CH F&E Connection point?

winker · 2 Feb 2004

I have always (lived in house 10yrs) had trouble with air getting into ch system somewhere, collecting in upstairs bathroom rad.

My Expansion is 22mm on flow side of the boiler and 50mm before the pump. The feed is 15mm on the return side of the boiler.

I have read that the best soulution is to have the F & E within 150mm of each other, between the boiler and the pump flow.

So why not just connect the feed to the expansion with a T near to the point of entry before the pump?

Any suggestions as to what is wrong with doing this appreciated.

oilman · 2 Feb 2004

You need to understand the function of the pipes you refer to as F & E. They are one pipe, the other pipe is the OSV (open safety vent) The safety vent is the first pipe that comes off the flow from the boiler. It should rise continuously and must not have any obstructions. The next pipe is the F & E (feed and expansion) and should be within 150mm of the OSV.

You say air is getting into the system. It could be corrosion gas ie hydrogen. Have you checked this? When was corrosion inhibitor last added to the system?

winker · 2 Feb 2004

Sorry.... tried to be clear giving info and then go and use the wrong terminology...doh.

OK, so can the f&e pipe be T to the OSV near the orignal OSV connection to the system?

ollski · 2 Feb 2004

Yep close proximity setup is vent, feed then pump with vent and feed within 150mm. Combined feed and vent must be in 22mm at least.

winker · 3 Feb 2004

So if I do T off the 22mm Vent, I should replace my 15mm feed with 22mm as well?

ChrisR · 3 Feb 2004

Don't tee into the OSV, tee into the heating flow pipe just after the OSV. Otherwise the bubbles have to go up while the water comes down. That does happen with 22mm, but only just.

You CAN have the pump in the return, though it isn't ideal. Mines's been in the return for the last 20 years. The result is that small leaks have sucked air in, because the system is mostly under negative pressure. I'll be flushing the resultant sludge out and replumbing thes summer!

sterose · 3 Feb 2004

oilman said:
You need to understand the function of the pipes you refer to as F & E. They are one pipe, the other pipe is the OSV (open safety vent) The safety vent is the first pipe that comes off the flow from the boiler. It should rise continuously and must not have any obstructions. The next pipe is the F & E (feed and expansion) and should be within 150mm of the OSV.

You say air is getting into the system. It could be corrosion gas ie hydrogen. Have you checked this? When was corrosion inhibitor last added to the system?

We're not going to start that Hydrogen debate again are we oilman...

Did we ever find out whether that guy with "hydrogen" in his system, actually had hydrogen in his system?

winker · 5 Feb 2004

Thanks for the advice guys.

I have just finished rejigging the pipe work in a very confined space (ended up cutting a hole in a bedroom cupboard wall (built in) to gain acces to parts of it).

Space was so tight I had to replace the gate valves on the pump with the shortest ones I could find, to gain enough extra in the run to put in an air seperator.

The system filled like a dream (one weeping compression joint, not bad realy, out of about 10 solders and three compressions). Air just gushed out off the bathroom raiator, the one that used to take for ever to bleed.

So lets just see how it goes.....

Once again thanks for the advice...Nice to see peolpe taking the time to help others.

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CH F&E Connection point?

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