V4043B -which way round?

[dfoss]

I am preparing to fit a 28mm Honeywell V4043B normally open 2 port zone valve in a gravity flow circuit in a pump bypass. The idea being to allow maximum thermosyphon when the pump is not called to run but shutting when the pump comes on. (The smallbore and thermosyphon share this pipe at this point)

My question is in relation to the direction of flow.

The thermosyphon is quite gentle but the pump is capable of 5M head and has to push the smallbore as well.

The differential pressure quoted for the 2port valve is 0.45 bar max (4.59M head)

So in service the valve will see the highest pressure in the direction against the thermosyphon flow when the pump is running and the valve is closed.

Which way round would you fit it? Arrow with the thermosyphon or against it?

 

[doitall]

I think you should do a sketch

 

[dfoss]

OK - just have to figure out how[/img]

 

[dfoss]

http://s153.photobucket.com/albums/s240/dfoss880/?action=view&current=Pumpcicuit003.jpg

Can you read this picture?

This system has worked well for years with a non-return valve where I want to put the two-port, but as the gravity was fairly weak the non-return never opened and eventually stuck shut. Having just invested in a more expensive woodburner I want to protect it a bit more - also not just rely on the flow through a swtched off pump (which has been OK for all this time - but the new boiler is a bit more powerful)

 

[Norcon]

Where is the cold feed connected?

 

[dfoss]

nearer the boiler - there are no valves between the boiler and the header/expansion or the cold feed - was that your concern?

 

[Norcon]

Yes that was my concern.

Install the valve with the arrow in the thermosyphon flow direction.
The differential pressure they quote is in relation to the flow through the valve.

Thus with thermosyphon it will never reach the maximum they state.

 

[dfoss]

Thanks mate

 

[doitall]

What is the purpose of the valve.

Would be better to put the pump in the by-pass and leave the gravity open circuit.

In fact it would be even better putting the pump in the heating return.

 

[dfoss]

"What is the purpose of the valve?"


The purpose of the bypass and valve is to further reduce the resistance to gravity flow when the pump is not running. The valve will be normally open but shut when there is power on the pump.

The sketch is a line diagram not a drawing and in fact physically the valve is on the straight run as you suggest and the pump bypasses it. (the valve will replace a check valve that never opened in practice) Both pipes are the full 28mm anyway. Without a valve preventing it the pump just recirculates through the bypass, (hence my original question "which way round is best" when considering the differential pressure on the valve when shut)

The pump is allowed to see both the heating return and the gravity return to accelerate the flow in both - and that works very well - the pump comes on for me when a pipe stat sees plenty temperature at the woodburner. When shut down further the woody only heats the thermosyphon.

Last week I tried it with the pump seeing the heating circuit only as you suggest and an injection tee driving the gravity - but did not achieve the nice balance I have now. Currently while waiting for the V4043B I have a full flow ball valve in it's place and by measuring temperatures when everything is in steady state I can tell I get about 25% more flow in the gravity -pump power off - with the ballvalve open.