Reverse circulation or not?

[Dermo1]

Hi

Hope you guys can help me please.

I recently removed an old system gas boiler for a customer which was open vented and feeding a copper cylinder and heating circuit with no zoning. Its a 3 storey home which had storage heating in the top 2 storeys.

Sometime in the past another plumber ran two pipes ( flow and return) from the downstairs heating circuit to upstairs so radiators could be plumbed in upstairs at a later stage.

I removed copper cylinder, fitted a pressurised Ariston combi gas boiler to give the customer instant hot water. Used the old 22mm expansion and cold feed pipe to act as the return for the upstairs radiators and removed the expansion tank in the attic. I then used one of the pipes which the last plumber had ran upstairs to act as a flow for upstairs and fitted 5 new rads upstairs. I fitted 2, two port motorised valves on the returns to zone upstairs separately from downstairs.

Thought everything was fine until the following day the home owner rang to say downstairs was heating even when it was turned off. It's a small circuit with just 5 rads. 2 or 3 are heating pretty well, even though return pipe is closed off with the motorised valve, and stone cold.

Is this a one pipe circulation?

To fix it do I:
A. Fit another ABV
B. Motorised valve on the flow
C. Non return valve on the flow
E. ?

How do I prevent this happening in the future?

Any feedback much appreciated.

Thanks
D

 

[doitall]

Ok what have I missed.

You did say combination boiler, so how can you get a back flow.

 

[Dermo1]

Yes its a combi

Problem is I now have 2 separate heating zones. When i turn the bottom of the house off to heat upstairs downstairs heats also

 

[doitall]

Can you do an as fitted drawing, sounds like you have the returns cross connected, the flow and return must be connected together before they become common with the other zone.

A drawing of the pipes should show the problem.

 

[Dermo1]

Think your right.

Imagine this, flow and return leave the bottom of the boiler straight down to the floor. The return is T'd off and below that is the motorised valve for downstairs. Off the branch of the "T" is another motorised valve for upstairs return.

Problem is flow is common to both circuits and I've no idea where in the circuit upstairs flow is taken from. Im guessing off the end of the circuit.

I cannot remedy the flow pipework without ripping up the whole house.

Thing is how do I remedy it without too much work?

Thanks
D

 

[doitall]

You can't. and the zone valves are better on the flow anyway.

The flow and returns must be independant to each zone, any cross and you'll get a backflow.

 

[Dermo1]

I have to sort this or I don't get paid!

I've seen this before on an oil boiler where pump was on the return and motorised valves were on the return.

Surely swopping the valves to the flow still wont sort it.

So there is no fix other than another flow back to boiler?

 

[Dermo1]

Can you explain at least where it is getting its return from?

Is it one pipe through the flow or where.

 

[doitall]

if you turn both zones on and mark the flows to each rad, then shut one zone off you should be able to tell which rads are reversing by feeling the pipes.

The only solution will be to repipe the problem.

For what it's worth I would expect it to be two pipe system.

 

[Dan Robinson]

If a repipe is out of the question, the Honeywell evo home with a load of HR80 travel heads might be a solution.

 

[Dermo1]

Thanks guys for your help!

Having drawn the system on paper. I can now see exactly what's happening.
It's actually turning the circuit on the bottom of the house to a 1 pipe system, and normal flow is in reverse.

If I was to fit non return valves or one directional rad valves ( if there is such a thing) to one side of one, or more rads that should sort the problem.

Strange how I havn't come accross this more often in all my years of plumbing.

Thanks again

D

 

[doitall]

Post the drawing.

 

[kevplumb]

ey up scruff

thought yed gone to meet yer maker yer owld git

 

[doitall]

One day Kev no doubt

What on earth will you newbees do then for information.

Good to hear from you again mate

 

[kevplumb]

we plod on in your boots bonny lad

cos those of us who can had good teachers

know how

500 kw ladle heaters

• kevplumb
• 1 Dec 2012
• 2

go play with them bad boys
all made with my own fair hand