Boiler plugged into switched socket

[dawnfrances@outlook.]

hi does anybody know the regulations on combi boilers they have fitted a new boiler sent a gas engineer to wire up thermostat and wired it to a plug that is in a double socket with switches is this safe

 

[Madrab]

Why did they send a gas engineer to wire up the thermostat, should have been an electrician?? The gas engineer should have been the one that fitted and commissioned the boiler.

Best practice is to wire everything that sits on the boiler to the same Fused Spur, that ensures that everything has a single safe point of isolation. Dangerous to do it any other way IMO.

Tell them you're not happy with that and want it done properly.

What make and model of boiler is it?

 

[oldbuffer]

It is permissible to wire to an UNSWITCHED socket, although as Madrab points out, a single fused spur for all boiler connected electrical items is by far the best option. The reason for an unswitched socket is that the plug must be removed to disconnect the boiler, and this disconnects both live and neutral. If a switched socket is used:
1. There is a risk of turning the switch on again, making the system live.
2. Even if turned off, there is a risk that a neutral fault / mis-wire could leave the system live with respect to earth. It is only relatively recently that some (but not all) switched sockets are switched in both live and neutral lines.

 

[dawnfrances@outlook.]

They have wired it to a plug then plugged it into a double socket with 2 switches the gas engineer wired the thermostat but is not an electrician

 

[ericmark]

It is clearly good to have all central heating powered from one socket, I favour a socket, as it allows the use of an alternative supply during a power cut, but unless a cover is fitted,

it can be unplugged in error, however to isolate a FCU it needs a double pole switch, with a means to lock off, removing the fuse and putting a lock through the fuse holder will stop it being powered up, but both neutral and line are considered as live, and lock through the fuse holder leaves neutral connected, and a lock on the plug

is more universal to a lock on the switch of a FCU.

If the supply is TN-C-S then isolation is not so important, switching off is often as good. But with TT then isolation of both live wires is more important.

Having said that, my central heating is now all on a single switched FCU. Which is supplied from an UPS, so I have no need to supply from a generator etc. It would not be permitted for me to supply boiler from a plug and socket as the supply is not protected by a RCD, there is automatic disconnection with an earth fault by the inverter, but it does not comply with the correct British Standard, so the sockets from same supply for freezers, are RCD sockets.

I have criticised the use of USB supplies to Nest Gen 3 thermostats, as unless the USB supply comes from the same supply as the boiler, the boiler will fail to run during a power cut, as no power to the thermostat. Either items supplied from the single socket or FCU or from batteries. Powered from a USB adaption is the same as any other second supply to a thermostat.

This is written from an electrical engineer's point of view, so in conclusion I would want a lockable cover over the plug and socket, even a tie wrap is good enough, does not need to be a lock, but nothing wrong having boiler fed from a plug and socket. In fact, some advantages, but also nothing wrong using a FCU.

Technically, my FCU does not comply, as can't lock it off. Can't even fit a lock on the RCBO, as it comes direct from the inverter. I could feed it from a RCD socket, looked at using a RCD FCU but could not find a type A RCD FCU. As to switch, clearly if using a RCD FCU or RCD socket, the test button doubles as an on/off switch, so no option, has to be switched.

 

[CountryFan]

The way I read this: gas engineer has wired up the thermostat to a plugtop and fitted to a double socket outlet - regards safe it would seem safe, but impractical, as you lose a socket and isn’t isolated when the boiler is. The gas engineer doesn’t have to be an electrician to wire up a thermostat, I do these all the time and I’m not an electrician and am a gas engineer.

How is the boiler wired @dawnfrances@outlook.? What type of thermostat? Could you also answer @Madrab’s question?

What make and model of boiler is it?

 

[JohnD]

1. There is a risk of turning the switch on again, making the system live.
2. Even if turned off, there is a risk that a neutral fault / mis-wire could leave the system live with respect to earth. It is only relatively recently that some (but not all) switched sockets are switched in both live and neutral lines.

The same arguments apply to an FCU

So what's the real reason you don't like plugs?

 

[ericmark]

It is permissible to wire to an UNSWITCHED socket

Why the capitals for unswitched? In fact, why even say unswitched? I will admit I see very little advantage on a switch with a socket, but any RCD socket is clearly switched, as with an RCD FCU, so there are cases where we have no option but to include a switch.

2. Even if turned off, there is a risk that a neutral fault / mis-wire could leave the system live with respect to earth. It is only relatively recently that some (but not all) switched sockets are switched in both live and neutral lines.

This means a FCU is a non-starter. Can you see the problem, in case you can't, it is switched on, so neutral not isolated, this works be it a switch, switched FCU, or socket. And it can also be locked on, of course. Fan isolators come with locks, ⁣but

not seen the method to lock off a switched FCU yet, other than as shown. One could use a grid switch, so lock and fuse, but nothing wrong with plug and socket.

Best practice is to wire everything that sits on the boiler to the same Fused Spur, that ensures that everything has a single safe point of isolation. Dangerous to do it any other way IMO.

Who says, and why? The single point of isolation is always available, all consumer units seem to have an isolator, not worked out why? As to work on it, HSE rules say isolate elsewhere. Yes, I know we do use the one in the consumer unit, and to have to turn off the whole house, is rather inconvenient, however it is still the single point of isolation with most homes, not mine, you can turn off the main isolator and the boiler will continue to run, in fact you can draw the DNO fuse, and it still runs, I expected some comment from guy changing the meter, that central heating still running, but he did not say a word, maybe more common than I thought?

 

[Madrab]

Who says, and why?

The manufacturers - they ask for a single point of isolation of any and all controls connected to the boiler and where possible sited next to the appliance. Others say the connection can't be more than 1m away from the appliance. I've yet to come across an installation where the isolation point couldn't be sited next to the boiler, with some extra cabling if needed. Rarely is the boiler sited next to the domestic CU.

Some manufacturer do suggest that either a double pole fused connection unit or an unswitched socket and fused plug can be used, others don't suggest the plug option but do stress the double pole, some specify that if the appliance is located in an area that could be damp, a fixed connection must always be used. So I always default to use a FCU with neon, also so it can easily be seen the supply is energised.

 

[ericmark]

Single point of isolation is covered with plug and socket, as to unswitched socket, that seems rather odd, as we seem to be moving more and more towards being able to switch off before unplugging.

It is like the EICR saying we must inspect anything not classed as portable, so we must remove covers for the electrical connection on boilers during an EICR. There is a valid excuse if it clearly says to be removed by gas safe registered personal only, but I have not seen anything like that.

Personally I feel an appliance is tested with the inspection and testing of in service electrical equipment, and the EICR only covers the installation, not current using equipment, our testing stops at the socket, but when a FCU is used, then we need to test the equipment as we know most PAT testing done with a PAT testing machine, so will not be done by that person.

So using a FCU does open up a can of worms.

 

[bernardgreen]

If the boiler is supplied by a plug in a socked then removing the plug will provide perfect isolation but at the same time it will remove the Earth connection. This could leave the boiler and metallic pipework without an effective Earth.

 

[Jurassicspark]

it will remove the Earth connection. This could leave the boiler and metallic pipework without an effective Earth.

Not a problem as the pipework will be connected to earth somewhere.

That's why a boiler flame rectification still will function even if there is no earth at the plug/fcu. It can take parallel paths such as the mains water/gas bond.

 

[Madrab]

So using a FCU does open up a can of worms.

I'm not an electrician so this is dipping into an area that I'm not qualified in so cant really argue the merits for and against but I'm sure the manufacturers will have covered all that off as part of their compliance with all the relative UK/EU standards. If they didn't then they couldn't and wouldn't ask for it.
I certainly don't think they have something fitted that would be in any where controversial nor comply, as that would leave them open to all sorts of trouble and litigation.

 

[ericmark]

We talk about a single point of isolation, but my home does not have one. I have four, one for the DNO supply, two for the DC supply from the solar panels, and one for the UPS supply from the solar panel inverter.

When one thinks about it, the whole idea of an UPS, is so we don't rely on a single point.

Since my central heating is supplied by the UPS, it is important that parts are not turned off with a power failure, in fact a number of items are, my router, and two hubs, plus a socket adaptor which doubles as a signal booster. I am sure the central heating will continue to work, although not as well, when these items fail in a power cut, but however much we strive for a single point of isolation, today something is still likely to have another feed from somewhere.

 

[Harry Bloomfield]

Since my central heating is supplied by the UPS, it is important that parts are not turned off with a power failure, in fact a number of items are, my router, and two hubs, plus a socket adaptor which doubles as a signal booster. I am sure the central heating will continue to work, although not as well, when these items fail in a power cut, but however much we strive for a single point of isolation, today something is still likely to have another feed from somewhere.

It would be usual to add notices, when there is more than once source of supply, feeding an item.

My entire heating system, is fed from one MCB. That feeds a DP isolator in the airing cupboard, where the main control and terminal unit is located, that is connected to the boiler in the kitchen, via ebus which is also provided with a DP isolator.