I am currently working on a Lochinvar water heating system,
model # CWN0745 S#L951036. The problem has come down to the fintube coil restricted on the outside causing the burner to lockout. The diff. pressure of the comb. air is 3.5 iwc. , the inlet gas is 6.5 iwc. , manifold 4 iwc. on both manifolds and the draft pressure is -.01 iwc. According to the man. the draft should be between -.01 and
-.08 iwc. Talked to the factory rep. and he said to clean the coil in place and install a draft inducer with a
baremeteric damper. He also said that the min. return temp. for the heater section should be 140 deg f. to prevent
condensing . They want to run the supply temp. at 104 to prevent scalding from hand sinks in the day care area. has anybody used a heat exchanger with a 3 way valve between the heater and storage tank on an application like this ?
Thanks for the input Bob.