Unable to find header tank!

Cheers MANDATE,

Yes, there's a little pressure guage on the top of the fire extinguisher. The needle's currently reading about 1 bar, maybe a wee bit less.

There's a length of hosepipe attached to the bottom of the thing.

MANDATE said:

Another thought! If the red vessel is a expansion vessel, there will be schieder valve to attach air pump to re charge vessel, so have you located that?

Click to expand...

What's a scheider valve? Where about would it be and what sort of air pump would I attach it to?

mobileman said:

Cheers MANDATE,

Yes, there's a little pressure guage on the top of the fire extinguisher. The needle's currently reading about 1 bar, maybe a wee bit less.

There's a length of hosepipe attached to the bottom of the thing.

MANDATE said:

Another thought! If the red vessel is a expansion vessel, there will be schieder valve to attach air pump to re charge vessel, so have you located that?

Click to expand...

What's a scheider valve? Where about would it be and what sort of air pump would I attach it to?

Click to expand...

He means a schrader valve, it's the same sort of valve as you'd find on a bicycle or car tyre. It'll most probably be on the bottom of your red expansion vessel, but that only needs pumping up if it's lost pressure, it's not there for repressurising the system.

There will be a metal braided hose attached to a couple of valves somewhere, that'll be what you need to refill your system, take it up to about 1.5 bar initially if you're still bleeding the system, bleed as much air out as you can (you may need to repressurise again but bear in mind that the final pressure when the system's full and cold should be about 1 bar).

Run the system for a few minutes after you've filled and bled, you might find that you need to bleed a bit more out and repressurise again.

Thanks muggles,

That's really useful.

Yes, there's a braided hose at the bottom. Kinda like a tap connector. From memory there is a little isolation valve down there too - the kind with a little screw in which need to be turned so the slot is inline with the pipework in order to let water through.

So, I just turn this and fill until the pressure goes up to 1.5bar and then bleed away. If pressure drops then attach a car tyre pump to the valve (wherever that may be - I'll find it over the weekend) and blow it up a little. Then bleed again and so on until only water caomes out of the bleed valves?

Is that right?

Thanks to everyone for your help. It's helped me begin to understand a type of heating system that I have never come across before.

If pressure drops just open the valves to refill again. The pressure should be about 1-1.2 bar when system is off.

Water expands when heated, so the extra volume it takes up has to go somewhere.
In the vented system the water is open to atmosphere, so excess volume is pushed back in header tank.
In a sealed system, you have to have a expansion vessel. The vessel is divided with a diaphram so water is one side and air on the other side.
When the water is cool, the water pressure should be about 1 bar, but due to expansion when heated it will go to about 2 bar.
Sometimes the expansion vessel loses all its air pressure and there is no volume left for the water to expand in.
Consequently the water pressure will go from 1 bar to say 3.5 bar and in doing so it will open a pressure relief valve and the excess water will escape, usually through pipe leading outside.
These vessels are pre charged on the air side using a pump. The schieder valve is what you have on your car or bicycle tyres. so you would use a car tyre pump.
When filling the system with water, it needs to be set at 1 bar and to manage that there needs to be a pressure gauge on the water side.
Having said that if it is exceeded, it can be lowered by bleeding a radiator.
It's not clear if the gauge you mention is an air pressure gauge or a water pressure gauge. Do you know what pressure was on this gauge after draining?

I think you've mis-understood something.
Air!
The expansion vessel should have a air pressure of about 1 bar when fitted to the system, this is before any water is put into the system. This air pressure can be adjusted if needed using a car tyre pump to increase it or depressing the valve pin to lower it. A air pressure gauge is required to check the result.
Water!
You use the braided hose with valve to transfer high pressure mains water to the system water, You observe the water pressure gauge while doing this and if you exceed the required water pressure then lower it by bleeding a radiator.
You don't use a car tyre pump on the expansion vessel or the valve pin to adjust the water pressure.