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[EE Farm Boy]

I have my DHW plumbed with a flat plate exchanger, with a bronze pump on the bottom that circulates the water via an aquatstat when the hot water in the tank drops below 120 degrees.  When taking a shower after 5 min or so the water turns extremely hot requiring you to turn the shower down then it turns cooler and you have to turn it back up.  I have a Honeywell mixing valve after the exchanger before going to the house fixtures for safety.  I thought maybe it was due to the pump kicking on and off but wasn't for sure.  Any ideas on the cause and how to address the issue? 

Thanks,

[slimjim]

Good morning EE, I think you should turn up your Aqua-Stat first and turn down your mixing valve if you need to, sounds to me like your recirc pump is short cycling due to low water temp demand or temps are low enough in the tank that the mixing valve can't compensate.

[EE Farm Boy]

The taco aqua stat I currently have clipped on to the copper pipe is preset to on at 95 and off at 120 so I can't adjust.  Does anyone know of one that is set higher?  The other option is just to buy a Honeywell that clips on but it was about double the price of this one.   

[RSI]

Where does the water from the plate go back into the tank? If it is something like a sidearm connection, my guess is the cold water going into the tank is going to the bottom, making the pump run continuous and raising the water temperature.

It sounds like you have the mixing valve set too high. Just pull the aquastat off the pipe so the pump runs till the tank temp goes up a fair amount then set the mixing valve.

[Bud Man]

I have a sidearm on my LP water heater. When I started the boiler this year I noticed the settings for the shower were set to a lot more cold than usual.

This morning while my wife was in the shower, I heard the LP kick on for the water heater. Don't know if this has happened before but I will be watching it tomorrow.