Air getting into combi system

hubb

Ok, I have a combi that has been working fine since we had it over 2 years ago. Just a few weeks ago we had TRV's fitted and since then air has been getting into the rads. usually the bathroom rad (the last one with no TRV) is the one that gets air but now the two bedroom rads are cold in patches. One of them is hot at the top and cold at the bottom, mainly left side. The other is hot at the bottom and cold at the top. Sometimes I hear a high frequency whining sound when heating is on. The boiler when heating hot water from the taps sometimes starts making a whooshing rushing noise that never used to happen.

I can't bleed the rads because the bleed screw has rounded off and I also can't budge the larger housing hexagonal shaped nut with pliers.

I contacted the plumber and he said it will have nothing to do with the TRV's. Any guesses ?

Myser

The high-frequency noise is usually the TRVs on the brink of shutting off. The wax capsule ones are noiser than the liquid capsule ones. The cheaper/older ones tend to be wax capsule.

Try adjusting the setting on the TRVs to stop the noise.

If the system was completely drained (and hopfeully inhibitor added), you will need to vent the air in the radiators a few times.

If you can't open the bleed valves, they will need to be replaced. Have you tried a bleed valve key with a larger handle?

The whooshing sound may indicate an airlock in the system. Incidentally, what is the pressure gauge currently set to on the boiler?

keystone

Plumbers right - its nothing to do with the NEW TRVs he's fitted but it is to do with the air that he's left in the system.

It is very very difficult even if you try very very hard to airlock a pressurised system. You do, however, have air rushing about inside rather than it being airlocked and thats what's causing the whooshing noise.

Would your inability to bleed the rads have been experienced by him after he drained it (assuming he did drain it of course and not change the valves "live" but even if he did there would still be some air getting in.) so he just walked off and left air in 'em?

Get him back - and he can fix your bleed valves whilst he is at it. BTW you shouldn't be using pliers (shiver) on the hexagonal part of the valve really. Try an adjustable spanner.

Cheers.

unclebulgaria

I disagree with it not being the TRV's. (sorry KS)
I've not heard new TRV's making high frequency noises on the verge of shutting down, unless they're crap?
Some cheap TRV's when put on the wrong side of the radiator will whine or sometimes chatter. They sell them as Bi-directional but they don't work well on the wrong leg.
If the TRV stops whining when its setting is altered it could be on the wrong leg, I say could be as I'm not there to see it.
Some well known makes have a little ring you move to stop this problem.
Air in the system could be as KS said, left over from the system being drained and not bled properly. Also no treatment will cause air to be produced.

keystone

unclebulgaria wrote: »

I disagree with it not being the TRV's. (sorry KS)

Oh no need to be sorry old chap. On the basis of

I've not heard new TRV's making high frequency noises on the verge of shutting down,

I stand by what I said. But

unless they're crap?

would put an entirely different perspective on it.

Some cheap TRV's when put on the wrong side of the radiator will whine or sometimes chatter. They sell them as Bi-directional but they don't work well on the wrong leg.

I suppose that if he's supplied cheap and nasty TRVs, might have put them on the wrong end AND left the system full of air then perhaps he shouldn't get paid but Silver should probably still get his nosebag for being a good boy tied up in the street all day.

Cheers

Myser

hubb wrote: »

Didn't see him put any inhibitor in system. I would do that myself if I knew how. My whining will stop when I get to the bottom of this ;-)

Was the system completely drained to fit the TRVs?

You should add or top-up the inhibitor ASAP depending on the above! It can be added to the system at the filling loop or a towel radiator. Be sure to drain a little water out before adding it.

There are special dispensing kits available which make it easier to inject at the filling loop. Have a look at Fernox and Sentinel - two well known brands.

unclebulgaria

LOL I changed a whole house full of cheap TRV's recently with the same problem. The plumber fitted every single TRV on the return which normally wouldn't be a problem but the TRV's weren't good quality. A slight adjustment stopped one valve and another would start.
I have to be honest I've seen Bulldog but not fitted them, I try to stick to Danfoss and Drayton now as I've never had problems with em.
Aren't Bulldog sold at Homebase? I maybe wrong.

Myser

Bulldog are made by Pegler and sold by many large chain plumber's merchants. They use a wax element and are bi-directional, which means that they can be fitted on either the flow or return pipe of the radiator.

keystone

Putting in too much inhibitor can be just as damaging as not putting in any at all. Do nothing on this until you have clarified it with your plumber. If he did put inhibitor in he should have removed the sticker from the empty bottle, dated it and and placed it on or near the boiler.

In any event if it does need the stuff the simplest way to introduce it is via a ½" BSP male elbow temporarily in place of the damaged bleed valve you have just removed in order to replace it.

And stop making excuses for him. Inexperienced start up or not you are paying (or have paid) him to do a job properly and professionally. If he's dabbling above his pay grade then he shouldn't be.

Cheers

Myser

keystone wrote: »

Putting in too much inhibitor can be just as damaging as not putting in any at all.

I remember speaking to Fernox about this and there is no harm in adding more inhibitor to the system. From their website:

There is no detrimental affect from overdosing the system but under dosing can result in reduced protection.

southcoastrgi

unclebulgaria wrote: »

Some well known makes have a little ring you move to stop this problem.

good job you didn't meantion Danfoss RasC or i might have thought you worked for them & it was spam, oops i just did

Myser wrote: »

I remember speaking to Fernox about this and there is no harm in adding more inhibitor to the system. From their website:

they will tell you anything won't they, adding too much inhibitor can & will cause problems as it starts to foam.

Bulldog valves are cheap & nasty