24V Thermostatic Actuator (Zone Valve) for SSM & BSM Manifolds, 4-wire
Mfr Part#: SSM201
What is the difference between the 2 wire and 4 wire?
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SSM101 is a 2-wire model. SSM201 is a 4-wire model (with end switch). Purpose of the end switch is to delay start-up of the circulator pump until the actuator is fully open (~3-4 minutes). End switch design prevents pumping against a closed zone valve (actuator) and prevents early wear and tear of the components in the system. Regular SSM101 model does not have this functionality and in most instances will require creating a bypass using Taco 3196 model or similar, so as to bypass the flow of water (between the supply and return manifolds) until the actuator is fully open.
Answered on 9/20/2016 by PexUniverse Customer Service