Browse Forums General Discussion 1 Jun 01, 2007 9:37 am Hi all,
I have no clue about this but we need to get the overhead powerlines to be relocated underground and Alinta gives us the option for single vs 3 phase. the latter is dearer by about $150 . Any ideas about the pros and cons of both? Any suggestions as to which ones I should opt for? cheers, VP Re: Underground powerlines- single or 3 phase? 3Jun 01, 2007 11:39 am Thank you.
I also thought that $150 would be nothing compared to future hassles. We do plan to have 1 or 2 airconditioners in the house. What needs to be conveyed to the electrician? apart form location for future wiring for A/C and do it in 3 phase??... correct me iF i AM WRONG. VP Re: Underground powerlines- single or 3 phase? 4Jun 01, 2007 12:12 pm I am a bit rusty on all this but I'll give it a go. Anyone who knows better, please chime in.
Not all AC units require 3 phase, most splits will be fine on single phase generally the ducted refrigerated units require 3 phase. 15A x 240V = 3600W on a normal outlet I think most lines comming into the meter box are 60A so you can drive quite a lot with single phase. Three phase will allow you to triple this but may well not be necessary. Remember that most AC units are quoted on their output power but it is their input power that matters in this case. Eg. an 8Kw unit may only actually draw 2.2Kw. From memory, 3 phase runs at 415V and when a single phase is tapped off, it is brought down to 220 or 240V. Bringing 3 phase to the home really means that you get 3 x 415V to your meter box which is then split up into 3 meters. The function may be combined into a single meter on the newer type but our rotating metal disk type required 3. I suspect that for most domestic applications, the voltage is brought down to 240V on all 3 phases but I am not sure. My brain hurts! 3xb Re: Underground powerlines- single or 3 phase? 5Jun 02, 2007 7:31 pm I have just read your post and would agree that 3 phase is certainly worthwhile for $150. The other thing to consider though is that you don't need to go 3 phase inside yet. You can have the 3 phase underground installed along with a meter, and leave the house running off 1 phase until you extend/renovate.
Another point is that you still only get 240 volts per phase. It is only when you test/connect between two phases that 415 volts is achieved. The main advantage of a domestic 3 phase arrangement is that the load of your appliances can be spread over 3 different supply circuits rather than just one. Hope this makes sense. Cheers Col Re: Underground powerlines- single or 3 phase? 6Jun 02, 2007 7:48 pm If I may summarise everything that been said:
1) For $150 dollars extra, get the three phase since there is no downside (apart from the small extra cost). 2) Only connect to one of the phases if you like and ignore the others until when and if you require to drive a large airconditioner or the like. If anyone has any technical questions regarding three phase versus single phase I can help you out. No question too small or large. Cheers, Casa Re: Underground powerlines- single or 3 phase? 7Jun 02, 2007 7:57 pm OK tech question:
I have 3 phase coming into my meter box. I have a 17.6kw ducted air con across 2 of the phases. Does this mean that the rest of the house is on the other phase? Could I have my theatre room on one phase and the rest of the house (incl air con) on another phase? Matt Re: Underground powerlines- single or 3 phase? 8Jun 02, 2007 8:23 pm mattwalker OK tech question: I have 3 phase coming into my meter box. I have a 17.6kw ducted air con across 2 of the phases. Does this mean that the rest of the house is on the other phase? Could I have my theatre room on one phase and the rest of the house (incl air con) on another phase? Matt (Odd to have two phases for the air-conditioning unit, but this is beside the point.) If you have three phases coming into the house with two phases going to the air-conditioning unit then it would make sense to drive the rest of the house off the third phase, but there is no technical reason to do so. You can take anything you want from any of the phases. If we look at the big picture it may help to explain why it doesn't matter what phase you connect to unless you have a two or three phase device. If you look in your street, assuming you have overhead mains wiring, you will see four wires on the power poles. (You may also have some higher wiring and this will be just three wires for the three phase power and these will be at a higher voltage). The four wires in your street are the three phases and a neutral. The supply authority will wire the first house to Phase A, the second house to Phase B, etc. Unless you have three phase power in which case they give you Phase A, B and C and the neutral. Houses are staggered on the phases to provide load balancing. It doesn’t have to be exact, but things run more efficiently for the supply authority if things are balanced. It doesn’t matter to the consumer at all. If you take everything off one phase, your neighbour will help smooth things out. When you connect between the neutral and any of the phases you get 240 V. If you measure the voltage between any of the two phases it will be 415 V (240 V x root 3). In summary, you can connect to any phase you want. Cheers, Casa Re: Underground powerlines- single or 3 phase? 9Jun 02, 2007 8:34 pm My mistake,
The AC unit is 3 phase. I misunderstood earlier... So it makes no difference then at all? Matt Re: Underground powerlines- single or 3 phase? 10Jun 02, 2007 9:06 pm mattwalker My mistake, The AC unit is 3 phase. I misunderstood earlier... So it makes no difference then at all? Matt That's right, put your three phase items on the three phases (obviosuly) and the rest on whichever phase or phases you like. Re: Underground powerlines- single or 3 phase? 11Jun 03, 2007 5:56 pm Here is what it comes down to
If you have underground power, do you want to dig it up yourself (it might be up to 1 metre deep!!) or pay someone to do it. hmmm, NO!! Correct Answer (can you guess what I have been doing this weekend except exchange power for watering system stuff.. ) $150 well spent. Overhead is different, but I agree still worth the $150. Adrian B Re: Underground powerlines- single or 3 phase? 12Jun 03, 2007 9:31 pm Casa2 mattwalker My mistake, The AC unit is 3 phase. I misunderstood earlier... So it makes no difference then at all? Matt That's right, put your three phase items on the three phases (obviosuly) and the rest on whichever phase or phases you like. all your single phase power circuits, ie. lights, GPO's, hot water , oven, hotplates etc would be balanced over the three phases. for example if you had 9x single phase circuits, your electrician would try to equally balance them over 3 phases like 3 circuits / phase. Anyhow this is your electricians job. Re: Underground powerlines- single or 3 phase? 13Jun 04, 2007 5:03 pm vpande Hi all, I have no clue about this but we need to get the overhead powerlines to be relocated underground I don't know why no-one else has mentioned it, but I think you'll find the total cost a bit more than $150. The 3 phase power will only be terminated so far. In the case of overhead to underground relocation this might be a case of disconnecting the overhead power connection point where it enters the house and then joining it onto the existing mains feeding the house. If the existing mains from the house connection point to the meter and switchboards is only single phase then the home owner is going to be responsible for this and may be quite a bit of money considering you may need switchboard / meter upgrades, additional cabling installed. Just thought I'd point this out. I can't see them hooking up 3 phase unless 3 phases have already been wired for. Re: Underground powerlines- single or 3 phase? 14Jun 04, 2007 6:03 pm thats a very good point
FYI i had 3 phase but on at my place, when building, and the whole lot including meter & run-in from dome came to $600. Re: Underground powerlines- single or 3 phase? 15Jun 04, 2007 8:08 pm A mate of mine has 3 phase in his meter box, but only a single phase A/C unit.
He got a sparky to wire up his A/V room to one phase on it's own, and spread the house, aircon & 15A garage power points across the other 2 phases. He reckons it's fantastic for getting rid of little clicks & pops & other interference noises from the A/V system, and well worth it. I know the missus can't stand me using the welder because it destroys the TV picture, but at his place, it's fine. 1 62025 Hi JW I just read your post and I find this situation quite strange. When we build, we get a temp pole for construction which becomes the permanent pole for one of the… 1 3947 1 4089 |