Motorised 2 port valve; what has slowed it?

[windbagUK]

I have a Samsung Air Source Heating system, which been throwing a E911 error after 6 years of working fine.
The 911 error is nominally "insufficient flow". Open Fernox magnetic filter and am amazed how beautifully clean the circulating fluid is.
Look at the flow gauge and note is in the tolerance limits for the system throughout the "DHW on" switch-on that is when the error kicks in.
After discussing with Samsung technical, a finger was pointed at the DHW 2 port Honeywell V4303 valve having become "sluggish", ie not opening fast enough for the software of the control head to believe the flow has developed properly.

So bought a complete valve assembly and swap out (involving drain down).

New valve fixed the E911 error and system is working correctly as it was before the 911 showed up.
It also showed that it wasn't a Sika flow switch problem - as we also took it out and noted it was spotless and electrically correct.

So: look at the old extracted motorised valve to what might have caused "sluggishness" to develop:
Absolutely clean, both inside the valve and in the motorised head.
So clean you'd believe it has just come off the supplier shelf.
The ball on the lever is totally clean and the actuating lever turns easily by finger.
The motor has no dust present at all, spins totally free on it bearing and seems to have no difficulty opening the valve against the control springs when put back into position.
Under test, the old valve takes about 12.5 seconds to fully open on the bench. It is not "labouring" to do this, but I don't know how quickly a new one is supposed to take (I can't find any spec for this in the Honeywell spec/documentation)

So my query is: What aspect of aging could make a totally clean valve become "sluggish" ?

 

[Johntheo5]

I have 3 of these V4303s (22MM) on a conventional heating system and will check the time to fully open later, they are 11 years old.
was the 12.5 secs to fully open "visually" on the bench or when the auxiliary (end) switch contacts closed when checked with a multimeter?., don't know if the end switch is used in your application or not.

 

[windbagUK]

Thanks for the response, Johntheo5.
The 12.5 sec was 'visually', plus I can see the lever pressing down on the contact switch and could hear it click (which is how I stopped the timing)
As it happens, my Samsung system doesn't use that contact closure at all - all those extra wires are left unconnected.
What I don't understand is how the Samsung was deciding it was getting "low flow", when the visual flow gauge did not budge when the valve opened.
Unless the opening was "bouncing" the Sika flow switch. In which case, why would that have been happening?

 

[windbagUK]

The reasons I'm puzzled is that the main opposition to the motor turning are the built-in springs (the main activation lever is very easy to turn)
But springs don't get stronger with age - if anything the opposite.
Or the motor torque has dropped - but why, when it remains totally clean, dust free, main rotor spins freely on the bearings ?

 

[Johntheo5]

When you manually open any motorised valve, usually with one finger, you will feel a reasonably stiff resistance while pulling it across and latching it in, if you still have the old actuator and you unlatch it and keep you finger lightly on the lever you will feel it moving back while the spring(s) return it to the closed position.

 

[windbagUK]

Yes, that is what happens with both the old & new units.
Those are the springs the motor has to work against to operate the valve when powered up; the springs close it when powered down.
How does that help with understanding about what has changed with valve aging ?

 

[Johntheo5]

Just checked one of mine now (can't easily check the others) and it opens fully in 8 to 9 secs, I suppose it depends on the flow switch setting and the time allowed between getting the signal to open before flagging a E911, the ball may have some wear after 6 years as I would think that normally there should be a fairly big flow through these valves after say 4 secs or so, whether the 3 secs longer is enough to class as sluggish, don't know. You might check the time taken to open fully on the new valve.

 

[windbagUK]

I can well believe the new valve is faster. But that is the point.
WHY is it faster - or - WHY has the old one become slower ?
On the old one, there is no visible sign of wear on the ball.
I can see no obvious degradation of the old unit at all.

 

[Johntheo5]

My valves are 11 years old, the mains voltage was 236 at the test time, can you check the voltage while testing the old and the NEW.

 

[bernardgreen]

I can see no obvious degradation of the old unit at all.

The degradation could be shorting turns in the coils in the motor. This would cause a significant reduction in torque.

The resistance of the coil will be reduced but this reduction may be small and may not be obvious in a simple resistance measurement,

 

[Madrab]

It's just the motor getting lazy, most electric motors/pumps do that with age. Thermal/electrical/mechanical degradation are all typical culprits, thermal especially in CH systems. Hot electric motors aren't happy ones.

 

[windbagUK]

It's just the motor getting lazy, most electric motors/pumps do that with age.

? First I've ever heard about it. Do you have a source for that info?
If it is the case, then Electric Car owners are going to be up in arms.

 

[Mister Banks]

? First I've ever heard about it. Do you have a source for that info?
If it is the case, then Electric Car owners are going to be up in arms.

Most electric car owners will be up in arms when they find their car batteries need replacing and the car is a write off. This will likely happen before the electric motors degrade sufficiently to be noticeable

 

[windbagUK]

I'm seeing a drift into what physicists call "arm waving".
If electric motors lose torque over time, it is down to a physical change - like magnets getting weaker or coils shorting out.
But magnets don't get weaker (unless made to explicitly do so) and this is a motor running twice a day in a 90°C environment, max.
That is not what I would deem a "hot motor", and not enough to melt insulation on coils. Nor is the motor being worked hard. Estimate: 1000 minutes total run time over those 6 years, with plenty of recovery time between runs - an on/off duty factor of 0.03 %.
Which is in line with there being no signs of degradation.

Samsung know this is an issue (across the board of makes), so it is unlikely to be specific to my unit - like voltage or coils shorting.

As for voltage, this is a switched mains voltage down a dedicated line from a relay in the controller.
That won't have significantly drifted over 6 years.
The relay might have become a bit dirty, but the current draw from the motor is very small, so it is much more likely to fail than give a "low voltage".
In any case, the same mains delivery system is powering the new unit, and that works OK, so it can't be that.
Also, I'm doing tests on the old unit via a new electrical feed, so that eliminates that.
Motor bearing wear I could understand, but that becomes clear when you manually rotate such.
And springs don't get stronger to work against.

I'd welcome a testable idea.
- or -
Anyone have a source explaining motors getting weaker with time?

 

[Madrab]

? First I've ever heard about it. Do you have a source for that info?

First source I found ... there are many many others ... they've been rewinding electric motors for as long as I can remember for the very same reasons

Why do electric motors fail?

5 Reasons Why Insulation Deteriorates

us.megger.com

CH circulation pumps are well known for getting 'lazy' as they age.

Electric car owners are paying a lot of money for a very high quality, very advanced and highly designed electric motors ... I couldn't say the same for 2 port valves or other electric motors used in the same type applications