Boiler shutting down

[Dean Cox]

My boiler doesn't seem to want to fire up the central heating or it justs fires up and switches off the hot water...

Glowworm 70 boiler, 2 port valve and grunfoss pump. Open Vent system.

I recently drained down the system to swap the valves around on a few radiators that were fitted the wrong way round (See previous post!). Refilled and fired up the system all working no leaks etc, however i noticed that the boiler would switch itself off and restart again despite the room temperature not reaching the 30 degrees the room stat was set too ( i thought this may have been normal?!) So with everything working (or so I thought) I partially drained the system and added inhibitor). Refilled and fired up, some but not all radiators warmed up, so i tried to "chase the airlock out" by closing down the hot radiators. Then the boiler cut out and now (even with the radiators all open) it seems to refuse to start.

I can hear the valve motor working. The pump was working, but now doesn't seem to work (The boiler only seems to come on for a short time when I press the +1 hour on the timer). I have taken the screw off the pump and turned the immpellor by hand, all ok.

I suspect the boiler shuts itself down to protect itself from overheating? The boiler does have a safety cut out button, but this has never had to be reset. So could it be that the pump was on its way out when it was shutting itself down before and has now packed up? (When it was working I checked the speed and could feel it working at the 3 different speeds.)

It seems as if it has slowly gone wrong rather than suddenly stopped?

What are the things to check in order so that i can eliminate them?

Any help appreciated!

Thanks

Dean

[Set Square]

I don't quite understand your system. You mention *one* 2-port valve. What does that do? Is it fully pumped, or pumped CH and gravity HW?

Either way, I suspect that you've got a massive airlock - and are failing to circulate any water even though the pump is running. Presumably the F&E tank is working ok - i.e. there is some water in it, and any manual valves on the feed pipe from the tank to the primary circuit are fully open?

Do you have a bleed valve on the primary circuit - maybe in the airing cupboard near to the hot cylinder? If so, open that with the pump running at max speed. You may have to let a few pints of water out before the air follows it - so you'll need a bucket or something to collect it in!

[P.R.Brady]

This worked for me recently:

- stop the pump:

- bleed it.

- Disconnect boiler electrics to prevent overheating.

- Open the bleed screw on the pump just a little. Run it with cold water in the system and the air simply 'fizzles' out.

- when air stops bubbling, turn boiler on. Good luck! Phil

[Dean Cox]

As far as i know i only have one two port valve. I'm not sure how it's configured as it's mostly hidden behind some boards. The pump now no longer runs?? The F&E tank has water in it. No manual valves have been touched. There appears to be to bleed valves on the inlet and outlet pies coming out the top of the boiler (2 screw on caps) opening these just results in water coming out no air. However as the pump isn't running now I cant try this to see if it will pump anything out. I put voltmeter on the pump when the CH was switched on but no voltage appeared to be there?

Dean

[Set Square]

Does your boiler also heat the hot water, and does that work?

Are you sure that your 2-port valve isn't actually a 3-port valve (one inlet and two outlets)?

[Dean Cox]

Yes it heats the hot water also, but it is not working at the moment, however I have switched on the electric immersion heater. It is definately 2 port I have found the instrucions for it and i've just checked by feeling behind the boards! Well now I've taken the boards off and drawn a picture!

height of things in relation to each other are not exact. Am i right in thinking that when the central heating comes on it also heats the water whether wanted or not? Anyway still not working! Also I know it used to be oil fired before converting if this helps.

Dean

[Set Square]

Thanks for the diagram! Can't say as I've ever seen anything quite like it - before or since - so I can't begin to imagine how it's supposed to work!

What happens upstairs? Presumably some of those pipes connect to the HW cylinder, and some to radiators upstairs? Is there a thermostat strapped to the hot cylinder (not the one in the immersion heater) and connected to the heating control system?

[John]

Making a few guesses and a giant leap of faith I'd say your left hand "upward" pipe might be a return from the cylinder, the second pipe might be an old cylinder flow/feed/vent pipe from a header tank when it was an oil boiler. The third pipe looks like a heating return pipe which the motorised valve controlled via a thermostat/clock system from the oil boiler days and the fourth was the original heating flow. . Total guesswork but you may be able to progress from there. Swapping to a wall mounted boiler with one set of connections has been achieved inventively and the electrics could be a birds nest but if it worked before then something has gone wrong so a failed connection/component should be locatable with lateral thinking.

The two port valve may have failed (probably motor or possibly microswitch) so no power to the pump. try checking the connections particularly the orage and grey wires which are usually the microswitch leads. If the valve opens the switch will close across them. The wire taking power to the valve motor is usually brown and will be energised when heat is called by clock AND thermostat.

HTH

[Dean Cox]

Yes there is a thermostat at the bottom of the hot water cylinder, (Appears to be held on with gaffer tape). Looking at the duaigram again it would apear that the two pipes on the right that go upstairs and under ground are the CH feed and return to the upstairs and downstairs rads, The two pipes on the left must be the feed and return to the HW cylinder. I am assuming the single radiator from the boiler that is in our conservatory (The one on the right) was done like that because it was easy. I take it that by the position of the pump and valve that the water is only pumped to the CH when the valve opens and just feeeds the HW Cylinder when closed. As the pump no longer seems to come on, and there does not appear to be any voltage across it i'm assuming that the boiler is not sending any power out to it. So is this because of an airlock in the boiler??

Dean

[Dean Cox]

Ok I apologise, after removing another board up the wall I have found a second 2 port valve!! After removing the covers and pressing the +1 hour on the CH timer the lower one near the pump makes a noise and the springs move. Pressing +1 on the HW causes the springs to move on the upper one. I think I may have confuse the issue with my earlier drawing. There is just one radiator (In the conservatory) which I have shown, this is not all the radiators, which I'm now sure are fed and returned by the two right hand pipes (15mm). The two left hand pipes are 22mm and I guess supply and feed the boiler. I have updated the diagram

. I guess now that I have found the second valve it makes a difference!! However the system was working before and it is not now! No power to the pump, which had power before when it was shutting off after a short while before the rads reached the room stat temperature. As it stopped working after a partial drain down to add the inhibitor I am wondering if it is an airlock? I think i'm getting there, at least it isn't winter!

Dean

[Set Square]

Right - now it's making a bit more sense! What you have, in essence, is an S-Plan system. Have a look at the schematic and the wiring diagram for S-Plan at

and you'll get a fair idea of what you're aiming at.

In brief, you've got two 2-port valves - one for CH and one for HW - and one pump which pumps water round either or both circuits depending on demand.

The HW valve is driven by the programmer and cylinder stat, and opens when they are both calling for heat. Similarly, the CH valve is driven by the progranmmer and the room stat.

Each valve has an independent (or volt-free in the jargon) pair of contacts which are electrically separate from the motor circuit, and which close when the valve is fully open. These contacts both have their inputs connected to a permanent live feed, and their outputs connected to the boiler and pump. So the boiler should fire and the pump should run whenever either or both valves are open.

So if your pump isn't being fed with mains voltage, it means that either:

• neither valve is opening , [faulty programmer/stats/wiring/valve motors] or

• the valves *are* opening but are not switching the pump and boiler

This could be due to:

• faulty volt-free contacts in the valves, or

• failure of the permanent live supply (does it have a separate fuse?), or

• wiring fault

Armed with this explanation and the Honeywell wiring diagram, you will hopefully be able to trouble-shoot your system and find out where the problem is.

You may still have an air lock which will need to be sorted - but you've almost certainly got an electrical problem which needs sorting first.

[John]

SNIP

I'd hazard a guess that there has been an airlock which stopped circulation leading to tripping of a thermal protection switch which will require manual resetting. Find and reset this then with the boiler stat off you should be able to establish circulation. Once this is ok you can turn the boiler stat back up and get some heat.

[Dean Cox]

Thanks everyone so far.. There is a cutout switch in the boiler, however it hasn't tripped, should i look elswhere for one?

Dean

[Set Square]

That shouldn't stop the pump from running though - even if the boiler isn't firing. By all accounts the pump *isn't* being powered - so I think there's an electrical fault or blown fuse somewhere. Also OP says that overheat cutout on the boiler *hasn't* tripped.

[Set Square]

No, investigate the electrics. Start at the pump - which should be powered but isn't - and work backwards, using the Honeywell wiring diagram. With the both CH and HW on at the programmer, and both stats turned up, the Orange wire of both valves should be live. Check whether it *is* live relative to neutral with a 250+ volt AC voltmeter. If it is live but the pump isn't, there's a wiring problem between the valves and pump. If it isn't live, check the grey wires of both valves. They should be permanently live. If they're not, there's a wiring problem - or blown fuse - in the feed to these. If they *are* live, the volt-free contacts can't be closing - either because they're faulty or, more likely, because the valves aren't opening.

In that case, check whether the brown wires of the valves (motor feeds) are live. If they are - and assuming that the neutrals are correctly connected - the valves could be faulty. If the brown wires are *not* live, trace the wiring back through the thermostats to the programmer to find out why not. Etc.

[John]

This makes the assumption that the wiring is to standard and we don't know at this stage if the pump is fed from the boiler or a seperate wiring centre. As the story progresses information becomes available. Lets hope our OP is having some success at finding the fault

[Dean Cox]

Orange wires are live both valves appear ok (would the pump not start if one was faulty?), however the pump is not connected as per the diagram as the pump is powered from the boiler. (The wires from the pump go straight to some connections in the boiler (Glowworm Ultimate 70)). I think I would be happier if the red button at the front were tripping! I think maybe it's something to do with the PCB in the boiler?

Dean

[Set Square]

It *could* still be true even if the pump is controlled by the boiler in some sort of pump over-run arrangement. In that case, it would depend on the internal wiring and/or PCB of the boiler. For example, my Baxi Solo boiler controls the pump - but the pump still runs even if the boiler's overheat stat trips.

[Incidentally, it looks as if the OP's pump *is* controlled by the boiler - see subsequent posts].

[Set Square]

Ok, it looks like your pump is controlled by the boiler in order to provide pump over-run, so that your system isn't wired exactly like the S-Plan diagram.

In this case, the orange wires from the valves will be connected just to the boiler's switched live input and not to the pump. The boiler should also have a permanent live feed. Separate terminals on the boiler feed the pump. These should be live whenever the switched live is live, plus whenever the water in the boiler is above a certain temperature. The idea is that, once the demand is removed and the boiler stops firing, the pump keeps running for long enough to disperse the residual heat in the boiler's heat exchanger to stop the whole thing from overheating. Control of the pump feed will be via a relay or solid state logic on the boiler's PCB. It sounds as if something in that department may have failed if the boiler is getting a live demand signal but isn't firing and isn't running the pump.

Do you have an installation manual for your boiler? If so, does it have a diagnostic chart to follow when it's not working properly? Are there any LEDs on the boiler which light in sequence when everything is ok? If so - armed with a diagnaostic chart (if you have one) - you should be able to deduce what's working and what's not.

[John]

SNIP

Is there a Klixon type cutout inside the boilr case? Probably on the heat exchanger or flow pipe therefrom