pressurising central heating system

[Jim]

The radiator in my loft extension doesnt work because it is almost wholly below the F&E tank. It has been suggested that it could be converted to a pressurised system for around £120.
The boiler is a baxi set in a fireplace behind a gas fire.
Can anyone tell me what this involves and are there any downsides to this idea.
Jim

 

[MANDATE]

Why not raise the F & E Tank ?

 

[Jim]

unfortunately because of the way the job was done and the sloping roof,the f&e tank cannot be raised. The rad is also as low as it can be so I cant adjust as suggested.
Jim

 

[ChrisR]

You CANNOT pressurise back boilers, which is what you have. It would a) leak and b) be dangerous!

"almost wholly below the F&E tank"
Did you mean that? How far below? It might be slow to fill but should still work fine. Something else could be wrong - or a balancing problem.

 

[COG]

If you cant raise yore head have you considerd a Myson kick space heater, the highest point will only be 100mm from the floor (so more head) and in the summer you can switch the fan on to cool , ideal for lofts with often limited wall space

 

[Jim]

Thyanks to you all for info. Glad I asked as I would otherwise let some guy mess up my whole system. The F&E level reaches only one third of the height of the rad . I get no air out of it and no heat into it. Maybe the Myson is the answer.
Jim

 

[Jim]

Chris R mentioned you cannot pressurise a baxi gas boiler if set in the chimney breast. Just trying to understand why such a boiler cannot be pressurised if a boiler positioned elsewhere can . Could you help me understand please ?
Jim

 

[COG]

The baxi you mentiond was never designed to take pressure it uses a small cast iron heat exchanger

 

[corgiman]

The baxi you mentiond was never designed to take pressure it uses a small cast iron heat exchanger

This is not the case and as long as the expansion vessel has been correctly sized the there is nos reason for a back boiler not to be pressurised.

to pressurize a system you are in affect converting it to a "unvented system" for which you will require the following components;

pressure vessel... this replace the feed pipe and allows for water expansion during heating up

pressure relief valve ... this replaces the, incorrect named, expansion pipe and allows the safe discharge of water in the event of over pressurization

filling loop...as it says on the tin to fill and pressurize the system

and finally a pressure gauge to tell you the pressure

at present the heat exchanger in the boiler is subject (if you have a two story home) to appr 1 bar of pressure and a sealed system should be filled to about the same

Hope this helps a little

my advice is go for the little myson heater

 

[MANDATE]

I would not consider subjecting a back boiler or any other boiler to a pressure that it was not designed and tested for.
You are dealing with the unknown here. So this pressure relief valve (safety valve) is set to what figure? 2 bar? 3 bar? and what if the boiler bursts before the relief valve pressure is reached, you'll have one hell of a mess and scolding hot water in the wrong place and it don't just leak, don't forget it's under pressure.
If you want a pressurised system at least use a boiler designed for the job.
A boiler where a sample has been tested to destruction so you know it's up to the job

 

[corgiman]

I would not consider subjecting a back boiler or any other boiler to a pressure that it was not designed and tested for.
You are dealing with the unknown here. So this pressure relief valve (safety valve) is set to what figure? 2 bar? 3 bar? and what if the boiler bursts before the relief valve pressure is reached, you'll have one hell of a mess and scolding hot water in the wrong place and it don't just leak, don't forget it's under pressure.
If you want a pressurised system at least use a boiler designed for the job.
A boiler where a sample has been tested to destruction so you know it's up to the job

Further to this was concerned that I may have been mistaken in my previous reply so I called Baxi Potterton this morning to enquire as to the whys and wherefores of pressurizing a Back Boiler.

They replied that they are very happy for a back boiler to be pressurized as long as the boiler was not manufactured pre 1980 and is fitted with a over heat thermostat.

As to "testing to destruction" I was concerned about your comment that if the boiler was to be under three bar of pressure it would break I have serviced many a back boiler in four storey town houses when the head of water is extremely high ergo the pressure on the boiler is also high, so i also asked the nice man a Baxi Potterton what they test the back boiler to and recieved the answer 5 bar (which is the equivelent to nearly 200 feet of head)

So I still say if it makes life easier pressurize it

but I STILL would go for a myson kick space heater

Hope this clears things up a tad.

 

[Jim]

I am very grateful for your help and the effort taken to deal with my concern. I am going to have a look today at the Myson as I think I might as well leave well alone as the system is fine everywhere else.
Im confident the Myson will do the trick and probably be more effective than the normal rad.
Thanks again
Jim

 

[COG]

Just me being petty but you missed out that a s/system should have a MANUALLY resetable limit stat (so it does not re set and fire the boiler when empty, unless someone re sets it without checking the guage). That info from Baxi was handy but in still woudn't pressurise a baxi b.

 

[corgiman]

not being petty at all mate it was very remis of me not to point that out cheers