Worcester 230 - how to re-pressurise?

[raine]

Hi,

Sorry to ask dumb questions but I'm struggling.

I have an old Worcester 230 boiler (c 1994 I believe). I have recently been having to bleed the radiators almost daily, and some searching around on the web suggested that this might be caused by low boiler pressure.

I checked the dial on the front of the boiler, and sure enough, it is reading only 0.5 bar. So, I think I need to re-fill it, but I can't figure out how.

I've read this page:

//www.diynot.com/forums/viewtopic.php?t=38904

But I can't see anything that looks like the filling loops described.

Can anyone please help me find this loop?

This is what I see when I look at the underside of the boiler:

Worcester 230 underside

• raine
• 20 Sep 2011
• 1

On the wall behind the pipes is written in pencil (starting from left): Return Flow Cold Hot. There is nothing written behind the two rightmost pipes.

The three left-hand pipes, and the far right pipe, each have a screwdriver-type valve, and all were already set to On when I got there.

The Worcester user guide shows the following:

Worcester 230 user guide front view

• raine
• 20 Sep 2011
• 1

If it helps, this is the view with the front control panel removed:

Worcester 230 with front panel removed

• raine
• 20 Sep 2011
• 1

Thanks in advance for any tips on where to find the filling loop.

 

[raine]

Guess what? I answered my own question!

Hopefully this post can help someone else instead of me!

I looked in the cupboard below the boiler and I found this in there, which connects to the "Cold" pipe.

Untitled

• raine
• 20 Sep 2011
• 1

I turned this black tap on, and it started filling. The pressure is now at 1.3 bar, so hopefully no more repeated radiator bleeding required.

Sorry to bother everyone.

 

[MANDATE]

I don't understand how a low pressure affects the radiators, so you have to bleed them.
But I do understand if you bleed the radiators and allow water or air to escape, then the pressure will drop.
If the pressure has dropped under normal running conditions, it means the water has gone somewhere.
A small leak in the system would allow pressure to drop.
But with a combi it's more likely the expansion vessel may have lost some of its 'air' charge. This results in the vessel taking in more water than its designed to do and causes the pressure to rise further than it was designed to do.
If the 'air' charge is not corrected, the pressure will eventually reach 3bar and the relief valve will open and discharge water from the discharge pipe. The valve will close again, but the pressure will have gone down to about 0.5bar and topping up will be required.
A further problem is that when the expansion vessel has been corrected you may find the pressure relief valve has not reseated perfectly due to dirt on the seating face/rubber washer so there still exists a small leak, which means the pressure will drop even when the system is not operating with the pressure at its lowest.
With heating 'on' the pressure will rise so a small leak will increase and pressure will drop quicker.

 

[raine]

No, you're right of course. And thanks for the tips.

I think what I'm trying to say is that I've learnt over the past couple of days that boilers need to be at a certain pressure to run well, and that it can cause off problems if you try and run them below 0.5 bar.

In my case, that low pressure was causing the radiators not to bleed properly (not much happening when I opened the valve, and perhaps I was even letting more air in??). I've only recently moved in here. When I first moved in, the top one-third of the towel rad was cold, as was the top of two other rads, so I bled them. My understanding is that it's not unusual for pressure to drop over a period of a couple of years? Maybe the boiler pressure was already low, so the bleeding didn't work effectively, plus the bleeding made it even lower.

Refilling / re-pressurising the boiler is an easy thing to do before calling a plumber, especially if you have recently moved and don't know the history of the boiler, or perhaps if you've had some recent work done on the system.

This is something I'd never heard of before, so I guess there may be other people who don't know about boiler pressures either.

Of course there may be a bigger underlying problem, but I certainly wouldn't have wanted to call a plumber only for them to refill the system.

I'll keep a close eye on the pressure over the next couple of weeks and see if it changes.

 

[MANDATE]

Agree it pays to keep your eye on the pressure, but if you don't understand the operation of the expansion vessel you may think you have a problem when you have not.
Your pressure of 0.5bar may seem a little on the low side and some boilers have pressure switches which prevent them from operating at low pressures.
When the heating is on, the volume of water in the system increases.
The extra volume has to go somewhere and this where the expansion vessel comes in.
The vessel will have a flexible diaphragm with a 'water' side and a 'air' side.
The 'air' side when first installed is pressurised using car foot pump or bicycle pump to about 1bar. This pushes the diaphragm fully across so the vessel is completely full with air.
With heating on and expansion of water taking place, the water now pushes on the diaphragm and gradually compresses the 'air'. The air pressure rises and so does the water pressure.
The size of the vessel should be matched to the volume of the system.
So in operation the water pressure should rise about 1bar and when heating is off it should drop back to the original setting.
The water pressure should never reach 3bar, but if it does it suggests the 'air' charge in the vessel has been gradually lost over time.
In this situation the PRV operates and releases the high water pressure, the valve will close again but the pressure will be down to 0.5bar again.
Once opened the PRV is likely not seal properly and may need replacing.

If for example the water pressure has been set to say 1.5bar cold and the heating has not been on and the pressure drops overnight, that would not rule out the expansion altogether, but you would be most likely looking for a leak and a poor seating PRV would be the first place to check, followed by radiator valve spindles
If you're bleeding radiators it pays to increase the pressure a little before you bleed them.
As you say, see how the pressures change with heating on and off