No hot water - please help!

[dm7618]

Hi all,

This is my first post so excuse me if i don't give enough info/detail but i'll have ago!

I have a Glow Worm Hide away gas bolier and a basic gravity system.

I needed to replace the water cylinder as the old one sprung a leak, this has been done, but required some pipe wok to be changed. This no means the lower connector to the cylinder has horizontal pipework back to the pipe which then goes downstairs back to the boiler. First Question will this inhibit flow back to the bolier?

My problem seems to be that the boiler starts up fine and starts to heat the water, this flows to the cylinder, but doesn't flow round the coil, so the boiler only heats the water in the up pipe and one radiator that is connected to the hot water system until it reaches the temp erature setting and stops (as it should) problem is no hot water!

What can be stopping my flow around the coil in the cylinder?

I have drained the system mulitple times, flushed all pipes i can get at with a hose to check for blockages. Filled the system from the header tank downwards and from the drain plug upwards, bled the whole system but no joy.

The CH works fine, better than ever actually, but I would like some hot water!

Any help would be very much appreciated.
Thanks in Advance

 

[namsag]

You have an air lock in the gravity circuit, easiest way to clear it is to have the boiler running for just hot water and with the stat on its highest setting as it gets up to temp remove the thermostat phial from its pocket in the boiler heat exchanger. This will allow the water in the system to get a lot hotter than is normally safe and start to boil which will force its way past the air lock. You will get a lot of banging and thumping from the boiler as air clears ONLY allow the banging for about 20/30 seconds at a time if it does not clear turn boiler off for a bit and try again after it cools a bit. And remember to put phial back in pocket fully when job complete.

 

[dm7618]

namsag,

Thanks for the reply.

I have already tried this, letting the bolier 'overheat' twice.
As you said there was a lot of banging and water did seem to flow, but once cooled down and tried again properly the same thing happens.

The second time i let it 'overheat' longer (maybe 1 min) and the hot water reached the header tank via the hot water to the cylinder pipe overflow.

Do I need to do this more than twice?

If not, can you think of anything else?

Thanks

 

[ChrisR]

Does the flow pipe from the boiler go in the upper or lower connection on the cylinder? Has to be the upper one.

 

[dm7618]

Definately the upper one!

The pipes were only modified slightly from the original position for the new cylinder.

 

[PaulHF]

Thanks for your comments - it does sound similar. I'll let you if I discover any cure.

 

[PaulHF]

The suggestions given for your problem - removing the thermo phial etc. -seem to have worked for mine. Hope you find a solution soon. Thanks for your help.

 

[dm7618]

How did you do it if you don't mind me asking? I have tried a couple of times and not succeeded

Thanks

 

[PEDANTICVINDICTIVEMAN]

Are you sure the cylinder you purchased is suitable for gravity systems, where did you buy it from, some are only designed for fully pumped systems

 

[dm7618]

it was purchased from Plumbase. Its a 900 * 450 size and they said they only do one indirect cylinder

 

[dm7618]

i have just looked at the cylinder and checked the paperwork that came with it, no clues as to whether it is or isn't suitable, It just says indirect cylinder with a part number P003046

Is there a way of telling?

I will call them tomorrow and ask someone

If anyone has any more ideas i would be very grateful, just spent another 2 hours playing with it and still no proper flow, thanks again

 

[PEDANTICVINDICTIVEMAN]

People that sold it to you should bloodywell know, try phoning the makers and quote the numbers, good luck.

 

[dm7618]

Checked with the suppliers and the cylinder is OK.

They suggested that due to the system being completely drained I may have sluge somewhere in the system that may have come from the header tank when drained.

I did have some sluge in the bottom of the header tank so it sounds poissble.

What's the best/easiest way to completey flush the system out?

 

[dm7618]

Has anyone goy any more ideas? I have the weekend to try again, so reply would appreciate any help - THANKS

 

[dm7618]

come on guys anyone got any ideas? I am starting to get smelly and fed up with cold showers!