Honeywell zone valve end switches damaged but not destroyed by surge - difficult to troubleshoot

scraphound

I work a lot with Honeywell zone valves and I ran across an unusual problem yesterday. I thought I'd explain what happened for the benefit of others. The system I'm discussing has utilizes a total of four honeywell zone valves: three heating zones and a water heater, wired through a switching relay to the circulation pump. Our foreman was having a heck of a time figuring out an intermittent problem; the zone valves appeared to be working, but the switching relay wasn't always turning on. He had a volt / ohm / continuity meter but wasn't well acquainted with how to use it. I skipping the gory details, here is what I found.
The zone valves motors were working fine. They were pressing the end switch button inside the zone valve as designed. When the switch was closed (on three of the four zone valves), instead of going to the near-zero resistance expected from a closed contact I found a positive resistance of about 4 kilaohms (I dont' recall the exact reading but it was above 1k). In other words I found the contacts on the end switches had somehow been damaged but not completely destroyed.
This was in a Native village with running a microgrid. I asked around and found out the village had recently experienced a power surge. The three zone valves with partially-fried contacts had been actuated at the time of the surge; they all had the same symptom; high resistance at the end switch, but not a complete failure. The water heater zone was turned off at the time and experienced no damage.
The circuit I was troubleshooting was the equivilent to one, two, or three > 1k resistors in parallel. Overall resistance declines when you add more of the same value in parallel. When all three zone valves were actuated enough current flowed to actuate the switching relay, but when one or two closed the resistance was too high (that's why it was intermittent). I robbed a working switch from an old zone valve I had handy and got one of the heating zones working; I put the other two on manual, explained to the homeowner that only one thermostat would "work" until the other two zone valves were fixed, and returned to home base. I'll be sending out a couple of new power-heads to our foreman today.
It's interesting to me that the zone valve end switches were the only components in the system damaged by the voltage surge. The zone valve motors were ok. The transformer was ok. The switching relay was ok. The thermostats were ok. If anybody else out there has run into this issue it would be interesting to hear.

ScottSecor

We used to use Honeywell V4083 type zone valves exclusively for approximately twenty years. We probably installed about five or six hundred of them.

They were pretty reliable, but they did fail on occasion. Many of the failures we witnessed were simply a "bad" end switch. Early on we would simply swap the end switch, only to get a callback and finding the zone valve motor or gears failed. We learned that it made more sense to replace the entire zone valve head instead of just some of the components in the long run.

STEVEusaPA

Maybe the surge went thru them to ground.

Jamie Hall

If it cheers you up any, I've seen that kind of damage on contactors which weren't quite tightly closed and a high current went through them. Which may mean that those end switches weren't quite up to where they should have been anyway.

scraphound

Interesting responses. What was interesting is that all the zone valves that were open, three in total, suffered the exact same damage to the end switch. Not completely fried... just high resistance.

I'd be happy to discuss the strengths and weaknesses of residential zone valves in another thread. We have over 400 homes in our service area. The older systems have honeywell valves, the newer ones have Taco. In terms of reliability the Taco are vastly superior (good for another thread). Thanks again for the comments.

Zman

This is the first thing to go with the honeywell valves. I see it all the time with no electrical event to blame it on.
I often wonder if you really need end switches with a zone controller? If the circulator would be damaged by deadheading, it is not a bad idea to have the switches. With a delta p circ or a bypass valve, I don't see the need.

EBEBRATT-Ed

Used to have some finicky problems with Erie zone valve end switches

mattmia2

The contacts probably arced and burned, the surface of the contact is probably burned, they were probably open and it arced across the gap coating the surface of the contact in oxide. 4k is a lot(It might be a lot less when the 24v arcs through them as the close). My first question was were you taking them out of circuit or were you reading the resistance of the xfmr winding and the relay coil.

Are you sure it wasn't just one that was good, that the bad ones were able to energize the relay and there wasn't one good one mixed in? I see how the combinations could get very confusing very quickly, but it is possible that each contact provided enough current all added together to close the relay, especially if the resistance was less with 24vac than with the couple volts dc of an ohmmeter.

HomerJSmith

As Ronnie said, "Theorize, but verify."

I want to know why failures occur. Taking apart a micro switch is about as easy as saying "micro switch". Using a utility knife to pry off the cover, easy, and inspect the points. In a fix, one can sand the points with 220 grit wet and dry sandpaper or use a point file.

mattmia2

It is better to try cardboard and contact cleaner or alcohol first, sandpaper or a file that isn't designed for points will leave residue that will re-foul the contacts quickly if there is any sort of current involved.

Zman

Sometimes the switch is bad, sometimes the motor is tired and does not open it all the way, I have seen the teeth wear and cause it not to open all the way.
Long story short, the this honeywell valve is the most disposable valve on the market. I would just replace the head and be done with it.
https://www.supplyhouse.com/Honeywell-40003916-026-Replacement-Head-for-V8043E-Zone-Valves-8632000-p?gclid=CjwKCAiAp5nyBRABEiwApTwjXv4uxVCb2y3Yrjve5aEedvzuX6JJdS2Q-cijxpI9qlbJqr39aBXrGRoCN10QAvD_BwE

hot_rod

Vending machine switches activated by a plastic cam! Time to embrace better switch technology in zone valves.

Hermetically sealed reed switches are a better choice they are best suited for handling very low currents common with digital controls. Zone valve micro switches are not usually rated for low draw loads, they need a minimum “sealing current” across those silver contacts
Switches have both a high and low current rating,
Open contacts are sensitive to dust even airborne contaminants.

mattmia2

contacts are either designed for small signals and are plated with something that is designed not to corrode or are designed for handling power and are designed to arc and clean themselves when they open and close.

hot_rod

mattmia2 said:

contacts are either designed for small signals and are plated with something that is designed not to corrode or are designed for handling power and are designed to arc and clean themselves when they open and close.

On some switch designs the contacts sort of slide as they come together, wiping contacts, to help wipe any containments. A more expensive design, I doubt any zone valves have that type of micro switch? The zone valve micro switches I have autoposied just snap together, pushed by a cam or eccentric.


The challenge is with digital signals in the milliamp range, those pushed together silver contacts are not usually the best design.
A reed switch is closed with a magnet so you get a solid, tight closure every time and containments are locked out by the resin seal. But you give up some of the high current rating with a small zone valve reed design.

We strongly recommend you wire our reed switch Z-one zone valves thru a relay box, the relay in the box handles the load, the reed switch is the "trigger. So you have the best of both designs, the reed for todays modern digital signals, and enough capacity thru the relay box to handle 5 amp loads.

mattmia2

Relays designed for audio/video/rf usually have gold plated contacts so they dont oxidize. Reed relays are a little bit fragile mechanically.

hot_rod

mattmia2 said:

Relays designed for audio/video/rf usually have gold plated contacts so they dont oxidize. Reed relays are a little bit fragile mechanically.

Actually reed switches can be very rugged, they are used all over your car and truck, also common in heavy equipment , forklifts, bulldozers excavators, etc.

Went we went to a switch manufacturer searching for a more durable ZV switch this was the recommendation for severe duty applications.

We wanted a sealed, long lasting low amperage switch, a reed type is ideal.


https://www.reed-sensor.com/applications/automotive/

mattmia2

Maybe the ones i have had experience with were used because it was the cheapest relay they could find and weren't made very well. It seems the reed would fatigue or kink and stick open or closed.

hot_rod

mattmia2 said:

Maybe the ones i have had experience with were used because it was the cheapest relay they could find and weren't made very well. It seems the reed would fatigue or kink and stick open or closed.

I suspect like any other product there are good, better, best quality. Value engineered or uber engineered switches.
When you work with a switch manufacturer you can tell them the cycle life you want from the switch.

We cycle tested some of those Sunnywell zone valves from China, less than a years worth off service before switches, bearings, motors started failing.
The cycle testing on the Caleffi Z-one exceeds 20 years at 5000 cycles per years on a valve.

mattmia2

you also have to be very careful with application that they will never see back emf from a coil or induced current from a long wiring run and any number of surge or near lightning strike conditions unless you've protected the contacts because they are so small it doesn't take much to weld them closed or burn them.