External Expansion Vessel Question

[maverick718]

Basically if possible i need to fit a external expansion vessel. I have a System boiler with an unvented hot water layout. What i want to know is would it be possible to fit it in the airing cupboard where the hot water cylinder is situated. I won't be fitting it as i aint a plumber but if possible when my fitter comes I would like to know if this is a viable solution.

Thanks in advance

 

[GQuigley67]

the engineer will know the best place to put expansion vessel wouldn't worry too much

 

[maverick718]

The only reson im asking is that my boiler is in a kitchen cupboard so not a lot of room there and the only accesible place where theres pipes is the airing cupboard where the HW Cylinder is.

 

[tamz]

If it is a system boiler it will have a built in expansion vessel.

 

[GQuigley67]

as long as its on the heating circuit then should be fine

 

[maverick718]

It has Tamz but its not allowing us to repressure it thats the reason for fitting an external one.

I aint familiar with layouts bit I have a sealed system with HW cylinder but no tank in loft. It says unvented on the cylinder if that helps

 

[tamz]

That shouldn't stop you repressurising it but if it has failed it take very little to repressurise it and when the system heats the pressure will rise too much and the pressure relief valve will open. The EV may just need repressurising. You can fit an external one if you like as most that are built onto the boiler are a pain to change.

 

[markproperjob]

the hot water cylinder is totally seperate to the boiler/radiator system.
the boiler should have its own red vessel built in, if not visable its in the back of boiler. nasty!
i have fitted external vessels for customers and left faulty boiler vessel in place, the external vessel is cheaper to buy and fit, and is always of a bigger capacity than built in vessels anyway.
its reccomended to fit an external vessel as well as boiler vessel on systems with over 10 radiators.(i think its 10!) as the boiler vessel is not sufficient to cope with the requirements of larger systems.
the airing cupboard should be fine, as long as the plumber has access to the heating circuits 22mm return pipe it will be possible to fit it. or in the attic with an extension pipe 't'd from the return pipe ?
im assuming you will have an automatic pressure relief valve and system filling loop built into boiler?

 

[Blackcatgas]

the hot water cylinder is totally seperate to the boiler/radiator system.
the boiler should have its own red vessel built in, if not visable its in the back of boiler. nasty!
i have fitted external vessels for customers and left faulty boiler vessel in place, the external vessel is cheaper to buy and fit, and is always of a bigger capacity than built in vessels anyway.
its reccomended to fit an external vessel as well as boiler vessel on systems with over 10 radiators.(i think its 10!) as the boiler vessel is not sufficient to cope with the requirements of larger systems.
the airing cupboard should be fine, as long as the plumber has access to the heating circuits 22mm return pipe it will be possible to fit it. or in the attic with an extension pipe 't'd from the return pipe ?
im assuming you will have an automatic pressure relief valve and system filling loop built into boiler?

Agree with the above.

 

[maverick718]

Yes the boiler has a built in filling loop and PRV. There are quite a few pipes in the airing cupboard where the HW Cylinder is and it was a friend who is a gas engineer who suggested it but he wont touch it as he isnt qualified on the water side of plumbing. I know that i have a sealed system and a unvented HW system. Thats all I can forward onto you as my knowledge is limited. The EV is situaled at the back of the boiler and when we press the valve in, no air or water comes out. My gas friend put a foot pump on the valve to try and repressurise but it wouldnt allow him to pump as if it was blocked which led him to believe that the EV was faulty. The reason for suggestin to put an external EV in the airing cupboard was that there is limited room in the kitchen cupboard where the boiler is.

Hope it helps

 

[tamz]

It is impossible to pump it up while the system is still under pressure.
You need to isolate the boiler and either open the prv (bad idea) or loosen a nut and allow the boiler to drain. Then pump it up but it takes a while with a footpump. A portable power pack with a compressor is much easier. As you pump it more water will drain from the boiler. When done reconnect the nut and fill the boiler again.

 

[maverick718]

We followed all what u have just described. The system was drained. He works for british gas as a heating engineer. I should have explained in greater detail. When he tried to pump it up, the foot pedal was really solid for him to pump.

 

[tamz]

He should push harder. It will pump up if the pressure is off.

 

[maverick718]

Is it common for it to be hard to pump up? Could the diaphram be damaged?

 

[tamz]

If the diaphram was burst there would be water at the schrader valve. Even if he has drained it, it is better to undo a nut on the bottom of the boiler and put a bucket below. Some times the diaphragm can stick to the insides of the vessel. It will move if you pump hard enough.

 

[markproperjob]

the top 22/28mm pipe from the side of an unvented cylinder will be the return to boiler pipe, if of course its an indirect cylinder and not an electrically heated only direct cylinder. the 22/28mm pipe that enters the cylinder @ 18'' below this pipe will be the feed pipe from the boiler, which enters the cylinder, then forms a coil of pipe inside the cylinder that heats the water via conduction before leaving the cylinder via the upper pipe to return to the boiler for reheating. Make sure you get a reccomended, compident plumber to check this out on site, DONT try and have a go or get unsure chap to fit anything to an unvented cylinder, as they have a VERY dangerous potential!

im fairly sure-and further input would be appreciated here- that it would be ok to have the expansion vessel pipe 't'd off this top return pipe, as the heating circuit and dhw circuit share a common return pipe, which would allow the system to expand normally if a vessel was installed in this way.

 

[GQuigley67]

wouldn't the DHW already have a funictioning EV ? I believe as long as the External EV is tee'd into the heating circuit pipe then it will do its job, i.e the flow or return pipe before it connects into the unvented cylinder