linking 1ph gen set to 3ph installation?

[knight1]

I am working on an installation which is soon to be changed form 1ph 100a TT to a 3ph TNC-S. They currently have a generator back up which starts up automatically on failure of supply.

Is it possible and within regulations to connect the generator to one phase of the new 3ph system?

 

[boatnik1]

I would think this would be out of order to just connect into one phase on the supply, but, if whatever circuits where critical could be run from a single phase which was through a seperate CB which was supplied via a contactor energised by the other two phases then you might get away with it just supplying this seperate phase.

Somebody else, not me, might be better versed in the regs on this one

Much better option would be to purchase a 3P Gen-set and offset the cost by selling the single phase unit.

There are quite a few used sets about and the cost is pretty similar for either a single or three phase set of equal KVA.

 

[baldsparkies]

The best way forward would be to install seperate distribution boards isolating essential and non essential supplies. You will also need a voltage monitered change over panel along with precautions as per dual supplies. Can't think of any regs that would prohibited single phase generators applied within a 3 phase install. Definately contact manufacturers regarding change over panel requirements, now your going to 3 phase mains. The most critical consideration is correct segragation of generator supplied circuits, as said check with generator suppliers on this one regarding the c/o panel, that is a must.

 

[Guest123]

Theres no reg against it but you need to be really careful with how you do it.

Never been keen on this arrangement myself, what type of installation is it on??

The best way forward IMO is deffo a 3P geney, everything all nicely balanced and rosey.

 

[baldsparkies]

Theres no reg against it but you need to be really careful with how you do it.

Never been keen on this arrangement myself, what type of installation is it on??

The best way forward IMO is deffo a 3P geney, everything all nicely balanced and rosey.

All things considered would take Lenny's advice. When you weigh up the costs involved to make the system safe for use, its an uphill struggle, it would be best to start from scratch as said, although your changeover would take care of the phase balancing when going from 3 phase mains to single phase generated supply ie linked change over contactor with mechanical lockout.

 

[Guest123]

A lot of this would depend on what type of install this is and wether ther are any critical circuits to think about.

At the mo everything is single phase so you will be replacing DB's and balancing out circuits I'm guessing. If it is at all possible to get all the circuits that need the geney back up on one phase safely and harmoniously with regard to the other two phases when mains powered then all well and good. With the correct switchgear and monitoring devices and labels all should be well.

But as I sais previously 3P setup would be my initiative.

 

[baldsparkies]

A lot of this would depend on what type of install this is and wether ther are any critical circuits to think about.

At the mo everything is single phase so you will be replacing DB's and balancing out circuits I'm guessing. If it is at all possible to get all the circuits that need the geney back up on one phase safely and harmoniously with regard to the other two phases when mains powered then all well and good. With the correct switchgear and monitoring devices and labels all should be well.

But as I sais previously 3P setup would be my initiative.

Agreed, more practical and probably the cheaper option.

 

[knight1]

Thanks for the advice. The installation is domestic, rural. 3 buildings, House, Pool House(with heating & kitchen), and garage(incorporating snooker room with electric heating, 8kw sauna). The Pool House has just been built and can quite easily use 65A on it's own. There are no real 'critical' circuits I guess, it's more inconvenience as in the past the have had power cuts.

I think I will take your good advice and suggest a 3ph gen. The 1ph link was a bit worrying.

Regarding the balancing, this is another question as the only area I feel I could breakdown between phases is the house. The Pool house is fed by 25mm 3c swa, the garage by 16mm 3c swa. all from the existing previously 'homemade' distboard. Any suggestions? I was considering using a phase for each building but balancing the house as much as poss. using an MEM board with RCBO's.

 

[boatnik1]

It all sounds like a nightmare balancing act, 65A in the poolhouse, 35A in the garage/sauna, and possibly nothing in the house if everyone is in the leisure buildings. It would be sort of pointless to split the house into 3P if the others were on 1P each. better to wire each area as 3P inc. 3P water heaters and pumps in the leisure areas.

A generator trying to sort that lot out would have a heart attack.

I'd hate to be paying the electric bill for that lot at our current N.I. rate of 15P/unit +VAT and service charge.