Vaillant ecoTec 831 problem

tramlink · 1 May 2008

My newly installed Vaillant ecoTec 831 is doing two things which puzzle me, and may be related :-

1) With central heating off - when I draw cold water, on turning the tap off the pump starts and the pressure gauge drops. There is no sound of water passing through the radiators, so I would say it is pumping against a closed valve. This happens intermittently, the pump staying on for about 15 seconds after which the pressure gauge returns to normal. Sometimes the gas valve symbol appears on the display and the "hot tap" symbol both of these going off within a second or so. On one occasion the burner also came on briefly.

2) With central heating on and burner on - if I draw cold water, when I turn the tap off the burn stops, the pump continues running for 10 seconds or so, shuts off, then restarts almost immediately followed by the burner restarting. This also happens intermittently.

The installer says that the 831 "sometimes gets itself in a knot".
The first one seems to me to be a possible software problem.

Any ideas would be very welcome.

Regards

Geoff Smith

gasgeezer · 1 May 2008

sounds like air in the pipes causing water movement look for a dead leg in the pipe work

gas4you · 1 May 2008

Definately a dead leg. Assuming you had a HW cylinder removed, look in there for a stub of a pipe (22mm) sticking out of the floor.

This pipe either needs to be removed, or simply have and air bleed cap fitted to remove the air.

simond · 1 May 2008

Why would the pressure gauge drop?

Are you sure the filling loop isn't half open?

tramlink · 2 May 2008

Thanks to all who said it is a dead leg - just what the installer says, although he thinks it's more to do with the number of bends and having pipes below ground floor level.

Something to work on.

Cheers

Geoff Smith

tramlink · 3 May 2008

> Why would the pressure gauge drop?

The digital display correctly shows the pressure rising, but the analog (manometer) gauge shows it falling.
My installer reported this on Vaillant's helpline yesterday but, because it isn't on their computer system, couldn't get any sense out of them - he's awaiting a call-back from someone with technical nous.
Although it's not a fault that affects the working of the kit, I feel it should be dealt with under the 2 year guarantee.

As to the dead leg problem itself, the installer has convinced me that nothing can be done because of the layout of the pipework. But I've now found that if I turn the cold tape off slower than I had been used to the problem doesn't arise.

Cheers

Geoff Smith

Gasguru · 3 May 2008

Have you checked all possible dead legs....washing machine connections (especially the hot which are often not used anymore), old dishwasher connections, outside tap. Are you on a shared main? Perhaps next door could have dead legs.

It's perfectly normal for the pressure gauge to fluctuate a little when the pump kicks in. Depending on it's connection (positive or negative side of the pump) will determine whether it falls or rises. With some boilers it can move as much as 0.25 bar.

simond · 3 May 2008

The digital display correctly shows the pressure rising, but the analog (manometer) gauge shows it falling.
My installer reported this on Vaillant's helpline yesterday but, because it isn't on their computer system, couldn't get any sense out of them - he's awaiting a call-back from someone with technical nous.
Although it's not a fault that affects the working of the kit, I feel it should be dealt with under the 2 year guarantee.

As to the dead leg problem itself, the installer has convinced me that nothing can be done because of the layout of the pipework. But I've now found that if I turn the cold tape off slower than I had been used to the problem doesn't arise.

OK, thats a slightly different scenario. I don't think there is anything wrong with your boiler.

My votes now go on a dead leg.

PS: Some Croydon installers give 5yrs rather than 2yrs on a Vaillant job

.

jcorbin · 3 May 2008

simond";p="896795 said:
PS: Some Croydon installers give 5yrs rather than 2yrs on a Vaillant job .

Click to expand...

Good afternoon simond 5years parts and labour on an ecotec 837 plus with weather compensator ?

simond · 3 May 2008

tramlink · 6 May 2008

Thanks all

I've decided to live with the problem as it doesn't arise when a toilet is flushed / dishwasher or washing machine run, but only when I use a cold tap. Turning off slower than I was used to the problem doesn't occur.

Still awaiting a response from Vaillant, though, as to why the digital pressure reading goes up but the analog goes down - or have I misunderstood and that is caused by the dead leg too?

Cheers

Geoff

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Vaillant ecoTec 831 problem

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