Fully pumped or Gravity fed heating systems, dumb question?

[B19GRR]

Hi,

We've recently moved in to a new place with the joy of oil heating, recently we've noticed that the central heating is somewhat intermittent but the hot water side of things is fine. I was having a nosy at the controller (Horstmann thing) and noticed a leaflet for it tucked behind a pipe. It said that if it was a gravity fed system then the central heating control wouldn't do anything and that it would all be down to the hot water setting to determine the central heating times too. That sort of makes sense as the heating only seems to come on if the hot water's on.

Erm, too much blah above, simple question really, will our system be gravity fed? Cold tank in loft, hot tank in airing cupboard (crap hot water pressure in bathroom next door )?

Cheers,
Rob

[Mr Pointy]

Can you find a pump in either of the HW or CH pipe runs? it should be somewhere visible like with the boiler or in the airing cupboard with the HW tank. If you can't find one then it must be a gravity system & worth looking at getting it changed to fully pumped.

[B19GRR]

Thanks, pump found!



So I guess it the heating and water controls should be independent. We had a power cut the other week and I noticed that the time/day had gone wrong on the controller, I wonder if anything else has gone wonky, it's a Horstmann CentaurPlus C27, just having a nosy of the user guide here:
http://www.horstmann.co.uk/downloads/ElectronicDoc...

ETA:
Just checked with this manual, it's got the blue jumper in so set as a fully pumped system:
http://www.horstmann.co.uk/downloads/ElectronicDoc...
Which worries me as to why the heating only seems works when the waters on, d'oh.


Cheers,
Rob

Edited by B19GRR on Friday 23 September 17:01

[markjo]

if its like our old system, the hot water will always be on when the boiler is switched on, no seperate water or heating only.
What i did as a make shift til I replace the whole system is to add a wireless stat into the system which switches the pump on or off.
So only the hot water get topped up then switched off via the boiler stat, and the heating only comes on when the wireless stat drops below x temp...

[Mr Pointy]

A power cut couldn't mess up the pumped/gravity configuration as it's set by a link in the back of the programmer: see the second page of the installation manual.

http://www.horstmann.co.uk/downloads/ElectronicDoc...

To see this you'll have to take the programmer off the backplate (easy enough to do, see the guide). Note live mains will be around the pins on the backplate if you do this without isolating the circuit. If the link is in it's set for pumped, out it's set for gravity. If the link is out then it would be odd given the valves in the HW & CH pipes (the silver boxes with black leads coming out of them).

I'd suggest a brain reset to start with if you don't feel confident taking the programmer off the wall. A new battery wouldn't go amiss either. You could try identifying which type of installation you have from the circuit diagrams as well & I'd hazard a guess at number 7. After this it's either more diagnosis with a voltmeter of call in a professional.

[Arthur Jackson]

I'd set both cylinder and room stats to 'calling' i.e. turned up and then see if switching on the heating and hot water separately opens and shuts those two motorised valves.

[B19GRR]

Fiddling around with the small stat on the cylinder does cause the boiler to fire up or turn off. Currently I've got the water set to 24hrs so pretty much on demand. We don't have another stat other than the dial on the boiler (well I've not found one), rads all have thermostatic valves. I'll go have a play with some dials anyway.

Cheers,
Rob

[Dogwatch]

B19GRR said:

So I guess it the heating and water controls should be independent. We had a power cut the other week and I noticed that the time/day had gone wrong on the controller,

Sounds as if the 'long life non-rechargable battery' mentioned in the notes has had too long a life and expired. Wouldn't surprise me if it is cheaper to get a new programmer than a new battery.

[B19GRR]

OK, had a fiddle, with water off/heating on there's no amount of dial turning to be done that will get the boiler fire. Once the water is turned one there's a ticking sound for a few seconds and then the whole system fires up, rads are warming up now.

The dial on the boiler goes up to 90C and was clicking around the 80C mark

ETA:
Just turned the tank stat back down to 50C (still stupid hot) and the system has shut down again.


Cheers,
Rob

Edited by B19GRR on Friday 23 September 17:41

[Mr Pointy]

Are you sure there isn't a room thermostat somewhere? It sounds as if this is set to a low temperature & the system just isn't calling for heat.

[Arthur Jackson]

I'd guess (just based on a feeling..) that the heating valve is stuck open a bit, but not enough to fire the microswitch. See if the manual lever moves the valve when you push it across.

[dirkgently]

Arthur Jackson said:

I'd guess (just based on a feeling..) that the heating valve is stuck open a bit, but not enough to fire the microswitch. See if the manual lever moves the valve when you push it across.

That would be my guess too.

[B19GRR]

Ahhh, well if the heater valve is the lower one on the vertical pipe then the lever is completely loose. When I slide the lever on the higher valve it's stiff and when let go moves back on its own. So I guess that's a borked valve then? Are they simple enough to replace and does the joy of Screwfix stock them?

Cheers,
Rob

[Arthur Jackson]

Turn off the power to the system and see if the lower valve lever is still loose. It would be loose if it was 'calling', but should spring back like the other one if you turn the power off.

[B19GRR]

Arthur Jackson said:

Turn off the power to the system and see if the lower valve lever is still loose. It would be loose if it was 'calling', but should spring back like the other one if you turn the power off.

Ahh, yup it sprang back when powered off. When heating was turned on though it didn't make the ticking noise the other one does when the water is turned on prior to the boiler firing.

Cheers,
Rob

[Arthur Jackson]

Essentially it should open if the timer calls (and the stat if you had one). Same with the other. It may be that the microswitch is dead so it's opening, but not firing the boiler. (Power is permanent on the grey wire and back out on the orange.) If it is open it will heat the rads when the hot water valve fires the boiler (via ITS orange).

[B19GRR]

Yep, it's a dead microswitch, the actuator arm contacts fully with it, just pressing it does nothing. Pressing the hot water valve microswitch causes the boiler to fire up. Looks like it should be simple enough to change the whole unit, found a new one on ebay for £32 delivered.

Fingers crossed that will sort things out. Thanks for all the advice!!

Cheers,
Rob

[sploosh]

My system sounds very similar.

Make sure all the rad valves are turned on - fair chance the person you bought the house from will have turned them off as these systems tend to "bleed" hot water into the CH side of the pipes even when the CH switch is off.

Flick the controller so the CH is on and turn up the thermostat on the boiler so it fires up.

............. and give the pump a whack with a mallet.

Good chance this will fix the problem.

I'm not a plumber (can you tell!) but I have to go through this process about this time of year, every year.


Those pumps are bulletproof but do sometimes need some persuasion.

[B19GRR]

Just to wrap this up, I fitted the new valve head and job sorted, lots of lovely central heating on demand - just when we need it most

Thanks all!!

Cheers,
Rob

[Arthur Jackson]

Good work, Rob.