Central Heating

[bainbrig]

The ‘charging’ tap, which you can turn to let more water into the system, is stuck closed. The attached gauge is reading high - usually 3 bar, now 5.

Baxi Combi. We’ve got an engineer coming Monday, but is the high pressure a problem?

Could we lower it by bleeding a radiator of some water?

Suggestions welcome.

BillB

[New Judge]

"P.S. Good luck getting a sauce pan under the drain cock outlet, unless the pan is two to three inches tall,lol."

Indeed!

When I installed our central heating I provided the drain cock just inside the back door so a short hose was needed to run the water out to the garden. I then had a conservatory built so the back door was no longer the back door. I got the builders (who had to shift the boiler as part of the conservatory job) to provide a drain cock outside the house so when the system needs draining the drain cock simply needs to be opened to release the water into the garden. I still have problems with the washer sticking as described by Sparkly, though.

[SparklyKid]

Hi NJ. Did not know you were a DIY wizard as well as your many other talents, respect.

A little tip I learnt many many years ago. With the CH system fully on and rads scalding, if a rad bleed is necessary , just a couple of turns, do not take it completely out. Unless you have a spare nipple insert and a pair of welding gloves.

[bainbrig]

Right. Photo below. (And obviously my mind has GONE thinking the gauge was somehow adjacent to the tap, when in fact it is on the bottom of the boiler...old age).

Main pic shows scruffy boiler cupboard.

Inset pic shows a better view of (a) the stuck black 'charging' valve (far right), and (b) next to it, a standard brass stopcock - is that the drain point?

https://www.dropbox.com/s/2kkf4269dhvzyyd/boiler.jpg?dl=0

BB

[SparklyKid]

The black plastic tap in the closed position and above the flexible pipe is , most likely, the tap to allow the pressure to be increased by adding water into the pressurised system.

The tap to the left is not for draining purposes. Not sure , but, it maybe to shut off the cold water supply to the boiler, effectively not allowing the hot taps to be used. A simple test would be to turn this bras two armed left clockwise and see if the hot water cannot be drawn. This will in no way effect the central heating as , in a combi, it a separate pressurised system.

I would, in any event, spend half an hour with a pan and bleed a rad to reduce the pressure, it does seem quite high, aim for 2 tops.

Keep us posted.

[TonyV]

If you don't have small saucepan, use a large baking tray, where's there a will, there's a way.

[SparklyKid]

If all is working and engineer due Monday I would be happy to wait once pressure reduced, might take a while bleeding a rad, but I would do that. Pull up a chair, cup of tea , but don't unscrew the bleed screw more than a couple of turns.

[SparklyKid]

The problem Tony is that the stopcock valve is notoriously difficult to free after a long time in the closed position.

[bainbrig]

I appreciate the advice, and I appreciate the efforts - not the least from people I've been at logger-heads with in the past.

Don't be too nice, or in my generally-depleted state, I might cry.

BB

[melv16]

A 4 pint plastic milk bottle has worked for me in the past. Shape the base of the bottle to fit round the bleed er housing on the radiator. This can be done with scissors.

[SparklyKid]

Nowt wrong with loggerheads,lol. Whilst we do not always agree, any of us, we can be helpful.

[TonyV]

Yes Sparkly a sharp tap with small hammer will normally loosen bleed valve if it's stuck

[New Judge]

"The tap to the left is not for draining purposes. Not sure , but, it maybe to shut off the cold water supply to the boiler, "

Almost for sure. You can see the 'T' joint taking the feed to the filling loop so it is certainly a mains inlet.

[The Builder]

Sorry to see that you're in trouble again, bb. Plenty of good advice given already.

Most pressure relief valves will operate around 3 or 3.5 bar. 5 bar is unusual. Your "dribble in the alley" is, from a safety point of view, a good thing. However, at 5 bar, I would expect more of a flow (as has already been pointed out.)
Possibly, the relief valve is faulty, not opening fully.
so, maybe faulty valve or a flow sensor somewhere.
Also possibly, there's a leak in the heat exchanger which is over-pressurising the system.

More likely though, is that pressure vessel has lost its air pressure somehow (usually a ruptured diaphragm.) The pressure vessel is a small tank that accepts normal water expansion as the temperature of the system rises. If this expansion vessel fails (it may just need pumping up), then water expands too much and is thrown out of the system.

Reducing pressure somehow may well bring the pressure down to the right level........... but, as the system cools (when the heating goes off), the pressure may not be enough to restart. (Usually around 0.5 bar.)

So, no help, I'm afraid. Too many ifs and buts. Until Monday, keep an eye on the pressure. That's all you can do.

My bet? ............ you need pumping up, bb. Boiler guys just use a car foot pump usually.

[Tuvok]

Is there a model number for your boiler.

[bainbrig]

Builder. Always cheering to hear your friendly words, all of which noted.

Tuvok. Currently stuck in my chair with my leg off (don’t ask) but I’ll dig out the model no. later.


BB

[andres]

When I had a similar problem (gauge read 3 when it should be between 1-2).I bled one radiator using an empty baked bean can and just giving the key a couple of turns. Took quite a while but managed to lower it to 1.6.
Do you have Emergency Home Cover for heating and hot water just in case things go wrong over the weekend?

[TonyV]

Andres hopefully system will work over the weekend without any intervention.

[TonyV]

Maybe just some way of lowering pressure in system?

[Tilly2]

Use a rectangular cooking bowl.

[TonyV]

Tilly2 just anything that will catch the water