prevent both units from running at the same time - but that is also one more thing to fail, and if that interlock fails or gets confused then both the systems will not operate, instead of being independent like if they are on separate circuits.

One other thought, though sometimes having two units does give you a desireable backup - especially if medically necessary, but if you existing unit is on the older side (over 10-15 years old and certainly if over 20) or your evaporator coil (commonly a $1000-1500 replacement item) is over say 15 years old, it might pay to look at possibly installing a larger cooling/ heating capacity unit replacing the existing one, if you are looking at having to replace it fairly soon anyway. Generally speaking, one larger unit is both more efficient to operate than two, and upsizing to one larger unit is commonly far cheaper - like commonly 40-60% or more assuming no new ducting is needed - than two units, so be sure to consider that possible savings.

A newer larger unit replacing your existing one, if it is older, would also have a higher operating efficiency so you would have some A/C season power savings there too unless this house is quite strung out so the conditioned ari run to where the new unit is planned would be inordinately long and result in a lot of heat/cooling losses.

Electrical contractors can give you a quote on this, given the nameplate info off the new unit - some heating and A/C contractors installing such a unit will also handle the wiring (usually by hiring a subcontractor).

Answered 2 years ago by LCD

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