Heat pumps and 3 phase

[bushmanpat]

Do all heat pumps require 3 phase power? I'm thinking of one for a ground sourced water to water hydronic floor heating system. And any extra info on 3 phase would be appreciated as I'm a bit of nubie re: electricity. :ohcrap:

cheers

[Smurf]

In short, no. Generally the larger units are 3 phase. For household use, you ought to be able to get a single phase unit that's big enough unless it's a pretty large house.

Note also that, and this varies from area to area, the term "heat pump" most commonly refers to a reverse cycle air-conditioner and does not specifically mean a ground sourced unit (though they too are heat pumps). Bit like how the word "automobile" most commonly means a car but by definition includes any road vehicle with an engine.

So be careful when getting quotes that the "heat pump" really is a ground sourced system and not an air sourced unit if that's what you want to buy.

If you do decide to go for 3 phase, you WILL need some signficant electrical work done. New cable run to the house and some switchboard work too. Check the cost of this and that there is 3 phase power out the front of the house (usually is but not in some situations especially in rural areas).

[bushmanpat]

The house hasn't been built yet, or even designed, so I have total flexibility with what I do. It is in a rural area, so not sure if 3 phase available. I'll have to check it out.
The system I'm looking at isn't really all that common in Australia because most Aussies live in a hot climate. But I'm in Lithgow, which is notoriously cold. I'm told a few people here have what I'm looking for. It might be a case of asking a few questions around town, and then knocking on some doors.
I'm basically looking at a buried ground loop, heat pump, and in floor hydronic system. If possible, I'll use it (in combination with maybe solar or gas) for the hot water.

[Smurf]

I'm pretty sure that you can get domestic sized ground source heat pumps in single phase. You shouldn't need any other heating source if it's done properly.

[moonos]

For large compressors, it is more efficient to use 3 phase. I think from memory that the 3 phase are also quiter (but I could be wrong)

[Smurf]

For large compressors, it is more efficient to use 3 phase. I think from memory that the 3 phase are also quiter (but I could be wrong)
Agreed. But single phase is still highly efficient compared to simply using an electric heater etc. 3 phase would be nice, but I wouldn't go to massive trouble (that is, expense) to put it in unless it's the only option. Easy if it's overhead mains out to the street. Not worthwhile in my opinion if it means major trench digging or the utility has only run 1 or 2 phases past the property.

Check to see what it will cost is my best advice. Then decide.

[woodbe]

It probably depends on the size of the unit required. When ours was quoted, the only unit that had enough power for the load only came in 3 phase. Luckily, we already had it, a previous owner must have run a machine shop in the basement or something...

woodbe.

[GraemeCook]

Some of the information that you have been given may be a little out of date.

The old non-inverter type of motors in heat pumps have now been almost totally superceded by the much better inverter types. The old heat pumps were either on or off; the newer inverter ones have the motor run at a lower speed when less heat is needed. This is much more efficient, quieter and more comfortable than the non-inverter style. Most, virtually all, inverter heat pumps are single phase. Even if you go single phase you will still need an extra power circuit as they require a lot of capacity at start-up.

Some models will allow you to run the domestic hot water off the same heat pump as the house heating. This is normal in America & Europe, less common in Australia.

We looked at hydronic geothermal heat pump four or five years ago but gave up for two main reasons.
* cost of buried/drilled heat exchange loop was exorbitant, and
* suppliers were few and all orientated to commercial installations, not domestic.

Still the hydronic geothermal heat pump efficiency factor of from five to eight is still very attractive when compared to conventional heat pumps factor three and gas/electricity just under one.

Keep us posted, please.

Cheers

Graemefile:///C:/DOCUME%7E1/Graeme/LOCALS%7E1/Temp/moz-screenshot.jpg

[bushmanpat]

Thanks guys.