Garage circuit tripping

[Milleniumaire]

I recenlty had a new consumer unit installed as part of an extension (including a new kitchen with lots of new, high powered appliances). The CU is a hager and has a 16A MCB for the garage circuit, which includes the boiler, unvented cylinder + emmersion heater, electric doors and 3 double sockets, one of which has a fridge freezer permanently plugged in.

When I try to use my Clarke Power Washer, while plugged into one of the garage sockets, it always trips the garage MCB circuit - every single time! I managed to get is started once and it then ran okay, but haven't been able to repeat this. If I plug the Power Washer into a utility/kitchen socket, which is on a 32A MCB circuit, it works fine. Prior to the new CU I never had this problem.

The electrician that did the work (at the recommendation of the builder) charged a lot more than was expected (even the builder was surprised), so I'm reluctant to use him again. However, as he is familiar with my setup I've asked him to give me an idea of cost to resolve this issue and asked what he might do. His response was to arrange to come round and spend a couple of hours investigating the issue, then he would be able to tell me what the problem and solution is.

A couple of hours sounds excessive and costly to me. Clearly, the issue is with only the garage circuit and only the Power Washer causes it to trip. By the way, I had the Power Washer checked by machinemart as I had assumed it had an electrical fault. They told me there is nothing wrong with it!

Anyway, I was reading about Type B and Type C MCB's and to me as a layman, it would seem that replacing the hager 16A MCB Type B, with a 16A MCB Type C may resolve the issue according to some info on the TLC website:

"....for electric motors or low voltage lighting the use of a type B MCB may give unwanted tripping and the choice of a type C MCB will probably solve the problem."

I totally understand that I'm not qualified, but I get the feeling this issue has a simple solution and the electrician's suggestion that a couple of hours will be required is a little excessive.

Please feel free to put me in my place, but is there anything in the possibility of using a type C MCB? If so, I will discuss it with the electrician. I don't want to do this if it is a stupid idea

 

[EFLImpudence]

It seems as if you have deduced what the problem is but you should not just fit a C type MCB without ensuring the circuit is suitable. It probably will be but we can't tell from here.
It will need an electrician with suitable equipment to test or measure.
You may find a 20A or 25A B type would solve it - again depending on circuit.

As for all those items on a 16A Circuit/MCB - very bad design.
The immersion would normally have that on its own leaving a little for a small item.

Boiler and immersion on same circuit?

 

[Milleniumaire]

I may have got it wrong about the immersion heater being on the same circuit. I'll check when I get home.

My deduction is based on the fact that it is the startup of the Power Washer that is the issue, nothing else. I have gone through a lot of testing to determine this, ensuring EVERYTHING was unplugged on this circuit. I don't think it is a wrong assumption, but I agree, possibly switching to a higher rated MCB may also solve the issue. If a higher rated MCB is required, then surely this indicates the "wrong one" was used in the first place? But then, why do all my other Power Tools work okay and ONLY the Power Washer trips the circuit, and only the garage circuit?

Regarding the "bad design" comment, this enforces my thoughts that getting the same electrician back may be a mistake and I should try someone else, but according to these forums, most electricians are "cowboys", so I'm not sure how to find a "good one".

 

[securespark]

Yes. When you see the electrician maybe you could discuss this with him and suggest that he has installed an inadequate circuit for your needs.

A regular (assuming 2.5) radial is protected by a 20A MCB, so why he used a 16 I don't know, especially as the immersion is on this circuit and it is normally on its own (as EFLI pointed out).

If the spark knew about the loads to be connected to that circuit, he has cocked up, to my mind.

 

[EFLImpudence]

If a higher rated MCB is required, then surely this indicates the "wrong one" was used in the first place?

That may be taking it a bit far as he may have not known you had such a machine.

However, if the circuit is suitable for a 25A MCB then it was just silly/pointless fitting a 16A.

But then, why do all my other Power Tools work okay and ONLY the Power Washer trips the circuit, and only the garage circuit?

I do not know the specifications of the washer but am assuming it is inrush current tripping the 16A MCB which it would not do to the 32A.

Regarding the "bad design" comment, this enforces my thoughts that getting the same electrician back may be a mistake and I should try someone else, but according to these forums, most electricians are "cowboys", so I'm not sure how to find a "good one".

That's life. The only good ones are retired and on the internet.

 

[Milleniumaire]

securespark, I'm fairly sure the old CU didn't use anything less than 20A MCB's for any of the socket circuits, so that fits in with what you are saying and why I never had an issue with the Power Washer before. 5 x 20 is obviously higher than 5 x 16 and although not a huge difference, may be just enough to get the Power Washer started.

That's life. The only good ones are retired and on the internet.

It does appear that way

 

[ban-all-sheds]

That may be taking it a bit far as he may have not known you had such a machine.

But if he really did put the boiler, immersion heater, electric doors and sockets on a the same 16A circuit he's made precious little allowance for any machines.

However, if the circuit is suitable for a 25A MCB then it was just silly/pointless fitting a 16A.

Maybe it was a fully configured CU, with a bunch of 6/16/32A devices, and the LGFNG of an electrician CBA to swap any out?

 

[Taylortwocities]

The only good ones are retired and on the internet.

 

[ban-all-sheds]

 

[Milleniumaire]

The immersion would normally have that on its own leaving a little for a small item.

I checked last night and can confirm the emmersion is on its own 16A circuit, assuming that's what is meant by "Water Heater". The 16A garage circuit has "Central Heating" and "Sockets", but it also includes the electric garage door.

Interestingly (or not!) I noticed the "Ground Floor Lighting / Smoke Alarm" circuit uses a hager NCN 110A C10 MCB, which I assume is type C. All the others are Type B's. I assume this is because the garage is fitted with flourescent lights.

Looking at the hager website, they appear to sell a version of the type B MCB that has all the characteristics of the type C MCB!

 

[Taylortwocities]

Looking at the hager website, they appear to sell a version of the type B MCB that has all the characteristics of the type C MCB!

But the characteristics are NOT the same.
The essential difference is the box that is marked "curve". One is a B curve and one is a C curve and that is the key, important and essential difference.

This will explain it more. CLICK ME

 

[ban-all-sheds]

So will our very own Wiki....

 

[securespark]

That's life. The only good ones are retired and on the internet.

Didn't know you were retired too!

 

[EFLImpudence]

Oh, yes. I'm ever so old.

My little girl's 43

 

[securespark]

WTF is LGFNG??

It's not in all the cool trendy guides to internet slang...