ARGO Boiler Controller Intermittent Failures

KBenn27

I have an Argo ARM-3P the latest one installed 6/16/22 by a local supplier. It controls my oil boiler through a L8148 controller. I have 3 zones: Priority zone to my hot water tank & two heating zones on separate thermostats. The heating zones seem to function fine but I am having intermittent failures of the system to generate hot water – It seems to work for a few days/weeks after attempts to fix and then I get a cold shower.
In the course of trying to fix my system the supplier:
• First replaced my original Argo controller
• Replaced the power switch (thinking the unit was getting low voltage);
• Replaced the zone valve controller (Honeywell 40003916-048)
• Replaced the thermostat (Honeywell Aquastat L60006A).
That supplier ran out of ideas and now their service manager is ghosting me. I took over troubleshooting and found/did:
• The ARM-3P is “cold start” wired to the L8148. The water heater thermostat loop is hooked to the zone valve controller and thermostat using the onboard 24VAC terminals on the controller. There are a couple of interesting symptoms that made me think the problem was a low power condition: First if I directly jumper the priority zone TR to TW connections the unit starts the boiler, operates the zone valve and generates hot water. Second, if the water is cold and the thermostat is calling for heat the zone valve motor gets hot. So, I shortened/simplified the wiring between the Argo, zone valve controller & thermostat and added an external 24VAC 56VA external transformer. Same results.
• Thinking maybe something damaged the zone valve controller (like the heating when not running properly) I bought a new one. When I went to install it, I found the valve isn’t turning freely so it needs to be serviced before I install the controller.
• As I wanted to have hot showers while working on this issue, I left the zone valve open and wired in a manual switch between the TR to TW connection. Turning on the switch 15 minutes prior to needing hot water and off afterwards allowed for continuing supply of hot water.
• After a power outage, I discovered that the controller was functioning again without the manual override. We have run since the fall of 2022 with the system in this configuration. The heating zones worked fine all winter. Sometimes the hot water was extra hot due to the zone valve being stuck open and allowing heating while calling for heat. Randomly, once every month or two the system doesn’t start the hot water (typically find cold shower in AM) and I go switch it on, wait 15 min & shower. Once showers are done, I switch off power to Argo, wait 5 minutes, turn it back on & it starts working like ‘normal’ again.
I’d really like to get this fixed properly & figure I need two things (one I know & one I don’t)
• Need to service/replace the wetted portion of the zone valve.
• Need to determine what is wrong with the controller. Is it possible that something was damaged during all the troubleshooting? If so, then why does it work sometimes? This makes zero sense to me… Have you ever heard of an issue like this? I did send an email to Argo last fall early on in my troubleshooting but never heard back from them.

HVACNUT

The ARM-3 is a circulator control, not a zone valve control. 

So there's not 3 circulators? 

Can you show the wiring?

KBenn27

Yes, there are also 3 circulators: Bell & Gosset NRF-22, Could they be the problem – it is the one part not yet touched…

HVACNUT

Is that the only zone valve? There's 2 sets of wires connected to the priority TT. One set comes from the water heater zone valve end switch. Where is the other from?

109A_5

Hello @KBenn27,
Seems to me, if your manual override switch was 100% effective it is not an Argo ARM-3P issue. If the zone valve does not close its end switch reliably when the L60006A calls for heat the valve may be not be opening all the way, you said it turns hard "I found the valve isn’t turning freely".

When it acts up it should be easy to determine what stage of the system is not working correctly, however you need a Multi-Meter. During a normally operating Priority Zone Call, test point "VAC 1" should be 0 volts at the end switch and at the Argo ARM-3P Priority Zone TR - TW. Test point "VAC 2" should be in the 24-26 VAC area.

KBenn27

Hello @HVACNUT
The second set of wires on the priority TT goes to my manual override switch. It lets me put a direct short across those terminals which when switched immediately switches on that zone and provides ‘normal’ heating function to the hot water tank.

Hello @109A_5
The intermittent failure was underway today. I’ll work on getting the last row in the below listing of values
State: VAC 1; VAC 2; Transformer VAC
Calling for heat but not running: 25.5; 26.5; 26
Not calling for heat: 25.5; 0; 27
Calling for heat – override on: 0; 26; 26
Functioning properly & calling for heat: not tested yet

109A_5

Hello @KBenn27,
If I understand your data correctly, it looks like the 'End Switch' is not closing when it should. This may be a mechanical issue if the valve can not travel its normal full travel.

The Red circled value should be 0 Volts (End Switch closed). Like when the override switch is closed.

HVACNUT

What's the purpose of the zone valve? No flo check on that loop?

What's the purpose of the "manual override switch"? If you close TT with an open L6006A, it'll run the circulator but it won't move any water.
Why bypass a safety?

KBenn27

Hello @109A_5
Thanks for the help. Sorry I was traveling and it took me some time to get to your thoughts and try out a solution. I pulled the motor off the zone valve (which isn’t moving real well) to free its full range of motion and so far it seems to be working. I’ll give it a few more weeks and if it works then I’ll get someone in here to fix the wetted portion of the valve. Thanks again for the help.

KBenn27

Hello @HVACNUT
Thanks for the questions. Sorry I was traveling and it took me some time to get back to you. See below for a diagram of the entire water loop – there are no flo check valves anywhere. The zone valve stops excess flow from the main circulator loop from pushing past the Bell & Gosset NRF-22 circulators and heating the water when the system is calling for heat. I know this happens as the 2nd floor hot water baseboards get hot in the summer when the system calls for hot water if I don’t isolate them by shutting off the manual valves when I shut off the thermostat for the summer. If there was just a direct thermostat connection to the priority zone then the hot water could overheat due to excess flow. The boiler is set to 135F so the hot water could get overly hot.
The help from 109A_5 has pointed me towards a mechanical problem stopping the zone valve controller from properly switching. Isolating that issue has (so far) seemed to address the issue.
The only reason for the manual override switch is to let me generate hot water while figuring out the root cause of this issue. I’m on this forum to figure that out and get the system working as designed.

HVACNUT

Unless the bypass short enough for P/S, the circulator on the return is drawing from every zone whenever its energized, especially if there's no check valves on each zone. The circulators don't have internal flo checks?

That return circulator is the only thing providing direction of flow. If not set up P/S, it's useless, but needed in this case. 
Either add flo checks and remove the return circulator, or add the flo checks and recipe it P/S. The makeup water should also be brought to the extrol location.