|
|
|
#21
05-25-2002, 05:17 PM
|
|||||
|
|||||
Dolphin Ampmasters
Quote:
Steve 
|
|
#22
05-25-2002, 05:24 PM
|
|||||
|
|||||
|
Dolphin Ampmasters
Darren, I am interested in your MAG7 and MAG9.5 tests today. After reading your tests of the Ampmaster (which I drool over) I was immediately curious of the power consumption of my pair of MAG pumps, which are also a 7 (skimmer) and 9.5 (circulation)
I am just wondering if it wouldn't be more energy efficient to just use a larger pump like an Ampmaster to do both tasks for me?
|
|
#23
05-25-2002, 09:56 PM
|
|||||
|
|||||
|
Dolphin Ampmasters
Hello Steve,
I'm an audio fanatic. That's why I did EE. What I was referring to was mostly the amplifiers and speakers. If you want to discuss these off-topic stuff, you can e-mail me.
|
|
#24
05-25-2002, 11:37 PM
|
||||
|
||||
|
Dolphin Ampmasters
Hi. Been lurking here for a while but feel I have to jump in on this thread.
It is standard to measure amp draw on a power lead directly at the connection to the motor. If the motor manufacturer's (Emerson) amp rating on the nameplate is 1.3A and you are drawing 2+ amps the motor is in an overload condition and should heat up and kick out the internal overload. If this isnt happening, I would suspect that the test method is off - perhaps a false reading re: true rms. The motor can not run properly in excess of the manufacturer's ratings no matter what is attatched to it. "The thing is by using this pump you are getting a much more efficient motor than what is probably in a jacuzzi pump" - ummm, not necessarily. Motors such as these are very similar in efficiency - you might be getting a more efficient mating of pump and motor at the particular operating range. ".. the more head ou put on it the harder the motor has to work.. and the more power it draws" Actually, with centrifugal pumps it is the opposite. At zero head the pump is moving the most amount of water, is working the hardest, and is drawing the most power. As the head increases, the flow decreases so the pump is moving less water and the load decreases which = less amps. "If the plackard onthe jacuzzi says it draws 4.5 amps I'd bet it draws a lot more" No, it cant draw more than the specs on the motor sticker. The motor on this type of pump will probably have two ratings amps and service factor amps (sfa) and will draw close to the max sfa numbers. "JFYI, hot tub pumps are never rated at 0 head so infact there out put in all realaty will probably blow the dolphin away." Most centrifugal pumps will be "off the curve" at zero or very low heads, try to pump too much water, and overload. Thats why you dont get a 0 head rating. "I can not imagine the power cord be dissipating "that much" power. It is impossible for the cord to have enough impedance to cause that much of line loss." I agree. Look elsewhere I think. Jim
|
|
#26
05-26-2002, 01:27 AM
|
|||||
|
|||||
|
Dolphin Ampmasters
Hey Jim nice to see ya. pumps is a big part of my work, we even had to build gear pumps and centrifical pumps on the layth from scratch.
I agreed with your post except for two things (and they were both kinda the same) please do think bad of me as I know computer chats can seam cold but I think you are thinking of another effect that is a result of a centrifical pump not working right. well maby I can explain this with out making anyone mad. Oh and don't mind my spelling I am a engineer not a english teacher :D :D Quote:
Quote:
as you add head to the equasion you add pressure to the inside of the casing which inturn creats the effect of making it harder to pump. when this happens the pump speed slows down and you get less out put. the motor will try to maintain the rated speed but if the head gets higher it can't and does its best at a slower speed, hench the lower output at higher heads. the part you are right about is that when you reach a point of high head pressure that the impeller in the pump isn't rated for your shear streeses insidde the pump become so great you generat slip. this causes the impeller to overspeed and if the motor is equiped with a overspeed trip it will trip, if not it will spin fast with no output and overheat untill it either burns itself out or the motors thermal overloads cause it to shut down. [ 25 May 2002, 21:53: Message edited by: StirCrazy ]
|
|
#27
05-26-2002, 02:17 AM
|
||||
|
||||
|
Dolphin Ampmasters
Hi Steve. No offence taken but I think you should check your theory. What you are saying is more applicable to positive displacement pumps (gear, vane, diaphragm, piston) but not centrifugals.
"BUT as you reach the limit of the pump you will get a increase of shear between the moving water and the stationary water which will cause cavatation and can airlock your pump (in extream cases) in any case this will also cause heat and if it goes on to long it can destroy your pump." Cavitation occurs when the pressure at the inlet of the pump is reduced to the vapor pressure of the fluid being pumped and the fluid "boils". This occurs at low heads/high flows or when there is a restriction in the inlet piping. It doesnt generally occur at low flow/high head. Check the npshr vs flow on a pump curve. The heat produced in a pump at low or no flow is from friction not cavitation. "If we go y your statment any power head in a tank should trip out.. this doesent happen.. because ) head is the easyest state to pump in." Umm, yes it does happen. "the part you are right about is that when you reach a point of high head pressure that the impeller in the pump isn't rated for your shear streeses insidde the pump become so great you generat slip. this causes the impeller to overspeed and if the motor is equiped with a overspeed trip it will trip, if not it will spin fast with no output and overheat untill it either burns itself out or the motors thermal overloads cause it to shut down." No, at high head/no flow the motor could run forever. What happens is the water overheats from recirculating in the pump head and eventually melts (if its plastic) and siezes - then the motor quits : ) Also, if you follow your line of reasoning, a motor by itself (no pump-no load) will over speed. Well, ac induction motors cant really over speed - rpm is a function of number of motor poles and frequency Jim [ 25 May 2002, 23:18: Message edited by: JimE ]
|
|
#28
05-26-2002, 03:52 AM
|
|||||
|
|||||
|
Dolphin Ampmasters
positive displacements slow down all right when they is a restriction.. then they shut down :D seen some one shut a pump dischagre by accadent and it wasn't pretty :D :D
I did type that wrong was mixing stuff up hehe when I talk about a centrifical pump slowing down, I should have said it is a small amount and it usaly is right back up to speed. as the amount of shear inside the pump will increase lowering your output. it is not lowered by the motor slowing down.. sorry for the confusion.. "Cavitation occurs when the pressure at the inlet of the pump is reduced to the vapor pressure of the fluid being pumped and the fluid "boils". This occurs at low heads/high flows or when there is a restriction in the inlet piping." yup it also occures inbetween the impeller and the viens when the pump is reaching its stall out speed or when you are trying to pump a fluid that is to viscus for the style of centrifical pump you are using. "The heat produced in a pump at low or no flow is from friction not cavitation." yes the heat is from friction of the water shearing (I didn't stat this to clear) but in adition to the heat from friction you can also end up with cavatation inside the pump on the low pressur sides of the stationary viens which accelerates the wear inside the pump. you stated that a centrifical pump will trip out at 0 head. you have me totaly baffeled with this statment I have one in my fresh water tank and it never trips out.. I don't understand why you think it would.. I am sure lots of people have power heads going in there tanks constantly with out them tripping out all the time.. heck my power filter is 250 gph it is running at 0 head all the time and it never trips out. unless maby we are having some semantics about the term "0 head".. of course 0 head would be impossable as you have outlet piping of the pump its self, but when I use the term 0 head it is to refer to a state that you would get if you put the pump submerged in a tank of water so it draws water directly in its intake and discharges directly back into the tank with out having to lift the water "No, at high head/no flow the motor could run forever. What happens is the water overheats from recirculating in the pump head and eventually melts (if its plastic) and siezes - then the motor quits : )" I know what you are saying but if you dead head you will start to generate heat.. aat a point the water inside the casing will start to boil off lowering the resistance of the water, this will make more heat and destroy the pump if the motor doesen't trip first. "untill it either burns itself out" was refering to the pump.. sorry I didn't make that clearer [img]smile.gif[/img] I thik we are pretty much on track (some quick typing on my part with out reading it over first) but there is still confusion on this 0 head thing, I have had lots of power heads over they yease and they all ran in the tank fine.. so unless it is a confusion like I stated above you have me confused on that one.. Steve
|
|
#30
05-26-2002, 04:53 AM
|
||||
|
||||
|
Dolphin Ampmasters
Hi,
Since the ampmaster pump is still relatively new, I think the pump is still a bit tight (i.e. tight bearings, new brushes and etc). Give it about 200 hours or so of break-in...then re-measure. I agree that if the ampmaster is drawing more current than what it is registered to draw, then you might be having some problems. It is illegal to falsify power ratings -- otherwise what is the point of posting power ratings when you know that they are false. - Victor.
|
Linear Mode
