Discuss Open vent boiler distance from vent. - OK? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Hi there.

Fresh over from Electricians forum..

I built an extension. My old boiler (1970’s, half gravity, in-wall vertical sectional concrete flue) - has all gone.
75% re-do of the rads and plumbing underway.

New boiler location will be on the outside wall of extension which is now ~6M from the original boiler. HW tank and feed from loft tanks are vertically above the original boiler location.

My best bet I believe is to stick with an open vent boiler. The vent, inlet, pump, valves (S plan +) and distribution manifolds will be in the location of the old boiler. The expansion pipe and feed can run vertically up from this location.


drawing.jpg

The new boiler flow and return (22mm) will both need to take an inverted loop then a "uninverted" loop from the new build outside wall, beneath the new floor then above a ceiling to come out at the proposed location of the vent/inlet/pump. Horizontally this is about 6M, pipe length probably 9M. Should I expect any problems with this distance? I am assuming it would be essential to add some T pieces and air valves near the boiler for example, and the high points, also drain cocks, but this leads to two little questions:
  • Air exit valves near the boiler?: I want to come out the bottom of the boiler to keep it tidy, so how do I arrange this re air vents? (Also any problems re excess heat and valve seats so close to the boiler?). Do I use automatic valves?
  • Is it OK to have an inverted loop and ~ 6-7M of 22mm pipe between boiler and Open vent/Inlet/Pump? Might I expect any other problems?
Or..
If I decided instead to use a system boiler, (pressurized), the pump and expansion vessel (now both in the boiler) there would be ~6M plus the inverted loop under the floor before the valves and manifolds. Is this a more sensible option? I want to avoid too many pipes under the floor, so I’d sooner do the S plan+ distribution in the old boiler location where there is also more space.
 
I'd be inclined to go for a system boiler, that solves your venting problems at the boiler end anyway.

Why can't you go low level where the old boiler wass? It would make for less pipweork and make things self venting.
 
You would have to go fully pumped for a start, so I'd be inclined to go for a system boiler too.

With the new extension, will the total floor area of the house be over 150m2? if so, you will need zoned heating too.
 
The old location is internal to the house. Vertical sectional concrete flue within the wall is incompatible with condensing boiler. Also no drain.

Fully pumped has never been a question yes of course.

If I go for the system boiler, that would seem to be perhaps the nicer way to do it really. I guess for S plan+ I'd just run the 3 valves remotely in the old boiler location. I've already put the cables in for that so it makes sense. If I don't do that, I've got to put all three flow pipes into the floor, so and the the gap I have cut in my screed could be getting tight for all those pipes, especially since I will be insulating them, and it needs to contain hot and cold water and gas also.
 
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