Hot water goes cold unless it is trickling out

[uk-Pedro]

Hi,

I'm hoping someone has had this problem before and solved it and can help...

I've a combi boiler and when I switch on the hot water from any of the taps in the house everything seems to work fine. Water starts to flow and warm up but after a few seconds when the water is hot the flow rate drops off and if I don't open the tap more the combi will switch off. If I open the tap a bit more the hot water will continue. If I open the hot water tap fully then I only ever get cold water.

Anyone seen this sort of behaviour and know how to cure it?

Any help appreciated.
uk-Pedro

 

[payney1974]

You need to call an engineer in. It will take him 5 mins to diagnose.

 

[learningplumin]

HI, payney just out off interest, how come it would take an enginneer 5mins, too sort out, if you are one, and still have not told the OP, what the problem may be?
Don,t want to sound, in conflict.
Just interested!

 

[payney1974]

HI, payney just out off interest, how come it would take an enginneer 5mins, too sort out, if you are one, and still have not told the OP, what the problem may be?
Don,t want to sound, in conflict.
Just interested!

Yes i am a breakdown engineer and a very good one at that thanks! People on here are all trying to help but unless you are there with the boiler in front of you its hard to tell the guy what needs doing as there are a procedure of checks to go through! I personally am not an engineer that walks into a property without tools and says oh yes its your Plate to plate or its your filter blocked on the cold inlet etc etc! When i order a part it is 100% the CORRECT part!! And i dont order 3 or 4 parts just to be sure!! Tell me do you honestly think if you were called to this job you couldnt diagnose it in say 20 mins???

 

[newbie1]

plate heat exchsanger would be my long distance diagnosis as well
why doesnt op just call an engineer
the best you can hope for on the net is a guide the problem being being in front of the appliance makes all the diff
did a vaillant same thing took out old dhw exchanger didnt seem blocked at all but it was
boiler work cannot effectivley be done over the net as part b works with part c that tells part d so you have to physically get in there to check things

 

[stevetheplumber]

the section of the mis youve primted is the central heating pump chart you need the dhw output

 

[uk-Pedro]

Thanks for your help guys.

The reason I'm on here is to try and see if what is wrong with my boiler is easy to fix and if it is and it's safe, I'll have a go myself. If it's something complicated or if I deem it unsafe to have a go then I wont. At the end of the day it's my choice if I want to try and fix something myself or not, and it's everyones choice if they reply with helpful information or not and in general people do.

If something is easy to diagnose in person then it shouldn't be any harder to diagnose over the internet with enough explanation but it's up to the individual person helping if they want to take the time and effort to explain or not. Like payney1974 says, there are procedures to diagnose something. These procedures aren't known by me or your average end user but they can be followed by most people.

Anyway, thanks for the help.

Regards,
uk-Pedro

 

[learningplumin]

HI, PAYNEY, I have no doubt you are an engineer, but I do doubt, you can diagnose a fault, 100 per/cent correct?

 

[stevetheplumber]

HI, PAYNEY, I have no doubt you are an engineer, but I do doubt, you can diagnose a fault, 100 per/cent correct?

none of us is ever a hundred per cent right learning but if youve been fixing boilers for a few years you can normally be right 98 per cent of the time
and if you know the =make and model you can often narrow it down before you even see the boiler as same boiler have same faults

 

[payney1974]

HI, PAYNEY, I have no doubt you are an engineer, but I do doubt, you can diagnose a fault, 100 per/cent correct?

YOU NEVER answered me! Could you not diagnose this fault in 20 mins ? If you are an apprentice i apologise but you do seem to be taking the p*** now a little!

 

[learningplumin]

NO, need too get shirty payney, all I sayin very hard too diagnose 100% correct, first time.
After all you offered, four reasons that may be possible.
You can shout, if you wish.
Not an apprentice.

 

[payney1974]

NO, need too get shirty payney, all I sayin very hard too diagnose 100% correct, first time.
After all you offered, four reasons that may be possible.
You can shout, if you wish.
Not an apprentice.

Your not listening! Ive offered four things that it could possibly be, in front of the boiler it would take an experienced engineer 10 mins max to diagnose which one. When you turn on a hot tap on a combi system and the pressure is good but then slows down on every dhw outlet in the property its obviously a blockage of some sort (do you at least agree with that?). When you turn off all dhw outlets eventually the pressure at the outlets will equalise with the mains pressure (Thats why it seems ok at first) then as soon as a outlet is opened the pressure is reduced due to the blockage.( sorry i cant put it any simpler than that) At along distance guess (and thats all it is, a guess) it would be plate which is so easy to check you can just whip it out fill with water and then hold it vertical, the flow rate on ch side should be exactly the same as dhw side (thats a tip just for you learning) . As ive said before we are just trying to help but it is very hard to diagnose correctly over the Internet, have you added anything worthwhile to this thread or do you just want to talk down to more experienced engineers?