No hot water

[SteveRobert5a]

I have a 20 year old Megaflo system driven by a oil boiler, and never had this issue before. The water in the tank is cold, the system is switched to on, but nothing happens - the boiler isn't heating the water. I know the boiler is functioning otherwise, as is the pump because I can turn the central heating system on and the boiler fires and the pump pumps.
I'm assuming there's an electrical problem then: tank thermostat being the first suspect. The Honeywell 2way valve to the tank is closed, and when I move it manually to the open position, again, nothing happens (would I expect the boiler to fire and the pump to operate?)
This may be a coincidence but a hot water tap in a mainly unused shower room had been left slightly open for several days. The electric immersion has been used for hot water topping up due to guests being here so we didn't notice the issue until the immersion was switched off.
Is there something else I may have missed?

 

[Gasmk1]

the valve for hot water opens and makes a micro switch to give power to the boiler and pump the problem is more than likely the synchrony motor in the valve, if you are good with electrics you can trace problem yourself either new motor or new valve head

 

[SteveRobert5a]

the valve for hot water opens and makes a micro switch to give power to the boiler and pump the problem is more than likely the synchrony motor in the valve, if you are good with electrics you can trace problem yourself either new motor or new valve head

Thanks - I've had microswitch issues with other motorised valves in the past so maybe this is the problem.

 

[Ric2013]

Thanks - I've had microswitch issues with other motorised valves in the past so maybe this is the problem.

I think what GasMK1 means is the problem is more than likely the synchrony [synchronous] motor in the valve.

Personally I'd be inclined to test whether the system is attempting to power up the valve or not. I'm not really a fan of changing parts at random as a process of elimination: at that point you may as well finding a decent tradesman who can test before replacing. As you say, I'd suspect other things too, but agree GasMK1 is right in that the valve is generally the least reliable component.

 

[Gasmk1]

I think what GasMK1 means is the problem is more than likely the synchrony [synchronous] motor in the valve.

Personally I'd be inclined to test whether the system is attempting to power up the valve or not. I'm not really a fan of changing parts at random as a process of elimination: at that point you may as well finding a decent tradesman who can test before replacing. As you say, I'd suspect other things too, but agree GasMK1 is right in that the valve is generally the least reliable component.

I did say if you are good with electrics and my starting point would always be checking wether power to valves, as they are indeed the weakest point.

 

[SteveRobert5a]

I think what GasMK1 means is the problem is more than likely the synchrony [synchronous] motor in the valve.

Personally I'd be inclined to test whether the system is attempting to power up the valve or not. I'm not really a fan of changing parts at random as a process of elimination: at that point you may as well finding a decent tradesman who can test before replacing. As you say, I'd suspect other things too, but agree GasMK1 is right in that the valve is generally the least reliable component.

If the system is attempting to power up a faulty motorised valve, then if I manually move the valve to the on position, wouldn't you expect the system to work? If, on the other hand, the systems isn't calling for heat because the thermostat thinks it's hot enough, moving the valve to on wouldn't make any difference would it?

 

[EvilDrPorkChop]

If the system is attempting to power up a faulty motorised valve, then if I manually move the valve to the on position, wouldn't you expect the system to work? If, on the other hand, the systems isn't calling for heat because the thermostat thinks it's hot enough, moving the valve to on wouldn't make any difference would it?

No as manually opening the valves doesn't close the microswitch which triggers the boiler and pump. The valve has to be powered up and the motor take it further to trigger the switch.

The only valves that trigger the microswitch in manually on are the DanFoss Valves.

 

[SteveRobert5a]

No as manually opening the valves doesn't close the microswitch which triggers the boiler and pump. The valve has to be powered up and the motor take it further to trigger the switch.

The only valves that trigger the microswitch in manually on are the DanFoss Valves.

Ah - thanks - that's very useful. The central heating system valves are Danfoss and they fail every 2 - 3 years. The Honeywell has lasted 10 years or more.

 

[SteveRobert5a]

No as manually opening the valves doesn't close the microswitch which triggers the boiler and pump. The valve has to be powered up and the motor take it further to trigger the switch.

The only valves that trigger the microswitch in manually on are the DanFoss Valves.

That's really helpful. I've removed the actuator, can operate the microswitch and it indeed triggers the system, so I'm assuming it's the synchron motor for now.

 

[SJB060685]

That's really helpful. I've removed the actuator, can operate the microswitch and it indeed triggers the system, so I'm assuming it's the synchron motor for now.

Synchron motors can be picked up for quite cheap and some additional connectors where you cut the old wires.

 

[SteveRobert5a]

Synchron motors can be picked up for quite cheap and some additional connectors where you cut the old wires.

Ah but: I just removed the motor and applied mains to it, and it operates - quite a lot of torque as well on the gear. So maybe it's not the motor...?

 

[Gasmk1]

you need to check wether getting 240 to the motor if not then you need to check why not is there a call from timer is stat calling

 

[EvilDrPorkChop]

Ah but: I just removed the motor and applied mains to it, and it operates - quite a lot of torque as well on the gear. So maybe it's not the motor...?

It will be, either that or the base is knacked.

TBH I always just replace the top.

 

[SJB060685]

Then either the valve spindle has seized or an electrical problem between the programmer and motor feed.

 

[SteveRobert5a]

you need to check wether getting 240 to the motor if not then you need to check why not is there a call from timer is stat calling

Yep - my first guess was maybe the stat. Will check...

 

[SteveRobert5a]

Yep - my first guess was maybe the stat. Will check...

I know when I'm beat: no power at the valve when there should be. the valve stem rotates easily enough. I tried tweaking the stat temp control on the tank but that made no difference - time to bring in a pro.

 

[EvilDrPorkChop]

I know when I'm beat: no power at the valve when there should be. the valve stem rotates easily enough. I tried tweaking the stat temp control on the tank but that made no difference - time to bring in a pro.

Hi limit stat tripped out. Reset it.

 

[SteveRobert5a]

Hi limit stat tripped out. Reset it.

Didn't know such a thing existed, and had a close look at the stat, as far as I could - it's quite inaccessible. There was a little red button which, when pressed, barely moved but made a click sound. Hey presto - the system is working! So huge thank you to everyone who has offered help and advice, especially EvilDrPorkChop who nailed it. For his efforts I am pleased to award him with this glittering trophy:

 

[SJB060685]

Didn't know such a thing existed, and had a close look at the stat, as far as I could - it's quite inaccessible. There was a little red button which, when pressed, barely moved but made a click sound. Hey presto - the system is working! So huge thank you to everyone who has offered help and advice, especially EvilDrPorkChop who nailed it. For his efforts I am pleased to award him with this glittering trophy:
View attachment 61406

The thing is if the limit stat triggered once, it may happen again. If it does it needs a qualified person to look into.

 

[SteveRobert5a]

The thing is if the limit stat triggered once, it may happen again. If it does it needs a qualified person to look into.

Agreed - will need to keep an eye on it.

 

[EvilDrPorkChop]

If it's around 20 years old, the estate I live on has them all. I have had a High Limit that's been faulty and kept triggering for no reason, i've had to replace it and was fine since but they're usually pretty sound. As SJB060685 has said though there maybe a reason for it why it's triggered.