CH on when only HW selected

[Keith77]

Hi Folks,

this is my first post here so please be gentle!

The last few days I have noticed that whenever the HW is on, the radiators are getting hot too, this is with the programmer set to HW only. I've done some tests and wondered if anyone can point me in the right direction...

The programmer is a Potterton EP2001. Its connected to a Honeywell V4073A1039 valve, my suspicion is either the valve or the programmer is faulty. I've measured the voltages on the valve wires and they are as follows:

HW+CH on: white 240V, grey 240V, orange 240V
HW only: white ~75V, grey 240V, orange 240V
CH only: white 240V, grey 240V, orange 0V
All off: white ~40V, grey 240V, orange 240V

This does not seem to agree with the Honeywell docs for the valve which says:

HW only: no power
HW + CH: white 240V
CH only: white 240V, grey 240V, orange 240V
Hold last: grey 240V, orange ~100V

Any ideas? Which is most likely to have failed?

- Keith

 

[twgas]

looks like valve fault, remove powerhead and check spindle on valve body is free to move - dimple on valve cover means it is removable

 

[Keith77]

Thanks I will check it. Also, the thermostat on the HW tank has 3 wires coming from it, one (blue) connects to the valve orange wire, one (yellow/green) to the valve grey wire and the other (blue) goes off to the controller.

This seems a bit odd to me - is this normal?

 

[Keith77]

looks like valve fault, remove powerhead and check spindle on valve body is free to move - dimple on valve cover means it is removable

There is a dimple on the valve cover alright - have undone the screw but its not obvious how the cover comes off - does it slide off lengthways or just pull off?

 

[twgas]

yes it is normal - need a OFF from stat so heating can work on its own - unusual to have 2 blues, are you sure its not brown to contoller/common

 

[twgas]

pull away from body (sides and top come off, the ends remain attached)

 

[Keith77]

Sorry twgas, yes its a brown to the controller not blue.

OK a good tug and the cover came off, it looks like the valve is stuck in the mid position (makes sense, that is CH+HW on) as changing the programmer settings does nothing.

Can't see easily how to check if the spindle is free to move - does the whole top silver part come off, if so how?

 

[twgas]

2 brass, cross or star head screws (depends on age), one next to earth wire and one diagonally opposite.

 

[Keith77]

2 brass, cross or star head screws (depends on age), one next to earth wire and one diagonally opposite.

OK, got to the spindle, it moves only a little before meeting resistance - maybe 20 degrees. Not sure how hard to try and move it - should it be easy to turn?

 

[D_Hailsham]

OK, got to the spindle, it moves only a little before meeting resistance - maybe 20 degrees. Not sure how hard to try and move it - should it be easy to turn?

It will only move about 20 degrees, that's enough to move the ball from the A port to the B port. It should be easy to move. The resistance will be the rubber ball coming up against the A or B ports.

in your original post you queried the voltages. I have rearranged them to make comparison easier. K=Keith, H =Honeywell

H - HW only: no power
K - HW only: white ~75V, grey 240V, orange 240V

Both are correct!
When HW only is required, the motorized valve is not used as the spring loaded valve automatically has the B (HW) port open. The Grey wire will read 240V as it gets this from either the HW OFF terminal on the programmer, or from the HW Satisfied terminal of the HW thermostat. The Orange reads 240V because it is connected to the same terminal as the HW call terminal of the HW stat. In this case the boiler is controlled by the HW stat. The 75 volt on the white is due to the circuit design and not relevant in this situation.
++++++++++++++++++++
H - HW + CH: white 240V
K - HW+CH on: white 240V, grey 240V, orange 240V

In this case the grey should have 0 Volts. This suggests a wiring error.
++++++++++++++++++++
H - CH only: white 240V, grey 240V, orange 240V
K - CH only: white 240V, grey 240V, orange 0V

The orange should read 240v The fact that is doesn't suggests that one of the micro-switches is not changing over.
++++++++++++++++++++
H - Hold last: grey 240V, orange ~100V

This occurs when the valve has been on CH only and the rooms stat turns off the boiler. The valve does not return to the HW position but stays in the CH position. There is no flow as the pump is not running.
In this situation, the voltage on the orange is deliberately reduced to ~100V so it is insufficient to run the pump or open the gas valve in the boiler.
++++++++++++++++++++
K - All off: white ~40V, grey 240V, orange 240V

Not sure what you mean by "All off" Does it mean that the programmer has CH and HW turned off and the thermostats turned down or what? In this case the white should read 0V; the grey, 240V and the orange 0V.

Here's the wiring diagram for a mid-position valve - might be worth checking that your system is wired correctly.

View media item 70

 

[Keith77]

Thanks D_Hailsham.

The wiring should be correct as nothing's been changed here, and up until the last week or so the CH was definitely not coming on. It's been off all summer, but was turned on briefly a couple of weeks ago, then off again - so I suspect somthing happened then.

With the cover removed so I can turn the spindle, and with the boiler and pump running, there is a sudden jerk if I turn the spindle from right to left or left to right. I presume this is the water flow switching from HW to CH or vice versa. That would tend to indicate the valve is operational, and either the valve motor/circuitry is faulty, or the programmer is faulty?

 

[D_Hailsham]

The wiring should be correct as nothing's been changed here,

Agreed, it should be OK; but ...

With the cover removed so I can turn the spindle, and with the boiler and pump running, there is a sudden jerk if I turn the spindle from right to left or left to right. I presume this is the water flow switching from HW to CH or vice versa.

What's it like when the boiler and pump are not running?

That would tend to indicate the valve is operational,

Agreed, subject to above.

either the valve motor/circuitry is faulty, or the programmer is faulty

Check the Programmer outputs with everything disconnected before deciding to buy a new one. You should be able to get a replacement actuator for your motorized valve.

 

[Keith77]

What's it like when the boiler and pump are not running?

Same, but with no jerk - I was expecting the spindle to rotate more, I presume the CH+HW is midway between the two positions?

I tried setting the spindle in both positions and checking if the radiators were getting hot, and in both positions it seems that hot water is pumped to the radiators. I don't suppose the valve itself can fail open to both A and B circuits? It doesn't seem likely, but it seem puzzling why I can't manually turn off the CH feed.

Check the Programmer outputs with everything disconnected before deciding to buy a new one. You should be able to get a replacement actuator for your motorized valve.

I'll give it a go tomorrow.

 

[D_Hailsham]

I was expecting the spindle to rotate more, I presume the CH+HW is midway between the two positions?

Yes, CH+HW is midway.

If you read How a Mid position Valve Works you will see that the spindle only rotates 10°-15°.

I tried setting the spindle in both positions and checking if the radiators were getting hot, and in both positions it seems that hot water is pumped to the radiators.

Then the valve could be letting by, caused by a damaged or faulty ball. This will mean a complete valve, not just the actuator.

Check the Programmer outputs with everything disconnected before deciding to buy a new one.

I should have said you need 240v from CH ON, HW ON and HW OFF.

 

[Keith77]

Just an update... I finally got the time this morning to fit a new diverter valve and it seems to have cured the problem. With HW only on, the B outlet is hot and the A outlet isn't, as it should be.

Thanks everyone for the help.