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Honeywell Aquastat died, need advice on replacement/ upgrade options

Any and all help/ advice is greatly appreciated! :)

I have an EnerJet Natural Gas Water Boiler

(1) Taco circulator pump (pulling)
(3) Thermostats
(3) Honeywell V8043E1012 zone valves
(1) Honeywell L8148E Aquastat Relay
(1) Automatic Gas Vent Damper
(1) High Temperature Limit Switch (I'm guessing), in the exhaust hood
(1) Honeywell VR8300C4506 Step Opening Dual Standing Pilot Gas Valve

Sometimes heat doesn't come on when called, upon inspection of the Aquastat, the relay switch is out, pulling on the tab makes the contacts and the boiler fires right up, circulator pump runs, zone valves open, etc.
If it then let go of the relay switch tab everything shuts off instantly.

If I take a small piece of plastic and wedge the relay switch tab so that it connects, then the boiler everything will run and it automatically shuts off when the high temperature limit is reached.

  1. I added third zone (thermostat + zone valve) a few years back, it never worked quite right, only sometimes. I've been told that my aquastat cannot handle a 3rd zone, and I'm past what the transformer can handle.
    I have since been running the 3rd zone with the thermostat off, zone valve locked open, and adjusting a ball valve that I put in the line for that zone. So that zone gets some heat when the 2nd floor calls for heat... not ideal but it has been working.
  2. As I believe the Aquastat is broken, I could either replace the Aquastat with the same model or could I make this setup a little better and get my 3rd zone working properly by installing a Taco ZVC404-4 4 Zone Valve Control Module
    My thinking is that the Aquastat (a new one) could be used together with the Zone Valve Control Module. Also another thing is that all the 4 wire leads from the zone valves are a birds' nest, and the Zone Valve Control Module would clean that up nicely.
  • I've read from many that the relay switch often dies in this Aquastat... would a Beckett AquaSmart 7610B Boiler Temperature Control be a better choice?
  • I'm assuming the Taco ZVC404-4 4 Zone Valve Control Module has a built-in transformer - correct?
  • If not, would I be buying a separate 40 VA transformer, I'm guessing so.
  • If I'm going with the Taco ZVC404-4... do I need the same Honeywell L8148E Aquastat? or could I get a simpler model since some functions would be handled by the Zone Valve Control Module?
  • There are wires coming from the Automatic Gas Vent Damper, no molex in my current Aquastat, and some of the wires connect to the gas valve, a sensor with a resistor by the pilot tube, and to the High Temperature Limit Switch. I'm guessing this is because all four require 24v power. Not sure how to connect this back up since the new Aquastat seems it will have a molex connector.
Which terminals on the Aquastat would still be used versus those on the Taco ZVC404-4?
i.e. C1, C2, L1, L2, B1, B2, TV, W, T, Z, etc.

I assume L1, L2, B1, B2 will still used in the Aquastat
I think the Taco ZVC404-4 would power the C1, C2...
How would the Taco ZVC404-4 connect back to the Aquastat? especially regarding TV, W, T, Z