Has my boiler been installed correctly?

[nmg196]

Hi,

I had a new boiler fitted today (Vaillant, heat only, open vent, 2 x two port valves) to replace an ageing boiler which had a couple of issues. It has been installed by a Vaillant accredited, Gas Safe registered installer. However I'm not sure it's been installed correctly for two reasons:

1. One change was that my new boiler requires a pump-overrun. He ran a new permanent live to boiler to facilitate this and the pump is definitely overrunning exactly when it should. HOWEVER, the central heating valve currently closes the second the thermostat shuts off. This doesn't seem right to me as it means that if the hot water is also off, the pump is pushing against two closed valves, which makes it much louder and sometimes vibrates the surrounding pipework (probably enough to wake us up!). I'm not a heating engineer, but it seems wrong/pointless for the pump to be on if both valves are closed. This will mean there is a very high pressure on the 'flow' side of the pump. There is surely no point in pump overrun unless the overrun causes the water to flow through the system (and boiler). Presumably the valve should remain open until the pump has shut off? Am I right in assuming it's not correctly wired?

2. Secondly, he also installed an automatic bypass valve on the boiler as apparently this is required for the boiler's warranty and also building regs. However, I'm not sure he's installed it in the correct place. He has installed it directly over the boiler between the flow and return (where they come out of the boiler). The pump is NOT inside the boiler (it's not a system boiler) - it's in the airing cupboard. So again, this doesn't seem right. This valve could only ever activate if the boiler became completely blocked (seems unlikely) and more importantly, it will NOT activate under any other circumstances - including if all TRVs shut off (not that I have any) or both valves are closed, as the boiler itself would be an easier path for the water in this instance. It seems to me that this would only be an acceptable location for an automatic bypass if I had a system boiler with integrated pump, but I don't - my pump is in an airing cupboard several metres away on another floor. The installation manual I was given with the boiler seems to show the bypass valve should be fitted "at least 1.5M away from the boiler" and also that it should be installed after the pump, not before it.

Am I misunderstanding something here, or am I right about the above two concerns? I just want to double check I'm not being the idiot customer before I query him on the above two issues.

Many thanks,

Nick

 

[Dan Robinson]

I'm not a heating engineer, but I *am* an engineer

However...

The Bypass should be after the pump and before the zone valves.

School boy error on the part of the installer.

 

[Agile]

He have been too accustomed to fitting system and combi boilers!

But to do that he must have been so preoccupied with something else as its such a basic mistake!

Is he going through a divorce or is his parent dying?

Tony

 

[jackthom]

The standard way of wiring this sort of 2 port valve system doesn't really allow for a sensible water path during the pump overrun period, when both valves are closed.

If the automatic bypass valve had been installed correctly and it was a decent distance from the boiler, there would then at least be some volume of water left circulating during this time to help carry off the residual heat.

As it is now, the pump and boiler probably won't last long if the bypass isn't moved.

 

[nmg196]

OK. Assumming, that the auto by-pass is moved to the correct place (after the pump) is it normal on an open vent system that that will come into use every time it's in pump-overrun mode? I was expecting the pump overrun to circulate water around the radiators rather than through the bypass valve and that the ABV would only come into play if all the rads were off for some reason?

EDIT: Ahh, Jack's just answered this question as I was writing it. Thanks

 

[Tibbot]

Vaillant accredited hey! I s*it 'em.

 

[gasanstuff]

no TRV's?????

 

[nmg196]

No, there weren't any when I moved in and I've not really had any cause to fit them. The house seems to heat up very evenly. Besides, I fitted 12 in my last house and 11 of them stopped working within 2 years.