I have a utica sfh3100w oil fired boiler with 2 zones. I've lived hear about a year and never noticed before, but the thermostat that runs the first zone off a honeywell L8148A AQUASTAT starts the boiler and also the circulator for that zone. Recently I turned the thermostat on the second zone up to start the boiler and found out that it doesn't start the boiler, justy the circulator for that zone, so it circulates cold water. Is the unit bad or is there something else I might check. It's a honeywell R845A relay. I looked at the aquastat and can fire that with the cover off by pressing in on what looks like a relay or switch. The r845a has a similar switch which when I press it in does nothing. Could it be the wiring. They both run taco circulators. Thanks for any hints or suggestions, lots of wires to trace.

Hi! kasey54

I have a dual zone boiler, with the honeywell L8148A Aquastat, but its done with piping an valves.
Here's the wiring diagram for your r845a see Fig 7 & 8

Can't tell if it's supposed to control burner also.

One of the other guys 'll be along shortly.

K

Many times only one control starts the boiler and pump for the main zone with the additional control only causing the pump for the second zone to start. This can be a normal situation and changing the system to operate differently will require a visit from your local boiler service professional and additional relays.