3 phase planning

[DaveH]

I have a new 3 phase connection going into my build shortly. There will be no 3 phase equipment initially - it was more about future proofing as the extra cost was very little over a single phase install.

 

My Sparky is being very slow at getting back to me so I thought I'd turn to the collective knowledge on here in the meantime. I've not dealt with 3 phase before so any advice is appreciated. Are there any good deals to be had on 3 phase boards at the moment? I will also be running a separate, smaller 3 phase board in the detached garage. Any particular best practice to follow? Pitfalls to avoid?

 

Thanks in advance

 

[joe90]

I have lots of woodworking machinery in my workshop and it’s all single phase, however I am considering a two post lift for my car restoration and all the second hand ones on Ebay are 3 phase ?.

[PeterW]

If you’ve not already done the connections I would take the 3Ph to the garage and run a single phase back to the house. Other than incidental stuff like induction hobs, house loads are usually much smaller than garage loads such as machinery and having the hassle in the house of 415v potential and the other stuff isn’t worth it in my opinion. 

[Nickfromwales]

10 minutes ago, joe90 said:

I have lots of woodworking machinery in my workshop and it’s all single phase, however I am considering a two post lift for my car restoration and all the second hand ones on Ebay are 3 phase ?.

I'm sure you can get single phase to 3 phase convertors. Dont quote me on it though  

[Nickfromwales]

6 minutes ago, PeterW said:

If you’ve not already done the connections I would take the 3Ph to the garage and run a single phase back to the house. Other than incidental stuff like induction hobs, house loads are usually much smaller than garage loads such as machinery and having the hassle in the house of 415v potential and the other stuff isn’t worth it in my opinion. 

Much cheaper on CU's ( consumer units ) then too  

[PeterW]

7 minutes ago, Nickfromwales said:

I'm sure you can get single phase to 3 phase convertors. Dont quote me on it though  

 

You can, but they are eye watering in price for anything big - £6-800 last time I looked. 

[Nickfromwales]

1 minute ago, PeterW said:

 

You can, but they are eye watering in price for anything big - £6-800 last time I looked. 

Not that bad if it saves you a few £k on a new lift  

[Jeremy Harris]

8 minutes ago, Nickfromwales said:

I'm sure you can get single phase to 3 phase convertors. Dont quote me on it though  

 

 

You can.  My old compressor ran on one for years.  New they are pricey, but I picked up an old second hand one pretty cheaply.  All that was in it was a transformer and some big capacitors, IIRC, plus a starter relay that switched in extra big capacitors to handle the motor start load.

[joe90]

13 minutes ago, Nickfromwales said:

I'm sure you can get single phase to 3 phase convertors. 

Yes but as Jeremy says, new, they are pricey so not sure it’s worth it.

[LA3222]

@DaveH I have had a 3ph connection put in.  My set up at the minute is that a Hager 4 way distribution board is installed in an external kiosk.  I then intend to have sub mains (seperate 3ph distribution boards) elsewhere - I.e. I will run a 3phase connection to the garage where I intend to have a 3ph electric car charger, and then another to the house. 

 

As an aside I don't know the extent of your knowledge but you can run single phase connections out of the board as well - I.e. a 4 way board gives you 4 x 3phase O/P or 12 x 1phase O/P or any combinations therein.

 

I currently have a single commando socket connected with a 16a Hager RCBO in the board.

 

I settled on Hager as a decent quality make for all things electrical - no other reason than I'd seen it mentioned on here a few times.  My sparky seemed to agree Hager is good.

 

As far as cost - yeah 3ph boards are more expensive than single phase but in the grand scheme of a self build I see little impact on the overall spend.

[scottishjohn]

the ramps in my garage have motors that can be wired either single or 3 phase

ramp only need a 2hp motor so --so a single phase 2 hp is no problem 

I ,ll sell you one if you like !!

2 poster hoffman 3ton

[ProDave]

I would echo the recommendation to get the 3 phase incoming supply terminated in the garage and have a small 3 phase board there. Then a single phase submain to the house and have the house just on 1 phase.

 

Single to 3 phase converters are not brilliant. The transformer and capacitor ones are a compromise and not all loads like them, the other sort is a rotary converter (motor / generator)  Surely someone must make inverter converters now as well (think variable speed drive at a fixed speed) But having the 3 phase in the garage means you don't have to bother with that.

 

Conversely I run my lathe on a 3 phase variable speed drive just driving a single phase motor, just because a previous employer was throwing one away.

 

Not all domestic electricians understand 3 phase so you might need to choose carefully. 

[scottishjohn]

you can get up to 5hp single phase motors  now 

 but iwill be looking at a 3phase supply if possible for new build  -for all my lathes ,millers ,welders etc

but with modern invertor tig welders you don,t need 3 phase anyway --just i have a 375 amp synchro miller tig machine

and the new units are much cheaper as well--you used to need 3phase to get good smooth welds at big amperages--not now with invertor 

 

Edited January 2, 2019 by scottishjohn

[joe90]

1 hour ago, scottishjohn said:

I ,ll sell you one if you like !!

 

That would be good but we are at opposite ends of the country!! , how much?

[scottishjohn]

6 minutes ago, joe90 said:

 

That would be good but we are at opposite ends of the country!! , how much?

£1000  can be seen working before you unbolt it to put in on your trailer

 

 not trying to put you off --but if you have the space +height i would go for 4poster with "wheel free" beams  if i was having one ramp only 

Edited January 2, 2019 by scottishjohn

[jamiehamy]

Single phase ?

[joe90]

https://www.ebay.co.uk/itm/2-POST-LIFT-CAR-VEHICLE-RAMP-HOIST-4-TON-NEW-999-18-month-warranty/321740808920

 

i am getting too old to crawl under cars nowadays.

 

?

Edited January 2, 2019 by joe90

[le-cerveau]

I have 3-phase installed at the house.  We have an 18 way unit in the plant room, that is 18 x 3-phase ways or 54 x single phase ways and there are only 5 spare single phase slots left!!

 

Everything is spread out on its own circuit with RCBO for all (except the fridge/freezer circuit).

 

This is the layout:

 

The Garage 3-phase supply is for future use (car charging) and is a 32A supply to support whatever come along.

 

I need to get the electrician to do some swapping of circuits/phases as L1 is lightly loaded and L2 and L3 have a heavier load, my induction hobs can draw 7.2kW each, in preparation for future battery systems (when prices drop to the appropriate level).

[scottishjohn]

15 hours ago, joe90 said:

https://www.ebay.co.uk/itm/2-POST-LIFT-CAR-VEHICLE-RAMP-HOIST-4-TON-NEW-999-18-month-warranty/321740808920

 

i am getting too old to crawl under cars nowadays.

 

?

wouldn,t have it as  a gift -no stabilising bars going front to back from 4 bolt bases to spread load from bases

£1000 brand new gives you a clue on the quality 

had enough garages +ramps and seen all the problems of ramps fitted to doubtful floors

you start swinging on a g/box and it is easy for them to come loose from floor 

If you are going use that --then floor needs to be minimum 8" with lots of weld mesh  and BIG bolts 

 

http://www.garageequipmentdirect.co.uk/contents/en-uk/d12.html

look at second one down --"boston " that is actually a hoffmann under different name --and is same set -up as ones i have -you can swing on it all day and it won.t tip over

Edited January 3, 2019 by scottishjohn

[jamiehamy]

1 hour ago, scottishjohn said:

wouldn,t have it as  a gift -no stabilising bars going front to back from 4 bolt bases to spread load from bases

£1000 brand new gives you a clue on the quality 

had enough garages +ramps and seen all the problems of ramps fitted to doubtful floors

you start swinging on a g/box and it is easy for them to come loose from floor 

If you are going use that --then floor needs to be minimum 8" with lots of weld mesh  and BIG bolts 

 

http://www.garageequipmentdirect.co.uk/contents/en-uk/d12.html

look at second one down --"boston " that is actually a hoffmann under different name --and is same set -up as ones i have -you can swing on it all day and it won.t tip over

Mine is secured with the stipulated 5nos. M18x160mm anchor bolts per side. 'swinging' on a gear box is more likely to disturb the vehicle on the arms and not going to make the slightest difference to the security of the posts. For something that takes 2t per side, if an 80kg human can pull it from the ground then I'd say you'd be lucky not to already have been flattened! 

[DaveH]

Thanks all. I had heard the Hager stuff was decent quality.

 

Regarding the suggestions to put the incoming supply to the garage and then a submain to the house - all the ducting is now in place to bring the supply into the plant/utility room and the cable is going in on Monday (Northern Powergrid are coming to excavate the main in the road tomorrow). I will be running SWA cable back to the garage to a separate smaller 3ph board as my intention is to install a ramp at some point and as some of you have pointed out, 3ph garage/workshop equipment can sometimes be easier to come by especially secondhand.

 

I always go over the top with the spec, although this does affect the budget somewhat! I like to futureproof! If I decide I want to use a standard single phase CU in the house is it acceptable to simply use one phase and leave the other two terminated? But also run all three back to the garage?

 

Any diagrams or photos of 3 phase installs would be much appreciated to help me get my head around it (so I know what I'm talking about when speaking to the sparky!)

[DaveH]

7 hours ago, le-cerveau said:

I have 3-phase installed at the house.  We have an 18 way unit in the plant room, that is 18 x 3-phase ways or 54 x single phase ways and there are only 5 spare single phase slots left!!

 

Everything is spread out on its own circuit with RCBO for all (except the fridge/freezer circuit).

 

This is the layout:

 

The Garage 3-phase supply is for future use (car charging) and is a 32A supply to support whatever come along.

 

I need to get the electrician to do some swapping of circuits/phases as L1 is lightly loaded and L2 and L3 have a heavier load, my induction hobs can draw 7.2kW each, in preparation for future battery systems (when prices drop to the appropriate level).

 

Thanks for that. That looks very similar to what I had in mind.

 

One thing I wasn't sure though - from a safety point of view are there any issues having multiple phases in one area? I have been advised so far to keep each floor on a separate phase.

[PeterW]

5 minutes ago, DaveH said:

ducting is now in place to bring the supply into the plant/utility room and the cable is going in on Monday

 

No issue there putting the main switch in the house and taking a single off the incomer and taking that into a standard CU and running a 4 core 10mm across to the garage sub main. 

 

Just because you have the 3Ph into the plant room doesn’t mean you have to use all phases in the house. 

[DaveH]

21 minutes ago, PeterW said:

 

No issue there putting the main switch in the house and taking a single off the incomer and taking that into a standard CU and running a 4 core 10mm across to the garage sub main. 

 

Just because you have the 3Ph into the plant room doesn’t mean you have to use all phases in the house. 

 

Thanks Peter

[Ed Davies]

If you have a three phase meter do exports on one phase (e.g., from PV) cancel imports on another? If not, as I suspect, then it's probably best that any loads likely to be running when any PV is generating be on the same phase as the PV.