Help with pumping over on incorrect system layout (I believe!)

[uwavetv]

Hi

Would really appreciate if someone can help, done the 100 hrs on the web trying to fix myself but need guidance.

I have a two story house with boiler in external garage. I have recently added eTRVs on all but 1 rad, cleaned system etc. Issue is when I have only say three/four rads open the flow is poor through them and goes up and out the vent pipe (path of least resistance I assume) not as bad on pump setting 1 but on 2 it is a full flow out the vent. Pictures below, any way I can stop this, looked at combining the Vent and Feed but not sure where to join and also would have the filling air lock issue associated with this but would rather that problem than the circulation up the vent and down the feed.

Any guidance much appreciated
uWave

 

[Whyme]

Be very careful messing with the systems vent btw.

 

[kris]

its real simple if you look at your drawing, there's nothing stopping pumping over but if you moved the motorised valve next to boiler then , also little problem with vent as depending on the system , ie fully pumped the position of the vent is paramount I E teed off beside the boiler, the position it's in is per for Gravity but not fully pumped

 

[townfanjon]

Google close coupling ...... its a bit hard to explain on here, alter it to that , and it will be fine, somebody may help and put a pic up for you .

 

[kris]

Here DIY Heating Plumbing Tips 6 - Installation And Maintenance of The Circulator

 

[uwavetv]

Thanks guys
Kris, yes would move the motorised valve to boiler except I would need to bring the vent down to it and it is not practical as it is outside.
I will look into close coupling hopefully I will get somewhere...

 

[doitmyself]

The problem is caused by having the feed and vent pipes on either side of the boiler. This was OK when the boilers had low resistance cast iron heat exchangers, but a big no-no for a modern boiler with a high resistance aluminium or stainless steel exchanger.

Did you have an old boiler replaced within the past few years and have now got round to installing TRVs in place of manual valves? That could explain why the problem has only now occurred.

Which make/model boiler do you have?

The manual bypass should be replaced with an Automatic Bypass valve.

 

[Best]

Bypass valve should be beside the boiler, I think.
If the system is sound enough, oil or gas systems should be sealed type, which is a very easy conversion for a pro. That way, no open vents.
I see you are from N.I. Most heating systems over here were open vented and it is a common problem deciding how to prevent pumping over if altering the system or adding trvs

 

[lame plumber]

bypass should be as far away from the boiler as you can reasonably allow, to allow for some loss of heat on the circuit. Boiler mfis will give a minimum distance

 

[Nostrum]

I would simply cut and cap the existing cold feed where it tees into the bottom of the coil, and then tee into the flow as close as you can to the open vent after the tee piece.

No need to pressurise, you'll also do away with any potential blockage in the cold feed tee, should work just fine.

 

[Best]

Likely an oil boiler heating system and little odds if the bypass valve is closer to the boiler, as it won't do any harm IMO.
Combining the feed and vent pipe is preferable than it pumping over, if there is no other straight forward possibility, but I find systems with combined feed & vents absorb air and can have corrosion for some reason.
Take a good look at the sealed system option, as it is far superior

 

[uwavetv]

Thanks guys.. I have a Warmflow 90/120 boiler..in is in from new at house build in 2001..I added the trvs last year and suffered from overpump ever since..I have an abv purchased and planned to change out on drain down to fix this issue...on this I plan to install abv across the motorised valve at entry to coil instead of across coil that way if it has to operate it will dump heat into the tank..though it has just struck me that if this was continuous it may overhear the tank water as I assume if I was in CH only the tank stat would not be operational?? Any comments on this config? On the overpump issue I am a little uneasy about going sealed due to all the pipes buried in screed and potential leaks..perhaps I am being over cautious...

 

[Elgordo]

Better to place it across the coil , it could as you suggest allow too much flow to the cylinder and mightn't cure the pumping over , connect across cylinder before the mv and join the vent and feed pipe then dose with plenty of inhibitor !

 

[doitmyself]

I plan to install abv across the motorised valve at entry to coil instead of across coil that way if it has to operate it will dump heat into the tank

The ABV has to be:

1. Between flow and return
2. After the pump
3. Before any motorized valves

It can be installed either in place of the existing manual bypass valve or before the feed from the boiler divides to CH and HW.

An ABV is not there to dump heat but to provide a path for the excess pump pressure, particularly where TRVs are installed.

Compared to modern condensing gas boilers, your boiler's heat exchanger has a very low resistance. So the fact that the feed and vent connections are on different sides of the hex may not be too important. However the vent pipe should be before the pump (it appears to be after - assuming the pump is in the boiler). Warmflow would the best people to advise you.

In any case, the way the vent pipe has been connected will not help (I'm assuming the diagram is an accurate representation of the physical reality). This is because it is easier for the water to travel straight up rather than turn the corner to the valve. This can be overcome by moving the vent so it connects to a horizontal pipe.

 

[uwavetv]

OK 10:4 on abv I will put in t across the coil... If I try the combining as suggested above I will still have the vent after the pump but I am assuming that the combined now has the feed pressure from the header tank therefore more resistance than before and hopefully the flow will not be up the vent.(unless of course it needs to)
Again appreciating the help..

 

[Best]

OK 10:4 on abv I will put in t across the coil... If I try the combining as suggested above I will still have the vent after the pump but I am assuming that the combined now has the feed pressure from the header tank therefore more resistance than before and hopefully the flow will not be up the vent.(unless of course it needs to)
Again appreciating the help..

No, what the combined feed and vent will mean is that there is no path for the water to flow and return. Because you have effectively one single pipe used as a feed & with a vent teed off it, then for the water to flow up it has no path of return, if you know what I mean.
The way yours is done will mean the water goes up the vent & the displaced water is replaced from the heating tank down the feed, - basically like a radiator.
The point above about the position of vent on end of tee is an interesting one, but if the water has an easy route it will take it on a twin feed & vent set up, no matter how you tee off.
Tbh, I do not like the combined feed & vent as I know plenty of jobs suffer from magnetite on those systems. The close coupled arrangement is perhaps better, but I also think it is not that good & I know air can be an issue.
Sealed system is the way to do it. If the pipe work seems sound I would go that method, but plastic push fit is a worry. The extra pressure is not huge - system only needs a max of 1 bar usually with oil boiler

 

[doitmyself]

OK 10:4 on abv I will put in t across the coil

Before the motorized valve, i.e in place of the existing bypass.

Check with Warmflow before you decide to use a combined feed and vent.

 

[uwavetv]

Hi yes sorry I meant before the MV not directly across the coil...thanks Best for the guidance I would go on sealed but not sure the whole system is all pushfit plastic apart from 0.5 m off the boiler... I once plumbed a whole renovation (that I though I was staying in) in full 22mm copper apart from into the rads (15mm) and it was a dream.. Hot rads, flow etc.. etc anyway those pushfits i have now make me nervous...and yes exactly as you say the current system is up the vent and down the feed as I have no level change in the f&e tank ...

 

[uwavetv]

Hi again, just to check on suggested options I have updated the drawing, am I correct in Ting into at point "1" on my schematic or what about "2" and point "3"?
Also should I change the feed down from tank to 22mm to match the vent?
Thanks again

 

[ShaunCorbs]

can i ask where are you calcs to say you need your vent 1m above your f+ tank, and get and heating engineer in before you break something

 

[IDCHAPPY]

Seal the system.

 

[uwavetv]

Hi Shaun, the 1m is where the heating engineer (paid with hard earned cash) came to fix the problem, he moved it up from 0.5m.. job done, wallet lighter....

 

[ShaunCorbs]

Hi Shaun, the 1m is where the heating engineer (paid with hard earned cash) came to fix the problem, he moved it up from 0.5m.. job done, wallet lighter....

something is wrong if you need it that high on a normal domestic house

 

[uwavetv]

well from what I have picked up on this I have a system layout that is not suited to S Plan fully pumped and TRVs.. with not being able to get the feed and vent connections at the correct point in the loop.. so I am trying to make the best out of it...

 

[ShaunCorbs]

well from what I have picked up on this I have a system layout that is not suited to S Plan fully pumped and TRVs.. with not being able to get the feed and vent connections at the correct point in the loop.. so I am trying to make the best out of it...

what boiler and cylinder you got? (make and model plz)

 

[Best]

what boiler and cylinder you got? (make and model plz)

He said earlier that it is a Warmflow 90/120 oil boiler. Little odds really, - he should be getting a heating engineer in to sort it. Really silly trying to sort it by guess work and it's not a DIY task.
First thing should be considered is viability of sealing the system. Connecting the vent and feed together is not a fantastic solution.

 

[ShaunCorbs]

He said earlier that it is a Warmflow 90/120 oil boiler. Little odds really, - he should be getting a heating engineer in to sort it. Really silly trying to sort it by guess work and it's not a DIY task.
First thing should be considered is viability of sealing the system. Connecting the vent and feed together is not a fantastic solution.

+1 boiler is able to be used on a sealed system from new

 

[uwavetv]

I have a Warmflow B90-120 27 to 47 kW with a Riello RDB oil burner, pump is Wilo GOLD 50. Cyclinder make I don't know but it is a standard domestic I would say with one coil.......

 

[Best]

I have a Warmflow B90-120 27 to 47 kW with a Riello RDB oil burner, pump is Wilo GOLD 50. Cyclinder make I don't know but it is a standard domestic I would say with one coil.......

Well straight away it is wrong! The pump is wrong type.
Bad news is proper pump will make things worse if system remains unaltered.

 

[uwavetv]

OK, so recommendations on re piping/layout and or pump? what should I do and I would be fine with paying for a solution if someone comes here that knows what they are doing to correct once..

 

[Best]

Someone would need to look at it all, but I think there is nothing too bad about it at the moment that a few modifications won't fix.
It's either do something with the vent/feed, or change it to a sealed system, which is a very easy job & inexpensive.

 

[uwavetv]

OK, so if I was to go to a low pressure sealed how would the attached look in terms of the system diagram/setup, again please excuse the ignorance...

 

[ShaunCorbs]

OK, so if I was to go to a low pressure sealed how would the attached look in terms of the system diagram/setup, again please excuse the ignorance...


View attachment 22250

Doesn't matter mate as you haven't got your unvented ticket

 

[uwavetv]

Sorry Shaun don't follow you, where is the issue? Ta

 

[doitmyself]

The pump is wrong type.

In what way is it the "wrong type"?