DC pump for SDHW

Jack

for my house. I would be looking at a net metered system for the PVs but it would also be nice to have a dc pump for the SDHW system to run off pv power while the sun is out and the tank is calling. Suggestions gratefully received!

hot_rod

is this enough

gph and head for your job.? I have used a handful of these D-5 strongs with excellent result. I may know where you can get one already mounted in a solar pump station. Works best with a 30Watt PV panel.

www.lainginc.com/D5_Strong.htm

hr

Royboy

also Laing's D5-solar

is an option, if you don't need so much head. I really like the Laings compared to some of the more traditional brush-style DC pumps (March and Hartell) which are much noisier and have a shorter lifespan.

www.lainginc.com/D5_Solar.htm

hr - do you understand the differences between the two D5s: strong and solar, other than the greater head (twice as much) from the strong?

Laing says both pumps will run on 8-24v. curiously, their website shows a pump curve for the strong at 24v and the solar at 12v. and they make a big deal on the D5-solar page about integral optimizing for varying voltage - no mention of that on the strong page.

Bob Hutslar at Laing steered me toward a solar unit for direct PV connection. yet the strong page says they are good for direct connection to PV, too. wondering what you understand to be the differences and pros/cons of the two.

Roy

Sunrise Energy Services

hot_rod

Bob could

better answer that question. I needed the Strong to overcome the pressure drop in that stainless Solarflex tubing.

I have a 30W panel on the way for mine, I had an old 20W but I think the 30W will give me better performance.

The circ seemed to pulse a bit on low light days with the 20W, although it is a 20 year old panel!

Early D-5' had some issues, according to reports from the field, not sure if it was the basic D-5 or solar version

Also consider a solar controller, even for a PV powered system, it really helps the amount of control.

hr

Jack

HR, can you elaborate a bit more

"Also consider a solar controller, even for a PV powered system, it really helps the amount of control."

Assuming I move forward with this, what do you like for PV and SDHW controllers. For the DHW I still have a couple IE C-30's (remember those) from the 70's in the basement. Now if I can find the proper sensors. I know I have them. It is, where!

hot_rod

You don't always want

the solar pump to start when the sun hits the panel. Suppose the tank is still warm when the sun starts the pump. You would actually start cooling the tank. Then suppose the clouds rolled in and the pump stops. Now you have just dumped some or all of your stored hw in the wrong direction.

What the PV powered controller will do is allow the PV powered pump to run only on delta T. A better way to go. It can still modulate based on solar radiation so the variable speed function is still there.

This fellow, in Maine, builds a simple inexpensive PV control. I have used a few without any problems. www.arttecsolar.com


Resol builds a nice one, digital display, etc. It's the as their 120V controller with the transformer removed from the board, so all the same features. I may have a line on a few for test purposes.

hr

Jack

Transformers

I know you referred to this in the 120V unit but generally on units which require a transformer I always prefer to see an outboard mounted $20 transformer rather than the PCB mounted transformer. They do it to cut costs but you end up replacing entire costly pcb's as opposed to replacing the $20 transformer

jp_2

why not

a very small battery instead of using 120vac? keep it green.

Royboy

IMC now has a DC controller

on their website. I've been using their Eagle 2 controller lately and like it. The DC controller looks pretty much the same except for running off 12v DC instead of AC

http://www.solar.imcinstruments.com/