2 port / mid position valves

[timhoward]

I've been wondering....
There are two estates of bungalows near me, all built together, all with traditional system boilers with tanks and cylinder.
It seems to me that either the valve actuators work for many years, or on some properties they need regular replacement to the point I keep them in stock.
There are about 7 properties where they will routinely go through one in 12-18 months, even if I install genuine Honeywell heads.
Of late I've taken to manually operating the valve about 100 times before putting a new head on, and this does seem to on average extend the life of the head to about 2 years.

Does it seem reasonable to conclude that if they are regularly failing the issue is mechanical friction or limited valve travel and the motor is burning out ?
I'm considering if rather than just changing them I should say we'll try one new head and after that get a plumber in to change the whole valve body.

Any thoughts, similar experiences, wisdom?

 

[ruston]

Any chance there is no inhibitor in and the mechanical side is gunging up and causing the motor to give up the challenge.

 

[timhoward]

Any chance there is no inhibitor in and the mechanical side is gunging up and causing the motor to give up the challenge.

That would certainly be one explanation for the repeated issues. Thanks.

 

[UNG]

I've been wondering....
There are two estates of bungalows near me, all built together, all with traditional system boilers with tanks and cylinder.
It seems to me that either the valve actuators work for many years, or on some properties they need regular replacement to the point I keep them in stock.

Have you checked the wiring is correct I've found some in the past where the wiring was wrong and in certain situations would create problems

There are about 7 properties where they will routinely go through one in 12-18 months, even if I install genuine Honeywell heads.
Of late I've taken to manually operating the valve about 100 times before putting a new head on, and this does seem to on average extend the life of the head to about 2 years.

Do you apply any lubricant to the shaft when you manually operate it? I've found that even the slightest resistance can stop the motor fully operating the valve

Does it seem reasonable to conclude that if they are regularly failing the issue is mechanical friction or limited valve travel and the motor is burning out ?
I'm considering if rather than just changing them I should say we'll try one new head and after that get a plumber in to change the whole valve body.

Any thoughts, similar experiences, wisdom?

The only fix sometimes is to replace the whole valve I've not had to replace many over the years but it has fixed the problem
The only other one I've had is the motor head jamming where the gearbox drives the segment that operates the valve

 

[timhoward]

Thanks, yes I checked the wiring. I normally put a small drop of 3-in-one oil on the shaft. The last one I did required fair effort to turn.

A couple of the customers are understandably getting frustrated and typically ask if there isn't a different/better make or something. I've already explained that changing the whole valve would be required to use a different make.

I'm thinking the best advice for them would be drain down, chemical clean (or even power flush if a water sample merits it), then see how the valve feels, and if stiff change the valve. Obviously adding inhibitor afterwards.

 

[UNG]

Thanks, yes I checked the wiring. I normally put a small drop of 3-in-one oil on the shaft. The last one I did required fair effort to turn.

A couple of the customers are understandably getting frustrated and typically ask if there isn't a different/better make or something. I've already explained that changing the whole valve would be required to use a different make.

I'm thinking the best advice for them would be drain down, chemical clean (or even power flush if a water sample merits it), then see how the valve feels, and if stiff change the valve. Obviously adding inhibitor afterwards.

I use the 3 in 1 oil spray as I find it penetrates better than the 3 in 1 oil

If the valve needs replacing I go for the Drayton valves as Honeywell seem to be living on past reputation

 

[timhoward]

I use the 3 in 1 oil spray as I find it penetrates better than the 3 in 1 oil

If the valve needs replacing I go for the Drayton valves as Honeywell seem to be living on past reputation

Thanks again. I actually changed a Drayton yesterday for first time and it seemed a. I’ve product, in this case I’m sure the mechanical valve itself was to blame.

 

[brianmoooore]

Motor life shouldn't be affected by the valve being hard to operate since the motors are designed to be still powered when stalled against the end stop.
If a mid position valve is in the full heating position when the heating switches off on the programmer, it remains powered and stalled until the next time the water is heated, which can't be good for the motor's life.
I gave up using mid position valves many years ago, using only two port valves since, as this problem doesn't occur with them. I've also changed many mid position set ups to a couple of two ports when replacing valves.

 

[johntheo]

I've been wondering....
There are two estates of bungalows near me, all built together, all with traditional system boilers with tanks and cylinder.
It seems to me that either the valve actuators work for many years, or on some properties they need regular replacement to the point I keep them in stock.
There are about 7 properties where they will routinely go through one in 12-18 months, even if I install genuine Honeywell heads.
Of late I've taken to manually operating the valve about 100 times before putting a new head on, and this does seem to on average extend the life of the head to about 2 years.

Does it seem reasonable to conclude that if they are regularly failing the issue is mechanical friction or limited valve travel and the motor is burning out ?
I'm considering if rather than just changing them I should say we'll try one new head and after that get a plumber in to change the whole valve body.

Any thoughts, similar experiences, wisdom?

If mid position valves, then as stated in post #8, if the "last port of call" is the CH then the actuator will stay powered up say all night and probably shorten its life, maybe the properties with the short life span actuators have called for CH later than the HW?. If HW is the last call then the actuator is de energised.

 

[johntheo]

I also wonder in the mid position where pulses of DC voltages keep the valve where required against the spring pressure shortens its life, there must be hundreds of systems with UFH/2 port valves which are energised 24/7 for 9 months of the year, do these have reduced life spans compared to the conventional CH 2 port valves?.

 

[timhoward]

If mid position valves, then as stated in post #8, if the "last port of call" is the CH then the actuator will stay powered up say all night and probably shorten its life,

It's certainly an interesting factor. There's a John Ward video describing the inner workings of a mid position valve btw.
In the UK most houses would heat water at least once a day. Maybe the pertinent advice is to make sure the heating turns off before the water on the time clock settings to give the valve every chance.
Another factor is that if a small house has a dishwasher and an electric shower, the hot water may not in fact be used much at all, making the issue more prevalent as the valve could stay energised 24/7.
Thinking about it the one I just visited had the hot water control set to off.

(I'm not familiar with the UFH valves at all)

 

[johntheo]

or maybe make a dedicated HW call for a minute or two the last port of call for the night.

 

[Lucien Nunes]

What is the failure mode of these units that are being replaced so soon? Are the motors open-circuit, shorted turns or just seized?

I agree with @brianmoooore that for a 2-port, a stiff valve should not impact motor life but of course it might not complete its travel every time. If the valve is marginally stiff, a new freshly lubricated motor might reliably open it but as the motor ages, loses a little magnetism and becomes slightly stiffer itself, it might become unreliable even while the motor is in-spec.

I have often thought about the problem of mid-position valves being parked permanently at heating only with both channels off. The addition of a relay energised by programmer CH demand, with N/O contacts in DHW sat (valve grey lead), would stop that happening by releasing the valve back to rest position at the end of the heating period.

Are there any original motor-return valves like the original Satchwell Minival SM4203 still in service? I recall them being more reliable than they were given credit for. Their modern versions with an integral relay that mimic the operation of a spring-return type seem to have been a flop. The idea is sound, avoiding the need for either a permanently energised motor nor a yellow wire (sat feed) for the 2-port, but the construction quality has apparently been less than stellar.

 

[johntheo]

Your suggestion re the N/O contact may work, I did read somewhere that there was/is a fix for this but if so why is it not universally adapted. I wonder, if, in fact, the "permanently" energized mode is the problem at all.
I have always found it difficult to understand mid position valve operation anyway as it uses a very clever and ingenious method.
Below is my way of figuring out its operation, hope its correct!.

On CH only the valve is (240V) kept energised by the grey wire via SW1 only (HW off) to keep it in this position, on HW only the valve is in its unpowered state anyway so remains there.
If its in mid position, it is kept there by feeding 240V via the white wire through a diode and a resistor which reduces it to ~ 60/70 DC volts, SW1 is now also closed to the grey wire but no problem as no voltage from this wire. If you then switch off the CH first then the valve will return to its unpowered state which is HW, if you then switch off the HW there will be 240V on the grey wire but because SW1 is now opened from the grey wire then the valve will stay unpowered. But if you switch the HW off first then you will have 240V on the grey wire which will power the valve to CH only and it will remain there if you then switch off the CH, is this how it might work?.

 

[johntheo]

Here is a suggestion from wiki reader Anthony Ford.