Gravity (non) circulation

[JohnD]

My mother has an oldish system (but a modern boiler) with pumped CH and gravity DHW.

The DHW has stopped circulating through the boiler is running OK and the CH works.

There is a Cyltrol thermostatic valve under the cylinder. The cylinder is on the floor above the boiler, but about 5 metres along the landing with near-horizontal pipes. the pipework is 22mm. The pipes to the cylinder are not hot.

I have told her to turn on the immersion heater for the moment.

The circulating water is blackish and there is gas in the radiator in the spare room above the boiler, so I will probably give it a chemical clean and refill with inhibitor, aside from the current problem. I realise that this will not clean the non-circulating parts.

I have said I will have a look at it before calling in someone who knows better.

If I look for a sediment blockage or a jammed Cyltrol, is that reasonable?

I can bung the F&E if I have to take the Cyltrol off (I don't know if there is any free movement in the return pipe).

Any other suggestions?

 

[werewolf]

Empty F&E tank?

 

[JohnD]

Good idea. Now you say that, I remember now that the DHW stopped getting hot after I had vented that spare-room rad. Maybe that dropped the water level in the system. The cylinder is raised about 4' off the floor so that could have taken the level below the top of the coil.

I will have a look, also for a blocked feed. I will take a new ball-valve, and my aqua-vac to suck the vent if the feed is blocked (never done it before but I hear it sometimes works) especially in view of the black water and gas.

I have ordered her a Magnaclean and bought some Sentinel Cleaner and Inhibitor for her.

Fingers crossed... (I can only get up there at weekends)

 

[John_D]

Hi JOHND If the cylinder is primatic, the heat water will not be the same as F&E check on the number of drain valves. Primatic cylinders are not so common but there are still some out there.

 

[JohnD]

Thanks, it's not primatic

(pretty sure, as I have found the original instalation quote. Is there a way to tell by inspection?)

 

[ollski]

Thanks, it's not primatic

(pretty sure, as I have found the original instalation quote. Is there a way to tell by inspection?)

You'll pretty soon find out if you try to bung it . There will also only be one header tank.

 

[JohnD]

There is one header tank in the loft (same as i have at home) which I bunged successfully last time I changed some rad taps. I can't find a drain-off anywhere.

Isn't there a way of identifying a primatic by looking at it? the installer's quote didn't mention a primatic cylinder, but he did recommend Fernox. When were Primatics popular?

 

[iangh]

in the 60s and early 70s?
Usually says on it in letters, printed on.
But the big clue is - one header and feeder tank, often in the airing cupboard above the HWC, to save effort etc.

I boiled one once , with a solid fuel boiler, the bubbling was weird, and the water hot?

 

[JohnD]

This house has a big cold-water cistern in the loft, which feeds the bathroom taps, and a F&E, also in the loft, which feeds the boiler and rads.

A new cylinder was fitted in the last 10 years. There is no small cold tank above the cylinder (I have seen these in flats) nor has there ever been

 

[JohnD]

5 points to werewolf!

The F&E was indeed empty, apart from some brown sludge which I carted away in two or three wheelbarrows.

The ball valve had stuck "up" which considering it was 37 years old and shows no sign of having been previously replaced or rewashered is perhaps no surprise. The copper tap connector was actually sweated onto an even older lead supply pipe from a previous old coal-fired system. This must join onto the 110-year old iron supply pipe from house build.

I jiggled the old valve into life, but have now fitted a new one, and a lid. I took the opportunity to fit a full-bore drain off as I suppose I had better go back and clean the syst out another day.

 

[weareleeds]

Have you considered fully pumping system

 

[JohnD]

yes, but can't be bothered

 

[corgiman]

yes, but can't be bothered

stout fella