Argo AR842 Relay Chatter

lmco

I have a 30-year-old Argo AR842 with HW Priority, connected to a Buderus boiler and an Indirect Water Heater. A few years ago and perhaps after minimal water exposer, on rare occasion I would hear some relay chatter. I changed out the arcing relay and noticed another relay occasionally arcing. At this point I am easter egging the problem and to no avail. I was wondering if my power stealing thermostats and system age are producing this issue. Since the system is 30 years old, I am hesitant to replace the box, knowing that is a few years I will be replacing the entire system. Trying to understand if a voltage drop or old PCB mounted transformer is the culprit.

Big Ed_4

Is the voltage coming is in range ? Yes ,you can get chatter from one of the thermostat circuits . Any changes with that ?

EdTheHeaterMan

Are the power steeling thermostats also 30 years old?
If the power steeling thermostats are more recent, then I would ask if the chatter start around the time when the thermostats were replaced?
When I would Quote on a new system, I always like to quote all new controls and zone valves or zone circulators (depending on the system) and thermostats. that way i never have the argument about charging for a new thermostat or zone valve or whatever, during the warranty period, because it was not included in the price of the boiler job. So I understand your apprehension over buying a new zone relay panel only to have it replaced in a year or so.

You have 2 options, put a dumb thermostat on the problem zone(s), or get the new control that is compatible with the power stealing thermostats. If it is only a year old when you get your new system, the contractor may discount the job by an amount that will reflect the cost of the control. If the control becomes a problem during the new boiler warranty period, then you will just have to pay the difference if and when that happens.

OzoneSal

Just fixed mine, Give me a shout 

exqheat

disconnect the new thermostat. Jump the thermostat inputs to see if relay holds. If it does, It's the thermostat.

Jamie Hall

And check the voltage on the relay coil when it's energized. Some older relays, particularly, will chatter if the voltage drops too much.

That said, if the relay has been chattering, or you see evidence of arcing on the contacts, it is much better practice to replace the relay. Arc damage on the contacts can either cause them to not make when they should -- or perhaps worse to fail to open when deenergized, which can cause all kinds of mischief.