MCB tripping intermittently

[Buck Taylor]

• new build house 3 years old

• Cold water supply comes into the house at the kitchen

When turning the mixer tap on in the kitchen it sometimes trips the water pump, it does not trip the pump from any other point in the house either mixer or single tap.

I have changed the pressure reducing valve, renewed the mixer tap and fitted a non return valve on the hot outlet under the kitchen sink and replaced the 6a MCB.

Any help advice greatly appreciated.

 

[MFS Electrical]

you could always advise the customer to bath in the Clyde..

Bathe tel? But then again you scousers wouldn’t know about that.

 

[ferg]

The only time Scousers get near the bath is to nick the bubbles out of it.

 

[Silly Sausage]

The only time Scousers get near the bath is to nick the bubbles out of it.

That's when they're washing all the road dirt off their hands from all the wheels they've liberated.

 

[Buck Taylor]

So there's a 5A fuse and it doesn't blow?

Hi
Yeah 5amp fused switch next to pump, and has never blown.

 

[Buck Taylor]

To be clear now, you're saying the cold water feed to the pump IS direct off the mains supply?
If so, and next door is the same with the same fault, that's got to be the source of the problem.
Maybe there has been a change in the mains water supply pressure over the last six months.

All pure speculation of course!

PS, have you tried asking our watery friends on their forum?
Gas Engineer & Plumbing Advice Forum - https://www.ukplumbersforums.co.uk/

The cold water supply comes into the house in the kitchen and if I turn the tap on in the kitchen I get full pressure but the pump doesn't kick in.

It then goes through the PRV up to the water tank in the loft to then protect electrical devices! !
And that all makes sense.
I have changed the PRV, fitted a non return valve on the hot pipe to prevent any back pressure which could possibly stall the pump with a difference in pressure. and it only trips from this tap. Whether I use just the hot, cold or a mixture.!

 

[DPG]

The pump feeds the water tank? What are the other electrical devices that are connected? I'm confused. Is it just me?

 

[Generator]

Sorry, I'm missing a trick here - what does this pump do? Is it associated with the kitchen mixer tap? - if so, why? - it's elsewhere been called a shower pump!
Pumps are usually used to increase pressure - if so, what's the PRV for? Is there a combi boiler involved in this system?
Mixer taps are usually 'high' or 'low' pressure, depending on the pressure of the hot water supply - I've never heard of the need for a pump. Please clarify.

 

[DPG]

We aren't getting the full story here. Something is being deliberately missed out.

 

[Wilko]

We aren't getting the full story here. Something is being deliberately missed out.

Why feed a 5A fuse from a 6A mcb?

 

[Buck Taylor]

The pump feeds the water tank? What are the other electrical devices that are connected? I'm confused. Is it just me?

Apologies if there is some confusion, but do not intend to be nor am I hiding anything. If I turn on the cold tap in the kitchen it is from the main incoming water supply. (Hence no need for the pump to kick in) Every other tap in the house is supplied from the header tank in the loft and the pump kicks in. There is nothing else connected to the pump, and no combi boiler fitted either !

 

[Buck Taylor]

Why feed a 5A fuse from a 6A mcb?

Not sure but spoke with Grundfos and they say that this is correct?

 

[Buck Taylor]

I also changed the MCB to a type C as advised earlier?

 

[Wilko]

I also changed the MCB to a type C as advised earlier?

I have no clue how the pump has been plumbed, but I can comment on the electrical side and I might still be wrong . The MCBs will trip instantly if presented with a high enough current, which is what you are seeing. A B6A mcb will immediately trip with 18A to 30A, for a C6A it's 30A to 60A. Compared with perhaps a "usual" power circuit where a B16 will trip 48A to 80A and B32 will trip instantly with 96A to 160A. I don't know if the pump is busted, or if it's plumbed incorrectly, but I might try a science experiment with a B32 circuit and see if it pops the 5A fuse or runs.