Boiler aborting call for heat

beatnikbrew

Hello,

I've got a Weil-Mclain GGI 4PL series 2 propane boiler that supplies heat to our baseboards and an Amtrol hot water maker on separate zones. The baseboard heat works fine, I turn up the thermostat, the boiler calls for heat, turns on, no problem.

The hot water maker, on the other hand, can't successfully call for heat. When I turn off the thermostat from the hot water maker, the zone valve closes. When I turn it on:

1. The zone valve opens
   
2. The TSTAT/CIRC and LIMIT leds flash on briefly and then turn off
   
3. nothing else happens
   

I can get hot water by turning on the baseboard heat since the zone valve stays open and circulates the hot water to the insulated tank, but of course this isn't ideal. I'd appreciate any suggestions that might help troubleshoot!

mattmia2

Most likely either the end switch is broken on the DHW zone valve or the wiring to it is broken. There is a switch that closes when the valve opens to turn on the circulator or the boiler.

HomerJSmith

What make and kind is the DHW zone valve? Pics would help. What is the controller that operates the Amtrol?

beatnikbrew

mattmia2 said:

Most likely either the end switch is broken on the DHW zone valve or the wiring to it is broken. There is a switch that closes when the valve opens to turn on the circulator or the boiler.

Thanks very much for your help. It does seem like something is off on the zone valve as the motor seems very warm to the touch even when nothing should have caused it to actuate. I'm ordering a replacement valve head and cleaning the contacts/checking the wiring on this one in the meantime.

HomerJSmith said:

What make and kind is the DHW zone valve? Pics would help. What is the controller that operates the Amtrol?

It's a Honeywell 8935 with an end switch. I can get some pictures once I'm back. I'm not sure what you mean by controller for the Amtrol - it's just a dial thermostat and an aquastat as far as I can tell.

After cleaning and re-attaching the zone valve (which must have reset the boiler) it looks like the boiler can no longer ignite. The pilot flame comes on, but the gas doesn't light or isn't turning on. I don't know if this is related or something I did by mistake but if there's an obvious culprit there I'd also appreciate any insight.

EdTheHeaterMan

@beatnikbrew said
It's a Honeywell 8935 with an end switch. I can get some pictures once I'm back. I'm not sure what you mean by controller for the Amtrol - it's just a dial thermostat and an aquastat as far as I can tell.

When you say Honeywell 8935, Did you mean Honeywell V8043F ?

Some older Amtrol hot water makers have analogue (aquastat) dial thermostats. Newer Amtrol hot water makers have Digital controls with a thermistor in the tank. If you have the digital then you need to have 3 or 4 wires to the controller. If you have the analogue, then only 2 wires are needed.

Helps to know which controls in diagnosis

beatnikbrew

Thanks Edward. It's an older Amtrol without the digital controls. Only 2 wires.

Here's a photo of the zone valve. I read the number off the motor, so perhaps I was looking in the wrong place.

EdTheHeaterMan

That is the V8043 valve. It is printed on the other side of the actuator (opposite of the wiring terminals)

My guess is that your zone valve actuator (includes the motor and the end switch. Basically everything silver) needs to be replaced. Sometimes the gear that moves the valve gets worn over time. This means the valve will open but the end switch may or may not be activated. It can be intermittent, but as the gear ewars more and more, it will happen more often.

here is a good video on how a pro might change the actuator head. https://www.youtube.com/watch?v=bC8NORCDJ7Y
You dont need to purchase a complete valve. You can get the actuator only herehttps://www.supplyhouse.com/Honeywell-Home-40003916-048-Replacement-Head-for-V8043F-Zone-Valves

beatnikbrew

That's a helpful video, thanks! Hopefully the new actuator solves the problem - I'm a little concerned that after putting the problem valve back the boiler no longer ignites.

I appreciate all the helpful advice, everyone.

mattmia2

you can manually open the valve and jumper the end switch terminals or twist the wires together and see if the boiler fires. Keep in mind there is an aquastat with a high limit on the boiler and it won't fire if it is above the limit or has hit the limit and hasn't dropped by the differential.