Weird hot water issue

[Riley]

It might come to that but there’s just no logic to it

 

[Harvest Fields]

It might come to that but there’s just no logic to it

But that’s the only thing that has changed. (According to the customer)

 

[townfanjon]

No only since the taps were replaced. Unfortunately tenant can’t remember what sort of taps were there

This one gets better , its a belter !

 

[Riley]

Ha ha agreed. Tenant is not bad to be fair, pretty switched on but can’t really remember the previous taps as they were changed literally the day after they moved in. I think New taps it is

 

[PETE 123]

antiscald device in tap maybe operating if one fitted to that type

 

[plumbandplumber]

Is the dhw pipe out of boiler still hot when the water from tap has gone cold?

 

[Riley]

Certainly is

 

[Riley]

No antiscald

 

[ShaunCorbs]

its not new build is it?

 

[townfanjon]

Not teaching to suck the old eggs and all that , but have you tried running the hot tap with the heating off and seeing if heats going around HTG circuit , it is a Biasi after all

 

[Riley]

Ha ha it’s a valid point and may well be worth I try. It just seemed so odd that tap runs for 10-15 mins then goes Stone cold

 

[Riley]

its not new build is it?

No mate

 

[peter0504030201]

is your boiler pressure gauge set higher than 1.5 bar , The system may be slightly over-pressured , the increase in temperature results in an increase in pressure, this might push it over its limit and again it will cut-out ?

 

[Riley]

The boiler doesn’t cut our

 

[Gasmk1]

then if all else is ok it must be the bath taps. can you put your temp sensor on the hot flow from the boiler and watch that

 

[Riley]

then if all else is ok it must be the bath taps. can you put your temp sensor on the hot flow from the boiler and watch that

I completely agree with you from what I can tell the boiler works perfectly albeit is the Biasi

 

[fixitflav]

Yeah and the boiler continues to fire. It’s almost as if the hot water is diverting elsewhere but it’s not

The heat must be going somewhere. Are you sure the rads aren't getting hot (whether you want them to or not) when the hot runs cold? Might be problem with the 3-port valve in the boiler. I would switch it to hot water only mode and see if it happens, and if the boiler continues to fire if it does.
My son has a combi (Vaillant if I remember right) which was behaving oddly, not unlike your symptoms. They said it was an uncommon but known fault, and replaced the valve under warranty. Been OK since.

 

[Riley]

I went back last week the radiators are categorically not getting hot. I have quoted for new taps

 

[fixitflav]

I went back last week the radiators are categorically not getting hot. I have quoted for new taps

Sounds like you have discovered a new law of thermodynamics

 

[townfanjon]

I went back last week the radiators are categorically not getting hot. I have quoted for new taps

I wake up in the middle of the night thinking about this one, make sure you report back lol
If its the taps I will show my arse on the townhall steps.

 

[Harvest Fields]

I wake up in the middle of the night thinking about this one, make sure you report back lol
If its the taps I will show my arse on the townhall steps.

Make sure you get a photo

 

[townfanjon]

Make sure you get a photo

I will do a selfie with the mayor eh

 

[Riley]

Sounds like you have discovered a new law of thermodynamics

Ha ha perhaps I have, the only thing changed there is the taps, from speaking to the last tenant there was never a problem since they’ve put these ones on with a much greater flow there has been a problem. There’s no other logic to it unfortunately

 

[Riley]

I wake up in the middle of the night thinking about this one, make sure you report back lol
If its the taps I will show my arse on the townhall steps.

I’m glad it tortures your brain like it does mine

 

[fixitflav]

I’m glad it tortures your brain like it does mine

I still think the 3-port valve is the most likely culprit.

 

[Riley]

Right, update. Changed to quarter turn pillar bath mixer tap maximum 9 lpm maximum and the problem has gone. I cannot see what the reduced lpm would have done but it seems to have done the trick.
Thanks all for your thoughts it remains a head scratcher

 

[fixitflav]

Right, update. Changed to quarter turn pillar bath mixer tap maximum 9 lpm maximum and the problem has gone. I cannot see what the reduced lpm would have done but it seems to have done the trick.
Thanks all for your thoughts it remains a head scratcher

Not for the first time, I was wrong! Good that you've cracked it.

 

[Harvest Fields]

Right, update. Changed to quarter turn pillar bath mixer tap maximum 9 lpm maximum and the problem has gone. I cannot see what the reduced lpm would have done but it seems to have done the trick.
Thanks all for your thoughts it remains a head scratcher

You are welcome mate. Taps are a weird thing sometimes.

 

[ShaunCorbs]

24kw boiler ?

 

[Riley]

28 I believe mate

 

[ShaunCorbs]

28 I believe mate

Strange should be able to do more than 9lpm unless the plates shagged

 

[Riley]

Good point well made but boiler is literally only 9 months old. I mean it could be shot but......

 

[ShaunCorbs]

Might be worth a shout to the manufacturer

 

[Riley]

As I say though mate doesn’t affect any other outlet. Kitchen sink buckets out hot, basin buckets out hot. LL didn’t want floors up to check pipework etc so taps was his cheap fix. As I say just a mystery that hot would just cut out from the tap after 10-15 mins

 

[ShaunCorbs]

As I say though mate doesn’t affect any other outlet. Kitchen sink buckets out hot, basin buckets out hot. LL didn’t want floors up to check pipework etc so taps was his cheap fix. As I say just a mystery that hot would just cut out from the tap after 10-15 mins

It's one of those pita faults