refilling a sealed system - How?

mghants · 13 Nov 2005

I had to replace the circulation pump on my central heating so I drained the system (no isolation valves installed either side of the pump).

I have a sealed system
Boiler is a Potterton PrimaF
In the airing cupboard I have an expansion tank with a blue hose connected to the mains wtaer supply and to the regulator on top of the expansion tank.

I have tried opening the stop valve between the mains and the expansion tank but this just pressurises the tank to 2bar.

My question is - how do I re-fill the system? What is the secret?

Slugbabydotcom · 13 Nov 2005

I have tried opening the stop valve between the mains and the expansion tank but this just pressurises the tank to 2bar.

Now let some air out of a radiator and see if this pressure goes down.
I suspect that you know the secret but dont know that you know the secret

Use the force Luke

mghants · 13 Nov 2005

That's what I thought I needed to do but not even puff of air comes out. I have even tried undoing pump expecting a torrent of water - nothing..... Doesn't sffect the pressure either....

If I lift the pressure valve on the top of the tank - sure enough,water flows and down the overflow it goes.

I've even tried opening a bleed valve but still nothing - the system does not fill!

Paul Barker · 13 Nov 2005

Are you not describing holding open the tpr v alv e on an unvented hot water cyclinder?

This sounds too dangerous to progress by crystal ball. You'd better get some pictures to us or get someone suitably qualified round.

mghants · 13 Nov 2005

Pics attached.

Paul Barker · 13 Nov 2005

well done that man,

top picture the thing on the side of the hot water tank with a bent lever on it is the tpr valve, and has nothing to do with filling up your heating.

The orange expansion vessel above is on the heating system. The blue pipe is the filling loop. However acording to the pressure guage in the photo the system is pressurised more than enough. Is it a current picture? If so and you can't get water out of the rads you have something very strange going on.

Paul Barker · 13 Nov 2005

PS you have fitted ball style pump valves. Bad luck, when it's next time to rely on them you can't either get them shifted or they'll leak, should have got gate valve style pump valves. Secondly are they turned on? slot in line with pipe.

mghants · 13 Nov 2005

Hi Paul,

It is a current picture. I took it right after I was asked for a pic.

Yep - valves are open. Just in case I'd missed something - I took the pump off to double check the valves were open.

Whilst I had the pump off, I opened the stop valve - expansion tank pressurised to almost 2bar and that was it - no food from the open pipe!!!

If I pull up (or trwist it slightly) on the pressure valve on the top of the expansion tank then water flows freely out the overflow (the pipe right in the corner) so I know the mains supply is connected and water gets into the expansion tank.

Now... I just ran a bath for my wife and noticed the pressure gauge dropped to 1 bar as the bath was being drawn. It goes back to 2 bar as soon as I open the stop valve!!

mghants · 13 Nov 2005

I meant that the stop valve was open during the time I drew the bath. I guess that makes sense for pressure to drop as the cylinder is refilling.

If I close the stop valve and open then bleed valve (behind the stop valve in the pic) then water runs until the pressure drops to 0....

Slugbabydotcom · 16 Nov 2005

I've read the posts a few times and the only logical answer I can think of that fits in with everything is that there is a solid blockage in the 15mm pipe from the tee below the bleed vent to where it joins the 22mm pipes coming from the pump. The only possible explanation I have is that grease could accumulate there. I'm told that radiators are sprayed with grease to protect the insides from rotting before installation and it could be there because the system was not flushed properly when it was installed.
Now I have just read what I have wrote and it sounds a bit far fetched but thats the only reasonable explanation I can come up with backed up by the fact that grease would float up to this section of pipe as it is 'off circuit'. Unless anyone else has a brainwave on this I suggest you cut into that pipe and see whats in there.

mghants · 19 Nov 2005

slugbabydotcom......

I finally got back to look at his problem (been away so wife had cold house whilw I was in cosy hotel

)

I decided to un-solder the joint where the bend was instead of cutting the pipe. I was as sceptical as you but - BINGO!!!!!!!!!! It was blocked right on that bend - not even a little blocked but totally blocked.

Heating all up and running now - Thx to everyone for their suggestions.

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refilling a sealed system - How?

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