Weird Heating!

[misterhelpful]

Hi all,

First post in the Plumbing Forum so excuse any lack of technical details.

My sister has a problem with her central heating - it only seems to work when it feels like. (A bit like the rest of us, I suppose! )

She has a back boiler behind the fire, on which the pilot light is lit, but when the heating is switched on it currently fails to fire up but it works fine with the hot water. There is a hot water cylinder in the airing cupboard. The thermostat in the hall works fine when the heating is actually on, as does the control switch in the airing cupboard.

A couple of months back the three port valve was stuck and the heating was constantly on so I pushed the switch manually and everything began working properly again, until last weekend. Assuming it was a similar problem, yesterday, I went to push the switch manually again but it wouldn't move. The other switch on the valve was in the correct C position for the central heating only.

I could hear the pump below trying to work but it wasn't kicking in properly so there was no heating. However, last night my sister said there was a lot of gurgling and the heating came on of it's own accord but only the downstairs radiators were working. This morning the downstairs rads were cold but the upstairs ones were just warm!

I tried bleeding the rads this morning - the only one with air in is in the bedroom and there seemed to be lots of it. However, the air stopped coming out after a few seconds but no water came out so I think there is still a fair bit of air in it which is trapped.

There you have the problem, along with all the information I can think of, so can anyone please advise what the solution is:

3 Port valve?
Pump?
Boiler?
Airlock?
Other?
GHOST!?

Cheers,

mrH.

 

[oilhead]

Is there any water in the header tank? If yes, then pump sounds ropey.

 

[misterhelpful]

Is there any water in the header tank? If yes, then pump sounds ropey.

I can't say for sure as there is a loft conversion and the tank is in the most unaccessible position for me to check, especially as I am awaiting shoulder reconstruction. I do know that a plumber had to change the ball valve in it a couple of years ago because it kept overflowing.

The pump was what entered my head when I checked the wiki, but not knowing much about heating systems wasn't sure, hence my post.
A similar old thread I was reading suggested sludge could be clogging the pump. Does this sound a likely cause to you?
How do I manually turn the pump? The centre nut is accessible but the instructions are side on and I can't get my head in close enough to read them.


Cheers, mrH.

 

[oilhead]

What make pump is it with a centre nut? Myson CP? if so, loosen the nut, keep turning anti clockwise, this moves the rotor, you feel it locate.

 

[misterhelpful]

What make pump is it with a centre nut? Myson CP? if so, loosen the nut, keep turning anti clockwise, this moves the rotor, you feel it locate.

Unsure of the make as I'm not there at the moment, but I do recall having to do what you describe with it when my sister moved in about 10 years ago.

I'll pop in later on or tomorrow and give it a try.

Thanks for the advice so far, and if it doesn't work, no doubt I'll be back for more!

mrH.

 

[twgas]

I reckon your (or daughter's) 3-port valve is stuck, probably due to dirt in the system, and pump is going the same way for the same reason. Lack of system water may also be an issue due to the dirt, my advice is to get someone in if you are not physically very capable.

 

[bengasman]

Probably full of crap.
When is the last time the boiler had a full strip down service?

 

[misterhelpful]

I managed to get into the void in the loft yesterday (only now got out ) to find the header tank was empty and the ball valve arm was completely bent - don't ask me how - perhaps that plumber a few years back did it to stop the overflow as it will be a nightmare to change!

Anyway, I straightened the arm a bit which allowed the tank to re-fill. I then went and bled the rad that still had air in it so they are now all full, however, the heating still wouldn't come on until it suddenly started working about 20 minutes later.

The 3 port valve is now working but the pump still doesn't sound quite right to me, although it is still working today. Usually when the heating is put on constant, the pump kicks in immediately and the boiler fires up at the same time. Now, the pump sounds weak and the boiler takes a while to fire up.

The pump is one of these: PUMP which isn't quite the one I thought it was. I have a feeling it must have been changed when the insurance company installed a new cylinder after a leak 5-6 years ago because I definitely remember turning a black nut to get everything going when my sister bought the house.

The boiler had a service about 2 years ago and was fine before that, and since, but it must be at least 20 years old.

Any more comments appreciated.

mrH

 

[bengasman]

Back boiler needs a full service every year.

 

[misterhelpful]

Back boiler needs a full service every year.

I know that, but how many of us actually get them done?

The plan is for her to switch to a combi asap, but as it's not financially viable this year she will get it serviced and hope that any repairs don't cost the earth. That's the reason I'm trying to find out the cause so she can get an idea of a costs involved rather than just going with whatever she is told is necessary. I'm sure you will agree that, unfortunately, there are some dodgy plumbers/gasfitters out there that give the trade a bad name.

mrH

 

[bengasman]

Back boiler systems are often full of crap on the wet side, it sounds like this one is no exception.
See FAQ for flushing.