Back circulation

[m coyle]

How to stop back circulation from cylinder to back boiler.

 

[Dotty]

I take it you're meaning how do you prevent your cylinder heating the back boiler, yes? And is it solid fuel or gas?

 

[m coyle]

Solid fuel and oil

 

[Dotty]

Linked up at the fire?

 

[m coyle]

Linked up in hotpress with non return valve and motorized valve on oil boiler side, flow from back boiler is up and over attic, then dropped down to hotpress, with expansion of it.

 

[ecowarm]

You need to separate the two systems i.e neutral point like a neutraliser or twin coil cylinder.

You can't valve the gravity solid fuel side.

 

[m coyle]

Just wondering has anyone tried a non return valve on the return from cylinder to back boiler to stop back circulation,as it works opposite to what the back boiler works.

 

[Dotty]

Just wondering has anyone tried a non return valve on the return from cylinder to back boiler to stop back circulation,as it works opposite to what the back boiler works.

That would be an extremely bad idea mate, it count's as valving the gravity side. If the NRV sticks through inactivity it would have the potential to blow the boiler through the wall. It's a typical link up in that it's incorrect as they all are over here (you said hot press lol).

if it works ok other than bleed back I'd leave well alone, otherwise you may have to call someone in.

 

[Best]

If the primary flow has to rise into the attic & then down to the cylinder - like in a bungalow with the "hot press" & the back boiler not beside each other, then you will get heat reversing overnight. If the cylinder had have been at the other side of a wall to the back boiler & flow had been drilled through & taken to top of coil & vented, then no problem.
The hot cylinder fitted in the attic would solve your heat loss, but is probably impractical - cold tank needs above it, ect & also, not perhaps an ideal location for hot water!
A door type full flow check valve on the primary return close to cylinder & leaving the feed pipe seperate, would work, but it is not something to recommend as the primaries are not supposed to have valves on them!

 

[m coyle]

Sorry croppie,what did u mean by, it's a typical link up in that its incorrect.Should i do something to leave it a better system.There are four piepes to the back boiler.

 

[Dotty]

I mean typical as most of them are done over here. The property starts with back boiler on a gravity system, an oil boile is added later but instead of it being plumbed in properly, either using a neutraliser or twin coil cylinder, the pipes from the boiler are just connected somewhere convenient, either at the fire or in the hot press.

It's not right. But it works.

It'll cost a fair bit to be plumbed in properly. you just need to ask yourself whether you can put up with what you have.