Problem with Vaillant boiler trying to fire up when it shouldn't!

susieb1967

Can any of you help me?
Yesterday I had a new bathroom fitted (:j-waited 7 years!) To do this the plumber obviously had to turn the water off. Last night I noticed that when we turn the cold water OFF the combi boiler trys to kick in!! i.e the tap light on the boiler lights up and it makes a noise like its going to start heating the water, then switches off
The make of boiler is vaillant turbo Max Pro 28E

The water is still heating through the hot taps and the heating still works. Cold water still comes through the cold tap but I am baffled as to why the boiler sounds like it is firing up when I turn the tap off.......I also think it does it after the toilet has finished filling!!

Asked the plumber about it today, his response was also and he doesn't think its anything to do with his visit. Is it just a coincidence?

tsb

Have you noticed if the water pressure is higher than before.If it is try and turn pressure down at main stop tap and see if that helps

Canucklehead

Hi

Water hammer will do this ,(turning off a tap suddenly will cause the water to bounce back to the flow sensor in the boiler.) you might find that if you turn off taps slowly it won't happen.Fitting a shock arrestor/mini expansion vessel near the boiler should stop the problem.Do you have high water pressure?
http://www.rwc.co.uk/Product.aspx?page=CAT6 Scroll down to number 4.

Corgi Guy.

susieb1967

yes my water pressure does seem higher than before the work was carried out and it doesnt kick in if I turn off the taps slowly.......youre sooo clever!!
So it sounds like a need to take canuckleheads advice?
many many thanks for you prompt responses

susieb1967

oh btw i tried to turn the pressure down at the mains but will try it a little more- thanks

Canucklehead

Hi

You might benefit from a pressure reducing valve http://cgi.ebay.co.uk/comap-safeguard-pressure-reducing-valve_W0QQitemZ120158180562QQihZ002QQcategoryZ63907QQcmdZViewItem
Find a plumber who knows about these things!!!

Corgi Guy.

susieb1967

Cheers Canucklehead!
Hubbies just come back from pub and keeps trying turning tap off slow to try and catch boiler out!! ( It's keeping him quiet!) Will get in touch with plumber ASAP with you fab advice- its much appreciated

EliteHeat

You almost certainly have a "dead leg" in your pipe work. This is an excessively long length of pipe not attached to any outlet i.e. tap. This is full of air and not water. Air, being bouncy, will expand and contract in response to a tap being opened or closed. This can cause the boilers flow switch to be activated and the startup cycle being initiated.

This is very often caused by a poor conversion from gravity supplies to mains. In really bad cases when a shared mains supply is in operation, the next door neighbour can cause the same symptoms in your boiler.

The temporary fix is to bleed the air out of the affected section of pipe and the permanent fix is to cut it back as far as possible.

susieb1967

EliteHeat wrote: »

You almost certainly have a "dead leg" in your pipe work. This is an excessively long length of pipe not attached to any outlet i.e. tap. This is full of air and not water. Air, being bouncy, will expand and contract in response to a tap being opened or closed. This can cause the boilers flow switch to be activated and the startup cycle being initiated.

This is very often caused by a poor conversion from gravity supplies to mains. In really bad cases when a shared mains supply is in operation, the next door neighbour can cause the same symptoms in your boiler.

when I originally had my new boiler fitted, about 6 yrs ago, the plumber we had then disconnected the immersion tank, and an extra pipe had seemed to appear next to it...... this pipe was copper about 20mm and stuck up about 3 foot within the airing cupboard. The plumber had it capped off. This original plumber knew our plans for putting a shower in there and I presumed it was some kind of feed for that. However now its gone!! the plumbers from the bathroom fit have not used it for anything i.e new pipe work for bath and shower have gone in.

My question is.... do you think this pipe ( or lack of it!) has anything to do with my prob? I am thinking if it was filled with water b4= no problems, but if plumber has made it shorter and stuck it under floor somewhere and its full of air????

Canucklehead

susieb1967 wrote: »

when I originally had my new boiler fitted, about 6 yrs ago, the plumber we had then disconnected the immersion tank, and an extra pipe had seemed to appear next to it...... this pipe was copper about 20mm and stuck up about 3 foot within the airing cupboard. The plumber had it capped off. This original plumber knew our plans for putting a shower in there and I presumed it was some kind of feed for that. However now its gone!! the plumbers from the bathroom fit have not used it for anything i.e new pipe work for bath and shower have gone in.

My question is.... do you think this pipe ( or lack of it!) has anything to do with my prob? I am thinking if it was filled with water b4= no problems, but if plumber has made it shorter and stuck it under floor somewhere and its full of air????

Hi

Eliteheat do you think the above 3' of pipe acted as a shock absorber?

EliteHeat

Canucklehead wrote: »

Eliteheat do you think the above 3' of pipe acted as a shock absorber?

No, I think it was bled before and didn't cause a problem. Now, with this bit of new information re the disappearing pipe I suspect that it hasn't been bled at all. Mind you, I'm just [strike]guessing[/strike] hypothesising!

Why not try just finding it, extending it up a little and putting a manual air vent on it. Can't hurt.