An odd pump question (ME)

[Deleted User]

One of my associates posed an intersting question to me the other day. He's working on a drain back solar system that is "off grid"

A 009 is just shy of being able to get the water over the hump and establish a siphon on the down comer, so he proposed having a small pony pump (007) in series with the 009, then having a time delay relay drop out the 009 to conserve power once the downcomer is established.I've always be told that you should never mix pumps of different sizes either in series or parallel. That said, back in the days of extensive 4 way valves and glycol induction, it was quite common to have smaller pumps in series with larger pumps when filling the system with glycol and it worked just fine.

Any thoughts from pump manufacturers out there?

The solar system (PV) has a limited amount of power, and EVERY watt counts...

TIA!

ME

Jerry Boulanger_2

Pumps in series

When two pumps are in series each must have the same flow. The total head developed will be the sum of the pump heads at that flow. For example, if the flow is 5 gpm, and the 009 develops 8' at 5 gpm while the 007 develops 5' at 5 gpm, the series performance will be 5 gpm at 13'. So, although it is uncommon to see two different sizes of pumps in series, it will work for this application. Remember, however, that when running on one pump, the idle pump will be resisting flow rather than helping it, and will likely be windmilling.

Richard Miller_2

then

would paralell work here?

Richard Miller_2

then

would paralell work here?

Mike T., Swampeast MO

Crazy idea but...

...perhaps you could find a DC pump, use rated voltage for starting and after a time interval drop the voltage to a "run" state??

[Deleted User]

Pumps in parallel...

double the GPM while leaving the head untouched. In this case, we need more head.

ME

Richard Miller_2

duh!

I knew that. But I have an excuse. My brain is on drugs. Had a nasty abcessed tooth extracted about 90 minutes before I made that post. LOL

hot_rod

A supplier

I know used to practice doubling up pumps (flange to flange) for the reasons you mentioned, although he used same sized pumps. He started getting a lot of broken shaft returns. Makes me wonder if the lag pump gets windmilling backwards, then the power hits and snap goes the shaft??

Grundfos is having a pump class in July in KC. I got a list of "things I always wanted to know about pumps" I'll add that question for ya.

Here are some spy photos I snapped of their lab last week. Lots of cool hands on training stations. Love the clear pipe to see whats happening inside. This one pic shows a devise that uses RO discharge pressure to spin a generator. Used in large scale desalinazation (sp)plants.

hot rod

[Deleted User]

Thanks HR...

I was told, and actually saw with my own eyes, the fact that if a 120 volt single phase device (motor) is spinning backwards when power is applied to it that it will run backwards. Had it happen on a Tjernlund draft induction blower. Motor was being spun backwards by buildings negative pressure being drawn through the fan. WHen power was apllied, motor ran backwards. 120 volt single phase, no less.

Thanks for asking the question for me.

ME

[Deleted User]

Thanks Jerry..

I will pass this on to him.

ME

Brad_3

SDHW direct pumping

Though this doesn't address the question directly, I think it's relevant to the outcome of the system design in question.

Drainback systems are great for grid powered systems, I've installed and worked on some that have been in for over 20 years, very reliable and failsafe even during a power outage.

I think for an off grid solar system, which I've done a few of, the best way to go is a closed loop glycol system. Or in a no-freeze area just an open loop system. Then you can use a 5 to 30 watt solar electric (PV) panel (depending on system size) powering a DC pump like an El Cid. I've used this for many years with totally reliable results. And, it uses no power from the residential power system at all. Control of the pumping is inherent in the design so there are no electronics besides what's in the pump. Circulators running continuously during the day on an off grid solar power system is a load that is just plain unnecessary and very expensive when the cost of the PV panels is considered.

[Deleted User]

The guy they're building this for

is a living legend in the anals of solar history (John Klima for those who know him), and if anything was possible to be done with a DC system, you can bet he'd have already figgered it out. Thanks for thinking outside the box just the same :-)

ME

Joe_10

DC pumps

Have you tried Dankof Solar at Dankoffsolar.com? They have some pumps that will run on dc possibly panel direct to fit this need.They run dc panel direct for swimming pool filtration and saolr heat applications.
Joe

Steve Ebels

Can you find

A multiple speed pump that will supply the required head, wire it to a relay of your choice that will select first one, then the second speed?

hot_rod

I think

it depends on the type of motor. (shaded pole types perhaps?) I have tried spinning some motors backwards and hitting the switch. Most stop then rotare the correct way. I've tried it with pumps and blower motors.

Now we need a motor and a pump expert to chime in! Certainly the B&G folks know this stuff Where's Big Red when we need him

hot rod