? on plate heat exchanger

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

taxidermist

Minister of Fire
Mar 11, 2008
1,057
Fowlerville MI
If I were to put a plate HX on my DHW would it act as more of a on demand water heater? I would pump from storage to HX and start and stop the pump with a flow switch.


Thanks, Rob
 
yes, it needs to be generously sized to provide instant DHW. Also pipe it so it can be flushed of hard water deposits. Here is a drawing of a concept using solar and boiler back up for DHW with a plate HX and flow switch.

hr
 

Attachments

  • Picture 12.png
    Picture 12.png
    32.5 KB · Views: 346
I use my flat plate that way. I think it a 16 plate approximately 5x8 inches. My heat system plumbing is simple, I have the plate HX first and my water to air coil second in a series loop. I have a couple of ball valves to allow the water to air coil to be shut down in the summer. It works well as long as I have water coming form storage above 130 to 140 F. When the temperature gets down to 130 or so you have to have the hot water full on in the shower, but the temperature is fine for me. Usually my wife will start to complain the water is not hot enough at about this point. I have the a tempering valve on the DHW output from the HX just to be safe. To make the best use of the HX plumb it counterflow.

The flow switch has caused me nothing but trouble in the couple of years I have used one. I bought a paddle style first. It works ok, but the internal seal started to leak after about a year. I also had problems with it sticking in the on position from time to time. The sticking was my fault, I tried to adjust the switch to too low of a flow - it seems to work now that I have corrected my error. I thought I would be slick and bought a thermal dispersion flow switch from Omega - big mistake. I selected this switch as it should be sensitive enough to sense very low flow rates. Unfortunately, the switch operated correctly for about 1 month. I returned it for warranty and waited ~4 months for Omega to determine it was a faulty switch and send me a new switch. The second switch made it a week or so before it quit working. I've always had good luck with the stuff I've used at work from Omega, but this flow switch was a disappointment.
 
Status
Not open for further replies.