Does anyone have experience with Heliotrope General drain down solar DHW systems?

Andrew Rudin

I am having difficulty with my Heliotrope General drain down solar DHW system. The air vents do not vent the air effectively. The panels will fill with some water, then the sun will heat it to steam. I installed a second air vent, but that has not helped. Does anyone have experience with venting the air out of such a system?

matt_sunwaysolar

I'll start by saying that I have not used Heliotrope systems or equipment.

In my experience, if you're not able to force the air out of the system, you're not using a big enough pump or the pump is being impeded.

Is the system beginning to fill, but then "stalling out" before completing the loop? If so, I'd look at the pump. You may be able to test this'll theory of easily using a charging pump (at least 1/2 a horse) and cycling the solar loop. If you're getting the loop to complete with more power, you probably need a bigger pump. Flow meters are helpful also.

Any more info would be great.

Andrew Rudin

Thanks for responding Matt. A drain-down system fills by street water pressure. The tiny pump runs off a PV panel.

hot_rod

What type of vents are you using? Should be a high flow, ideally a solar rated vent. Those could be finicky systems. What type of drain down valve?

Andrew Rudin

I have a Watts 4A820 on the high manifold of the panels, next to a vacuum breaker for the drain-down. That vent didn't work consistently, so I added a T and about four feet of half-inch copper sloped so it would drain and added a Maid-O-Mist 75 off an elbow at the end of the copper pipe addition. That too has not been consistent. I am at the point where I won't leave it unattended. The steam pressure can get high inside the panels..

hot_rod

My opinion on those is to convert them to pressurized glycol or a true drainback, not drain down. Those drain downs gave the industry a black eye

solradman

Agree with Hot Rod. I have not seen a drain-down system with a pv powered valve in 30 years. We use to install them however the valves made by Sunspool would stick either opened or closed. The result would be freeze problems. Sunspool then went to the pv so the valve would exercise every day. They went out of business in the mid 80's. What I did like about them was the combo air vent/vacuum breaker we used called a Richdale, however I have not been able to find one since. Most of the systems were changed to either manual, fill in April/drain in November(depending on where you live) or drain-back which is what I too would recommend. Depending on the age of the storage tank you have some options there.

Andrew Rudin

I appreciate your response. My 2-panel system was installed in 1998 and worked flawlessly up to 2 years ago. I installed both Watts and Maid-O-Mist vents on it now, and the panels still don't vent air, so the water turns to steam. I ordered a Duda Energy vent today. Dan Holohan says maybe a Caleffi vent might work. We shall see.

matt_sunwaysolar

I know this is an obvious question, but what happened (changed) 2 years ago when the system began having problems? Anything specific?

Andrew Rudin

Not that I know of. Again, I appreciate your attention to this stuff.

kcopp

I second the Caleffi

Andrew Rudin

Thanks.

hot_rod

If the vents are failing due to over-heating then look into a solar version. This Caleffi has a 360F operating temperature. A pressurized system can easily exceed 300F during stagnation. Check the pump, some will lock out under high temperatures, also

https://secure.solar-rating.org/Certification/Ratings/RatingsReport.aspx?device=7142&units=METRICS

Andrew Rudin

How about the Duda Energy air vent? It's one third the price.