Since converting to led lights and solar Ive become obsessed with power usage in my bus. I realize the water pump doesn't get a lot of use but when you are on battery power only every little bit counts.
I just bought a TV for the bus based on the "Energy guide".
Has anyone done any research on water pumps and how would you determine the power usage of the current one?
Regards
Fred
DC on demand water pumps are what they are there is not much in way of saving 2 things factor into the DC pumps 1 flow the other pressure,AC pumps are different they will do the same output and pressure on 1 amp as the DC pumps do on 6.5 amps of DC power,For the past 15 years all the higher end RV's and bus conversion have used AC power for water pumps FWIW and they seem to last forever
Quote from: Fred Mc on September 19, 2018, 07:31:41 PM
Has anyone done any research on water pumps and how would you determine the power usage of the current one?
If you're serious about monitoring DC power usage then you need some kind of a shunt based battery monitor (Trimetric 2025 for example). If you've already got such a system then its pretty simple to monitor the pump's usage.
Quote from: luvrbus on September 19, 2018, 08:01:51 PM
... they will do the same output and pressure on 1 amp as the DC pumps do on 6.5 amps of DC power..
How many amps DC did it take to create that 1 amp AC though through the inverter? I'd be curious how many watts the AC pumps draw in comparison to the DC.
I would suspect that the high end units got REALLY tired of water pump failures and moved on to something more reliable...
How much water are you pumping? The opportunity for savings here are pretty small...?
happy coaching!
buswarrior
I have had both types of pumps
the 12 volt dc rv pumps will use a lot less power
the hunter water pump I have now is
10 amps at 120 volt a/c or = 10 x 10 = 100 amps on 12 v d/c through a inverter
to slow down the on off cycle and to save a little power you need a air expansion tank on the system
the pressure is higher with the 120 v unit
dave
I was making the comparison between the 2088 Shurflo DC and 4088 AC power pumps you see in RV's now not a $1000.00+ Headhunter pushing water in a 45 ft bath and a 1/2 motor home.
Manufactures are going with AC pumps because most are total electric running house type fridges anyways so the inverter is on all the time,the 4088 is 1 amp max on AC
Consider adding solar if you don't already have some. If you have some, add some more. You could add a bladder tank like they use in homes to extend pump off time, although it will run longer to recharge the tank, so it may not be any gain. Or add another deep cycle house battery. Or a tiny gas generator.
1 amp at 120V is the same as 10 amps at 12v, if it were apples to apples. It's not though, AC voltage uses a .707 power factor due to the sine wave. Which means of course, 1 amp AC at 120v is roughly equal to 7 amps DC at 12v. But then it isn't really 12v either is it? More like 13.2v really.
So the bottom line is that your 6.5amp DC pump is using just about the same amount of power (voltage x amperage) as your 1 amp AC pump. What a surprise! Oh, plus the loss through your inverter of course.
(did I get that right?)
Jim
Some DC water pumps are in 16 + amp range it depends on GPM and pressure.I have 2 Jabsco 6 GPM that I didn't use because they were 17 amps ea @12V
Simply put a clamp on ammeter around the water pump wire, turn it on and measure the draw. You need to separate the wires.
Quote from: windtrader on September 20, 2018, 11:41:51 AM
Simply put a clamp on ammeter around the water pump wire, turn it on and measure the draw. You need to separate the wires.
why it's written on the pump.gpms, amps and pressure
Not sure what you need power for, for a water pump. Mine works fine without A/C or D/C. ;D
Quotewhy it's written on the pump.gpms, amps and pressure
The actual draw depends on various factors such as head, hose diameter, distance, etc. Those figures are probably rated, meaning nominal operating specification.
Gary
Wife was a farm girl when they had those and barb wire phones and no refrigeration and wood stoves for cooking i, on the other hand, having been brought up in the city never had the pleasure of trundling 50 ft. in two fee of snow to sit on a frozen boad to go to the bathroom. Next thing you'll be suggesting ouitdoor toilets.Were trying NOT to go backwards. :) :) :)
Quote from: windtrader on September 20, 2018, 12:20:40 PM
The actual draw depends on various factors such as head, hose diameter, distance, etc. Those figures are probably rated, meaning nominal operating specification.
I don't where they get the figures from most call for 15 amp switch on the 6.5 draw pumps.then about 1 in every 25 owners don't use a relay per instructions they wire direct and forget about it,most of those pumps draw a small amount of current when the power is on, mine draw 15 milliamps ea when not running lol that is the phathom draw I look for some times for days
The listed amps is probably at maximum rated pressure developed.
Due to the continuous current of DC, as opposed to alternating current, the wear and tear on switches can be higher than expected. There is more arcing than an AC circuit which pits and burns switch contacts.
I'm guessing the need for a higher rated switch is to help protect against premature failure, as water pumps are often switched while under load.
Quote from: richard5933 on September 20, 2018, 05:13:24 PM
Due to the continuous current of DC, as opposed to alternating current, the wear and tear on switches can be higher than expected. There is more arcing than an AC circuit which pits and burns switch contacts.
I'm guessing the need for a higher rated switch is to help protect against premature failure, as water pumps are often switched while under load.
How does that affect a switch on a relayed circuit, my pumps are on a 30 amp relay for each pump ? I can see a 5 to 7 amp switch but not a 15 amp
Sorry - didn't catch the part about the relay. The pump we're using (Shurflo 2088 series) only draws 5 amps per the label on the motor. They recommend a 15-amp slow blow fuse. I've just used a standard 15-amp and have had no problems.
Not sure why anything more than a 15-amp switch would be required. It would seem on the surface that a 5-amp switch would suffice, but apparently they concluded that the pump can draw more than the 5 amps, possibly when under heavy load or pushing up against a large head?
All that said, if you're using a 30-amp relay then I don't see any problems at all using a switch with a lower rating. It only has to be enough to activate the relay. The instructions that came with my pump made no reference to using a relay, although I can definitely see the advantage to doing so in the future.
Quote from: richard5933 on October 03, 2018, 05:11:54 PM... Not sure why anything more than a 15-amp switch would be required. It would seem on the surface that a 5-amp switch would suffice, but apparently they concluded that the pump can draw more than the 5 amps, possibly when under heavy load or pushing up against a large head? ...
Excellent info, Richard, thanks. Just a guess, but it would seem that a water pump is likely to draw a pretty substantial start-up surge. That could be another factor.