Plus the inlet and outlet are parallel, rather than perpendicular, when it comes to DDC.

I was wondering about laying a D4 on it's side, pump inlet still facing the rear of the case, pump outlet facing the waterblock inlet level with the waterblock with a short section of tubing running straight to the waterblock. with a bay reervoir in the bottom bay and an external radiator with it's middle about level with the pump. The pump would never have to raise the water more than a few inches. But really what I was wondering about and assuming was that there wouldn't be any additional stress on the bearing. I was also wondering if getting all the air out of the pump would be a problem.

Please excuse me if this all sounds a bit naive but I've found that the best way to learn something you don't know about is to ask questions. If your going to ask questions you might as well ask someone you think will have the right answers. I can't think of anyone better than the people here.

edit sp

That's what I did with CSP-750 MkII pumps for a while, but I've never tried it with Laing D4, and I can't do it with DDC due to its parallel fittings. CSP-750 isn't mag drive, though. :confused:

-Ed

10 characters

OK I understand about the no effect . What about the other two questions: bearing stress / air pocket

please bear with me guys I'm not an engineer

if it is ok to mount the pump on its side, . . . . .

bleeding ? no idea, depends on the layout and your effort in bleeding
with a connection pointing UP, a bubble can rise - otherwise you rotate the pump or case

these were rhetorical questions I'll more than likely mount it conventionally but my mind likes to go over ideas from the sublime to the bizarre :-)

"these were rhetorical questions"
congrats, you made my ignore list

LoL (10 bleedin chars!)

oh, my apologies

The Pro top is actually a product from www.watercool.de, which alphacool (amongst others) are selling. There are further details, pics here in their forum.

Whist it may look a bit bling in plexi, thet's just the consequence of his choice of materials for a very functional housing. What you get form this thing is tapped G1/4 outlets for your choice of fittings and mounting for a 3.5 bay. He's actually tapped another inlet vertically, so you could use a directly mounted header tank if you prefer. Might this improve performance at the margin?)

Can anyone forsee a problem running two of these in series?

That would give 26 ft of head and 1.5 - 2 gpm.

This happens to be VERY close to Cathar's ideal of 23 ft and 3.5 gpm.

Also, re: an earlier comment about why use two smaller pumps:

I have tried to find pumps in the UK which do these sorts of head pressures, and they don't get any cheaper than about £179. Two of these small Laing pumps cost £100 in the UK and produce 17 ft and 6 gpm (D4) or 23ft and 1.5 gpm (DDC), so I don't understand an argument AGAINST using two pumps?

Maybe things like Iwakis and the like are more easily available / cheaper in the states (I suspect so!)?

I just finished my system about 2 days ago, I am using a DDC pump with a Weapon 2-302 Heatercore+Shroud, 7/16" ID Tygon tubing, and a MCW6002A waterblock, and I have been having an issue where the pump fails to start with the system. Once it is going, there have been no problems, but I don't know whats up. I got this pump very recently, should I just try to RMA it?

if you bought it from Swiftech or a distributor, give me a call at Swiftech

We had this problem and it turned out to be the PSU. We used a EG701P PSU and replaced it with teh EG701VE-AX and it worked fine after that. The only difference that I noted between the two PSU's was one has active PFC while the other doesn't.

Has anyone experience of runnign these at variable voltage? I was considering controlling from a T-Balancer (rated 15W per channel 0, 6-12V).

know the specs
start at 9V, run at 8V
no tach output below 12V
max rated voltage 13.2V

outside of these limits the pump may perform but is not warrantied to do so

addendum
I have tried several on low voltage and at just above 7V they stop, starting is more variable but at 9V they all start reliably

DC pumps are not sensitive to active PFC.

I think the controller will spin up fans at 12V to start, but I realised the probelm is that it can only do 15W in PWM control mode ( at opposed to 'attenuated').

Is that pump likely to be PWM-friendy?

Oh and the current draw is ~1A?

Surely pwm on a pump will cause premature wear + extra noise...?

I have not messed with the Laing pumps and PWM,
the DD site suggests something - but evaluate before trying ?

Why more wear? Noise maybe, depends on the motor and the PWM freq.

Maybe pumps are an exception, but in general, things tend to last longer when the load placed on them is constant than when it fluctuates frequently. Cars last longer when the majority of driving is done on highways than if they were driven predominantly in a city. Light bulbs last longer when turned on and left on than if they turned on and off frequently. That sort of thing. PWM is like accelerating and decelerating over and over again, rather than just running it at a constant speed. I would imagine there's going to be some additional stress involved in that.

Maybe I should contact Laing on this one....

Brushless motors work by pulsing the current to the motor windings on and off already; PWM should not significantly affect their lifetime. It will tend to make them run a bit warmer at low speeds as the coils are being fully energized each pulse rather than partially, but in return you get much better torque.
Unlike a light bulb brushless motors don't experience significant thermal shock from switching, and a car engine is so radically different they are not comparable.

The coils are partially energized in a steady DC current scenario? I was under the impression that simple brushless motors fully energized coils in sequence, and very complicated DC brushless motors use microcontrollers to send a shaped pulse of voltage/current to reduce noise and increase motor lifespan.

By partially energized I mean if you feed a 12V fan 6V it'll only put 6V through the coils - that's partial energizing by my book. ;)

Ah! I understand. You were comparing PWM at a given CFM versus CFM regulation done by DC voltage adjustments.

Would it be that the coils are the same temperature for both schemes or even lower temps for the PWM? Input power for a given RPM should be similar for both PWM and DC methods, no? And if it is the same, then the wasted power would be the same.

No, I haven't gone through the math or done any practical testing, but I was curious if anyone actually knows.

I know brushed DC motors run hot at low RPM with PWM, and buzz too. Not sure on brushless. I believe input power may be lower for PWM which would imply that heat should be less though I have no data on that. May do some testing at some point (currently lack both a PWM controller and neccessary equipment).

I thought that the Liang pump was already equipped with an electronic dc-ac converter. In that case you couln't use PWM to regulate the motor. :shrug: