Pump limit per header?

derlabzs

derlabzs

derlabzs

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Joined
28 Nov 2018
Posts
237
Location
London
Hi all, hope you are well.
I've looked around but did not find a answer for that.
Is that alright to have about 4xD5 pumps hooked up to one PUMP header of the motherboard as long as the only wires present are the "tach" and "pwm" as the pumps are or molex or sata powered?

TIA
 
@mercyless well.. it's complicated.. is all that hardware that got accumulated overtime and, I decided to put to use this weekend..
7800x3d + 7900xtx (450w) + 4 screens that pump a lot of heat to the room which does not have good air circulation..

The actual setup with 2xD5 + cheap barrow + 2x1260mm + 4x360mm gives me about 135l/h on 100% - to avoid having thermals climbing up I need to keep the pumps at 80% (120l/p)..
Any less than that thermals will slowly go up.
It is a very restrictive setup with gpu + cpu + ram blocks, plus few QDCs (7 to 9, not sure), even more 90 angle fittings, 2x1260mm and a stack of 4x360mm rads.

If I run the above with 2xD5 + barrow at around 65% (100l/h) thermals start to climb up slowly. If I run it about 90% (120l/h) thermals decrease to a very comfortable level, therefore the need of a fourth pump. I could however sell all 4x360mm rads with the fans and all, but I already have all that here dusting up so I've put it to use.

edit

chatgpt is scary.
I've asked about having the four pumps in the same header as long as I'm using just the "tach" and "pwm" wires. It went a bit further and reminded me that I just actually need 1 "tach" wire, which is useful because I'm crimping the cables myself. It gave a whole sensible answer that I'm perplexed.
Then I described well the loop and it's parts, plus a ball-park of 45/90 angled fittings and the mot****er said four d5 pumps and that three D5 pumps could potentially suffice, mentioning a Overkill Factor.

Anyhow, I will split the fans in pairs of headers, it's safer, just more work crimping, sleeving...
 
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Yeah, no problem controlling the speed of multiple fans with the one PWM signal, but you can only monitor the speed of one using the tacho input. From memory, the fan pulls the tacho signal low twice per revolution which the motherboard uses to calculate the speed, so having multiple fans on the one tacho line messes that up. Most fan splitter cables only have one fan connector wired back.
 
Thank you @bjmnz for reassuring that. But I will separate the pumps into two headers, to be safe as I noticed that once I have three pumps in the same header, the total l/p goes down to 136l/p. When I disconnect one of them (therefore it runs at a 100%) it goes up to 146l/p. If I reconnected it, it goes back to 136l/p. It's strange as there's just the tach and pwm wired to the header so the only thing I can think of is a limiting factor I don't know about - as pumps can't be capped by the slowest one etc.
 
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I dont think it would be tac related. This is fundamentally daisy chaining multiple fans to a single header - it only reads the closest one.

More likely one pump is creating a mini vacuum and slowing flow down depending on where they are located in relation to restriction and other pumps. You most likely check is to put them on individual headers and check if rpm is erratic.
 
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Well, all sorted guys, thanks for the inputs.
I've splitted the 4 fans into 2 headers using only tach and pwm wires. Working like it should. Cheers all.
 
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