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CWA400 Supply in concentric layout question

Practical Motorsport Wiring - Professional Level

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Im just about finished with the design on my engine harness. My last remaining power supply to design is for a CW400 electric water pump. The pump documentation calls for a 36 Amp draw max. The documentation does not show under what load (pressure and speed) this max draw happens at. I imagine that will be 100% duty cycle at max pressure?

Im using an MS3470L24 61 position for bulkhead connector. I wanted to ask for real world amp draw experience of others running this pump.

If I go by max amp draw I will have to use 5 pins on the connector for power supply to the pump (following 7.5 amp max for size 20 contacts).

So main question is what will you suggest for supplying the pump, use 4 pins with each running 16AWG M22759/32 or 5 pins each running 16AWG M22759/32. I will be using the proper size 20 pin that accepts the 16 AWG wire. The run is ~60 inches from bulkhead to pump.

Bonus question if anyone is running this pump with a PMU16 what outputs are working for you. I am not sure on whether to run 2x25 amp outputs or 3x15 amp outputs combined.

This is my first attempt at a concentrically twisted harness so I welcome any and all suggestions.

ps:Elite 1500 ECU will be controlling pump with a PWM signal.

It may be easier, and neater, to use a single out/sink to control a suitable solid state relay/switch, as they are capable of rapid switching*, unlike conventional solinoid based types.

*Check with the supplier and/or manufacturer, but most are good for up to 1000 Hz, and some higher than that.

Hey Gord, thanks for the reply. But I'm a little unclear on what you are trying to get at. I don't have any issues/questions regarding "switching of the pump". The pump has the high frequency switching built into it, only need to feed it a PWM signal, which the Elite 1500 will do. So no need for a solid state relay.

My main question is regarding actual power consumption of the pump while in use and how many pins I should designate in my bulkhead connector to properly supply the power to the pump.

Uh, you do realise what relays are, and why they're used, don't you, and why I specifically said solid state?

Hi Michael,

What I understand Gord is saying is to not run that sort of load through the connector at all, just have the control signals coming through and then provide the high current power for the pump using a SSR that is linked directly to the battery (via the starter motor main supply or similar). A potential draw of 36A in a fairly constant state is producing a fair amount of heat into the loom at that point. If those wires are buried in the loom layers plus having a layer of heat shrink over the top it is increasing the risk of a thermal failure of the loom.

Thank you Stephen. I understand the risk of running the high amperage thru the loom and that is a valid concern of mine as well. That is what I was hoping for data from someone who was running the same pump with a PDM (PMU16) to confirm if it runs at a fairly constant +30Amps. Worst case I can run a separate sub harness just for EWP power supply, not as clean as I wanted but may be safer. I still have quite a few pins free on the bulkhead connector so that is why I was considering running the EWP thru the main harness. Safer definitely will be to supply the pump thru a separate breakout harness off of the combined PMU pins and not thru the main bulkhead.

Gord, my apologies if I misunderstood your suggestion. I am very aware of what relays are. I don't want to run the pump thru a separate SSR, frankly I see that as a waste when I still have plenty of outputs available on the PMU. I don't see why running a separate SSR will be different, the PMU16 is still solid state switching plus the main reason of running it thru the PMU is so I am able to monitor power consumption on the components including the electric water pump.

My use of the CWA 200 saw 11-13amps when working properly. When we still had air in the system, it would only run 7A and the car was overheating. Using the current draw of the pump turned out to be a good diagnostic that the coolant system needed bleeding!

I also advise running high-current power through a separate "power loom", fans, pumps, etc. It actually works out pretty well, since that loom has mostly connections straight to the PDM/PDU.

Awesome David, that is the main reason I am powering the EWP with the PMU, that is an excellent example of diagnosing coolant issues with the current draw information from the PMU.

So, since the CWA400 flows almost twice as the CW200 at similar differential pressures I suspect the power draw on CWA400 could be closer to the 24-30 amps when running properly.

I am leaning more and more towards a separate "power sub harness" I could run both fans an the EWP on that one.

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