Any plumbers out there...?

[slow-lane-Matt]

Can anyone answer or comment on this..?

I've got gravity fed hot water
pumped radiators

All was working, then had new cylinder fitted to provide second heat exchanger for wood burner.

Now gravity fed hot water does not heat up.

The wood burner circuit is separate and works fine

Should gravity alone be enough to transfer heat to cylinder - currently it makes scary banging noises then vents out to overflow, ie hot water is not
flowing through the heat exchanger. Maybe due to blockage - or boiler heats up water too quickly so boils before convention current created

If the pump is on for the radiators (they work) no hot water or venting

Seems wrong to have pumped and gravity fed circuits in parallel, surely the pumped circuit will take almost all the hot water leaving very little to find its way down the gravity circuit...

Any comments ? is the setup fundamentally wrong - or very likely, am I displaying my ignorance.

I know you all like photos - here's one of the old boiler !
(I have checked and replaced the Honeywell head/valve)

 

[SteveGTU]

Hi Matt
Don't know if you've resolved this yet but I'd say the coil is trapping air ! The highest of the three pipes in the pic needs to raise towards the vent and yours looks like it goes down then up. Any air would naturally get stuck in the top of the coil and cause the banging noise and stop circulation .
Set up sounds ok as this was fairly common years ago although if you converted it to a fully pumped system it would be far more efficient

 

[subheatadey]

Not knowing what you have done though it doesn't sound too clever i would be very wary. I am guessing you have replaced the original cylinder which would have been a primatic or direct cylinder and fitted a indirect cylinder in its place?

 

[slow-lane-Matt]

Thanks for the comments. The cylinder was replaced by a professional plumber when we had a back boiler fitted to wood burner,
but apparently he f*ed it up and the problem is exactly as SteveGTU describes. The system traps air in the entry to cylinder. That pipe should be fitted downwards so air flows up to overflow in attic overflow and doesn't block entry to cylinder.

Temporary fix was slackening bolt to release the air, longterm will get pump fitted.

(Was helped by a plumbers forum - what did we do before the internet!)

 

[SteveGTU]

Glad you're sorted Matt, nothing wrong with you're system so long as it's installed correctly
Wish I could sort my van as easy

 

[adelec15]

Hi Matt
Don't know if you've resolved this yet but I'd say the coil is trapping air ! The highest of the three pipes in the pic needs to raise towards the vent and yours looks like it goes down then up Baignoire à porte. Any air would naturally get stuck in the top of the coil and cause the banging noise and stop circulation .
Set up sounds ok as this was fairly common years ago although if you converted it to a fully pumped system it would be far more efficient

Me anyway, it's my pet peeve and I prefer to call a professional to do this kind of thing.