Three Zone Valve Actuator End Switches Fail at Once???

allgoodnamestaken

Hi. My home has a propane boiler with radiant baseboard heat. There are four zones, three for living spaces, and one for the off-boiler hot water tank. The four zones are activated with Erie AG13A02A 2-Position Normally Closed Actuators. My house was built in 2005 and I've since had to replace the actuators for living the three living space zones after the motors failed (probably within the last four years). Whereas the hot water circuit still has its original actuator.

Prior to the Thanksgiving holiday week, I had been heating our home with just the wood stove. But since we were going away I turned on the heat for the three zones to make sure everything worked before we left. Everything worked fine.

When we left I set the thermostats to 55F. Looking back at my thermostat usage history (via Nest) it appears everything operated appropriately for several days, with the thermostats calling for heat a couple of hours each day.

Then beginning on Wednesday, Nest shows that the thermostats called for 24 hrs/day of heat. And when we arrived home on Sunday the house was around 50F with all three zones calling for heat.

I went to the boiler room and found that all three actuators motors had opened their valves. But yet the boiler was not on. I lowered the thermostats so they stopped calling for heat. Then I manually operated the actuators and they still didn't work. I tried each a couple of times and I did get some false starts from the boiler, but nothing consistent. I also check to make sure all the wiring was secure. And everything appears in order.

I haven't had time for further troubleshooting. But I'm assuming the end switches are bad. But what would cause all three end switches to fail at the same time and in the same manner?? I'm at a loss.

mattmia2

Maybe the 3rd of the 3 end switches failed and it was only heating when that zone was calling. Looking carefully at the pattern of zone calls could probably determine if that was the case.

I suppose if they hadn't been used in a long time, something sticking in the motor or in the valve itself could have caused them to not reliably move all the way to close the end switch too.

I'm not sure but I don't think that the manual lever is supposed to close the end switch.

allgoodnamestaken

mattmia2 said:

Maybe the 3rd of the 3 end switches failed and it was only heating when that zone was calling. Looking carefully at the pattern of zone calls could probably determine if that was the case.

I suppose if they hadn't been used in a long time, something sticking in the motor or in the valve itself could have caused them to not reliably move all the way to close the end switch too.

I'm not sure but I don't think that the manual lever is supposed to close the end switch.

Those are plausible failure points, it just seems crazy to me that all three would fail, or that two had failed sometime over the summer and the third went just now.

pedmec

You might have lost a transformer. How is the nest being powered? A lot depends on how everything is wire. I doubt that the three end switches are failed. More likely that the circuit on the end switches have broken.

hot_rod

I think that valve needs to power open to make the end switch. Are these powered from a relay box?

allgoodnamestaken

pedmec said:

You might have lost a transformer. How is the nest being powered? A lot depends on how everything is wire. I doubt that the three end switches are failed. More likely that the circuit on the end switches have broken.

Two of the three Nests have a common wire. All the thermostats are serviced by a four wire bundle. For whatever reason there is no continuity on the two spare wires for the third nest that would let me setup a C wire. So far I haven't run into any trouble with that Nest thermostat lacking a C.

I double checked the wiring at the boiler and everything seems secure. I jostled everything around to see if I could locate a loose connection, but no luck.

allgoodnamestaken

hot_rod said:

I think that valve needs to power open to make the end switch. Are these powered from a relay box?

Not sure if there is a relay or not. There definitely is a transformer mounted externally on the boiler cabinet. The other wiring (aside from the thermostats) comes from within the boiler cabinet (the boiler is a Peerless Series PSCII)

pedmec

Let me rephrase. Whatever power is going thru the end switch might not exist.

allgoodnamestaken

Am I right that it couldn't be the relay or transformer because the hot water tank thermostat can still call for heat without a problem? It uses the same connections as the other zones.

HomerJSmith

You don't have enough power. Change the transformer to a 75VA transformer. Evidently, the boiler only has one transformer and that transformer is mounted externally. Yes, it does have a relay. A pic of the transformer would be helpful.

You currently have a 40VA transformer that runs everything. The 3 Nest thermostats plus the synchronous motors in the zone valves plus the boiler demands. You're three card short of a full deck.

hot_rod

Sounds like the valves have worked in the past, but not since the Nest stats were added?

Matt_67

We used a lot of those pop top valves 10 - 15 years ago and I’ve seen what you’re describing before.  One end switch fails and it’s not noticed, the second one fails and it’s still not noticed, the third one fails and then everything is out.  The end switches aren’t as reliable as the motors on those actuators.  I would definitely troubleshoot the end switches a bit more to make sure there isn’t a failure in the boiler enable circuit but it doesn’t surprise me that all three were bad.

HomerJSmith

I wouldn't replace the 40VA transformer with a 75VA transformer. I would just add another 30-40VA transformer to the existing 40VA transformer. That would give you 70-80VA to the sys. Cheaper and easier. The fact that 3 ZV motors failed all at once is a 6 Sigma event. Not probable.

hot_rod

Matt_67 said:

We used a lot of those pop top valves 10 - 15 years ago and I’ve seen what you’re describing before.  One end switch fails and it’s not noticed, the second one fails and it’s still not noticed, the third one fails and then everything is out.  The end switches aren’t as reliable as the motors on those actuators.  I would definitely troubleshoot the end switches a bit more to make sure there isn’t a failure in the boiler enable circuit but it doesn’t surprise me that all three were bad.

A typical ZV may cycle 5000 times a heating season, based on the ones we have datalogged. Those micro switches are typically 100,000 cycle life, of course it depends on the life they live, dust, contaminants, etc.
So figure a 20 year switch life, give or take..

HomerJSmith

I will tell you how to test the switch. Remove the valve cover and locate the micoswitch, a 1-1 1/4" black rectangle with (yellow and blue wires) going to it. Depress the switch lever (sometimes white) with a thin screwdriver or such and see if the boiler kicks on. If so the switch is most probably ok.

Matt_67

@hot_rod Maybe it’s not the contacts but the way the switch is actuated? In the original post the OP mentioned boiler “false starts”. I’ve seen that too - the switch makes momentarily, starting a call for heat and then opens so the boiler shuts down. Almost like the cam that makes the switch goes past it’s high point if that makes sense.

mattmia2

Matt_67 said:

@hot_rod Maybe it’s not the contacts but the way the switch is actuated? In the original post the OP mentioned boiler “false starts”. I’ve seen that too - the switch makes momentarily, starting a call for heat and then opens so the boiler shuts down. Almost like the cam that makes the switch goes past it’s high point if that makes sense.

Or the cam wears down or the gear jumps a tooth.

allgoodnamestaken

The end switches can be replaced without replacing the whole actuator right? Does anyone know what kind/or where I should order replacement switches?

HomerJSmith

Test the switches first as I said. Micro-switches have a label printed on the side of the switch with a model # and rating. Look to match the connection tabs which have a hole in them to solder the wires to.

This is the usual kind, but check with the one in the ZV. https://www.allelectronics.com/item/sms-602/spst-snap-action-switch-16-amp/1.html

hot_rod

Erie had a repair kit, I don’t recall the switch being in it, or sold separately If it is the gear or cam, a new switch may not be worth perusing for a 2005 actuator?

allgoodnamestaken

Matt_67 said:

We used a lot of those pop top valves 10 - 15 years ago and I’ve seen what you’re describing before.  One end switch fails and it’s not noticed, the second one fails and it’s still not noticed, the third one fails and then everything is out.  The end switches aren’t as reliable as the motors on those actuators.  I would definitely troubleshoot the end switches a bit more to make sure there isn’t a failure in the boiler enable circuit but it doesn’t surprise me that all three were bad.

It does seem to be the case that the switches were going one by one but the remaining functioning ones hid the problem. That or there was some sort of electrical event that fried the switches (but nothing else in my house) while I was out of town.

The boiler enable circuit seems to be fine because the indirect hot water thermostat and its zone valve can still trigger the boiler and it uses the same circuit as the three other zones.