CH vent & supply pipe combined?


Postby KBarton » Fri Apr 03, 2009 10:34 am

Hello all

Have been checking over my CH system - its fully pumped, open vented, microbore to rads - 2 separate valves after the pump instead of a 3 way.

Have seen many references about pipe layout mention order should be boiler flow - cold feed - open vent - pump.

My layout is boiler flow - combined vent/feed - pump.

The T piece on the flow from the boiler, before the pump, goes up towards the F&E tank and a T on it then branches to the bottom of the tank for the cold feed and the other branch goes up over the tank for the vent.

Is this layout OK as I have only seen mention on the web of separate pipes for feed & expansion that should be close to each other and between the boiler & pump?
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Postby rosebery » Fri Apr 03, 2009 5:59 pm

Nothing wrong with it.

Do you have an air separator fitted?

Cheers
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Postby plumbbob » Sat Apr 04, 2009 11:38 pm

Whilst there is no reason to change a combined feed/expansion if all works fine, it is not accepted as good practice to combine the two. It can lead to trapped air, and are often beasts to fill.

The positioning of the feed and expansion connections to the system are straightforward. In the event of a boiler thermostat failure, the boiling water and steam must have an unhindered route to the expansion pipe. The feed pipe must be in close proximity to prevent a pressure differential between the two pipes causing over pumping or sucked in air.

Imagine if the expansion was immediately in front of the pump, and the feed just before it. The pump would push water up and over in to the tank.
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Postby KBarton » Mon Apr 06, 2009 8:03 am

Thanks both.

No - I don't have an 'air separator' in the system. Should I? - I do have a radiator that seems to need to be bled every couple of weeks, which is why I have been investigating the layout of my system.
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Postby rosebery » Mon Apr 06, 2009 10:30 pm

"It can lead to trapped air,"

"I don't have an 'air separator' in the system."

Thats why I asked the question.


"I do have a radiator that seems to need to be bled every couple of weeks, which is why I have been investigating the layout of my system."

Sludge is the most likley culprit - when was it last cleaned?

Cheers
rosebery
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