Boiler isolator on kitchen grid switch

[Stuckinarut]

Yes, Because the installation instructions state that a 3amp fuse is required.

https://www.draytoncontrols.co.uk/sites/default/files/2024-04/LP112%20%28U.%26I.%20Guide%29.pdf

Boiler mi's usually state it too.

I have seen programmers fried because a 13amp fuse was left in the isolator FCU and a short occurred on the heating thermostat.

So the fuse protects the cable up and downstream, or just downstream?

 

[Taylortwocities]

From the spec, the contact rating is max 6amp or - I guess 2.5amp inductive. (I’m supposing that’s what the figure in bracket is). So a fuse less than the rating is necessary.
Other Diadem models have larger contact ratings. See the TLC document!

 

[Taylortwocities]

So the fuse protects the cable up and downstream, or just downstream?

Electricity isn’t exactly like water!
When there is a load on a circuit, the lowest fuse/MCB etc is the protection limit for the cable as well as the boiler, programmer, pump, valves, etc.

 

[EFLImpudence]

 

[Taylortwocities]

View attachment 362216

Whoops

 

[ericmark]

In days gone by, we would fit grid switches as freezers did not have an internal switch to defrost them and washing machines could go walk about if the weights came loose, and we are instructed items must be isolated elsewhere before working on them, so there is a need to isolate the boiler before the heating engineer does any work on it. However, in practice I note my guy works live.

For a portable appliance, the fuse in the plug protects the cable, this allows the use of thinner cable, however with a fixed appliance the manufacturer can stipulate what they want, be it a semiconductor fuse, a type A RCD, a MCB or a simple BS1362 fuse, it is their call.

In the main we aim to supply the whole of the central heating from one switched FCU or batteries, there are exceptions, like Nest Gen 3 thermostats often powered by a USB outlet, but this makes supplying the heating from UPS a bit of a problem, so we aim for just one common isolator for all the central heating.

The building regulations do stipulate heights of items needing manual manipulation and reading, it is claimed to be for the disabled, but easy for a wheelchair user to reach the floor, but to reach the wall at the back of a counter is rather hard, so the rules don't really make sense, and in Wales work in a kitchen is notifiable but not in England, so it all gets rather confusing.

We have Part P, L, F, and M which can all affect what can be done. And also BS7671 with is actually not law, but can be used in a court of law.

However, if some common sense is used, and the home is not rented, who will ever know if you don't comply with all the regulations and laws? I am sure we all break laws without even knowing we have done so. If renting OK then you have to be a lot more careful, but owner occupied, who will catch you?

 

[EFLImpudence]

however with a fixed appliance the manufacturer can stipulate what they want, be it a semiconductor fuse, a type A RCD, a MCB or a simple BS1362 fuse, it is their call.

Can they, do they?

You would think the manufacturer would fit a fuse in the product - like a boiler - if necessary. Oh, they do.

The building regulations do stipulate heights of items needing manual manipulation and reading,

They recommend.

If it is your house you can put them where you want.

 

[ericmark]

Can they, do they?

May be not with a boiler, but they do with other appliances.

 

[EFLImpudence]

Do you mean extractor fans?

 

[EFLImpudence]

And...

May be not with a boiler, but they do with other appliances.

Are they justified in doing so?

 

[ericmark]

Are they justified in doing so?

In the main yes, I worked on a batching plant, it arrived as 22 articulated loads, but since one wheels, it is portable equipment, the PAT test, or service as we called it, took three electricians a whole day.

We tend to assume everyone works on the same equipment as we do, and forget not all equipment is small, worked in Hong Kong on a tunnel boring machine, again technically a train, and again portable. Even if it had a 10kV supply.

Clearly on this thread we are not talking about machines so large, but the rules are designed to cover all, not just domestic, and many of the machines I have installed I had to make fit in the building and install the distribution units where they can be accessed, no point having a fuse against a wall, so the installer has to place the equipment so it can be maintained.

As to at what size one expects all to be included within the machine, and at what size we expect to have external control and protection not so easy to qualify. But we see some EV points where all is within the unit, and somewhere we expect a type B RCD on the feed. We see the same with PV installs, why should a boiler be different?