The idea of running a sprinkler on the roof was originally tested by an HREG member named James, who used a sprinkler for one summer and discovered a 30% decrease in his electric bill (after taking into account the rise in his water bill). However, having a shingle roof, I was somewhat concerned about damaging that type of roof.
I had to put in a new building in a hurry because a tornado had touched down on my property and caused severe structural damage to my home. I put in a metal building and specified that it must be able to handle a sprinkler system on the roof for cooling. My roof is a 1-in-12 pitch made of galvalume. The sprinkler system itself is 1/2" PVC run up the outside of the building and weighted down with sandbags at the ground. I am using three sprinklers, all full-circle, to cover a 40' x 70' building. I have drains for the system at both ends of the building. My husband built the control unit by taking the solenoid from an old washing machine (so it operates on 120V) and wiring it into a relay timer from Mid-State Electronics in Bryan, TX. The timer is an IDEC electronic timer, model GT3W-A11AF20. It uses a standard octal pin arrangement that relays use, therefore a standard relay socket. The coil is rated for 100-240VAC, the contacts at 5A @ 120VAC or 30VDC, or 3A @ 240 VAC. There are 2 contacts on the timer, so I ran the solenoids we are using in parallel, which gives me a max of 10A out. This timer can be programmed for any configuration of outputs you want, using T1 and T2 any way you want.
In 2005, we had to replace the sprinkler heads. An interesting discovery: the cheaper sprinklers work better. The metal ones don't stand up to the heat and they clog easily. As of 2007, we have run the system for 6 years. We did have to flush the system with the sprinklers removed to eliminate built-up algae, but we are on a well so our water is not chlorinated. Our water has a high salt content that has gotten much worse since the Tenasca power plant went into operation in Shiro. The timer is still working perfectly and the PVC pipe on the roof is still in good condition.
Submitted by HREG member Kim
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