Mystery, missing open vent on F & E tank.

[Dannypipe]

Hello all.

Got called to a late job (6pm) tonight. Someone saying their F&E tank was overflowing.

I get there, and yes the ball float valve was passing. (The float was under water too).

Thought to myself, nice simple job...then notice...there's no open vent. I then notice the bent peice of discarded 22mm pipe which would have been the open vent.

Spoke to client. British Gas did her boiler change in 2004. I looked at the invoice. They charged her for 'pipe alteration in 22mm'. Amongst other things.

Anyway, the client said she had to pay for BG to come back as she complained of air in the system. The engineer who came out said the first installers had cocked it up and it was sucking in loads of air. I can then only presume he went on the cut out the open vent.

I really had to look at it all very carefully to ensure I wasn't missing something, which would make me look like an idiot when BG came back out.

I then advised client, told her I would help as much as I can. She's now calling BG, I await their answer.

I've seen funny things done to open vents, Put to one side of the tank so it'll miss. Cut too long, Cut too short, but NEVER cut out all together.

Anyone else?

 

[diamondgas]

Hey danny,
Has the feed and vent been combined into one? Common alteration done providing the mfi allows it ...

 

[Dannypipe]

Surely with a combined feed and open vent you would still expect to see a loop of copper over the tank? Open to atmosphere.

What if sediment/sludge blocked the cold feed. Seems bad idea.

 

[dontknowitall]

Presumably it's not a combi boiler and this is an unused tank (but not decomissioned)?

Assuming it is a standard boiler then you're definitely on the right tracks.

 

[diamondgas]

Well in theory all you should have moving up and down the combined pipe is water! anything else in the f&e tank point's to serious problems. The system is still open to 'atmosphere'. In general as long as the appliance has an overheat cut-off preventing the appliance from reaching critical temp the f&e does just what it is meant to do; replace water lost and take up the expansion in the system. Bit like and expansion vessel only the water is allowed to expand into the atmosphere! ... The combined f&e needs to be 22mm minimum.

 

[WHPES]

For some installations it was common practice in the 70s to cut costs by just using use a 22mm pipe from the bottom of the tank for feed and expansion and not have a swan neck, or if a swan neck existed just to tack it onto the feed pipe. The feed pipe often just connected into the top of the DHW cylinder coil for convenience (rather than onto the primary circuit by the boiler), making it a pain to get air out of the radiator system (which more oftenh than not with this set-up was a single pipe system to save on installation costs)

Such system are unsatisfactory as they take ages to fill and bleed, and are prone to blocakges. Where I come across them I usuall remove them and convert to a sealed system.

 

[stevetheplumber]

ive never seen m'is that allow no vent combined yes but that usually meant taking the cold feed in to the vent what boiler is it so we can check the mi's?

 

[diamondgas]

Check these out from Myson apollo .. fitted until the 90's or thereabouts and the designe principle continued until sealed systems became the norm! Note the vent only required if a valve is fitted to the 22mm f&e pipe ...

 

[WHPES]

Most of the time where I come across them they are connected to where the air vent is shown at the top of the cylinder coil on your LHS diagram.

 

[paulnwales]

them diagrams are ancient, you need a vent now. have done for a long time.

 

[diamondgas]

A cobined F&E became common practice to overcome the different pressures produced +&- on the f&e pipes. Along with fully pumped sytstems came microbore pipe which also brought along pumping over and flow 'surges' up and down the f&e pipes. Many reasons as to why, bi-pass incorrectly set up, pipes wrongly positioed etc... To overcome ingress air and 'surging'. a single feed f&e became the practice ... That was until sealed systems became the norm. rarely, i may add, were pressure relief valves fitted!

 

[WHPES]

Rip out and convert to sealed sytem

In 2004 the system you describe was well obsolete by then

 

[richw]

we did sites years ago with just a 22mm combined vent/feed from the base of the header. was resonably common.

 

[diamondgas]

them diagrams are ancient, you need a vent now. have done for a long time.

Paulnwales, please check out [DLMURL]http://www.idealheating.com/downloads/manuals/201787_inst.pdf[/DLMURL] page 11. NEW installations for Ideal Mexico. The use of combined f&e is still relevant today and can save a great deal of grief when an open system is the only option...

Without checking other manufacturers of appliances suitable for open systems I'd guess they'd all conccur on the alternative of combining the f&e pipes... You'll note that it is feed and expansion and not for venting. If you're faced with an issue regarding older open vented systems and concerned about pressurising them there are alternatives options still available that are relevant today...

Hope this has been of some help...

 

[Dannypipe]

Many thanks for all comments. I've told client to call BG, personally I think it's wrong, but appreciate the comments, even the ones when it says its ok.

The boiler is a Glow Worm Micron. Don't know what model micra, but my guess would be the smallest model they make. This house was very small, one bedroom.

Hope that BG don't come back and say I'm wrong as it will make me look a fool. I haven't come across this before and said I feel it should have been converted to a sealed system.

 

[tamz]

Diamondgas beat me to it but this is a standard method of connecting for low head situations with low water content boilers.



It may be old but it works well enough. It prevents pumping over and drawing air because of the volume of water. The expansion loop itself is irrelevant as it will still expand.

 

[paulnwales]

Paulnwales, please check out [DLMURL]http://www.idealheating.com/downloads/manuals/201787_inst.pdf[/DLMURL] page 11. NEW installations for Ideal Mexico. The use of combined f&e is still relevant today and can save a great deal of grief when an open system is the only option...

Without checking other manufacturers of appliances suitable for open systems I'd guess they'd all conccur on the alternative of combining the f&e pipes... You'll note that it is feed and expansion and not for venting. If you're faced with an issue regarding older open vented systems and concerned about pressurising them there are alternatives options still available that are relevant today...

Hope this has been of some help...

cheers i had a look at it, but in that case you also need a air seperator and auto air vent installing, i personally would not be keen on doing it..

 

[Dannypipe]

Wish I had this information before I advised the client. Its obviously fairly rare as I've not come across it before.

As I said, the original installers left the vent in place. The second BG guy (who the client says was an older guy) said they had plumbed it up wrong, and must have cut the open vent out. I'd like to convert it to a sealed system...however I've advised the client to contact BG. They may now be on the phone to me, telling me to go back to school!!

 

[paulnwales]

Wish I had this information before I advised the client. Its obviously fairly rare as I've not come across it before.

As I said, the original installers left the vent in place. The second BG guy (who the client says was an older guy) said they had plumbed it up wrong, and must have cut the open vent out. I'd like to convert it to a sealed system...however I've advised the client to contact BG. They may now be on the phone to me, telling me to go back to school!!

just tell them in your opinion (thats if you agree) and many others its not great to do, there is enough space above f&e to put one in so as far as im concerned it should be there.. there is a reason that its not really done anymore. over many years huge amounts of money has been spent on research into these things, if it was a great idea then the swan neck would never really be used. thats just my thoughts tho.

 

[diamondgas]

Wish I had this information before I advised the client. Its obviously fairly rare as I've not come across it before.

As I said, the original installers left the vent in place. The second BG guy (who the client says was an older guy) said they had plumbed it up wrong, and must have cut the open vent out. I'd like to convert it to a sealed system...however I've advised the client to contact BG. They may now be on the phone to me, telling me to go back to school!!

I happen to come from the old school where this was the norm Dannypipe. If you came in to this industry when sealed systems were the norm you'd know no different especially when you expect an open vent and feed seporate ... Always learning and still am 30+ years on .....

paulnwales -- I agree I'd rather seal the system myself.. Nice to know that there's an alternative when you get that iky feeling something might just not take the strain!!! lol

 

[paulnwales]

my thoughts would be if the first installer put it in and the second changed it.. was it changed correctly? i have seen some strange systems in the past 15 years or so that seem to work fine untill you change one little thing. cheers for the info tho... do any other manufactures allow it do you know?

 

[paulnwales]

let us know the outcome dannypipe please.

 

[Dannypipe]

Well many thanks for all the comments. Still lots to learn!

I'll see what comes of it and will report back with the conclusion. Checked the MI, and it seems a combined feed/vent is allowed. Oh well, I wasn't to know, I'm 32 so it's been sealed systems on everything I've installed, and always a swan neck open vent on the header of existing systems that I've worked on. No one knows it all!

 

[tamz]

The drawing in the ideal book is just an improvement on an inverted feed. Also "old technology" that works.
The purpose of the aerject is to act like a small header and slow the water down as it passes through. The feed(exp) within 6" is to keep it within the neutral pressure zone. The head can be kept even lower using this method.

 

[tamz]

Just about every boiler manu who do regular boilers will allow combined feed expansions. There are many ways to skin a rabbit and they only list the most common ways.
Here is another one from Vokera mynute he