OWB system plate heat exchanger fouling?

[mgp141]

I've got a Polar G3 OWB and Baxi propane backup feeding an air handler and in floor heat. When propane is on the Baxi provides about 150degF at the in floor hot manifold. With the G3 running I'm only getting about 90 degF at the in floor hot manifold, it hardly keeps the house at 22 degreesC.

From the OWB water is 190degF. It comes into the water to water HX at 172degF and out at 144degF. The HX send to floor loop is 92degF and HX return from floor loop is 77degF.

Does this indicate the HX isn't providing enough heat transfer between boiler and indoor loops?

I've got grundfos ups15-58fc pumps on both loops.

 

[NSMaple1]

Maybe?

How old is this setup? How old is the problem?

 

[rancher2]

Do you have a mixing valve not working properly ?

 

[mgp141]

Setup is from 2002. House is new to us (first heating season) so not sure if it is an existing problem.

There is a mixing valve on the radiant heat side of the HX but I'm not really sure how it works. The mixing valve is across the HX send and return with the outlet of the mixing valve to the pump suction side. Also to the pump suction side is the HX send directly. I isolated the mixing valve (ball valve on both hot and cold in) and saw no change.

 

[NSMaple1]

Btw 150 going into floors is a lot hotter than most always used or recommended.