Radiators filling with air - bleeding not working

cdb

Looking for advice please. The radiators upstairs are only partially working so the bottom third of the radiator is hot while the rest is cold. When I bleed a rad air escapes at first but slows and stops before it is fully bled, so the top 1/4 or so is still cold. If I bleed another upstairs rad afterwards hardly any air escapes. Within the last few days the radiators are back to the same situation, 1/3 full, 2/3 air.

We have a fairly straightforward system, downstairs gas boiler with two pipes (in/out) and a pump, the pipes go upstairs to the hot press where there is a T-junction with one feed going into the cylinder, the other going has a motorised valve that allows me to close the radiator feed. There is a red coloured pressure device about the size of a football in the hotpress.

Any suggestions on what it wrong? Is it a problem with pressure or is the system leaking somewhere. All advice and suggestions welcome.

novarock

at the highest point in the house there will hopefully be a pressure guage with a tap/valve beside it. It sounds like there is not enough water in your system, so you need to open this tap until the guage reads 1 bar of pressure, and then bleed again. Do this process until you have water coming from all the rads..

cdb

novarock wrote: »

at the highest point in the house there will hopefully be a pressure guage with a tap/valve beside it. It sounds like there is not enough water in your system, so you need to open this tap until the guage reads 1 bar of pressure, and then bleed again. Do this process until you have water coming from all the rads..

Thanks novarock, the highest point would be the attic so I'll look at the pipes up there.

ntpm

novarock wrote: »

at the highest point in the house there will hopefully be a pressure guage with a tap/valve beside it. It sounds like there is not enough water in your system, so you need to open this tap until the guage reads 1 bar of pressure, and then bleed again. Do this process until you have water coming from all the rads..

I aggree that system pressure must be low.
But generally I would put the filling loop/ top up valve near the boiler or in the hot press near the expansion vesel.

Normally there should be a reducing valve fed from the mains and pressure gauge ( or the boiler may have a pressure gauge). This should read around 1 bar when sytem is cold and will rise to around 2 bar when system is hot.

It is unusual to have a top-up valve in attic unless there was modifiction done to the house and the system was converted from an open vented system to a sealed system, and the plumber decided to fit the valve in attic.
IMO this is not good practise as it may not be easy to access attic for homeowners!!


Any time you vent the radiators you will need to top up the system pressure.

novarock

im just going by how it works in our house! Im by no means a plumber... If you saw our heating system you would laugh, it looks like it was installed by monkeys.

kay 9

novarock wrote: »

im just going by how it works in our house! Im by no means a plumber... If you saw our heating system you would laugh, it looks like it was installed by monkeys.

There was alot of shamble work done in bygone years by dumb monkeys alright and all honest and skilled plumbers incl. myself have to deal with some unbelievable s**t rather often. It's gone past the point of funny anymore to be honest. How they got trade certs is beyond me:mad:

Sparkpea

find the pressure guage and filling loop and fill it up to about 1.5 bar then bleed your rads, check the pressure again and leave it at about 1bar when cold.

ntpm

novarock wrote: »

im just going by how it works in our house! Im by no means a plumber... If you saw our heating system you would laugh, it looks like it was installed by monkeys.

No disrespect intended.:o


Unfortunatly pay peanuts get monkeys...:D

cdb

Got it sorted last night so thanks to everyone for the helpful advice.

If it is useful to anyone else this is what I did. There was a round red tap on one of the pipes in the hotpress that led up to the attic. It was in the fully closed position so I opened it a little and noticed a surge of water for a couple of seconds. After this I bled the upstairs radiators and they filled completely. I opened the tap again but this time didn't notice any water flow. Checked the upstairs rads thing this morning and they were hot from top to bottom so it looks like that did the trick and the heating is back working like it should.

Just out of interest, I didn't see a pressure gauge anywhere on the system, is it necessary to set the pressure @ 1.0 bar as recommended?
And the expansion vessel, do I need to adjust it or does it manage itself? I noticed that there is a valve on the top of it - it looks like a valve on a bicycle tube with a small pin in the centre. Adjust or leave it alone?

Thanks again for the helpful advice.

ntpm

Well done.

You need a pressure gauge because you could overpressurise the system.
When the system is cold it should be around 1.0Bar. As the system heats up the water expands up to around 2.0 Bar.
Then returns to 1.0 Bar when it cools down.

There is a pressure relief valve (PRV) in the system ( possibly at the boiler). This is pre-set to 3Bar. At which the pressure( water) will be released.

If you set the cold pressure to high, say 2.0Bar, the system will expand to above 3 Bar and the PRV will realese the water.

Also the pressure valve lets you know is you are loosing water from a leak etc.

You do not normally need to do anything with the expansion vessel.