I'm not sure where the problem is but our Suprima 80 boiler still gives us hot water, but the radiators are all cold. The single thermostat (a Honeywell 3 x 2" fawn box) is in the lounge and seems to make no difference. I have tested it for power and it's there. We did have a slight water leak in the summer, which resulted in a little water coming down the wall it was on, but it was only a few drops. I'm pretty sure all was working OK until about 2 weeks ago. The CH and HW lights are on, so the control box in the kitchen seems OK. We have, once in a while had the Suprima 80 having its red light flash through what we suspect may be dry joints on the boiler control board (or the boiler not lighting), but as I say, the central heating was working after this period.
I'm looking through the Potterton manual, but any suggestions would be gratefully received).
Since posting this I've been looking through old posts to this newsgroup on Honeywell 3 way motorised valves (A, AB and B for Central Heating, CH&HW and Hot Water), pumps getting clogged and so on - especially after a long period where the CH has been switched off over the summer. It's all been very enlightening.
The three way valve has a manual lever which *does* fire up the boiler but not for long alas. If I leave it latched manually to one side, the radiators will heat up for a while, but not stay hot. I'm not sure what this means as I'm not really sure what the manual lever actually does and why if it is latched in one position, the heating doesn't stay on. If the actuator inside the valve has become clogged or the PCB has failed, does the manual lever override this somehow? I guess I should open it up and check that the lounge thermostat triggers the actuator but I thought I should ask here just in case someone can suggest something else I should also look into. We have hot water.
I'm not sure off the top of my head if manually latching the valve into the mid position by means of the lever also operates the appropriate microswitch to call for heat from the boiler. Should be easy enough to verify for yourself though (check the SL terminal on the boiler when you do this). If the valve is not opening and it's not because it is physically jammed the that suggests that either the programmer + thermostat is not energising it, or the motor in the head has had it.
Try keeping the manual lever pulled to the fully open position. In a three way valve, there are usually two switches to be operated by the zone gear. One side opens the heating and the other the hot water for example. So the manual lever may not be fully engaging to keep the heating on full time. If you hold it fully open with a bit of string or tape for a while, you'll find out if it does keep the heating going, and so you've found your culprit for the fault.
I don't think it does. I think the micro-switches only switch the boiler and pump on in the full CH position. But the manual lever only moves the valve to the mid position - where it relies on the HW/tank stat feed to run the boiler. If you force the valve to the mid position with the lever, the rads will get hot as long as the boiler and pump are running. But as soon as the HW water demand is satisfied, this will stop - which accounts for the rads only being hot for a short time.
So we need to find out why the valve isn't moving to the mid or CH positions under its own steam. There are two possibilities. Either there is a problem with the CH feed from the programmer and room stat, or the syncron motor in the actuator is duff. You can test the feed by finding the end of the white wire coming from the actuator. If the system is wired as per the Y-plan schematic in
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it will be on terminal 5 in the junction box. If this is live but the valve stays in the HW position, the motor is duff. If this isn't live, there's a problem with the programmer or room stat.
This is exactly describes the problem it seems to me.
I will therefore test the white wire as advised. I had the cover off the Honeywell thermostat in the lounge yesterday, rotated the dial a few times, and even cleaned the innards with a q-tip (we have an unusual amount of dust where we live). The thermostat does "click" when it crosses one point, but that seems to be at about 18 degrees and it doesn't ever fire up the boiler as you might have guessed.
One thing I find puzzling is that when I force the lever on the 3 way valve to the right, it is clearly against resistance, much like rotating a geared motor. Although the boiler then fires up for a very brief period (only a few seconds if the HW is switched on via the programmer) the lever then moves bag to the centre of the three way valve unit unless latched (which makes no difference to the boiler anyway). The instructions viz a viz the honeywell 3 way valve I have seen say that the housing is held on with two screws, but I only see one. If I take that silver housing off, should I be able to see the motor do its stuff?).
The only thing that stops me calling someone out is that I am wary of all sorts of engineers these days - but as you can imagine, I have a very unhappy, cold partner who naturally blames me for it not working (how do they work that out? ).
I'll try that - but it looks like the boiler is switching off because the HW is too hot. If I leave the HW off for a few hours and put it back on again, the rads will heat up for a while - until the water gets up to temp again - and then of course - as the boiler is not firing up for long, the pump doesn't run and the water doesn't flow round the CH system.
The white wire from the thermostat in the lounge - that's in the Honeywell three way valve under the silver housing yes? That should go live when the room thermostat is increased? I take it we are talking mains voltage here not +5 or 12V?
I tested the white wire to the Honeywell valve. It is permanently live regardless of the position of the room thermostat.
I then switched off the HW on the programmer, and held the metal lever to the right, instead of letting it lock in the position. This seemed to keep the boiler fired up and the radiators started heating up and as of writing, appear to still be heating up. The boiler is now on without switching off. I have left the room thermostat at about 22 degrees and plan to turn it down to about 15 in about 30 mins just to see if it is controlling the system.
(30 mins later - turning the room thermostat down, does switch off the boiler. Turning the room thermostat back up, does fire up the boiler). There is, therefore, at least a working link between the thermostat and "boiler". The room thermostat only seems to click when it traverses 19 degrees though - always has?).
Does this suggest that the motor in the 3 way valve has seized or failed and needs a) cleaning or b) replacing - or might it be the microswitches?
Can I do any harm by leaving the manual lever in that fixed position? (it's currently held further over to the right. To be clearer, the valve assembly's lever is on the A side of Honeywell box not the B side. I have secured it towards the viewer with a matchstick as when it is just pushed up into the cutout, the boiler goes out - I've tried bending the end of the lever with pliers to give it more "reach" but the matchstick works to take up the slack so that will have to do for now).
-------------------------------- mains in | | | honeywell |
white wire lever ---| 3-way valve ms | ms=microswiches
I tested the white wire to the Honeywell valve. It is permanently live regardless of the position of the room thermostat.
I then switched off the HW on the programmer, and held the metal lever to the right, instead of letting it lock in position. This seemed to keep the boiler fired up and the radiators started heating up. As of writing, the CH is working and the thermostat is working fine.
Does this suggest that the motor in the 3 way valve has seized, or failed, and that it needs a) cleaning or b) replacing - or might it be the microswitches?
Can I do any harm by leaving the manual lever in that fixed position? The lever is currently held further over to the right. To be clearer, the valve assembly's lever is on the A side of Honeywell box not the B side. I have secured it towards the viewer with a matchstick, as when it's just pushed up into the cut-out, the boiler goes out. I've tried bending the end of the lever with pliers to give it more "reach", but the matchstick works for now, and is taking up the slack.
-------------------------------- mains in -> | | | honeywell | lever ---| 3-way valve ms | ms=microswiches | w | w= white wire
------------------A----------- -----------B------------- | A | | B |
I understand that I can just replace the assembly within the housing on top of the pipes. How difficult is this, and how much should I pay for one of these? Can anyone suggest a good/reliable supplier?
I've been away for several days, and unable to respond further until now. Have you sorted it in the meantime?
If you do need a replacement actuator for your Honeywell 3-port valve, check out RKM Heating Controls at
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They have them for just under 50 quid. [Other makes are cheaper, but may not fit your Honeywell valve].
They are easy enough to fit. Don't know the Honeywell one in detail, but there should be a couple of screws holding it onto the 'wet' part of the valve. Line up the D on the shaft with that on the actuator, and screw it on. Make a careful note of which wire goes where *before* disconnecting the old one!
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