Intermittent Hot Water

[laceypa]

This is probably an easy one to answer, and I will need to get a plumber to come fix the problem anyway but I just wanted to get an idea of the potential problem.
I have a Vokera combi boiler. We have no issues with the heating at all, which works fine. But the hot water through the taps is intermittent. Typically in the bathroom you need to run the tap for a good minute before the water comes through hot. It then continually cycles hot/cold/hot/cold. I can get enough for a sinkful for washing up, shaving (not in the same sink!) etc, but no chance of running a full bath of hot water. Luckily we have an electric shower but the problem is frustrating.
Anyone know what might be the problem?

Thanks

 

[Softus]

Yup. Do you know why type of boiler and system you have?

 

[Slugbabydotcom]

Yup. Do you know why type of boiler and system you have?

.
I have a Vokera combi boiler.

Do you know what model Vokera it is?

 

[Softus]

Yup. Do you know why type of boiler and system you have?

It was a typo - for "why" please read "which".

I have a Vokera combi boiler.

Do you know what model Vokera it is?

Slugbaby - it isn't a model Vokera, it's a real one.

 

[Slugbabydotcom]

Yup. Do you know why type of boiler and system you have?

It was a typo - for "why" please read "which".

I have a Vokera combi boiler.

Do you know what model Vokera it is?

Slugbaby - it isn't a model Vokera, it's a real one.

If I really thought it was a model of a Vokera model I would have asked which model of which vokera model it was; if I realy wanted to know. If it was not a working model it wouldn't need fixing anyway as it never worked in the first place. So when I say I would have asked as much, then that refers to a hypothetical situation which only proves the point I was trying to make.
Now if it was a working model of a Vokera model then it would probably be a full scale prototype. [There's no point in making a scaled version!] In which case it would not be available to the public.

So I would like to repudiate your idea as I said what I meant and meant what I said

 

[laceypa]

its an Excell 80 SP AND thanks for the wiseguy logic lesson sluggy- but i thought this was a site where people could get help and advice on their plumbing problems from qualified professionals - not designed for some ego trip grandstanding. keep your solipsisms for yourself

 

[Softus]

...I said what I meant...

Perhaps, but you didn't write what you meant.

keep your solipsisms for yourself

Coo blimey Slugbaby - you've really done it now.

 

[Rob]

possibly a partially blocked HeatExchanger or might just be diaphragm. Could be many things!

 

[Slugbabydotcom]

keep your solipsisms for yourself

Coo blimey Slugbaby - you've really done it now.

If I was so solipsistic then none of you would exist. It was merely a rebuff of Softus' paronomasia. Please excuse my merry banter


A strange thing is that it's almost 3 years since I saw the following in an email from Merriam Webster: -

The Word of the Day for Oct 30 is:
solipsism \SOH-lip-sih-zum\ noun

: a theory holding that the self can know nothing but its own modifications and that the self is the only existent thing

its an Excell 80 SP

Theres not a lot of them round here so not much I can tell you about them specifically.

You can get the manual here Go in as an installer and click on literature then discontinued products

I too would be suspecting a blocked heat exchanger or faulty thermistor for starters. As stated it could be more or less anything so best get it looked at.

 

[DP]

Most likely cause of such water delivery is due to dirty system. System cleansing (using chemicals) should improve situation.

Might also help if the boiler is serviced as stated in the manual. Rupture diaphragm (happens often on this boiler due to design of the HW manifold) will not cause the boiler to cycle.

Great boiler. Well worth looking after. Years of service to be got yet.

 

[nickso]

if it goes hot/cold continually it can be as simple as a blocked venturi or a dodgy air pressure switch.....had this a few times with the excell after trying all other avenues....this is a well known fault with vokera and it was their tech guys that told me about it

 

[laceypa]

I let this lie for a while as I got distracted with something else.

Further info - when you turn on the tap, the outside vent starts spewing out steam - easily visible in the current cold weather. You can see from the steam being let out that the boiler heats away nicely, then suddenly just stops. The water goes cold again for a few minutes, then all of a sudden the steam appears again and the water gets hot again.
Problem is much worse in the bathroom which is upstairs, than in the kitchen where the boiler is only 6 feet below the level of the tap.

Does this help with the problem diagnosis?

 

[Slugbabydotcom]

Further info - when you turn on the tap, the outside vent starts spewing out steam - easily visible in the current cold weather. You can see from the steam being let out that the boiler heats away nicely, then suddenly just stops. The water goes cold again for a few minutes, then all of a sudden the steam appears again and the water gets hot again.

This is merely indicative of when the burner is firing

Problem is much worse in the bathroom which is upstairs, than in the kitchen where the boiler is only 6 feet below the level of the tap.

Does this help with the problem diagnosis?

It could be of help if you happen to have less than the required 2.8 litres per minute flow rate at an outlet.