C-Plan Upgrade - Fitting the 2 port valve

[Mark Trueman]

Hi,

I may be attempting to fit a 2 port valve to my gravity hw this weekend. However, placement of the valve may turn out to be a problem.

I know that the valve has to go after the venting pipe, so the options are....

Between the venting pipe T and the cylinder - Impossible, as there is only a few cm of space between the two.

On the return, after the cylinder, very difficult for a relatively amature plumber like myself. Access at the bottom of the cylinder is limited, and the return pipe comes out of the bottom of the cylinder and bends all over the place to go through the floor and return to the boiler.

I was wondering if an easier option would be to move the t fo the vent so that its lower down, and then i can fit the valve above it.... for example.. cue cruddy ascii art

Current system

_____ |vent | | cyl |---| | | | | flow

New layout

_____ | | |vent cyl |---| | | | | | V | | |__| | |

V is the 2 port valve Is there any problem with the vent t being lower down the flow pipe?

[Mark Trueman]

Dont know what happenned to that ascii art. Suppose thats what you get posting through google groups

[Set Square]

Yes, it's not easy to convey a clear picture with it!

Any chance you could stick a photo of your cylinder and its pipework on a website somewhere, and post a link to it?

Is there room to extend the upper coil connection horizontally, to make room for the valve but also to allow the vent to connect at the same level?

Does your boiler have an overheat cutout stat? If so, you may get away with putting the valve in the return pipe on the boiler side of the feed pipe. [There are others with more expertise than me on this - hopefully they will chip in].

[Mark Trueman]

I might be able to put a photo up later when i get home.

There wont be room to extend the upper coil horizontally, as the cylinder is in an airing cupboard that is only slightly bigger than the cylinder itself. There is only about 1 inch of pipe visible between the tank connector and the T for the vent, and then about 1 inch of space between the T and the wall of the cupboard!! Needless to say, its a pain to get in there - took me a whole day to fit a new cylinder a while back which normally would have taken an hour at the most!!

Is there a reason why the vent has to connect at the same level as the entry to the cylinder?

Not sure about the overheat cutout stat. I was under the impression that 99% of the old gravity heating boilers did have this (its an old baxi bermuda 401 back boiler)

It seems that C-plan conversions are your niche Set Square. Looking through previous posts on the subject, your name pops up more than most.

Cheers

Mark

[Set Square]

I'm not absolutely sure. The default with gravity systems seems to be to connect the vent pipe to the highest point - but I'm not sure whether it's de rigeur. Others may care to comment.

On my fully pumped Y-Plan system, it certainly *isn't* connected at the highest point - both the vent and F&E pipes are connected into the flow pipe under the airing cupboard floor, just before the pump. But the requirements for gravity systems may be different.

If it's similar to 2 Baxi Bermudas which I have owned in the past, it

*won't* have one. The Bermuda has a large heat exchanger - which holds a lot of water - and can take care of being able to operate with virtually no flow without any danger of the residual heat causing the water to overheat.

I have certainly suggested them several times since converting a gravity system to C-Plan is often the simplest way of providing a boiler interlock where there wasn't one before. I have a very good understanding of how they work - but have never been in a position where I have needed to implement one myself.

[ritchieaber]

You have to have the vent at the top of the coil otherwise you have an air lock and no way to vent it. It is a problem in tight cupboards like this. All I can suggest is that you turn the flow pipe towards the front of the cupboard, near the floor, then up and back to the coil connection, move the vent to the "front top corner" and put the valve on the horizontal bit between there and the coil...