Isolator vs Transfer Switch for generator (or both)

[AJB Temple]

This is an elaboration of a previous question.

It is my intention to have a smart meter installed and an isolation switch at the same time. Just waiting on a date.

However, given three days of storm power cuts I am now also thinking of adding a transfer switch so that my 8Kw petrol generator (16amp and 13amp outputs) can be plugged in to the main house CU (limited circuits, no EV and kitchen is on a separable circuit with its own RCBO and CU). Supply is 100amp single phase, T-N-CS.

I am wondering if a transfer switch would in effect do the same job as an isolator? At first sight at least it seems logical as the purpose of the transfer switch is to prevent generator power going back down a supply line. Obviously if used as an isolator, then the generator would not be plugged in.

Generator is an outside Honda unit, pull start rather than auto. Clearly put in a suitably ventilated place.

The main house CU is important mainly to run the sewerage pump, oil central heating starter and pump, and LED lights. Not necessarily a high load.

All wiring is modern (2018 and 2020) and full RCBOs. All Hager.

 

[James]

100 Amp single-phase Generator Changeover Switch Power Transfer 2 Pole

100 Amp Changeover Switch 100 Amp Power Transfer Switch 3 Position 2 Pole IP65 Dust & Splash Proof Suits L,N&Earth 240V Single Phase Supplies Single Phase use only Height 240mm Width 160mm Depth 165mm case (205mm approx including switch)

www.justgenerators.co.uk

let the smart meter guy fit the isolator,
after that is done, you are free to take the tails from the outgoing side of the isolator and put it into the changeover switch.

 

[brianmoooore]

Needs a mains isolator AND a change over switch. Isolator to be switched 'off' before C/O switch is turned to 'generator', and left off until after C/O switch is turned back to mains.
Also note that you will have to supply your own earthing arrangements, which will probably be TT.

 

[AJB Temple]

Thanks guys. Very helpful. Yes. I had realised I would need to install a TT earthing system. We already have one for the EV charger, but not in a convenient location. I have two four foot rods in stock and plan to install both a short distance apart using an excavator when I put some footings in.

For a transfer switch I think I prefer not to use a rotary switch as other people can find these confusing and it may not be me operating it. I will obtain an IP68 enclosed switch, and install that outside adjacent to the meter box within another weatherproof enclosure (just to be on the safe side) with a protected permanent socket for the generator (which is in fact 13/32 not 13/16 as I originally typed).

Our energy supplier is Octopus and they are truly hopeless at getting back to us re fitting a smart meter and isolator. The DNO is not interested and there are no seals on the incoming fuse, which they don't appear to care about either.

 

[brianmoooore]

The consequences of the generator 'feeding back' into the mains can be fatal to DNO personnel. A change over switch is required, and the isolator is there to back up that switch in case of failure.
How is a rotary switch confusing, especially if it is labelled 'generator' and 'mains'?

 

[AJB Temple]

It is not confusing to me. However, we have rotary switches on the boiler and sewerage plant isolators and both my wife and (German) in-laws say they find these confusing.

I am aware that feedback must be avoided. I referred to exactly that in my original post.

None of this is an issue if I am around. However, when we had the recent 3 day power outage I was in hospital and despite training and clear labelling ( I produced a laminated start up and connection guide) on the generator, no one was able to operate it. I need to make things very simple to avoid confusion, especially as the users are used to German plant (3 phase in their case) and German labelling (I will do it in both languages in future).