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Discuss No hot water in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
20
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

Gas Engineer
Messages
1,817
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
 
Messages
20
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

Plumber
Messages
2,958
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

Gas Engineer
Messages
1,817
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.
 
Messages
20
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

Gas Engineer
Messages
779
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.
 
Messages
20
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.
 
Messages
20
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

Plumber
Messages
1,913
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.
 

Gasmk1

Gas Engineer
Messages
1,817
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
 

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