Dolphin Ampmasters - Page 4

DJ88 · #31 05-26-2002, 05:39 AM

The current measurements I took were True RMS. As an FYI. I won't go into the pump theories.

How I was told that the wattage consumption and current numbers were obtained was by measuring one of the poles in the motor itself(the number one pole)to me this means only part of the motors draw is being tested. If I am wrong here someone correct me.

As an FYI. ok I don't have the first clue about how these motors/pumps operate when it comes to cavitation. but I just turned my Ampmaster on and measured the current draw as I varied the head pressure by opening and closing the ball valve immediately after the pump. As I increased head pressure(closed the valve and increased resistence to flow) the current dropped. I don't know what happens inside all I know is the numbers I have in front of me. The more head pressure the lower the draw. I don't explain em. I measure em. :confused:

I still don't know where the differnece in numbers is arising from but I have a feeling it is partially due to line losses(very minimally IMO) and due to the actual operation of the motor off of the test bench. When hooked up in a real world situation it is pulling 2-2.5Amps. and 222Watts after a short "warm up" period.

If I could take it apart and bench test it I would. But I paid $500 for this puppy and if I take it apart I void my 9 year warranty.

As I test more pumps I'll post the data. Jim, Steve. Keep talking. As you talk the more I learn.

Victor,

I agree there will be a break in period as tehre is with anythign mechanical, but enough to pull twice the rated current??? :confused:

I still think due to the set up of the motor measuring the power and current of one pole on an electric motor is not giving us all the numbers. As the motor spins will ther enot be a period where current is applied to more than one pole? not full "power" but a partial draw? if this is the case then won't the draw be more than the 150W and 1.3Amps that ONE pole draws?? I am trying to go back and remember my AC motor theory. and not having much luck at it.

JimE · #32 05-26-2002, 01:23 PM

Victor.

Not much to break in on these types of pumps - only 2 ball bearings - pretty negligable.

Darren.

"As I increased head pressure(closed the valve and increased resistence to flow) the current dropped. I don't know what happens inside all I know is the numbers I have in front of me. The more head pressure the lower the draw"

Exactly. I think someone pointed that out already : )

IME the only way you are going to get an accurate measurement at the low amps is to run directly through the meter - the 87 is rated for 10 amps I think. (double check yourself to settle fears of exploding meters : ) Disconnect a power lead at the motor and stick the meter inline. I dont know what the heck you've been told about measuring separate poles but I think thats BS. Maybe also check the voltage across the line terminals of the motor while running. IME I've also found that the true rms meters give a "false" reading compared to nameplate data in this type of situation. If you have a non-rms meter kicking around maybe see what that says. If you can get the motor manufacturers name plate data thats helpful - need service factor(SF), amps(A), and service factor amps(SFA).

$500 bucks! Yikes. Got to be a cheaper alternative out there.

Steve.

I'll talk more about pump "theory" when I 've got some more time.

Jim

DJ88 · #33 05-26-2002, 02:03 PM

Quote:

Maybe also check the voltage across the line terminals of the motor while running.

I'll try it. I don't like opening things up that are brand new but.... ok who am I kidding. I love opening things up. :D

Quote:

need service factor(SF), amps(A), and service factor amps(SFA).

SF is 1, Amps is 1.3. SFA isn't listed.

Quote:

$500 bucks! Yikes. Got to be a cheaper alternative out there.

That pushes as many GPH and even at 222W with as few watts consumed? Not even close. There are some but they can make some wicked noise that is for sure and cost even more.

StirCrazy · #34 05-26-2002, 03:21 PM

Quote:

Originally posted by JimE:
Steve.

I'll talk more about pump "theory" when I 've got some more time.

Jim

Cool, cuz either I am forgetting something (which it very well could be) or I was taught some bogus stuff (could be this to) :D

are you on the island? send me a e-mail maby if you are close we could get togeather for a coffee or something.

Steve

JimE · #35 05-27-2002, 02:02 PM

Quote:

Originally posted by StirCrazy:

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.

..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.. Steve[/QB]

Well, here we go. First I stated that *most* will trip out at 0 head and we were discussing your tub pump at the time.

Lets look at the power head first. I will give the disclaimer that I have never played with a powerhead but have other similar stuff. This is a *very* educated conjecture. First, the powerhead is operating at a very fixed/specific design point and is thus specifically built for the task (and is fairly atypical as far as centrif's go) Second, the discharge nozzle is sized to restrict the flow to certain rate (artificial head) - a flow rate that the motor is capable of handling. Should some poor misguided soul decide to tweak the powerhead a bit and drill out the nozzle (to reduce the back pressure so the pump can work easier!!!) - the flow rate will increase and overload the motor. Very certain on that.

The original start of the 0 head conversation was regarding the specs on your hot tub pump. Darren has confirmed for you my low head high amps theory. So as the head decreases, the flow increases, and the amps increase. If you look at the specs on your tub pump, at 30'/127gpm the pump will be working the hardest and drawing very close to the name plate amps. I draw this conclusion because that is where the manufacturer stops providing performance info as you stated. They dont stop publishing data because the pump will never encounter that situation (because believe me they eventually will in some application) Its because the manuf doesnt want you to f'in run it below this head. Why? Because as the head is reduced past 30', the gpm will increase, and remember our rule, the amps will increase and overload the motor. If the head is reduced further the pump will start cavitating like hell. This is not conjecture.

So now you're asking why dont they make a hot tub pump that can run down to 0 head ? Its all about design point and efficiencies. At the specific window/range of flow rate & head that your tub needs to run properly requires 1.5hp to spin the impeller. This window is usually in the pumps best efficiency range. Unfortunately that same impeller requires 2.5 hp to operate over its *entire* head range. Now do you put the extra hp on to cover a head range that shouldnt ever be encountered? Hell no. Just cut the curve off early and say dont run the pump here. That is why most centrifugals will overload at 0 or very low heads. The motor is sized to operate the pump in the effficientcy range and not over the entire head range.

With say the ampmaster and power filters they are designed to operate at 0/low heads so one wouldnt expect them to act up in this range. But dont expect all centrifugals to behave similarly as they are atypical in the wide world of pumps.

As far as the other stuff in your post the I dont quite agree with - well its not overly misinformed or misleading or dangerous and my typing totally sucks so.....

Talk to ya later.

Jim

JimE · #36 05-27-2002, 02:09 PM

Quote:

Originally posted by DJ88:

SF is 1, Amps is 1.3. SFA isn't listed.

If thats the motor spec that I dont think Dolphin is doing anything funny with their claims. This is the max amps (tested directly at the motor) and it plain cant be exceeded without the motor dropping out on overload. I dont think you are losing an amp in the power cord, it sounds like the pump is running properly (no excessive heat or kicking out), so I'd guess there's something wanky with the amp measurement. Dont know, but doesnt make sense.

Jim

JimE · #37 05-27-2002, 06:02 PM

Quote:

Originally posted by Troy F:
[QB.

Jim, it has been suggested that you can cut the nozzles off powerheads to give them a little less velocity while spreading out the flow. Is this something that you see cutting the life of the pump?[/QB][/quote]

Like I said, I havent specifically played with powerheads but have done much with similar submerged pumpheads - just on a bigger scale. On those the size of the discharge nozzle is the flow restrictor that keeps the pump/motor in an acceptable operating range. Mess with it and you have troubles. Would it have the same effect on a powerhead, I can only assume that. The nozzle is there for a reason - maybe just for velocity, but velocity = pressure (back pressure on the pump, reducing flow, reducing amp draw) Hmmm, but if the powerhead (with nozzle) were not running at the absolute max rating of the motor, there might be a little bit of wiggle room when the nozzle is cut off. Wouldnt know for sure unless a person did a before & after test with a meter. If the amp draw exceeds the marked rating, it will definately affect pump life.

Jim

Troy F · #38 05-27-2002, 06:42 PM

Thanks Jim.

JimE · #39 05-27-2002, 07:44 PM

Quote:

Originally posted by StirCrazy:
<blockquote>quote:<hr />Originally posted by JimE:
Steve.

I'll talk more about pump "theory" when I 've got some more time.

Jim

Cool, cuz either I am forgetting something (which it very well could be) or I was taught some bogus stuff (could be this to) :D

are you on the island? send me a e-mail maby if you are close we could get togeather for a coffee or something.

Steve<hr /></blockquote>Sorry Steve but my momma told me to never ever go and see men I met on the internet........and I'm not an Islander either.

Jim

Troy F · #40 05-28-2002, 04:49 AM

Quote:

Posted by Jim: Should some poor misguided soul decide to tweak the powerhead a bit and drill out the nozzle (to reduce the back pressure so the pump can work easier!!!) - the flow rate will increase and overload the motor. Very certain on that.

Jim, it has been suggested that you can cut the nozzles off powerheads to give them a little less velocity while spreading out the flow. Is this something that you see cutting the life of the pump?