CH working but no hot water

[dwemyss]

I have an old Vaillant combo heating system (model unknown) which has been acting up. CH works fine but when I try to get hot water it stops working. The system tries to start and gas comes on for about 20 seconds. The temperature indicator reaches about 60 then shoots up to near 100 then the gas shuts off. I hear a few thumps (water pressure no doubt) and then bar pressure shoots up and down slightly and temp drops to around 40. About 30 seconds later gas fires up again for 20 seconds and it repeats the above. No hot water but when I switch to CH everything is ok as long as I don't try the hot water.
Is it possible I have a pump not working which would mean the water being heated is not flowing and thus the temp rises quickly and then gas shuts off as a safety feature? That would make sense as once the temp decreases again it repeats itself.
Have had the problem for a couple weeks now and have switched over to elec hot water heater but switching to elec CH would be expensive as hell.
Anyone had a similar problem? Have read threads about diverter switches etc but doesn't seem to apply here.
Any help would be appreciated.

 

[GeckoGas-com]

If you have an electrical backup I will presume you have a cylinder and do not have a combi boiler at all ???

Please clarify.

 

[dwemyss]

I have the gas boiler that runs CH and/or hot water. If the gas fails I shut off the whole unit and switch over to a separate Elec CH/hot water system. I presumed the combo was for CH and hot water.
In any case any idea why the hot water not working if CH is?

Cheers

Dave

 

[Agile]

Unless you tell us the model number or post a picture I dont think we are going to be able to help you.

As you seem to be so vague about exactly what it does then perhaps you might be better off getting a competent engineer to fix it for you?

Tony

 

[dwemyss]

I'm not asking for anyone to fix it for me. All I am asking is does anyone have a general idea of what may be causing the problem so that when I do get a tech to come by and charge me a fortune I have an idea of wether or not he is ripping me off or not.
Aside from the last reply does anyone have any constructive advise regarding the problem rather than negative critisism of how much I know regarding these things?

 

[Agile]

when I do get a tech to come by and charge me a fortune I have an idea of wether or not he is ripping me off or not.

Firstly I dont see how you imagine we can make any sugggestions when you cannot tell us what model your boiler is.

Secondly, as we are so honest that we even give technical advice here completely free of charge, you must try to understand that we are not very pleased when we see people who do not trust our industry and expect that they will get "ripped off".

Why dont you call British Gas as surely you will be able to trust them?

As for your boiler, without knowing the model, then all I can say is that it might have a blocked secondary heat exchanger, but thats only if it has one!

Tony




PS Could you be ripping us off by not really being in Bosnia???????????

 

[dwemyss]

First off I trust most industries when I have even a vague idea of what problem may exist thus the inquiry on this site.
Secondly I will post a picture of the boiler so that you can see it and perhaps identify the model.
Third, and more importantly, I have been living in Bosnia since the war and everyone rips off everyone here. It's just the way it is here with anyone who works for a living. Pay sucks and they take whatever they can get. When they see me (Canadian) the price goes up double or triple. There are no true professionals the likes of British Gas or anything vaguely similar. There are also no warrantees or guarantees. When a problem arises it's like playing russian roulette as who to call and what to expect from whoever comes. No yellow pages offering choices either.
I am far from criticizing any professional trade. I am boiler inept and very shortly will be at the mercy of a "tech" who probably has high school education and speaks a language I don't fully understand and when a Bosnian talks technical words he may as well be speaking Japanese.
So I will post a pic or two and see if anyone can give me an idea of what is going wrong so that I can point and grunt something this fellow may understand.
Pics to follow shortly

Dave

 

[dwemyss]

http://www.facebook.com/album.php?aid=4744&l=5e28d&id=594273347

This link is a facebook page I created to display the pics. Only way I know how to upload on this site without going through site administrator

Hope they are helpful to someone

Dave