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Old 12-29-2011, 09:03 AM   #1
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2 thermostats one boiler


I have a Hydronic system that currently is running one manifold with two loops. I am adding one more manifold with 4 loops. I want to control each manifold with a zone valve. One manifold is for a small room where the temperature will be warmer than the other. My intentions are to open the zone valve 1 and fire the boiler with one thermostat and the open zone valve 2 and fire the boiler with the other thermostat.

-------ZV1----------Thermostat1
/
B
\
-------ZV2----------Thermostat2

My question is will this work or will I have a problem if both thermostats send voltage at the same time? This is a 24V system. Do I need a relay?

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Old 12-30-2011, 05:19 AM   #2
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2 thermostats one boiler


the zone valves will be tied together or piggy backed sending the call for heat signal to the boiler. I would add an additional transformer to run the zone valves though, probably 75VA.

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Old 12-30-2011, 07:44 AM   #3
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2 thermostats one boiler


The zone valves say that they use only 2Va, each the transformer is a 40Va, would you still recommend an additional transformer for a total of 4Va?
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Old 12-30-2011, 08:16 AM   #4
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2 thermostats one boiler


just wire each zone valve as if it is the only one when the stat calls the zone it swings end switch makes the cirulator and burner if the water is below setpoint within the boiler.the VA concern is the run out to the stats if there digital they might pull on the zone valves or chatter the circ/boiler relays wire it up and see if anything drags with the entire show running.once #1 ZONE valve/end switch calls the rest are going to follow from each stat so the circ/bolier will already be running...then on stats being satisfied the last stat will shut the show down once the valve closes and the switch opens..the TR on the boiler will handle the zones valves,but the stats are the drawalso in the VA totals
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Old 12-30-2011, 04:28 PM   #5
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2 thermostats one boiler


I like to add the additional transformer to cover my butt. Oversizing the Xfmr will not cause a problem and it leaves you plenty of room for add-on's later. Even if you add an additional 40Va xfmr it wont hurt anything. This also keeps the the zones valves isolated from the ignition circuit.
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