Some radiators fail to heat

[gboyd]

Actually, used my head a bit and checked the boiler pressure.

Was down at flat 0 after running the ls valve.

Let more water in and brought the pressure back to 1.5 then opened the same ls valve again and soaked .....

So looks to me like water flowing? Or am I wrong?

Thanks again.

 

[D_Hailsham]

Actually, used my head a bit and checked the boiler pressure.

Was down at flat 0 after running the ls valve.

I did say: 4. Open the LS valve slowly until you get a flow of water from the radiator connector.

With a sealed system (no feed and expansion tank) you will lose water and pressure when you open the LS valve

So looks to me like water flowing? Or am I wrong?

Yup, water is flowing down the return pipe to that rad.

Was that a good rad or a dodgy one?

Now test the others , but don't open the valve so much - a quarter turn should be enough - and certainly not for 15 secs. Just enough to prove water is flowing out of the LS valve.

 

[gboyd]

That was a dodgy rad mate.

Now tested on all three dodgy rads and one good rad.

Results are the same across the board, very good flow from the ls valves.

Not what I expected at all, running out of troubleshooting options.

 

[gboyd]

Read back through the faq and decided to check the pump.

I can confirm it is set to 3 and when bleeding the pump water started immediately.

I have tried everything, can anyone please offer me any further advice? I'm at a dead end now and desperate.

 

[gboyd]

Well things seemed to be going from bad to worse

It seems to be branching out from a CH problem to a DHW problem

My boiler fires up okay when the hot tap is turned on, but fails to stay hot for very long. After 20 secs or so the water turns luke warm then cold and then back to hot.

Water pressure is very good from all taps still and shower.

 

[mgunn]

The last bit sounds like a problem we had with our mixer valve in the boiler. Don't know the correct terms but if yours is anything like ours there will be a knob you can turn with a setting on it inside the boiler. Our plumber explained that it mixes the hot from the boiler with an additional cold feed to ensure that the domestic comes out a sensible temperature but sometimes they stick or even fail completely. We found by screwing it shut and opening it again several times that the hot water variation stopped after a while. Worth a try.

This doesn't solve your first problem which I also have - two rads that simply won't heat despite main feed pipes being hot - they are on the end of a spur so I know the rest of the house is fine. I shall be trying some of the above suggestions. Our recent boiler service highlighted a possible problem with the expansion unit in the combi boiler (turco) as it had to be empted possibly causing overflow and loss of pressure on a fairly regular basis. I wondered whether this could be part of the problem with the rads (furthest away) or if this is just a second issue to deal with!

 

[gboyd]

Thanks mgunn but I don't know anywhere near enough to be able to find this switch so might have to come back to that one later.

Regarding the rads ....

I have read a lot on the forums about pumps being the cause of cold rads.

I did open the front panel on the boiler and turn the large copper bolt and water immediately started to dribble out. Can anyone tell me how I would take it to the next step and be able to check that the pump is turning correctly and its not clogged up?

Also, I have purchase some Sentinel X100 and X400. I would like to know the correct steps for apply these products.

I have located the rad which is very near the boiler and has a drain pipe on the trv inlet pipe.

Should I open all trvs and ls on all rads then drain the system fully? Will this empty even the water in all the rads taking it from this pipe?

Once the system if fully drained, what is the best method to add the x400? Should this be added to the system whilst fully drained then fill the system and crank the heating on and let it do the rest?

I assume if the above is correct I then repeat the drain to remove the x400 (and hopefully any blockages) then add the X100 and refill the system again?

Lastly, if I have a build up of limescale in the boiler components (also read about this) is the above a good method or is there another product that I should try instead?

Such a nightmare, not only cold when sitting in my living room but now also cold when taking showers! Superb!

 

[Bahco]

I think its time for you to get someone in.

 

[gboyd]

Yeah me too mate but I've spent so long on it now I'd really like to solve it myself

You know the 'just one more thing to try then I'll call in the professionals'

 

[gboyd]

Could anyone kindly answers my questions above as I'm going to give this a shot tonight and any guidance would be much appreciate.

Last attempt before giving up .........