heating expansion tank back filling

[newbie1]

flushed system and changed boiler now expansion is filling up
dont think its pumping over but think its backfilling
pipework is cold feed in 15mm then expansion 22mm within 75mm of each other then pump
now this has worked fine up till now but in fitting inst from glowworm they have the feed and expansion the other way round
the feed is getting hot but expansion isnt

i am guessing at a blocked expansion or do i need to switch the pipework..might just add an expansion vessel and seal it

 

[Puddle]

coil in cylinder leaking through after power flush maybe ?

 

[newbie1]

no if the coil was leaking that would push up into the cws tank mine is going into expansion tank and my expansion pipe from heating system is cold but feed from expansion is hot

i would expect expansion pipe to get warm not the cold feed for the heating system

 

[mikeygas]

Mate, you need to switch the pipework around it should be :boiler, open vent, cold feed, then pump. You probably already know about the 150mm max. When re-doing the o/v and c/feed use mechanical fittings(i.e compression) where it tee's into the flow as this will make it easier to clean it out if there's ever a blockage in the future.

 

[newbie1]

yep thats what i was thinking as mine was done 26years ago and that was 15mm feed then 50mm later the 22mm expansion and then pump
but gloworm installation shows
22mm expansion then 15mm feed then pump
considering while its drained down might as well convert to sealed system using expansion vessel

 

[mikeygas]

Yeah the glow worm installation is the same configuration as in my post. It's upto you whether to convert to a sealed system but it is quicker, easier and cheaper just to re jig the pipework. Remember your old boiler had larger waterways than the new low water content boilers and back then there were different accepted methods of pipe layouts, today they reccomend as above (as long as boiler has an overheat stat/sensor). Let us know how you get on!

oh sorry newbie forgot to add that it's not pumping over up your expansion pipe as this is under negative pressure, however it is "pumping over/up" through your cold feed as this is on the positive side of your pump.

 

[newbie1]

yep def going up 15mm feed the expansion is stone cold

 

[helpsy]

no if the coil was leaking that would push up into the cws tank mine is going into expansion tank and my expansion pipe from heating system is cold but feed from expansion is hot

i would expect expansion pipe to get warm not the cold feed for the heating system

I thought if coil was perforated you would have the CWSC filling and the F&E overflowing as the F&E level is lower than the CWSC level.

 

[weeman]

if its continually back filling and over flowing its got to be coming from somewhere, my moneys on the cylinder coil

 

[Plucky]

As already stated it depends on the levels of the tanks as to which one back fills. I have had it twice before where coil has split after powerflush.

Drain header tank from heating and ensure heating pump is turned off. then observe to see if header tank begins to refill. If it does it will be cylinder swap time.

 

[newbie1]

cant see it being the coil
the cold feed to the heating flow is getting hot and the expansion isnt
both are located pre pump and its taking several days for the expansion tank to fill

 

[weeman]

isolate ball valve to f&e tank and empty tank if it fills its definitly coil

 

[ecowarm]

yep def going up 15mm feed the expansion is stone cold

Newbie1 is the F&E tank overflowing? also is the cold water tank filling even when no water used?

If not then,

It is usual for the system to expand up the cold feed.

If the level in the tank just goes up and inch or two and as it cools drops down again, then just make sure the float is possitioned low in the tank to allow for expansion. The water will expand aprox. 4% of the total system volume.
If its a large system it may need a larger tank to take up expansion.


Make sure cold feed / open vent right way round as stated above.

Eco

 

[newbie1]

thats my point as it stands at present
15mm feed/then 22mm vent then pump
in instalation inst they have it
22mm vent/then 15mm feed then pump

 

[ecowarm]

swop it over as per instructions

eco

 

[weeman]

when you say the tank is back filling, is it filling up past the ball valve and over flowing and staying like that until emptied or is the level just rising up and down a lot?

jamie

 

[newbie1]

fills up past ball valve so i have been draining it off

 

[ecowarm]

what size system newbie1

 

[tamz]

Mikey gave you the cure in his 1st post
you need to switch the pipework around it should be :boiler, open vent, cold feed, then pump.

And the reasons in his second
it's not pumping over up your expansion pipe as this is under negative pressure, however it is "pumping over/up" through your cold feed as this is on the positive side of your pump.

There is however an underlying reason for it doing this. Check pump position and speed. Work out the index circuit and match the speed to suit.

 

[mikeygas]

Cheers for the back up Tamz see ya in the CC!

 

[newbie1]

mikey didnt disagree just letting the topic run

 

[mikeygas]

No worries , let us know how you get on with it!

 

[newbie1]

my son keeps pushing for making it a sealed system as he gets discount on parts through work so will either go sealed or alter pipework
as allways finding time to work at home is hard
for the moment i lowered the level in the expansion a bit to allow for expansion without hitting the overflow..have to bear in mind my system was done 26 years ago but have to say 2 guys 2 days from stopcock to full 3 bed heating and bathroom plumbing
thats when b/gas were good mind you it wasnt done on the books but guess 80% of my stuff came from there

 

[mrlennie]

Why is there a rule about 150mm between the cold feed and open vent pipe?

and where does the 150mm apply , is it on the pipe that joins them together or is it when they come up to the f and e tank?

 

[weeman]

how does the configuration of pipework increase the volume of water in a system??