Constant trickle of hot water into F&E tank

[Neddy1984]

Hi guys,
there's a continuous trickle of hot water into the F&E tank in the loft which is worrying me. There's a 15-60 pump on the system which when turned down to speed 1 still only slightly affects the trickle of hot water. would fitting a 15-50 pump help to stop this? Obviously the vent pipe is higher than the cold feed and the continuous trickle suggests this is more than just expansion within the system, the pump is actually over pumping. Any suggestions would be greatly appreciated.............

 

[diamondgas]

Neddy1984 do a search of these threads on pumping over. .... Get it sorted as a matter of urgency!!!

Your system is rotting away merely untill you sort it out. Raising the height of the vent pipe is a quick fix but you need someone in to check out the respective position of your feed, vent & pump...

 

[SafeGasInstall]

get a local heating engineer to check all the system ,could me many things that are wrong

 

[Neddy1984]

the cold feed is just before the pump (which is near the boiler downstairs) and there are 2 vents, one teed off the return pipe near the H/W cylinder upstairs and another teed off the primary going into the indirect cylinder so that both the heating and primary circuits are vented into the f&e tank. would fitting a less powerful pump and raising the height of the vent prove a solution as everything is working fine within the system except for the fact that hot water is venting too high back into the f&e tank and causing the tank to be hot. its not overflowing through the overflow pipe tho, so is there any real dangers caused by this as the water in the tank isn't heating up more than 70c as its limited by the boiler............
Ideally there would have been just the one vent sited before the cold feed but this would mean taking down a wall which hides pipework from a previous 1 pipe heating system.

 

[Halesowen1]

Is it a new system or just started happening, anything new been added to system. Any more info would help.

 

[Halesowen1]

I only see the point in the one on return, as you say you wanted both primary and heating vented, well the one on the return will do both these jobs. I would cut and cap off the one on flow to cylinder. Just put a thumb vent where this vent is.

 

[Neddy1984]

its a new system, but due to the piping route being behind this wall I was talking about (which runs the height of the house), we used some of the existing older pipework and decided to vent off the return instead of off the flow before the cold feed as per usual. Basically without removing this wall we couldn't feed a new pipe up inside this wall so thought it would be ok to instead vent off both the primary and the heating from inside the h/w cylinder cupboard. so everything is vented and safe!!! I'm just worried about the heat within the f&e tank as obviously this is bad and causing freshly oxygenated water to constantly enter the heating system which will lead to corrosion.
will simply raising the vent pipe as high as possible and fitting a 15-50 pump instead of the more powerful and current 15-60 pump solve the problem? or will I have to remove wall, fit a single vent before the cold feed?

 

[Neddy1984]

thanks again in advance for any comments and i appreciate the comments left already

 

[PowerFlushAssoc]

Unless the system is piped incorrectly - problem always existed. It is probably a sludge build-up where the down feed and vent pipe meets the return pipe, just before the pump. It will need to be cut out and cleaned/replaced. If it has not been done, a power flush would be a good idea afterward or the build-up will happen again.

 

[Halesowen1]

You are not taking a vent from heating and one from primary. The one from the return in A/C is the return pipe (Boiler Return) and other from flow before coil is also (Boiler Flow), so no direct to heating pipe. But the one on the return is joined to return so will do both heating and boiler circs. No need for open vent on the flow before the cylinder, just cut that and fit a thumb vent.

 

[diamondgas]

Neddy 1984 ... At the moment and if best you only have continually re-oxygenating water circulating the system ... that stuff loves to eat new copper, iron etc ... If you stop the pumping over without altering any of the pipework then you'll then be faced with "surging" ... This can also increase oxygenated water entering the system adding to the deterioration and early demise of your new boiler and/or its component parts!

If you have a new appliance fitted then you should be able to 'combine the feed and vent' which does away with any pumping over etc... You could also 'seal' the system!

 

[Neddy1984]

this would usually make sense but seeing as I haven't been able to fit a vent until after the 3port valve, it'd be unsafe to do what you suggest. the overflow of water is also mainly coming from the heating circuit and not the primary as I found out today. I also tried fitting a 15-50 pump and extending the height of the Vent loops into the F+E tank but this made absolutely no difference so I think I'm gonna have to do what I should have done 1st time round and open up the wall to configure the pipes correctly.

 

[fuzzy]

Hi guys,
there's a continuous trickle of hot water into the F&E tank in the loft which is worrying me. There's a 15-60 pump on the system which when turned down to speed 1 still only slightly affects the trickle of hot water. would fitting a 15-50 pump help to stop this? Obviously the vent pipe is higher than the cold feed and the continuous trickle suggests this is more than just expansion within the system, the pump is actually over pumping. Any suggestions would be greatly appreciated.............

pumping over, how long it been like this? could be a blcoked feed if recent, if always prob a incorrect vent inlet pump position

 

[Neddy1984]

thanks Diamond, my previous comment was for the comment before yours. I had thought of combining the vent and feed but the previous feed was run in 15mm and is one of these pipes behind this wall i keep referring to, so I used this pipe as 15mm for a feed is fine but manufacturers instructions on the Vaillant 428 says minimum of 22mm for the expansion pipe. is this just over compensating or should i follow this instruction? I mean, I could very easily cap off the additional vents i've stuck in and use the 15mm as a cold feed and vent.

 

[fuzzy]

this would usually make sense but seeing as I haven't been able to fit a vent until after the 3port valve, it'd be unsafe to do what you suggest. the overflow of water is also mainly coming from the heating circuit and not the primary as I found out today. I also tried fitting a 15-50 pump and extending the height of the Vent loops into the F+E tank but this made absolutely no difference so I think I'm gonna have to do what I should have done 1st time round and open up the wall to configure the pipes correctly.

it wont mate, it shouldnt be under positive pressure, try to sort this

 

[fuzzy]

the cold feed is just before the pump (which is near the boiler downstairs) and there are 2 vents, one teed off the return pipe near the H/W cylinder upstairs and another teed off the primary going into the indirect cylinder so that both the heating and primary circuits are vented into the f&e tank. would fitting a less powerful pump and raising the height of the vent prove a solution as everything is working fine within the system except for the fact that hot water is venting too high back into the f&e tank and causing the tank to be hot. its not overflowing through the overflow pipe tho, so is there any real dangers caused by this as the water in the tank isn't heating up more than 70c as its limited by the boiler............
Ideally there would have been just the one vent sited before the cold feed but this would mean taking down a wall which hides pipework from a previous 1 pipe heating system.

that dont sound right, heating is the primary circuit, HW is the secondry, you say the secondary water is vented above the F&E cistern?

 

[Neddy1984]

it wont mate, it shouldnt be under positive pressure, try to sort this

thanks fuzzy,
what i meant was when the vent is configured properly, i.e, before the 3 port valve, it allows expansion for both the primary and heating circuits. whereas at the moment in my case if I put a thumb vent on primary circuit instead of an expansion vent all the way up to f+e tank, pressure could potentially build up as the expansion would have no where to go.
I thought my little experiment would see me thru but it seems I've shot myself in the foot and this hollow wall will have to come down while i fit a single 22mm vent all the way up the house, unless of course i can use the 15mm feed as the vent too.....
thanks for all your comments

 

[fuzzy]

remember the vent is not there for expansion, the cold feed is

 

[Neddy1984]

sorry i've got my primaries and secondaries mixed up. do you see why i vented both the primary and secondary because I couldn't fit a single vent before the 3-port, I assumed it might be dangerous not to fully vent both.

 

[fuzzy]

you ideally need a seperate vent in 22mm a seperate cold feed in 15mm within 150mm of vent and then the pump

 

[diamondgas]

thanks Diamond, my previous comment was for the comment before yours. I had thought of combining the vent and feed but the previous feed was run in 15mm and is one of these pipes behind this wall i keep referring to, so I used this pipe as 15mm for a feed is fine but manufacturers instructions on the Vaillant 428 says minimum of 22mm for the expansion pipe. is this just over compensating or should i follow this instruction? I mean, I could very easily cap off the additional vents i've stuck in and use the 15mm as a cold feed and vent.

If the mi's ask for 22mm then that's what you'll need. I've only ever combined the f&e in 22mm, water expands quite rapidly when it reaches boiling point

Can you seal the system? That way you do away with all the pumping over.

 

[Neddy1984]

remember the vent is not there for expansion, the cold feed is

this now makes far more sense!! thanks a lot.

 

[fuzzy]

the total expansion should be 4% absolute max and should easily be taken up in the f&e. the fe should be set low to allow for this, the water shouldnt come out the vent but travel up the cold feed to expand, and back down when it cools maintaing the same treated water in the system

 

[fuzzy]

the vent is there to allow air in when draining and air out when filling, it also keeps it at atmospheric pressure so there is never a rise in pressure

 

[Neddy1984]

well you're right, you can never stop learning!