no hot water but hot rads

[kennydig1]

we are fitting a new power shower so decided to fit new hot water cylinder,a new indirect, vented 900x450 the old one was 600x450.
connected the new one straight on to the connections for the coil, gravity feeding the baxi bermuda back boiler.
we have hot raidiators but no hot water.cracked open some connections but no hot water.
called out heating engineer he said it would be air, but no fix.
I called maker of cylinder, turns out it is only for a pumped system, silly me for that..
any way guy helping me called his supplier and got a gravity feed indirect cylinder.connected it all up and same problem!!!!!!!!!!!!!
can anyone help me sort this out as it would be much apprecited

P.S when you look in the 2 new cylinders the coils look the same ,maybe 7 or 8 coils quite tightly wound not a loose coil like the old cylinder.if that makes sense.

 

[45yearsagasman]

Are you absolutely sure that the gravity primaries are full of water and all air is vented. Do you have 28mm (1") gravity pipework? Cold feed not blocked.
Is all pipework original and not been altered in any way from original to accommodate the new cylinder?

 

[kennydig1]

heating engineer fitted a bleed valve off a radiator on the coil feed pipe.
pipework 28mm then reduces to 22mm just next to tank.
when I switched on heating this morning there was a bit off banging ang gurgling for about 30 secs.
engineer cut into cold feeed and checked it, and he blew around the pipes and the water was moving.

 

[45yearsagasman]

Your terminology is confusing. A pic of the system pipework on the cylinder would help. Your "engineer" sounds like a waste of time if he can't sort a simple gravity fault. I apologise for not understanding your post.

 

[spraggo]

Was the original cylinder a Primatic

 

[DP]

Is one of the pipes hot? Old cylinder coil would have been quite small, hence boiler would have, during HW heat cycle, most of the time asleep. Modern cylinders have much larger indirect coils to heat the water quickly.

If the system fails to work, might be an idea to fit a pump or convert the system to fully pumped. Be warned, each modification will need to be done correctly else there will be more tears. ENSURE FEED AND/ OR VENT PIPES DO NOT HAVE ANY VALVES, PUMPS, MVs etc fitted in them

 

[kennydig1]

Yesterday coil feed pipe was hot to just next to cylinder,we didnt get that before.
The new tank is a McDonald and the maker said it was suitable for gravity use.
Iam going to try to put some pics up.
I dont know what kind the old tank is,but the coil wasnt asd big.

 

[kennydig1]

I have uploaded photos, there on my profile

 

[picasso]

I wonder if the supplier of your cylinder has misunderstood when you asked for a gravity cylinder, I would contact them again and explain that you need a cylinder suitable for gravity primarys.

 

[kennydig1]

the supplier was asked twice.so to make sure as I had already got a cylinder for a pumped system.But when I looked in the cylinders the coils looked the same.

 

[spraggo]

Looking at the photos, the flow pipe going into the cylinder seems to be rising after the expansion tee and cuasing an air lock in the coil

 

[kennydig1]

if I loosen coil connections will that let any traped air out?

 

[45yearsagasman]

Yes that should let air out, but the main problem is pipe angles. All gravity pipework should fall back towards the boiler. That include flow and return.

 

[spraggo]

Fit the swan neck so that is fitted to the left hand side of the expansion tee and fit the short piece of pipe, now fitted to the left of the tee, to the right of the tee altering the expansion pipe accordingly. This will solve your problem.

 

[kennydig1]

The pipe feeding the coil is level(I had a spirit level on it) the swan neck is just lining the connection horizontally not vertically.
If anything the pipe coming out of the coil is low at one point by a inch.