|If your solar water heating system pump is located in an area that
is susceptible to freezing temperatures, and your heat transfer fluid is
plain water (not antifreeze), you will need to protect the pump and
connecting plumbing from freezes. Other equipment and plumbing in
the system may also need protection from low temperatures.
This page gives a couple ways that people have done this.
On my Solar Shed project, the pump is mounted just outside the heat storage tank. By running some of the tank insulation outside the pump, the heat loss from the tank keeps the pump above freezing.
By mounting the pump close to the tank wall and then extending part of the tank insulation outside the pump chamber will stay at a temperature that is intermediate between the tank water temperature and the outside temperature.
You want to be careful to not put so much insulation over the pump that it overheats when running on a hot day. You want to monitor the pump chamber temperature for a while to make sure it stays within limits.
I've monitored the temperature in both cold and hot conditions, and the pump area has always stayed well within the pump's allowable temperature range.
I've used the arrangement shown above for about 6 years, and have had no problem -- this has included ambient temperatures as low as 30 F below zero high temperatures into the 90's F.
Plumbing that needs protection in the area of the tank can be protected in the same way. The picture below shows the pipes that deliver heat from the tank to the house. The part of these pipes that extend above ground need freeze protection.
Pipes leaving the tank with the tank insulation extended outside the pipes to protect them.
This picture has some of the insulation removed.
The SolarFriend site shows a simple way to protect a pump from freezing conditions.
The lightbuld is turned on by a freeze protection thermostat and keeps the pump chamber warm.
The differential controller for my solar space heating system is located out in the Solar Shed, which sees quite low temperatures.
The controller is not approved to run in these low temperatures.
The controller could be handled in the same way as the pump, but just placing it where it will receive some heat from the storage tank, but it may be difficult to make sure that it stays within its approved temperature range with this approach.
The scheme I've been using is to place the controller in a box made from rigid foam board insulation. The insulation thickness is chosen such that the standby power use of the controller keeps the insulated chamber above the low end of its operating range in cold weather. In the summer, I remove the front cover of the insulated box so that there is no chance of overheating the controller.
Controller with the front part of the insulating box removed for the summer.
Got any good ideas on keeping equipment within its required temperature range? Please send them in...
Gary January 27, 2011