Fluke clamp on has a NIST caliberation cert.
measuring single DC line
do not understand why so low reading, brain fuzzy from holiday party doesn't help....

A clamp on meter cannot measure DC current -only AC.
It is all physics ...ie rising and falling magnetic fields aka AC. ;)
The reading you are getting is inaccuracy or noise on the DC line.

edit: spelling

Took some time to measure the PQ curve of RD-30 at 18.0v.

I arrived at the following curve. Everything above 6LPM is measured. The curve below 6LPM is what I extrapolated as I ran out of vertical height. I'll have to set up the tubing test outside the front of the house on the ground beside the main entrance stairwall landing and run tubing up to the roof peak (2-story house) in order to get more height and get a firm fix on the pump's peak dead-head, but I reckon somewhere between 7 to 8mH2O will be pretty close, and is not going to alter the graph in any dramatic fashion. I tried to measure peak dead head at 17.0v, but it was also above 6.0mH2O.

So yeah, 18.0v for the RD-30 is still very, very strong, but with a (relatively) lowly 28-30W power draw in the "typical" 6-10LPM range.

http://www.employees.org/~slf/curves...i-rd30-18v.png

This is one heck of a pump, with every single desirable characteristic you want, except for the voltage requirement. Strong, wide PQ curve, able to service both high and low restriction blocks. Very quiet. Moderate power draw. Fairly small (marginally larger than a D4).

I will do an "inline heat dump" test when I next get some time to complete the analysis. Still, even if it were dumping 100% of its power draw into the water as heat, this would still make the pump near ideal for dual-fan radiators or anything larger.

THe question at hand is at what voltage yeilds the best overall temps? What is the power draw at 24v and would the extra flowrate at 24v be negated by the additional heat? Also, may be a dumb question but are there any reprocussions of undervolting the pump? Now I'm really itching to get mine installed.

That really depends on how much heat the CPU is putting out, and how well your radiator is working.

A hotter CPU will benefit more from a hotter/stronger pump because the temperature delta bonus from the increased flow rate is greater with the hotter CPU.

The better the radiator, the stronger and hotter the pump can be without the water warming up by much. If the radiator had a theoretical C/W of 0 then you can stick a 1HP pump on there if you wanted.

Given your setup though, with a hot CPU and a strong radiator setup, you will be able to run the RD30 at 24v or even 26v and still see better temps, but overall I think you will basically witness a near plateau (~0.2C variation) between giving the pump 20v up to 26v, in which case you may as well just use 20v and be sucking down less power. Give it a go.

Even with my present 2 x D4's and the big 30x24cm radiator I see CPU temps plateau between 12-14v on the pumps, and above 14v the CPU temp will start to climb as the water starts to get a lot warmer.

Haven't measured power draw at 24v yet. My estimate would be around the 50W mark. I'll measure it when I next get the chance.

Should be no repercussions with undervolting so long as you're not right near the point where the electronics are struggling and the pump starts stalling. Really anything at or above 14v should be fine.

No. Clamp meter could measure DC current very well too but you need a special one.

Do you use them in France? :eek: In America inductive type meters don't read DC. The device would have to be very "special" indeed. It would also be very susceptible to local magnetic fields (much like a compass) and would have to be shielded and have provisions for hookup to earth ground or some low reference for the shield.

Granted, I was too literal in saying that it is impossible to construct such a device (or that they might indeed be available), but the clamp-on ammeters that someone asking questions here might have will not measure DC Current through the inductive (clamp-on) coil.

I am not getting in a flame battle here -say what you want. I am sure that I could learn something from you. If there is a common field test instrument that you are speaking of -please post so that I can investigate the instrument for my use at work. :cool:

You are totally wrong.
They are very common.

http://www.tequipment.net/AmprobeACDC-600A.asp
http://www.tequipment.net/AmprobeACDC-600AT.asp
http://www.inotek.com/Catalog/tifet.html
http://www.hotektech.com/GMCMetraclip70.htm

from here:http://www.etools.org/i4a/pages/index.cfm?pageid=1715

Five minutes with google.

Thanks for the five minutes. I am proved wrong.

hmmm, easy lads, I did make a mistake by grabbing the wrong clamp-on, wanted our Fluke 336 that happens to be out on a customer site

also lowered RD-30 to 21.1v (low as adjustment pot goes)

Cathar

What about the Mag3 pump? It outperforms the Eheim by far. Just wondering your conclusions on how it would factor in to this scenario. Thanks for such in depth study. It has shed quite a bit of light for me.

Similar specs to the MCP650 but tends to have sealing problems and leaks. Also the plastic barb threads are very weak and tend to crack unless you are very carefull. Other than that it is an OK pump.

ROFL!
-------------

yeah reading back on that it is kinda funny, but I was not trying to be faceitious (sp?).

I'm pretty interested in the undervolted RD-30, so I went around looking for some PSUs that might do the job, I found two that looked good to me, but wasn't sure which would be most suitable for the job. I found these two:

http://www.peaktopeakpower.com/catal...well/s-60.html http://www.peaktopeakpower.com/catal...well/s-40.html

I am thinking that, according to the data, the S-40 should do the trick, but I'm not sure how to tell how much the voltage can be adjusted - it gives figures all the way to 24v, but it says there is only a 10% voltage adjustment on it. Am I reading this correctly?

Just to be safe/sure I would probably go with a 100W rated PSU at the least, such as this one:

http://www.peaktopeakpower.com/catal...ell/s-100.html

Officially the voltage adjust is +/-10%, but my Meanwell 24v PSU goes down to 17.0v with the voltage adjust, and nikhsub1's goes down to around 14v so he says.

With nylon fittings and teflon tape I've had zero leaks on mine, but I will admit it is a bit noisy. And you do need to use silicone sealant in place of the crappy rubber o-ring on the intake. For under $40, it's a hell of a pump. I will be upgrading to an MCP350 however, since it is tiny, uses 3/8" barbs, is much quieter and has serious head, which is just what I need for my Storm G4. You could get two Mag 3's for the price of one Swiftech pump. But the Swiftech pumps have quality where Mag 3's don't. They're quieter and last a lot longer, so the price is justified.

I have only had mine down to 15v. I mean, that is what my voltmeter told me, but Cathar has seen my voltmeter, uh, I need a new one.

niksub-

Just wondering if you have found a company that actually stocks the RD30? I have called around to locate the pump but so far I have only found it available via special order. This means its basically full list which is around $275. Normally if a company buys them to stock they tend to drop significantly in price. Unfortunately $300 after shipping is a bit steep for me versus the more readily available pumps.

Any suggestions?

I am trying to source more of these pumps - the chap I got them from on ebay had 6 in a crate, brand new sold them for $110 shipped, I got 3. I am trying to see if this guy will lead me to where he got them, no luck yet though. When I hear, I will post.

I am kicking myself right now too. I remember when yopu 1st posted the link on OCF and didnt give it much more than a passing thought. I think if I saw the same right now I would of bought all 6 lol.

He told me he had 6. I also bought 3. I was actually disappointed when I saw that someone else was interested in them (on ebay). I have had a running auto alert on ebay for six months.

& I got one from the guy as well....

CoolRod:

Must give thanks from me and Sunwong for your incredible "work" on e-bay for the pumps... :) Really fine... ;)

We´ve bought also a Meanwell 24V PSU... So, you said that this PSU´s could undervolted to 15V? Hm, could be nice then to have not too much noise... Only with the voltage adjustment on the PSU, right? without any adaptor... if so, nice...

Thx again.
Kind regards,
friku.

(No final smilie..., sorry, remember bad things about it... Cathar, you know... ;) )

friku, what model PSU did you get? The meanwell's have very nice voltage adjustments, I was surprised. I only adjusted downward though, I did not go above 24v. You should have very little noise, just read Cathar's post. I think even 24v will be like 1250 noisewise, 20v very quiet but I've yet to get mine in my loop...

It´s the S-240 one. If this one could be undervolted should be nice,...

Cheers,
friku.

That is the exact one I have, you should be able to get it down to atleast 15v or so. But, I would not run the pump at less than 18v, it is nearly silent there anyway.

How silent would you say the 18v "nearly silent" is, specifically in comparison to an MCP600/Aquaextreme @12V which is too noticeable for my taste?

[I am unfamiliar with the sound levels emitted by the D4 @5v & Eheim 1250 as described previously by Cathar.]

PS - In case anyone in the UK is considering buying one new from official sources - price quoted from both Iwaki UK and a distributor range from GBP£247-303 + carriage!

Thanks Nikhsub1, can´t wait for having it installed... Probably in January I would have the system completely mounted...

Cheers,
friku.