How often do you clean Flat Plate HX?

[Bwhunter85]

How often if ever, do you clean or flush your flat plate HX for DHW? I have water softener before it hits the tank, but I was thinking on running some cleaning vinegar through it for annual maintenance? Haven't cleaned it since putting brand new in 3 years.

 

[maple1]

I haven't touched mine at all yet after 6 heating seasons. Likely varies widely with water quality. We don't have treatment, but we do have sediment filters. Also think our water is very slightly acidic - maybe that is helping things in this respect.

 

[E Yoder]

I haven't flushed mine in 11 winters. But I've seen them plug in 6 months in heavy lime water. Those are blowing elements in their water heater also, plugging coffee makers, etc.
I agree with maple1 it's all in what's in the water.

 

[peakbagger]

I think the proper time is "it depends". Water quality and design both factor in. Plate and frames are great if they are designed correctly. The best thing to do is put a good pressure gauge across the exchanger and check the pressure drop. Note I say one pressure gauge not two. Connect it to the inlet and outlet with isolation valves or three way valve on the inlet to the gauge. Read the pressure on the inlet then swap the valves and read the pressure on the outlet. Record the values and then trend. As long as you are using constant speed pumps that's going to show you when the heat exchanger is plugging. The reason for doing it this way instead of two gauges is most gauges aren't calibrated and can have quite a bit of offset, the offset can easily be confused with an actual pressure drop. With one gauge, no worry about offset.

I used to have to deal with plate and frames in an industrial environment on less than clean streams. It was rare to have them work out of the box correctly and the result would be plugging or high pressure drop. We pretty well expected that at some point after some period of use that we would end up having to add or subtract plates to get the velocities dialed in. If the service was particularly nasty I would go with spiral heat exchangers, not cheap but self cleaning most of the time and worse case if loosen a bunch of bolts and they could be pressure washed in place on the dirty side. They are expensive to build. We used to have service contract on all of out refrigerant systems where we paid a flat rate to Honeywell per ton. We didn't pay for repairs so they needed to do what they had to to keep the equipment running reliably. They acid washed every heat exchanger once a year.

 

[TCaldwell]

Just out of practice I acid wash mine once a year.