Motorised valve or boiler problem?

[GeoffDS]

I suspect the Danfosss HSA3 Actuator on my 3-way motorised valve, but before replacing it, I'd like to run through the symptoms to see if it might be a problem elsewhere (I had a new Vaillant ecoTEC 428 boiler installed last year, so I want to rule that out first).
The problem is the house is getting too hot.
When the room stat is up to temperature (satisfied) the boiler still runs and the radiators continue getting hot.
I checked today and the cylinder stat was on (calling for heat) and the room stat off (up to temp) but the 3-way valve was at position A for radiators (i.e. lever was free to move all the way to the bottom of travel).
At this point I checked the voltages at the HSA3 terminals as follows:
Blue Neutral
Orange 248v
Grey 133v
Brown/White 243v

I then turned the cylinder stat down so that it no longer called for heat. The valve moved back to position B under spring power and the voltages were then:
Blue Neutral
Orange 7v
Grey 240v
Brown/White 0v

Then I turned the cylinder stat back up again until it came on and measured again:
Blue Neutral
Orange 240v
Grey 124v
Brown/White 0v
The valve remained in position B (lever at the top).

It seems to me that the actuator is sticking in position A when it shouldn't, but these voltages looked odd, especially the 133v and 124v.
Are these voltages what you would expect? Is the valve sticking in position A, or is this what should happen with these voltages?
Does it sound like a fault with the actuator, or is the new boiler feeding some odd voltage instructions to it. (Actuator and valve are about two years old).
Any advice welcome.
Thanks
Geoff

 

[Agile]

It does rather sound as if its jamming at position A.

Tony

 

[GeoffDS]

Thanks Tony,
I don't think it's jamming or sticking at A in the conventional sense, as it returns to the HW position B when power is cut.
It appears to be that the microswitch is either;
a) still receiving a signal to keep it at A when it shouldn't, or
b) NOT receiving the signal to let it go back to B when it should.
Which of these is more likely?
Does it point to a problem with the actuator microswitch or with the device (thermostat, boiler, programmer or whatever) that is supposed to be feeding it with the right signals.
And are those mid-voltages for real?
Geoff

 

[matt1e]

I then turned the cylinder stat down so that it no longer called for heat. The valve moved back to position B under spring power and the voltages were then:
Blue Neutral
Orange 7v
Grey 240v
Brown/White 0v

are you sure that it was the cylinder stat and not the room stat you turned down here? as its the room stat that should toggle the voltage on the brown/white.also the reduced voltage on the grey is normal and is caused by the internal circuitry inside the valve

anyway you seem to have a multimeter so the easiest way to check the wiring for you is as follows

disconnect the valve orange,grey and brown/white from the wiring centre (making a note of where they connect to ) then turn the the room stat down,and cylinder stat up and leave ch and hw turned off on the programmer

measure voltage on the valve wiring centre connections(the colours mentioned refer not to the disconnected valve wires but where they connect to in the wiring centre)

orange = 0v
gray = 230v (ish)
brown/white = 0v

now select HW on, the boiler should fire and measurments should be
orange = 230v (ish)
gray = 0v
brown/white = 0v

turn down the cylinder stat, the boiler should stop firing and measurments will be

orange = 0v
gray = 230v (ish)
brown/white = 0v

select ch on and turn the room stat up measurments will be
orange = 0v
gray = 230v (ish)
brown/white = 230v (ish)

turning down/off the CH at either the room stat or programmer should lose the voltage off the brown/white connection
tuning up/down the cylinder stat should toggle the voltage between orange and gray (as should switching HW on/off at the programmmer)

if the wiring checks out then the accuator/valve is at fault

Matt

 

[GeoffDS]

Matt,
This is just what I need to check it all out - thank you.
It was definitely the cylinder stat I changed, as that is in the airing cupboard where I was working. The room stat is downstairs and I had already turned that down to around 16 so it wouldn't cut in while I was checking the voltages. It did seem very odd to me that the valve would move back to position B when the cylinder stat was turned down, but that is what happened.
What I can't understand is where the 124v and 133v come from.
I'll check the wiring as you suggest this afternoon and will post the results later.
Thanks again.
Geoff

 

[GeoffDS]

OK Matt, this is what I found.
Disconnected the wires as you said, room stat down, cylinder stat up and CH and HW off at timer:

Orange = approx 7v to 8v
Grey = 248v
Brown/White = approx 19v

Turned HW on at timer:

Orange = 248v
Grey = 100v
Brown/White = 29v

Turned cylinder stat down:

Orange = 7v
Grey = 240v
Brown/White = 20v

Selected CH on and turned up room stat

Orange = 7v
Grey = 249v
Brown/White = 249v

Turning CH off at programmer, Brown/White down to 30v
Turning up/down cylinder stat toggles between:

Stat up: Orange = 240v, Grey= 99v
Stat down: Orange 7v, Grey = 248v

So where are those odd in-between voltages coming from?
Does this point towards a fault in the boiler control, or possibly the timer (which is quite old)? Or could they be associated with the pump over-run. I carried out the above measurements one after the other without waiting for the over-run to finish.

Presumably I can't assume it's the actuator now, until I've eliminated those odd 20-30 (ish) and 100 (ish) voltages.

Thanks again

Geoff

 

[MANDATE]

the 'grey' wire gets its power from one of two sources.
When HW is switched on and becomes satisfied, the cylinder stat diverts the power to the 'grey' so the valve can be driven forward from mid point onwards. During this travel a micro switch is triggered which allows power out from the valves orange wire. Hence you will find boiler stops momentarily and re-starts again.
This operation can't work if HW is not switched on. An alternative supply of power is provided from the HW OFF terminal of the programmer which also connects to the 'grey'.
It could well be a poor connection from one of these two sources which gives a reduced voltage.

Another consideration! Basically the 'white' wire and the 'grey' both feed into a micro switch (on different terminals) and output wire drives the motor.
In addition to this a modified voltage (used for holding the valve in mid position) is created using a pcb. This joins up with the output wire to hold the motor when the micro switch is triggered and the 'grey' wire is not live.
This modified voltage will back feed to the 'grey' and that may explain your odd voltages.

 

[GeoffDS]

Hi Mandate,
Thanks for the reply.
When the cylinder stat is turned down or if the HW is off at the timer, the grey wire is in fact 240v.
When the cylinder stat is turned up, I still get 100v on the grey wire and 240v in the orange wire.
So it seems that the grey wire is getting a voltage when it shouldn't. In other words, it's not getting part voltage because of a faulty connection. It is, in fact, getting 100v when it shouldn't be getting anything at all. so there must be a 'leak' across a terminal somewhere. It is probably this 100v that is causing the actuator to stick in position A.
It can't be the actuator itself causing it, as I had that disconnected when measuring these voltages.
I'm now beginning to suspect that the cylinder stat is not completely cutting off the grey wire when it toggles between on and off. Either that or, as you say, the timer is still giving 100v from the OFF terminal even when ON.
Does this sound right? If it is the cylinder stat it shouldn't cost too much to replace.
Thanks,
Geoff

 

[MANDATE]

You might find the thread below of interest, regarding reduced voltage on 'grey' wire


//www.diynot.com/forums/viewtopic.php?p=40979#40979

 

[GeoffDS]

Brilliant!
This is a really good explanation of what should happen. I've printed it out and am taking it to bed with me for a good read to try and understand it.
Thanks.
Geoff