Report on Taco Variable Speed Pump with Differential Controller

This is a report from Sean in Regina, Saskatchewan on a Taco variable speed pump that includes a differential controller for controlling a solar water heating system.

Thanks very much to Sean for providing this report!

Hi Gary,

I purchased the pump for about $680 CDN in July 2010. It’s used in a high head (31.5 feet) drain back system that includes ¾ copper pipe, one Thermal Dynamics collector, and the 200 gallon Soft Tank (see attached pictures). Total cost of the system was approximately $3,500 CDN. With government grants the cost was reduced to $1,200. It covers approximately 30-40% of our annual hot water needs.

I’ve been impressed with the pump’s performance to date. When the collector is 10 degrees above the tank temperature the pump runs for 3 minutes at full speed. The variable speed is nice because it slows the flow when there is cloud cover or the tank is nearing its maximum temperature. I guess the pump would cycle on and off without this feature. It strikes me that such a scenario would be hard on the pump given our high head. Furthermore, it would be less efficient.

A few notes on the pump: 1) It seems to have a good flow at 31.5 feet so I included a ball valve in the piping to the tank to restrict the flow rate to 1.2 litres/minute. I can’t rely on the variable speed to control the flow because the pump runs at full power for 3 minutes using the controller's drain back setting but it takes only 1 minute for the water to circulate through our system. Basically, if there were no valve restricting the flow the pump would run full and quickly cool the collector to the point where after 3 minutes the pump would shut off; 2) We have very cold winters where we live so the collector is covered with snow for 3-4 months. I noticed that when the temperature dips to -35C at night one of the LED lights on the controller blinks indicating a problem with the collector sensor. Just an odd thing that in no way affects the performance of the pump; and 3) My only (minor) concern about the pump is that the minimum tank temperature is 135F. We have young kids and I wish I could set it a bit lower.

All in all, the Taco-009 VT has been a very good unit for us. I highly recommend it.

Sean
Regina, Saskatchewan, Canada

Taco 009 VT variable speed pump with integrated differential controller.

Softtank hot water storage tank
The SoftTank from American Solartechnics

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