MD20RZ questions

[psychofunk]

The pump is already barbed for 3/4 hose so I was thinking it was probably designed to pump through 3/4 hose (yes I know brilliant observation ). I don't know if this is correct but I was under the imression that the pump fighting against the backpressure resulting from reducing the hose to 1/2 or even 7/16 would lead to added heat in the loop from the pump. Well the bottom line question is would I be better off with 3/4 inch hose from a custom res (that I am building) out to a 3/4 inch barb on a manifold that splits into (2) 1/2 inch barbs, one that goes to the cpu and one to the gpu. I was thinking this would lead to less restiction, right. Or would I still be better off with a reducer and a regular loop ( pump > cpu > gpu > BIPII > BIPII > res....).

[JamesAvery22]

I dont think parrallel loops are ever a good idea, especially when both parts of the loop need good cooling.

That iwaki has huge head, might as well use it.

[pauldenton]

Originally Posted by psychofunk

The pump is already barbed for 3/4 hose so I was thinking it was probably designed to pump through 3/4 hose (yes I know brilliant observation ). I don't know if this is correct but I was under the imression that the pump fighting against the backpressure resulting from reducing the hose to 1/2 or even 7/16 would lead to added heat in the loop from the pump. Well the bottom line question is would I be better off with 3/4 inch hose from a custom res (that I am building) out to a 3/4 inch barb on a manifold that splits into (2) 1/2 inch barbs, one that goes to the cpu and one to the gpu. I was thinking this would lead to less restiction, right. Or would I still be better off with a reducer and a regular loop ( pump > cpu > gpu > BIPII > BIPII > res....).

is this a "T" model with 3/4" barbs attached? or a non-"T" model? - if it's the latter i'm pretty sure the barbs are actually for 5/8" hose (they are 17.5mm in and 17mm out) and slightly too small for 3/4" (19.05mm)....

you can certainly stretch 1/2" tubing over them with a bit of work so you could just use 1/2" on the outlet etc., and larger tubing just from res to inlet....

[psychofunk]

Yeah you are right it is 5/8" and i plan to do exactly as you suggested as well as run in series. I do however have another question, the label on the pump states "voltage......100...V". Does this mean that if I connect to my regular house current that I am actually over volting the pump? Or am I fine plugging it into a regular US house outlet?

[brucoman]

that model was made for 100v.... I have a MD-30RZ 100v myself
yes, if you plug it into line power you are overvolting it
I use a AC variable transformer to power my pump, can get them cheap

FWIW I have adjusted voltage from 80 to 120 with neglible flow rate change but audible noise changes

[CoolROD]

Was the pump originally for 100V at 50 Hz?
Is so you are OK running it at 120 V at 60Hz.
That is really pretty common.

I assume it is a synchronous induction motor and not rectified to DC, etc.
If all of this is true then you will see a performance increase from running the pump on US power. The motor will be fine -the current is limited by inductance and your Volts / Hz ratio is fairly constant -so you are not really over voltaging the motor.

The synchronous RPM of the motor will be faster. (More Volume and Pressure) If it is a mag drive then there is some point where the pump will decouple from the motor and "slip" , but I suspect that that point is well beyond where you will be running. Again many designers assume that 100V / 50Hz motors will be run at 120V / 60 Hz.

If the pump wasn't originally designed for 100V / 50 Hz please disregard this post.

[psychofunk]

I am not sure but the pump sticker says (sorry no digi cam)

IWAKI MAGNET PUMP
MODEL MD-20RZG-1

MAX CAPACITY-------------------------13.5/15-------------l/min
MAX HEAD-------------------------------4.6/6.7-----------------m

RATED VOLTAGE-------------------------------------100--------V
RATED POWER CONSUMPTION------------------43/59------W
RATED FREQUENCY--------------------------------50/60-----Hz
INDOOR

SINGLE PHASE INDUCTION MOTOR
CAPACITOR-RUN

POLES---------------2
VOLTAGE----------100----------V
FREQUENCY-----50/60-------Hz
CURRENT------0.54/0.71------A
OUTPUT-------------20---------W

SPEED--------2650/3000----rpm
RATING-----------------------CONT.
CAPACITOR-------3.5----------uF
INSULATIONCLASSE

THERMALLY PROTECTED
DO NOT RUN PUMP DRY
BLAH BLAH BLAH LTD ETC
------------------------------------------------------------

So looking at it then would that (in the case where there are two numbers seperated by a "/" ) mean at 100v / 120v. I still actually want to find one of those " AC variable transformer" that brucoman mentioned so that I could play with undervolting. Any recommendations on a good one of those things to get. You have to pardon my ignorance but when I did a google I got nowhere so I will be basically asking the same question of one of the guys at home depot and I have more confidence in you guys. Thanks.

[pauldenton]

Originally Posted by psychofunk

So looking at it then would that (in the case where there are two numbers seperated by a "/" ) mean at 100v / 120v.

no the number before the "/" is at 50hz, and the one after is at 60hz (when the pump runs at higher speeds..) - iwakis are happy with either frequency: japan actually has both depending on where you are!

[CoolROD]

Variac is a common brand of variable transformer.
As is Superior Electric's Powerstat.

[psychofunk]

Originally Posted by pauldenton

no the number before the "/" is at 50hz, and the one after is at 60hz (when the pump runs at higher speeds..) - iwakis are happy with either frequency: japan actually has both depending on where you are!

Yeah but how is the speed determined. There is no switch on it, so is 50hz at 100v and 60hz at 120v?

Also, thanks cool for the name brand suggestions I am on to google right now.

[greenman100]

speed is determined by frequency and slightly by voltage.

[CoolROD]

The speed is determined automatically. The motor naturally tries to sync with the frequency of the AC sine wave. (Hence "Synchronous Motor")

The speed (in RPM) will be [the frequency (in Hz) x 120] / the number of poles of the motor stator (The way the motor is wound).

You would then multiply the result by some constant <1 to compensate for motor "slip". Slip has to exist for the motor to function.
I say constant, but this number will vary (a little) with motor load, etc.

For Instance @ 50 Hz: (50Hz * 120) / 2 Poles = 3000 RPM
-->Your motor nameplate says 2650 RPM at 50 Hz so you have .883 as your slip factor for real world RPM.

For Instance @ 60 Hz: (60Hz * 120) / 2 Poles = 3600 RPM
-->Your motor nameplate says 3000 RPM at 60 Hz so you have .833 as your slip factor for real world RPM.

edit: By running a synchronous induction motor at reduced voltage and constant frequency (as you would be doing with a variable transformer) you are allowing the motor armature to "slip" more thus reducing the motor speed.

The angular velocity of the AC current around the stator stays the same -you are just letting it outrun the armature by reducing the magnetic coupling between them. (You are reducing the motor torque)

[psychofunk]

Originally Posted by CoolROD

The speed is determined automatically. The motor naturally tries to....by reducing the magnetic coupling between them. (You are reducing the motor touque)

This is not bad for the pump though is it? Is there perhaps a better way to reduce the speed (noise) of the pump then using the variable transformer. Or am I just better off running the pump on good old american 120v house current?

[CoolROD]

Originally Posted by psychofunk

This is not bad for the pump though is it? Is there perhaps a better way to reduce the speed (noise) of the pump then using the variable transformer. Or am I just better off running the pump on good old american 120v house current?

Naah -you are fine (within reason). Increasing motor slip would normally increase motor current which increases torque which is why we use ac motors in industry -they inherently try to maintain constant speed. But since you are increasing motor slip by reducing the operating voltage your input (and output) power is reduced and the decreased impedence is offset by the reduced voltage. So the motor should not overheat.

Now -if the pump is fan cooled then excessive speed reduction will not allow the pump motor to cool properly and motor temperature will increase. You will just have to be the judge of that -just see how hot it gets.

[psychofunk]

I have started shopping for a variable ac transformer and I notice that they come in different ratings. I found one for $50 bucks that matchs what I want perfectly (0-120v) but it is rated at 2 amps. Is that sufficient for my use, the Iwaki MD20RZ? All I plan running on it is the pump.

Hey are these things noisey???

What about input voltage? Some say 110v and some say 120v? Sorry for the stupid questions but I know nothing about anything electrical other than it hurts.

I am looking at these two, what do you think?

http://store.yahoo.com/webtronics/ensavat.html

http://www.davesbargainoutlet.com/Vi...=PowerstatL10C

[CoolROD]

I like the first one (The Blue one). -More power, nicer, cheaper, voltmeter, etc.
Remember you can also use this as an (incandescent) light dimmer, soldering iron controller, etc.

Either input voltage is fine.

Either unit is more than than you need WRT power, but fine for sure.
(Look at the amps capacity -you only need >1A) Bigger won't hurt and could be more useful for "other" projects.

These are (nearly) silent. There may be a very slight 60 Hz buzz.

Avoid over-volting your motor (you will have this capability). You won't gain anything.

[psychofunk]

Thanks alot cool you have been a great help with this. As for overvolting, the only way that is going to happen is by accident, I am looking to run at 75-100v. I will run at 100v and reduce until I see a temp drop then bump it up a notch and keep it there perm. Oh yeah and the fact that thing has an input voltage of 110v is not a problem?

[brucoman]

110 input is what you want to plug into your house outlets

[CoolROD]

You will easily see 10 volts difference in 110 AC from different locations in the US. Some of the plants I operate in have 130 no-load volts. I don't think I have ever seen <100 VAC. I usually see about 115 VAC. In addition: While power utilities tightly regulate frequency -they spec voltage +/- 10% to be "normal" for some typical applications -and more variance for others.

I did find this link

edit: sp

[nikhsub1]

Below is all you need, thanks to greenman who turned me on to this for a 100v MD-30Z

Originally Posted by greenman100

16 ohm 50w wirewound resistor, and solder it inline, to the hot wire (not neutral). I'm telling you to go with the 50w, just because it's 50 cents more, and you won't be anywhere near the rated heat dissipation. Ask if you have any more questions.

[brucoman]

CoolRod:
During heavy summer load season we often see 98-105 incoming in our datacenter
BTW PacificCorp is a large customer of ours!

nikhsub:
ya a resistor would work, but I like a vari trans to play with lowered voltages with my my 100v MD30_RZ

[CoolROD]

And it (xfmr) is more efficient.
Series resistor is definately the cheaper route, but you have to know what voltage you want to end up with. Still you could buy several different ones to try...

Nik: are you getting 100V with that 16 ohms?

[nikhsub1]

Originally Posted by CoolROD

And it (xfmr) is more efficient.
Series resistor is definately the cheaper route, but you have to know what voltage you want to end up with. Still you could buy several different ones to try...

Nik: are you getting 100V with that 16 ohms?

Never used it with the pump, never used the pump for that matter, ask BillA, he's got it now.

[greenman100]

I believe I aimed for about a 12 volt drop when I speced the resistor.