Here is my scenario.
When I bought my house 4 years ago, we found it had an unused 3-phase supply. We later installed a RC Ducted air-con system and went with the 3-phase model. Power supply is from a street pole.
I am now planning on building two townhouses at the rear, keeping the existing house. This will mean I will need to install underground power for the townhouses as well as move the existing house to underground power. I have received a quote for 2 X Daiken RC Inverter Ducted a/c systems for the proposed rear units and the proposal suggested a 1-phase model. The equivalent 3-phase model is $660 more for each.
I have tried to get info from Western power regarding costs of moving to underground power and relative costs of 3-phase vs 1 phase, but they have requested I get an electrician to complete the appropriate form and submit. However, I am just in the planning stage and just want to see what the relative costs are, rather than apply for a particular configuration.
I know little about electrical issues so any help with some of these questions or other guidance would be appreciated.
1. I assume I have no choice but to go with 3-phase for the existing house when I convert to undergound. I have read on the web where 1-phase devices can run from a 3-phase source, but not vice versa. The existing air con is too new to replace.
2. If I have 3-phase for the existing house supplied from the new underground green dome, would I be right in thinking that 3-phase should then be available to all the units, so long as the correct cables are run to the new units from the dome. So the cost of providing 3-phase to all three units shouldn’t be much different to providing it to just one unit and having the new units on 1-phase.
3. I have read that 3-phase air con units are more efficient than 1-phase. Is the increased efficiency sufficient to justify paying $660 more per a/c system, in addition to any other costs identified in question 2.ChittasParticipant@chittasJoin Date: 2008Post Count: 7
Being a Sparky myself can give you some advice on your questions…
1) Yes your assumptions are correct that single phase appliances can run off of a 3 phase system and not visa versa. A single phase appliance uses one of the phases of a 3 phase system, where a 3 phase system requires all 3 to operate.
2) 3 phase is available at the dome and will be available for all of your buildings, The cost will be a little more as you will be buying a different type of cable with 2 extra cores inside, plus your meter box will need to be fitted with 3phase circuit breakers and meter etc, Not a huge cost but still a cost.
3) The new inverter type air conditioners are very efficient, quiet and do just as good a job if not better as a 3 phase unit. I have found as long as you buy a reliable and well known brand of air conditioner your generally cant go wrong, I
As far as the suitability for 3 phase to go onto your town houses i personally don’t think it is worth it. I have it my self and about the only thing i’ll be using it for will be for my workshop when I get around to building it (And thats mainly because I’m a sparky and more power I have available the better )
I hope this has helped.
Thanks J4son. That has been a great help.
Just to make sure I have got the correct meaning….
When you wrote “and do just as good a job if not better AS a 3 phase unit” do you mean that the Daiken is better when configured as a 3-phase system or that 1-phase is as good as if not better THAN a 3-phase. I can read it either way, so I’m not sure which you meant.ChittasParticipant@chittasJoin Date: 2008Post Count: 7
Yep sorry, Single phase is just as good if not better THAN a 3 phase unit. Technology has come along way, especially with the Inverter systems in terms of operation efficiency. But thats just my opinion. If your still unsure speak to somebody who works with them on a daily basis.
Thanks once again.mhopMember@mhopJoin Date: 2010Post Count: 1
For a residential house you generally do not need 3ph unless you have a large AC units or have a workshop and want to say do some serious welding. Single phase circuits can handle up to 32Amps, and mosly less, If you need more than than you will need to go 3ph.
You say the Daikin AC unit is fairly new so suggest you keep 3ph for the house, and only provide 1ph to the other places.
These days you should only ever get a inverter type AC system for residential applications, they are more energy efficient and keep closer control of temperatures.