S plan Fully Pumped Central Heating - Expansion Pipe Issue

[SquiddlyDiddly]

Hello,

I am looking for some advice - not a lecture.

My central heating and hot water system was changed a couple of years ago when I needed a new boiler.

Previously, the system was pumped CH and gravity HW.

The plumber that installed the new conventional condensing boiler gave me a fully pumped S plan system.

It has never worked properly since although we could live with it.

Recently, I managed to find out what part of the electrics he has not done properly and fixed that so the programmed worked properly, and now I am left with a fairly simple problem I believe.

The HW tank is in the loft with the header, expansion and cold water tanks.

The problem is that when the HW is programmed ON, hot water goes up the expansion pipe and into the expansion tank ad so I get a HOT expansion tank. The expansion pipe is situated on the input to the HW coil of the tank. This was where it was when it was a gravty fed HW system. But now it is a pumped HW system, the hot water is just pumped out into the expansion tamk.

I need to move the HW expansion pipe so that it is not in front of the pump but behind it but am not sure of the most effective place to take the expansion feed from.

Any ideas would be gratefully received.

Andy

 

[SquiddlyDiddly]

Following the advice of mysteryman, I embarked on the project to move the vent and feed to the return side of the boiler before the pump.

I only had time to do the vent as I had run out of coppeer pipe - on a Sunday.

To my horror when I restarted everything the vent still flowed with pumped hot water.

On looking at the pump amd boiler it appears the pump has been installed upside down and the flow connected to yhe return on the boiler.

Now it does work this way round up to a point but would appear to be a right mess with the vent still spewing hot water.

My next job would have been to bring the feed down and plumb into the return but with the pump upside down - or so it appears - I am not sure what to do now.

I enclose a couple of photos. The vent can be seen as it has a piece of polypipe in - soon to be replaced.

 

[Armo74]

No disrespect but looking at the photo's it might be an idea to get someone in. All the time the system is run like that it is doing more harm than good. Your correct the pump is upside down

 

[Space cat]

Sadly, I can't see your photos. (Don't know why. )

First things first, there MUST be an unrestricted upward path all the way from the top of the boiler's heat exchanger to the open end of the vent (except for the final bend at the top of course). If you don't have this, you risk trapping air in your boiler with disastrous results.

You would probably have done best to leave the vent where it was, presumably at the top of the cylinder heating coil, and moved the feed pipe to the same position. You can even tap the feed pipe into the side of the vent if that's more convenient (although I would form a little U-bend down there to stop air from bubbling up the wrong pipe.

If you choose to move both feed and vent to a new location (the same one) as suggested and arguably the most elegant solution, don't forget to add a bleed valve at the top of the coil where the vent used to be.

Edit: Spot the silly mistake! (Answer below)

 

[SquiddlyDiddly]

//www.diynot.com/network/SquiddlyDiddly/albums/10193

I don't know if you can see these now.

As I have already brought the vent down and the feed is on its way, I am planning to tap the feed into the vent - with a U turn as you suggest.

Thanks for reminding me about the bleed valve.

Andy

 

[Space cat]

First things first, there MUST be an unrestricted upward path all the way from the top of the boiler's heat exchanger to the open end of the vent --

You would probably have done best to leave the vent where it was --

And the silly mistake? There might be a motorized valve between the top of the boiler and the cylinder coil?

PS: I can see the pictures now. I'll study them latter.

 

[SquiddlyDiddly]

Space Cat

You are correct, the old postion of the vent and feed was on top of the coil and when the system was changed from gravity hot water to pumped hot water the vent just spewed out continuously.