Correct layout of pipework to/from F&E tank

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I have read conflicting advice about this on the Internet and would be grateful for a definitive answer regarding the correct layout of pipework to/from an F&E tank.

Firstly, please excuse the rather amateurish drawings. The large box at the bottom is the boiler and the circle is the pump. Hopefully the F&E tank is self-explanatory! The drawings purport to show a hypothetical layout of the feed and expansion pipes in a central heating system.

The system I currently have is a mess. The pump is in the flow. The cold feed enters the flow after the pump and the vent is on the return. We get pumping over and surges of very hot water into the F&E tank which leads to aeration of the CH system, hence I need to change the layout.

In the first drawing the cold feed/expansion pipe is immediately before the pump (which is in the flow) followed upstream (but less than 150 mm away) by the vent pipe. (I have also seen arguments put forward for having the vent next to the pump rather than the cold feed).

The second image shows the same configuration but in a vertical layout. Would this work? I’m not sure if it is ok to have a right-angle bend in the vent pipe though. I would prefer the second layout as it would be much easier to modify what we have and also I like the idea of having a greater head of water above the pump.

Any thoughts/ideas welcome. Thanks.

Gofer

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Pete - thanks for your response. My boiler is wood pellet fired - is combined feed & vent o.k. with this?

Gofer
The best way for the boiler would be feed direct to bottom of boiler and vent off the top then pump off another top connection - because it's solid fuel - can you do this ?
 
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Don't combine feed and vent on pellet.
Cold feed should be inverted (under the pipe on the horizontal drawing)
150mm between vent and cold feed.
 
Pete - thanks for your response. My boiler is wood pellet fired - is combined feed & vent o.k. with this?

Gofer
The best way for the boiler would be feed direct to bottom of boiler and vent off the top then pump off another top connection - because it's solid fuel - can you do this ?

Nige F: thanks for your reply. Probably the answer is no because in my simplified drawing I have not shown the rather complicated plumbing arrangement behind the boiler. The installer has fitted an Elterm mixer device with associated pump and air vents and I would rather not mess with this! I am not a plumber so I'm not 100% sure how this works but I understand that it regulates the return water temperature so as to avoid corrosion in the boiler heat exchanger.
 
Don't combine feed and vent on pellet.
Cold feed should be inverted (under the pipe on the horizontal drawing)
150mm between vent and cold feed.

Lee C - thanks for your response. I didn't think it was a good idea to combine the feed & vent in my case but to be fair to Pete he did not know that I had a pellet boiler when he posted. If I went for the vertical arrangement, how would I invert the cold feed? Would it be a matter of taking the 15mm pipe down a few inches from where it joins the flow pipe then back up vertically? Also is it ok to have a right angle bend in the vent pipe where it leaves the flow as shown in my sketch?

Thanks.
Gofer
 
Don't combine feed and vent on pellet.
Cold feed should be inverted (under the pipe on the horizontal drawing)
150mm between vent and cold feed.

Lee C - thanks for your response. I didn't think it was a good idea to combine the feed & vent in my case but to be fair to Pete he did not know that I had a pellet boiler when he posted. If I went for the vertical arrangement, how would I invert the cold feed? Would it be a matter of taking the 15mm pipe down a few inches from where it joins the flow pipe then back up vertically? Also is it ok to have a right angle bend in the vent pipe where it leaves the flow as shown in my sketch?

Thanks.
Gofer

LeeC - would be grateful if you could answer these last two points please. Thanks.
Gofer
 

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