vailant boiler

[alhendy]

Thanks in advance for any advice. I have Vailant combi heating 7 rads.
Heating doesn't work properly but hot water is excellent.
Upstairs rads heat up, but nothing downstairs, and I mean nothing. If I turn off all rads upstairs, over a period of maybe 2 hours the 3 downstairs will get 'warm'. If I have just 1 on downstairs it will eventually get hot.
Have had this problem for last few years, took out British Gas home care last year, they replaced printed circuit board which cured the hot water supply to taps, as I said this is absolutely fine, too hot really. Going to book a service for boiler in next few days.
Have read on many forums about balancing, which I have tried but only get to 3rd or 4th rad and then pointless as other rads dont get even warm (actually freezing cold to touch)
Have read about flushing myself and powerflushing, not sure yet.

Was planninng to flush myself this weekend and just noticed the digital display on the boiler, which shows when pump is running, rads on etc. It shows a flame symbol when boiler is heating and the temprature. The flame symbol only shows for 13 seconds then goes out for upto 3 minutes. during this time the temperature displayed goes from approx 55 to 81 and down again. This takes around 3 mins.
Any ideas. Blocked pipes/rads, internal boiler prob, incorrect initial install (was in place when I moved in 9 years ago) was rough around the edges install, no commisioning paperwork and floorboards wrecked in places etc.
Competent diy'er, but wont attempt electrics/gas etc but fine with pipework (with respect to plumbers I am slow and would never make a living at it, but plan it first)
Any thoughts or ideas before I spend a fortune on the wrong thing

 

[TCCHeating]

Have a look at the faq about how to perform a bucket test. Sounds to me like you either have a blockage or an air lock. Or the system could possibly be zoned??? Ie a seperate thermostat to the floor that is not working

 

[alhendy]

Thanks for that, gonna have a go tomorrow. Did take couple of rads of last winter and hosed them out.
Obviously not a plumber or heating engineer, but what I can'y get my head round is the boiler lighting for such a short time. How is it supposed to heat 7 rads in 13 seconds ?

Also forgot to mention whatever time of year or temperature, the light on the indoor thermostat when you turn adjuster always lights at 20 degrees. I would have thought it would light at the temperature in the hall where it is sited. It never varies from 20 degrees

 

[alhendy]

Could I just disconnect this thermostat to see if that heats all rads or will boiler not work without thermostat connected

 

[ianmcd]

It is an easy enough job to disconnect all external controls to rule them out but I doubt if that is what the problem is, you can try disconnecting them and insert a wire bridge out link where they were connected , I would be looking at your pump though or a blockage somewhere

 

[alhendy]

Thanks for the replies. Can I try flushing pipes and rads with a hosepipe, maybe from the connections at the boiler. Should I shut the lockshields and TRV's when or if I do this.

Is the pressure from the hosepipe higher than the pressure the pump puts out ?

Cheers again

 

[Agile]

Before getting involved in pipework you should be checking the most likely cause which is the pump.

The boiler information on the display ( if a more modern model ) will tell you a lot particularly the d40 and d41 readings.

I am assuming you have a 400 series boiler with an external pump which you can work on. See FAQ on this site.

If the pump is in the boiler then on your model you need a gas reg engineer.

Tony

 

[alhendy]

Vailant ecoMax 800 series, about 10 years old. Pump inside case. Not going to mess about in the case. We have BG Homecare 200 which doesn't include flushing. This is extra about £300 but they said not guaranteed to cure it. Just wanted to do anything I could before I call them out as have a £50 call out fee.
If they come out, can they identify if it is the pump by a simple test, like plugging in a laptop to a car's electronics ?
The Homecare does cover parts replacement

Hot water works perfectly, scolding hot. Does the pump operate this as well as heating ?

Thanks in advance and promise not gonna use any advice to **** about with boiler and blow my wife and kids up !!

 

[jackthom]

The pump does operate for DHW as well but it doesn't need to do so much work in circulating the water around the boiler heat exchangers.

 

[alhendy]

Have gone through house leaving one rad at a time on and they do all eventually get hot. Some quicker than others (the ones in order of heating when I tried balancing get hotter quicker)

 

[jackthom]

From the sound of it it's not a balancing problem. There's simply not enough water circulating through the boiler, and heating system, to carry away anything like the full heat producing capability of the boiler. So it comes on for a short while and trips off repeatedly.

The prime suspect would normally be the pump.

Alternatively a fair proportion of the pipework is sludged up, or there are other partially closed valves somewhere..