solar water heating, solar energy, residential solar panel
Written by Lisa Walsh

Question of the Week: Why Does My Solar Water Heater Run At Night?

solar water heating, solar energy, residential solar panel“If my collector is at 136 degrees, my TST (bottom of tank temperature) is at 161 degrees and my S3 (top of the tank temperature) is at 154 degrees – why is my circulator pump still running? Won’t this cool the bottom of the tank?”

SES says: The pump runs intermittently for a minute periodically when the collectors reach 240 degrees. This keeps the collectors from overheating. Your maximum tank temperature is set to 160. If the bottom sensor, the TST reading, exceeds 160 degrees, the controller will run the pump briefly in the evening to bring the tank temperature back down to 160.

It has been our experience that setting the max temp higher than 160 leads to overheating problems. Yes, you are losing a little heat from the tank when the cooling feature comes on, but at this time of year it is excess heat. You are producing much more hot water than you are using at this time. This is the summer solstice; the collector and tank temperatures will moderate in a few months. Some customers add an extra loop to their solar tank and use that excess heat to heat a swimming pool or hot tub. Most just use control features to manage the excess heat.

Don’t worry about the power consumption. The Grundfos Alpha pump only uses about 5 Watts whether heating or cooling the tank.

Written by admin

Wash City Paper DC Green

Real Estate Agency Literally Giving Away Money for Solar Installations

At the risk of appearing to favor one of the cooler real estate agents in town, I’ll just pass on the news that Green D.C. Realty is putting up its own money to entice homebuyers to put solar thermal installations on their new purchases. They’re calling it a “solar home coupon”: You buy a house with them, and they give you $2,000 towards the setup with Solar Energy Services, which will also help arrange near-term financing to tide you over until the federal and city tax credits come through.

As we saw with my story a few weeks ago, local solar companies are trying really really hard to get people over the hump to their first solar purchase. Green D.C. Realty is betting that the incentive will bring in enough business to make good on their investment.