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Plan to install a modine hot water unit in garage. Have 3 zones off boiler and adding a forth for modine. Have taco SR503 and picked up a SR501. Not sure of wiring the SR501 with the 503? Picked up a Honeywell L606C for the fan on the modine. Is this a straight forward line in to aquastat and line out to fan? Install on return? Thermostat on wall to Taco? Thank you. Rob