Water Pump Pull

BC_Warren · March 2017

I am just at the beginning of this venture into solar power, and am frankly a tad overwhelmed by the technical talk in even the beginners' forum.

In any case, I can see an early step is to determine the electrical energy needs of life in my old Boler. The biggest draw in the unit is the water pump -- the only other use of electricity is lighting: and those are all LED lights. My furnace is convection only -- a great energy savings from my last unit that had a furnace fan.

I have a small SHURflo water pump (a 911-352, if that makes a difference) and cannot determine either from the original documentation or online how much current it pulls.

Can anyone give me a ballpark estimate of how much I should allocate to a water pump?

I suspect it will not be long before I am familiar with such terms as amp/hours and the esoterica of battery technologies. Thanks for your help.

jonr · March 2017

It depends on pressure, but my guess is less than 5 amps. Better would be to measure it.

Horsefly · March 2017

I did a quick search, and 911-352 is the part number for the installation manual, not the pump.

Here's a link to the document I found that makes that reference. If your pump is the one described here, it's a 12VDC pump that draws something less than 5A. Award for @jonr for guessing right!

BC_Warren · March 2017

Thanks, guys -- that's great info. For the purposes of estimating power consumption, I'll just use the highest number (4.8 amps).

I hate to show such weak understanding of this stuff, but when I have a 75 watt panel how many amps can I expect to generate in a day with, say 5 hours of sunshine? I have calculated that 75 watts = 6.25 amps at 12 volts, but does this remain a per/hour rate since watts are a measure of a rate?

BTW: Horsefly, is that by any chance the name of your town? If so, I have visited a few times and quite enjoyed it.

Horsefly · March 2017

BC_Warren said:
BTW: Horsefly, is that by any chance the name of your town? If so, I have visited a few times and quite enjoyed it.

No, sorry. I showed up here on this message board last year to learn how to do a solar off-grid system for my family's cabin. The cabin is nearest a mountain peak in Colorado named Horsefly Peak. For my entire adult life, we've referred to visits to the mountains as "going up to Horsefly" or simply "Going up to the cabin." I didn't know there was an actual town named Horsefly. Where is it?

westbranch · March 2017

Close to where I live right now ~ 30 miles E.... different from where my Off grid system is...

Horsefly · March 2017

BC_Warren said:
I hate to show such weak understanding of this stuff, but when I have a 75 watt panel how many amps can I expect to generate in a day with, say 5 hours of sunshine? I have calculated that 75 watts = 6.25 amps at 12 volts, but does this remain a per/hour rate since watts are a measure of a rate?

I don't think anyone can do justice to that answer like Bill (@BB.), but.... You can't really directly translate the power for one load (the pump) to the power / energy from a panel. It's all part of a system, and that system probably needs to operate from midnight one day to midnight the next day. So it is not really a solar power system, but a power system that periodically is rejuvenated by the sun.

So, the way to do this is a little more complicated. Figure out all your loads (in Watts, which is power). You need to include everything, because even little things will impact your energy budget. Sounds like you have a start at that, but now you need to think about the "little things" like cell phone chargers.

Now factor / multiply each of those loads by how much time they are used in a 24 hour day. That is, if a light will be drawing 4W and is expected to be on for 4 hours per day, that is 16 watt hours (energy). Add all those up, and you have the energy consumption per day.

Now you have two numbers: The total watts (power) you may be using at any one time (assuming all the things are on at the same time as appropriate), and the total watt hours (WH, or energy) you will be using in a day.

Once you know the WH per day you'll need, you can calculate how much storage (battery) you need for energy. That has to take into account things like how you want to deal with no-sun / limited-sun days (more storage), and how much of your loads are 12VDC (like your pump) and how much are 120VAC. The 120VAC requires an inverter, and to size that you need to be using the maximum watts you need at one time.

The size of your battery and how much solar energy is available at your location will then lead you to how many of how big solar panels you should shoot for. There's lots of relatively simple math, but if you do the math you are much more likely to have a system that won't disappoint you and that maybe you can be happy with.

Now I'll wait for the better answer from Bill. ;-)

Steve

Iceni John · March 2017

I have two SHURflo 2088 pumps in my bus, and they each draw up to 7 amps at 45 PSI, but less at lower pressures. SHURflo also makes simple low-flow pumps and bigger high-capacity pumps - which one is yours?

John

jonr · March 2017

You can get a good idea of run time and watt hours if you know how many gallons per day you use. For example, 30 GPD might be 10 min/day and 11 watt/hrs per day (very little, probably less than a single LED light).

dennis461 · March 2017

BC_Warren said:

Thanks, guys -- that's great info. For the purposes of estimating power consumption, I'll just use the highest number (4.8 amps).
I hate to show such weak understanding of this stuff, but when I have a 75 watt panel how many amps can I expect to generate in a day with, say 5 hours of sunshine? I have calculated that 75 watts = 6.25 amps at 12 volts, but does this remain a per/hour rate since watts are a measure of a rate?

See if this explanation helps.
The number 75 is not a rate, it is an instantaneous value of energy.
Rate would be 75 watts per hour, meaning the energy source provides 75 watts for an entire hour, 75 watt-hours.

Now, if clouds roll in, night falls, and you only got good light for one hour in a 24 hour period, you generated 75 watt-hours for the day.

Next day, you get better daylight, let say 4 hours, then clouds and night, you generated 75*4= 300 watt-hours for the day.

I doubt you will get 6.25 amps from the panel. If you can find make/model of panel, you could then find the maximum power current specification, it will be somewhere near 4 or 5 amps.

And, that 4 or 5 amps will be at high noon only, lower on either side if high noon.
So, for ease of calculation, assume 5 amps for the hour splitting high noon (11:30-12:30), then lower numbers for the other hours of daylight. (So you never really get 75*4= 300 watt-hours)

Now take into consideration tilt and orientation component inefficiencies, and you get lower numbers

A particular day for me looks like this (tilt 22 degrees orientation 150 degrees so my high noon is around 11:15 AM)
In the table below, I would multiply each wattage by 30 minutes, then add up to get 15,368 watt-hours from a system designed with 5.1KW panel size.
time watts

8:00:00 AM	1240
8:30:00 AM	2014
9:00:00 AM	2620
9:30:00 AM	2952
10:00:00 AM	3144
10:30:00 AM	3221
11:00:00 AM	3399
11:30:00 AM	3303
12:00:00 PM	3075
12:30:00 PM	2956
1:00:00 PM	2813

BC_Warren · March 2017

Thanks again, guys. Your willingness to take the time to share your knowledge is very helpful. I am going to be using an existing system for the most part, but with your help, I have begun to much better understand what I have and as I move forward I hope I can make somewhat informed decisions about what I need.

I have been surprised at how much energy I can actually glean from solar. I ran my little ol' Boler for 12 days last summer after I bought it with no power other than the solar installed and was quite impressed that it worked so well. But now I want to better understand exactly what is "under the hood," and this has been extremely helpful. Thanks.

And, Horsefly -- the town that is named after you is in the Caribou region of central British Columbia, pretty much east of the larger city of Williams Lake (where I now suspect Westbank lives).

Horsefly · March 2017

BC_Warren said:

And, Horsefly -- the town that is named after you is in the Caribou region of central British Columbia, pretty much east of the larger city of Williams Lake (where I now suspect Westbank lives).

Well, my Horsefly (the mountain peak) is in sunny western Colorado. It's cold enough there, but nothing like western B.C. Plus, I get lots more sunshine! Good luck, and certainly come back here if you have more questions. I found this board to be awesome in terms of both the civility and knowledge of the "experts". Steve

706jim · March 2017

If it helps any, I used a 12 volt Jabsco pump to power my island cabin. It ran from a single 12 volt deep cycle battery for about a month before needing recharging. This was with NO solar panel whatsoever! So you might get away with your 75 watt panel depending on what else you expect the system to run.

oil pan 4 · March 2017

I used a 1.2gpm surflow pump on my diesels water injection for a while . At low pressure it would only draw 2 amps. At full cut off pressure, 90psi it would draw nearly 5.

Water Pump Pull

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