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I've been asked to rewire a heating system.
It's under floor heating downstairs and radiators upstairs. conventional indirect hot water tank.
It's plumbed with a 3 port mid position valve to select HW, heating or both.
Now the tricky bit.
The UFH controller has it's own built in programmer. It also has the facility to control the hot water times.
But at the moment, none of that is used and there's a conventional boiler programmer as well.
the customer wants the extra programmer removed and everything controlled from the UFH controller.
The available connections on the UFH controller are:
"HW thermostat" (two terminals for the tank stat)
"HW valve or pump" (N and switched L out)
"Boiler enable" (a volt free contact)
So the way it's supposed to work, is whenever hot water or heating is called, the volt free "boiler enable" contacts will turn on and fire the boiler. (not used at the moment, the boiler firing is controlled from the 3 port valve and tank thermostat, but it's not working properly)
Whenever the UFH programmer calls for hot water AND the HW cylinder stat is closed, the "HW valve or pump" output will be energised.
So here's the tricky bit. How to make that work with a 3 port mid position valve.
I can't see any way, as the conventional circuits require a "Heating OFF" signal which we don't have.
And I don't think suggesting he re plumbs it to use two 2 port valves instead is an option.
All I can think is a relay or two.
I throw it open to the forum to suggest something better.
It's under floor heating downstairs and radiators upstairs. conventional indirect hot water tank.
It's plumbed with a 3 port mid position valve to select HW, heating or both.
Now the tricky bit.
The UFH controller has it's own built in programmer. It also has the facility to control the hot water times.
But at the moment, none of that is used and there's a conventional boiler programmer as well.
the customer wants the extra programmer removed and everything controlled from the UFH controller.
The available connections on the UFH controller are:
"HW thermostat" (two terminals for the tank stat)
"HW valve or pump" (N and switched L out)
"Boiler enable" (a volt free contact)
So the way it's supposed to work, is whenever hot water or heating is called, the volt free "boiler enable" contacts will turn on and fire the boiler. (not used at the moment, the boiler firing is controlled from the 3 port valve and tank thermostat, but it's not working properly)
Whenever the UFH programmer calls for hot water AND the HW cylinder stat is closed, the "HW valve or pump" output will be energised.
So here's the tricky bit. How to make that work with a 3 port mid position valve.
I can't see any way, as the conventional circuits require a "Heating OFF" signal which we don't have.
And I don't think suggesting he re plumbs it to use two 2 port valves instead is an option.
All I can think is a relay or two.
I throw it open to the forum to suggest something better.
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