Central Heating 3 Way Honeywell Valve Head getting hot


Postby Cycletech » Sat Nov 15, 2014 2:15 pm

Hi All,
I replaced a 3 way valve as rads where getting hot when just HW on, that part is now fine. But after CH switches off, from room stat or from programmer/timer, there is a faint buzz coming from the valve head and after a short time the head becomes very HOT!
If I switch the heating off from the mains, I hear the valve return to rest, so I switch mains back on and the buzzing stops and the head cools down.
Has anyone had this fault or knows how I can test?
The A & B ports are the right way round and I have checked wiring. This fault may have been there before and what caused the original problem, there has also been a ticking noise coming from the valve, more noticeable after only HW used. The system is gravity feed and is HW priority

Thanks Martin
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Postby proptech » Sat Nov 15, 2014 6:35 pm

Hi Martin
That really doesn't sound right. When the heating is off, the valve should return to the hot water position, leaving nothing to buzz
But, before we go any further, exactly which valve have you fitted ? and which plan have you wired it to ? Are you 100% sure it is wired to that plan ?
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Postby Cycletech » Sun Nov 16, 2014 9:40 am

Hey Proptech

Thank you for your response.

The valve is a V4073

Wiring as image

Also I read this on the internet:

1. "The Honeywell V4073A motorised valve rests in the hot water only position (the heating port, A, is closed) when the valve is de-energised. However, if hot water was satisfied and heating was the last thing calling, the valve can remain partially energised with the heating port open."
Full story here http://www.lovekin.net/honeywell-motorised-valve-faults.html

2. "The Honeywell V4073A motorised valve rests in the hot water only position (the heating port, A, is closed) when the valve is de-energised. However, if hot water was satisfied and heating was the last thing calling, the valve can remain partially energised with the heating port open."

Disadvantages

Whilst the system is fairly simple, it suffers from two disadvantages. One is that a changeover tank thermostat is required which can mean that the wiring will need changing to 3 way + earth when updating older simple systems.

The other disadvantage concerns the durability of the valve motor but can be overcome by a simple alteration to the programming of the time switch. When both hot water (HW) and central heating is on (CH) the valve is in the mid position. When one demand turns off the valve will go to unenergised (CH off, HW on) or full on (CH on, HW off). When this last demand turns off the valve stays in the same position. This means that if CH is the last to turn off when the system goes off for the night, the motor will remain fully energised all night.

Whilst the motor is designed to be run stalled, it will be cooler and last longer if it is turned off completely. Searching on the web soon turns up the cry ‘my valve no longer works, what’s wrong’ and replacement motors are a common spare. The Honeywell spec states that ’Continuous operation of the valve motor at the fully open position is not recommended’ An extra £1 (very approx) electricity cost will result is a 6 watt dissipation over 6 months of nights.

Tip

There is a simple way to stop the motor running continuously stalled when the system is off and that is to program your time switch so that hot water is the last demand each day. On some newer programmers there are 3 slots per day. Programming the 3rd slot for 5 minutes after you have gone to bed will drop the valve back to the fully off position. This assumes that you have used enough hot water for the tank thermostat to come on."

Full story here http://www.ondotdot.pwp.blueyonder.co.uk/3port.html


Also I can get ticking noise from the head when only HW on!

wiring Andy.jpg
Wiring


Thank you Martin
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Postby proptech » Sun Nov 16, 2014 7:02 pm

As in your first post you said "hot water priority" and reading what you have copied from the web, I wonder if you've changed like for like, or removed a V4044 valve that would have been on a priority system.

The way the valve works is by using a pair of micro switches, and a diode that, put simply, supplies a DC current to the motor causing it to hold it's position.
The fact that you are getting a ticking says to me that the wiring is not to Honeywell's plan, or there is a defect causing the motor to keep moving, and actuating the switch.

Sorry to say, your diagram doesn't make a lot of sense to me. The only correct diagram is the one supplied with the valve, or obtained from the Honeywell website.
If I was on site, I would once again check, and double check the wiring, and that all other components are functioning as they should. Then, and only then, I would be looking at a valve defect.

Although a dodgy valve can't be ruled out, I would be a little surprised. In my experience 99 out of 100 problems with new valves are not due to the valve itself.
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Postby Cycletech » Sun Nov 16, 2014 8:37 pm

Hi Proptech

The valve I replaced was the same and the programmer is set to HW priority. And I am working to the Y plan
Wiring dig http://ww2.justanswer.co.uk/uploads/PL/PlumbersMate/2014-01-19_140230_y_plan.jpg

The programmer is a sunvic sunpro 2000 twin channel

The only thing is that the room stat is only wired with 2 wires not with natural and earth

I am more concerned with the valve getting hot and staying hot till HW is called for

Thanks
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Postby Cycletech » Mon Nov 17, 2014 3:55 pm

I have been reading more on that this is normal but nothing on Honeywell website!

"In the central heating and hot water "both off" state, the system wiring results in grey being live. If the valve happens to be in the A+B or A port open position, SW1 will have been operated, the motor will be fed with AC, and the valve will wind to open port A and stay there (although the orange boiler output will not be live). This is a fly in the ointment for this valve configuration: the motor can be left consuming power and wearing out its hot windings unnecessarily (the spec says the valve consumes 6W). This will not happen in the summer though, when heating is never selected: SW1 will be at rest, and the valve will sit un-energised with port B open"
Read here"
http://www.diyfaq.org.uk/plumbing/controls/midpositionvalve.htm

This sounds like the system is wired and working correct but there is a disadvantage, that the system when HW only turns off with no call for HW the motor will get hot and increase wear????

What I have found, but not sure if a fault, after I switch off CH and no call for HW, with the fault/buzz, I am getting a low voltage of 3.6v at terminals 4,5 & 8. 240v at term 6 & 7. Now if I turn up HW stat and then back down term 4,5,& 8 are now less than 1v.
If a currant of 3.6volts is a problem, I will disconnect each wire when in the fault position.
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Postby proptech » Mon Nov 17, 2014 6:43 pm

The wiring diagram you've linked to is the Honeywell one that was supplied, so all OK there.
Forget the voltages, you are bound to get induced low voltages as you describe, this will always happen when the conductors are in close proximity. In fact to test using voltages in this way can only cause confusion, don't do it !

So, if you are 100% happy that it's wired correctly, it's working as it should, and the motor is definitely at rest, there's not much you can do.
Please don't keep reading all that stuff on the net. The fact is that that valve has been around for very many years, and together with other makes of the same design, is extremely reliable.
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