Pressure relief pipework - Worcester Bosch 30CDi

[f0rmula]

Hi. I'm trying to get a Worcester Bosch 30CDi installed in our cellar. Does the pressure relief pipework have to drain downwards from the boiler, or can it come out of the boiler, and run up the wall to near the top of the boiler (but not above) to exit the house? The cellar is only half underground. I suspect that would mean that the pipe remains full of water after a vent, but I didn't think that'd be too much of a problem.

The manual shows it draining down, but doesn't put say it can't run a upwards then down outside.

http://www.worcester-bosch.co.uk/cache/file/483/greenstar-cdi-installation-manual.pdf

It's supposed to vent at ~3Bar, and maybe doing this would put pressure on the valve to stop it opening at 3bar, making it open at a slightly higher pressure, but as 1 BAR seems to be 33feet of water, and this'll be 1-2 feet, I expect the effect would be negligible.

I've been told that there's a Baxi that can definitely have the pressure relief valve higher up, but I don't want to have to get a specific baxi boiler just to save me digging a hole plus gravel trap outside the house.

Cheers for any opinions

 

[McCombi]

I would always run falling away from boiler if possible. Its designed to open at a certain pressure and take the water out and away safely.

 

[f0rmula]

I would always run falling away from boiler if possible. Its designed to open at a certain pressure and take the water out and away safely.

In an ideal world, I would have it draining downwards. But if it's possible to have the boiler in the cellar, that would give us an extra cupboard upstairs and keep the cellar as the plumbing/utility/electrics/commsroom as we'd planned.

Oh, and while typing, I've just had a call from a plumber. He's spoken to worcester bosch they've said their valve should drain downwards. However, he's said he can just put in a tee in above the boiler and use a different pressure relief valve above ground level. Sounds like my problem is solved, if this really is a good plan. I assumed the pressure relief valve was for the boiler itself, and you'd need to use the valve in the boiler, but perhaps not.

 

[McCombi]

If its a regular cdi being used for a sealed system then you could put the prv in a location to suit yourself, ie above ground level. If its the system model of cdi I believe the prv is an internal part of the boiler so if you're rising upwards from this valve then i wouldn't add another prv after the one in the boiler as it may not be enough pressure to open the 2nd one and the water will have no way of escaping.

 

[f0rmula]

If its a regular cdi being used for a sealed system then you could put the prv in a location to suit yourself, ie above ground level. If its the system model of cdi I believe the prv is an internal part of the boiler so if you're rising upwards from this valve then i wouldn't add another prv after the one in the boiler as it may not be enough pressure to open the 2nd one and the water will have no way of escaping.

It's a combi, no hot water tank, so the central heating system will be sealed, right? Is the pressure relief valve just for the central heating system, or for the hot water side of things too?

Cheers

 

[mickyg]

you can run it into a pump, pumphouse do a combined prv and condense pump for this application. Probably solve 2 problems in one, as no doubt you'll struggle for a condense outlet as well

 

[McCombi]

cheers mickyg I wasn't aware there was such a thing.

 

[Terry lambert]

The combined pressure releif and condense pump by pump house is a goog option but not cheap, I think valiant do one as we'll.

If you like the look of a valiant they do an up and over pressure releif and then you could use a normal comdense pump which might work out cheaper.