No hot water, heating ok

michaeljs

Hi

I have a conventional boiler, with hot water tank. Heating works fine.

Hot water isn’t working.

F&e tank is fine.
Header to 3 way valve is working as expected.

When valve is set to HW, nothing happens. If heating is on and then HW turned on, valve moves to HW position correctly but then all is turned off incl heating.

Immersion heats water fine.

To me, problem is either 3 way valve is not working (even though its header is), or thermostat on hot water tank is not working.

Any ideas as to what I can do or what else I should consider before calling someone out to replace the valve?

Many thanks

matelodave

Try taking the motor unit off the three way valve and see if it can be turned witha spanner or pair of pliers.

Some three way valves have auxiliary contacts which fire up the boiler and pump.

There are a few things to check such as the valve, the tank stat, the programmer if you've got one to ensure that the valve is operating and the boiler & pump are being energised when the tank stat calls for heat.

It helps if you've got a wiring diagram of your set-up and you know how to prod around it with a multimeter - not a good idea if you dont know what you are doing as mains electricity can kill.

michaeljs

Thanks for the reply.

Do you mean to take the whole head off or to remove the motor from within the head unit?

I have taken the head unit off and I can move the switch underneath (ie. On the valve) easily with my fingers.

Turning HW on activates the valve switch as expected.

michaeljs

No further input from anyone?

JJ_Egan

Turn thermostat to full on same with boiler .
See if you have HW .
No then probable valve is faulty and not opening HW port.
But clueless as to actual valve type .




https://www.heatingcontrolsonline.co.uk/acl-drayton-invensys-ma16793-midposition-motorised-valve-p-110.html

michaeljs

Thanks JJ.

I have tried turning thermostat up full. No HW.

So it seems the valve is faulty. Many thanks for your help.

C_Mababejive

Do you know what make and model of valve motor/valve assy it is? Is it a separate motor and valve body assy?

michaeljs

It's a Honeywell 3 way, V4073A1039. So yes it separates into two parts.

As mentioned earlier, I have already tried removing the head (motor) unit - which appears to be functioning fine. I can manually move the knob on top of the valve with my fingers (after removing the head unit) easily.

I don't think there's anything wrong with the motor unit. Possibly the valve itself is broken, but I was wondering whether anything else is worth investigating before replacing the valve (seeing as that would require a drain-down).

The only other thing I could think is wrong, is the thermostat on the tank.

Mister_G

michaeljs wrote: »

It's a Honeywell 3 way, V4073A1039. So yes it separates into two parts.

As mentioned earlier, I have already tried removing the head (motor) unit - which appears to be functioning fine. I can manually move the knob on top of the valve with my fingers (after removing the head unit) easily.

I don't think there's anything wrong with the motor unit. Possibly the valve itself is broken, but I was wondering whether anything else is worth investigating before replacing the valve (seeing as that would require a drain-down).

The only other thing I could think is wrong, is the thermostat on the tank.

I have exactly the same valve and the issue I had was with the microswitches in the actuator head. It is those that tell the programmer when heat is required, along with the appropriate thermostats (tank and room).

So although the motor was turning the valve to the correct position, there was no demand for heat as the microswitch hadn't made contact

Replacing the head solved the problem.

Before I did this, I did check that the tank stat was functioning correctly with a multimeter.

AndyPK

The tank thermostat is responsible for firing the boiler and pump up for HW. So that must be the issue.


Has nothing to do with the 3 way valve electrics


Could also be the timer.


Ideally need to test for power at the stat.
or rotate it round and see if it clicks at least (ideally when the water is warm but not hot)

michaeljs

Thank you Mister G and AndyPK.

Someone else I spoke to did mention microswitches in the header unit.

AndyPK, if the thermostat is gone, would the immersion still heat the water? Or does the immersion not pay any attention to the stat?


Either way, what I was trying to establish is whether it was the valve (not the motorised head) or something else that requires a system drain. I think you've given me enough info to make it worthwhile replacing the stat and/or header unit of the 3way before doing anything else.

Thank you.