An installer pipes up a two-zone, low-temperature radiant floor heating system to a conventional gas-fired boiler, as shown below. Zone valves are installed so that each zone can operate independently. Can you identify at least four errors in this design?
1. Whenever there’s a mixing valve in a hydronic distribution system there has to be a circulator between that mixing valve and the heat emitters. This is not the case in the glitch drawing. Remember: When flow exits a circulator all it “cares about” is getting back to the inlet of that circulator. In the glitch drawing there is virtually no “incentive” for flow to pass through the radiant panel manifold stations, even when the zone valves are open. Instead, it takes the short cut from the hot port to the cold port of the thermostatic mixing valves. This is sure to lead to an underheating problem.