Combi Gas boiler

[Pete999]

I know sweet F all about gas boilers so I need some help, all of a sudden when running the Bath the H2O goes from hot to cold, been ok for yonks.

N power engineer turned up today, and is trying to blame the new bathroom,a direct replacement of the old, I had a bit of a barny with the gas bloke, can't see how a new bathroom ( which was put in about 8 months ago) could cause this, anyone got any thoughts?

 

[Spoon]

Does it do it every time you run the bath? If so then get the missus to run the bath while you check out the boiler, to see what happens.

 

[Barry White]

I know sweet F all about gas boilers so I need some help, all of a sudden when running the Bath the H2O goes from hot to cold, been ok for yonks.

N power engineer turned up today, and is trying to blame the new bathroom,a direct replacement of the old, I had a bit of a barny with the gas bloke, can't see how a new bathroom ( which was put in about 8 months ago) could cause this, anyone got any thoughts?

It will be the hot water thermister either silted up or faulty. N power chap just didnt fancy getting his pants wet as its cold today.

Ps we have a Plumber on hear now that seems like one of the better ones maybe he will give you better advice

 

[Pete999]

It will be the hot water thermister either silted up or faulty. N power chap just didnt fancy getting his pants wet as its cold today.

Ps we have a Plumber on hear now that seems like one of the better ones maybe he will give you better advice

Thanks mate, thats what he came up with after I told him in no uncertain terms he was talking out of his backside when he said it was the new bathroom.

 

[Silly Sausage]

the H2O goes from hot to cold, been ok for yonks.

Has the 2nd Law of Thermodynamics only just recently arrived in your bathroom?

Does this combi only do the bath water? What about all your other hot taps?
I'm a bit mystified.

 

[Pete999]

Has the 2nd Law of Thermodynamics only just recently arrived in your bathroom?

Does this combi only do the bath water? What about all your other hot taps?
I'm a bit mystified.

Bath, Kitchen sink ,washand basin and C/H

 

[Last plumber]

I know sweet F all about gas boilers so I need some help, all of a sudden when running the Bath the H2O goes from hot to cold, been ok for yonks.

N power engineer turned up today, and is trying to blame the new bathroom,a direct replacement of the old, I had a bit of a barny with the gas bloke, can't see how a new bathroom ( which was put in about 8 months ago) could cause this, anyone got any thoughts?

Is this just when running the bath ?
Or are other taps effected ?
Which boiler is it ?

 

[Last plumber]

If it's just the bath, is that because you're running it longer than the basin/sink etc ?

Sorry couldn't edit the above, probably my computer skills

 

[Pat H]

Its not an issue with mixer tap is it?
Mains pressure on the cold side slightly less than mains on the hot side due to the restriction of the boiler. Could end up with the cold pressure holding back the hot if the mixer exit is restricted. Limescale or the like.
If thats the case individual taps will work fine only the mixer one shows the issue.
You can test by running the hot tap of tge mixer only to confirm good hot flow. Slowly turn on the cold bit by bit. Eventually you may find the water loses all hot flow and is just cold.

Or as mentioned the boiler could have a fault but if so every tap should show that.

 

[Pete999]

Is this just when running the bath ?
Or are other taps effected ?
Which boiler is it ?

Glowworm 30cxi running the bath and sinks

 

[telectrix]

could it be the length of pipe from the boiler to the tin bath in the back yard that's causing the problem?

 

[Last plumber]

Glowworm 30cxi running the bath and sinks

I know I may upset you by asking this but I do need to, when you say sinks, are we talking about the wash basin in the same room as the bath or the kitchen sink ? Does this happen at all draw offs ?

Have you tried leaving the tap running a while after its gone cold or do you turn it off ?

If you turn it off try running it for two min just to see if boiler fires again.
( does the boiler actually go out or does it modulate down and keep running )

That particular boiler only needs 1 litre per min of flow to operate the flow switch and I am presuming you have more than that from your taps.

 

[Pete999]

I know I may upset you by asking this but I do need to, when you say sinks, are we talking about the wash basin in the same room as the bath or the kitchen sink ? Does this happen at all draw offs ?

Have you tried leaving the tap running a while after its gone cold or do you turn it off ?

If you turn it off try running it for two min just to see if boiler fires again.
( does the boiler actually go out or does it modulate down and keep running )

That particular boiler only needs 1 litre per min of flow to operate the flow switch and I am presuming you have more than that from your taps.

 

[Pete999]

1 kitchen sink 1 wash hand basin and 1 bath hot water at all three outlets runs cold after about a minute

 

[Pat H]

Got to be the boiler hasn't it?
Give it a bash with a big hammer. Unlikely to help but you'll feel better.

 

[Last plumber]

1 kitchen sink 1 wash hand basin and 1 bath hot water at all three outlets runs cold after about a minute

Definitely boiler I'd say. changeing bathroom shouldn't effect boiler, only if flow rate is lowered a lot but it would need to be so low you'd notice. I mean a trickle.

Get him back ( or someone who knows what they're doing ).
It should be pretty easy to check it out. There's only a few of things it could be really. ( presuming heating is ok that is).

 

[Pete999]

Definitely boiler I'd say. changeing bathroom shouldn't effect boiler, only if flow rate is lowered a lot but it would need to be so low you'd notice. I mean a trickle.

Get him back ( or someone who knows what they're doing ).
It should be pretty easy to check it out. There's only a few of things it could be really. ( presuming heating is ok that is).

Thanks mate, I had the service company out, umed and ahed, Bathroom is the problem, dipstick, went away after ordering a thermistor and a pump FOC i hasten to add.

 

[Pete999]

Thanks mate, I had the service company out, umed and ahed, Bathroom is the problem, dipstick, went away after ordering a thermistor and a pump FOC i hasten to add.

Heating is AOK

 

[Last plumber]

Thanks mate, I had the service company out, umed and ahed, Bathroom is the problem, dipstick, went away after ordering a thermistor and a pump FOC i hasten to add.

It can't be the pump. Pump does heating too. If it was thermistor, I'd expect it to be wrong temp e.g. To cool or to hot. Wouldn't normally fire, get hot and then go off and stay off. Sometimes if they are completely shot at, it might prevent it from firing altogether. That's my experience anyway. If I suspect one I normally ring tech line and they give different ohms readings at different temps as you probably know. Just to rule it out.

 

[Pete999]

It can't be the pump. Pump does heating too. If it was thermistor, I'd expect it to be wrong temp e.g. To cool or to hot. Wouldn't normally fire, get hot and then go off and stay off. Sometimes if they are completely shot at, it might prevent it from firing altogether. That's my experience anyway. If I suspect one I normally ring tech line and they give different ohms readings at different temps as you probably know. Just to rule it out.

Thanks F14 is the code but it corrects itself if you turn the taps off

 

[Last plumber]

F14 is high temp on heating flow.
Could be a number of things. You need someone to test it really.
I 'm not going to guess and get it wrong, sorry.

 

[Pete999]

F14 is high temp on heating flow.
Could be a number of things. You need someone to test it really.
I 'm not going to guess and get it wrong, sorry.

Thanks mate eng coming back next week will let you know

 

[Toneyz]

We had this problem every couple of years with our combi boiler was to do with hard water area BG engineer had something fitted which is cleaned out on service. Do you loose heating as well

 

[Pete999]

We had this problem every couple of years with our combi boiler was to do with hard water area BG engineer had something fitted which is cleaned out on service. Do you loose heating as well

No just DHW

 

[solarsavings]

With the heating off run the bath tap and leave it running while you go to the boiler. is --- firing? if yes, put your hand on the pipes underneath. One of them will be hot. That pipe will be the heating flow. If it is you have either a blocked plate heat exchanger or diverter valve problem. If the boiler is not firing then it might be the dhw thermistor.............but it could be something else.

 

[Pete999]

With the heating off run the bath tap and leave it running while you go to the boiler. is --- firing? if yes, put your hand on the pipes underneath. One of them will be hot. That pipe will be the heating flow. If it is you have either a blocked plate heat exchanger or diverter valve problem. If the boiler is not firing then it might be the dhw thermistor.............but it could be something else.

Well thanks for that

 

[valleybilly]

HW Flow switch or gas valve

 

[Pete999]

HW Flow switch or gas valve

Let you all know on Wed when the eng comes back

 

[Barry White]

Remember pete I said the thermistor was scaled up or faulty or the BULB needs changing

 

[Pete999]

Update. Gas eng been changed thermister, pump, stumped eventually called Glowworm help line, heat exchanger blocked. £450 for replacement and £600 for a system flush, so gettin on for a grand for repairs to a 10 year old boiler, going for new boiler. I had the exchanger changed 2 years ago, sod paying that money every couple of years