Vaillant Ecotec Plus 831 losing pressure overnight

[tom609]

ok so maybe iam but new to this give a guy a break ha ha vaillant good shout though, needs to be sure its on the boiler though

 

[Rob Sale]

I will be calling someone else, someone who's knows the Vaillant like the back of his greasy hand! With a drop that big, are you saying it's more likely to be the boiler at fault? If that's the case then it's a slight relief as I don't fancy having to gut the flooring to redo the pipework!

Sorry I disagree with the comment that asking for MI's that tells me he is professional. And is going to follow manufacturers fault finding guide.

Check for big leaks around rads, look outside on the blow off pipe that boiler is not blowing off, if it is then get a GSR engineer to check PRV and expansion vessels and the pipe to the vessel.

 

[tom609]

expansion vessel definate common fault i agree but to call vaillant to represurise is over the top unless the vessel is faulty and even then

 

[Roger Welton]

I think an internal leak has been repaired (I'd hazard a guess at one of the rubber hoses) but electrics have taken a soaking so poss pcb, fan, gas valve, pump, etc. deff a job for Vaillant IMHO.

 

[tom609]

i agree though have dried them out before when the hoses have gone usually due to expansion vessel loss of pressure

 

[psk]

But are you also worried I may blow myself up?

that is the first step by you to trying your diy skills on your boiler now.
next you will be asking where is the expansion vessel and what to do about it.
just get a gsr back in and get it sorted

 

[herp_lee]

You need a gas safe registered engineer to come in, identify and repair the fault.

 

[Keefy]

Just been to a customers house to recommend a suitable shower for their new 'combi' which turned out to be an EcoTec Plus 624 (24KW). They've had the same problem as mentioned here with loss of pressure and leaks everywhere which has seen the engineer come out on numerous occasions without finding the fault. On the last visit the engineer gave them a brand new filling loop and told them to just top it up if it happens again. Unbelievable!

Going to go back in a minute to check for leaks but I've a feeling it may be the expansion vessel which I'm not getting involved with, they can get the gas engineer back AGAIN.

 

[Roger Welton]

Expansion vessels are basic stuff, always annoys me when I find them flat, as pound to a penny will need a prv also. It doesn;t take much to check them on a service, you're draining some water off to check inhibitor levels anyway why not drop a little more out to take pressure off and check vesel whilst you're there.

 

[bewsh]

You want to be checking the 15mm copper pipe which goes from the boiler through the wall to outside. If that is dripping/running then your PRV is passing. If it's passing, you want to be looking in to why the PRV has gone off in the first place.

Either the expansion vessel has lost it's air charge or the rubber diaphragm has perished and the air side is now full of water. If this is the case, when you're heating the water it has nowhere to expand to so the pressure on your boiler will keep going up until it hits 3 bar and then goes out the PRV. Easy way to check if there's an expansion issue - Top the boiler back up to 1.5 bar pressure, run the heating, if the pressure keeps rising to 3 bar, that's your problem. You could even have a blockage in the pipe which connects to the expansion vessel, I've seen this multiple times, specially on the ones with the flexi pipe connecting from the back of the pump housing to the expansion vessel.

Or, if the filling loop is passing, the pressure will keep going up even with the central heating turned off.

Or, another possible cause, but most unlikely is that the plate to plate dhw heat exchanger has pin holed, causing cold water to enter the central heating side.

If the PRV is passing, you can normally clean them up and they'll be fine, but sometimes you will need to replace them.

But whatever the cause, really you need to be getting a Gas Safe registered engineer back to check it all out.