goofy hot water problem

[ssupercoolss]

well, at least to me. i am getting warm water out of the tap instead of hot. it makes no sense to me. heres the setup - wood boiler in parrallel with the oil boiler, hot water coil in the oil boiler. when i was playing around with this the wood boiler was circulating water at about 170 degrees. i shut the valve for the cold water right before the mixing valve. no effect on temp or pressure at the tap. the plate that the coil is attached to is very hot. the pipe for hot water out is warm. the cold water in is cold. the well for the aquastat is very hot. so, this has me baffled. why am i not getting hot water? the pipe on either side of the mixing valve is the same temp. been down the broken mixing valve road before. could the hot water coil have built up some type of scale on the outside that basically insulates it? i'm stumped, and taking warm showers.

 

[BrownianHeatingTech]

could the hot water coil have built up some type of scale on the outside that basically insulates it?

Yup. It's a common problem with those coils. They can be acid-flushed, but there are no flat-out guarantees that the flush will work, or that the coil won't spring a leak as a result. But that's usually the first step that most folks try.

Joe

 

[ssupercoolss]

scale on the inside? hmmm...thought there might be some type of drop in pressure for that to happen. what kind of acid? i will have to take another look but it might be just as much work to replace it. thanks.