Combi Boiler - Hot Water

[WoodenPlank]

Hi all

Signed up in the hope of some help.

I have a newly installed (1 month ago) Worcester Bosch Combi Boiler (30i) converted from a vented system.

The problem is that the hot water cuts out after a few minutes. No errors are seen on the boiler, no reset is needed and no increase in temperature prior to it cutting out. (i.e. pilot light goes out). If nothing is done, after a minute or so the boiler will fire back up and hot water will be delivered again.

This is noticed most clearly in the shower due to time in use, but also at the kitchen sink. The only other taps in the house are the bathroom taps.

WB have come out three times and unable to figure out what's going on. Things tried:

• Temperature sensor replaced
• Control panel replaced
• Power kW reduced
• Flow restrictor replaced (the wrong one was apparently fitted to this boiler)

Another WB guy is coming over this week, I'm losing faith a bit or wondering whether this is the boiler, or whether there's a reason to think it's the pipes?

Any thoughts would be very welcome, at the very least I can ask them to check later this week!

Thanks

 

[ianmcd]

Possibly a mixer tap or thermostatic shower cartridge failure (and your boiler does not have a pilot light )

 

[JohnD]

converted from a vented system.

How much time did they spend flushing out the old sediment from the system?

Have you got a magnaclean or similar system filter?

 

[WoodenPlank]

Guys,

Thanks for the replies

Possibly a mixer tap or thermostatic shower cartridge failure (and your boiler does not have a pilot light )

We had an old power shower that is now isolated (valves closed) and not in use anymore. The shower (just the tap at the end of the bath with shower hose attached) and the kitchen sink are old mixer taps - I will investigate that

How much time did they spend flushing out the old sediment from the system?

Have you got a magnaclean or similar system filter?

They spent a separate day power flushing the system. We also have the Worcester Bosch Magnetic System Filter fitted

Thanks

Plank

 

[martyndc88]

How hot does the water get before cutting out ?
What temp does the boiler display show before cutting out ?

You can isolate the hot supply by turning the fourth flat headed isolation tap (from the left) under the boiler. (6mm spanner works better) isolate this and see if any water keeps running from your hot taps

Although I'm sure the WB engineers would have tried this

 

[WoodenPlank]

Hi,

It gets to ~60 degrees (at least, scalding without cold water mixed in!); temp on the boiler is set to 60 and the boiler displays 60.

I didn't mention in my original post, but we get hot water happily for a few minutes before it cuts out - not only that but it doesn't happen every time. Perhaps during 50% of the showers the boiler cuts out

Thanks

Plank

 

[martyndc88]

Hi,

It gets to ~60 degrees (at least, scalding without cold water mixed in!); temp on the boiler is set to 60 and the boiler displays 60.

I didn't mention in my original post, but we get hot water happily for a few minutes before it cuts out - not only that but it doesn't happen every time. Perhaps during 50% of the showers the boiler cuts out

Thanks

Plank

The boiler won't display 60, it will display the primary flow temp which will fluctuate up and down. Run a hot tap and keep an eye on this display.

 

[WoodenPlank]

Yep that's right I should have been more clear. It does fluctuate, above and below 60 but averages around 60 during operations. When it cuts out it I think its always below, I.e. 45-50

And regarding isolating hot water yes the WB guys have done that

Thanks

Plank

 

[martyndc88]

If it's cutting out around those temps you'll be getting around 35-40 degrees it water from your taps. Is that about right ?

I'm thinking the hot and cold pipes have been connected the wrong way around to the boiler.

 

[algas]

May be the shower flex if you have one they kink inside and reduce the flow, also could be the shower head not passing enough water so the boiler overheats and temporary shuts down, same with old taps that are corroded inside and don't open up fully

 

[rad33]

"If nothing is done, after a minute or so the boiler will fire back up and hot water will be delivered again."

Does this mean you just let the water flow and hot water will come back again?

 

[WoodenPlank]

Thank you all for the replies. I'm really grateful.

If it's cutting out around those temps you'll be getting around 35-40 degrees it water from your taps. Is that about right ?


I'm thinking the hot and cold pipes have been connected the wrong way around to the boiler.

I've not measured it, but it's scalding hot without mixing with cold water for shower. What other symptoms might occur if they'd been connected the wrong way round? If they have, obviously I need to be getting the installer back

May be the shower flex if you have one they kink inside and reduce the flow, also could be the shower head not passing enough water so the boiler overheats and temporary shuts down, same with old taps that are corroded inside and don't open up fully

Thanks for the thoughts. I think the taps in general, and corrosion is something I'm going to be investigating. The flex and shower head are pretty new and look kosher to me. However the cutting out doesn't look like it's due to overheating

"If nothing is done, after a minute or so the boiler will fire back up and hot water will be delivered again."


Does this mean you just let the water flow and hot water will come back again?

Yes that's exactly right. Water continues to be delivered, but obviously gets cold (i.e. as cold as cold tap) as the boiler is not heating it up. Eventually, in my own simple terms, it figures out hot water is in demand and starts heating up again.

 

[rad33]

I would try to replace the flow sensor as it may be faulty.
Looking at the parts, yours has wires coming out of it. If you can figure out a test for it and see what's happening when tap is on and hot water turns to cold.

 

[WoodenPlank]

Thanks again for all the replies

WB engineers came today. 2 of them this time!

They were here for a while. Apparently they now think the cause is that the cold water coming into the house is too warm. 22 degrees. Not sure I fully understand the logic, but they all they have done is reduced the power of the boiler again. Will monitor for the next week or so and see what happens...

 

[ianmcd]

well get more biscuits in because that is absolute rubbish