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Author Topic: System spikes 12vdc  (Read 5061 times)

Offline UKpirate3000

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System spikes 12vdc
« on: April 21, 2009, 12:09:14 PM »
Hi All, Apologies if I’m a bit of subject, this is my first post on this fascinating site recommended by a regular contributor. I live on a boat in the UK I run mostly 12 volt systems. The water Pump a Par max 4  model 31620-0292 keep failing, they don’t seem to burn out just stop working. My system consists of 6 Hawker powersafe 12v105f (105amp) power cells a silverline cb20-1 charger set to min 12a. This is charged to a stephill generator putting 220volts of fairly stable modified sine wave power, run for on average 2.5 hours a day. The max draw of the pump is 6amp at 10PSI and fuse rated at 10 amp. I think I need a put a 10 amp Diode in line on the positive, do you think this solve the problem? If so and ideas where I could buy one in the UK I’ve looked on line but to be honest, always best I find, I’m not sure what type of diode I need. Any advice with problem or potential suppliers would be greatly appreciated.

Offline Thaelin

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Re: System spikes 12vdc
« Reply #1 on: June 08, 2009, 12:32:22 PM »
   I feel the best thing to do there is to take one apart and trace the power
through it until you lose it. From what I gather, this is an AC motor driving the pump. With that, I would almost suspect the start/run cap going. That in its self dont sound right as I have seen motors run just fine. Contact the manufacture and ask if it is suited for modified sine use. That would be a good start anyhow.


Offline fritz

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Re: System spikes 12vdc
« Reply #2 on: June 08, 2009, 01:50:46 PM »
... the PAR MAX 4 is a DC pump available with 12/24V (!??)
So for the failing issue - the only stuff I can think of is that the brushes wear out .... but this sounds different.
Is there a thermoswitch inside the motor - which protects agains overheating ?
Does the puimp resume operation after failing ?
Using short wires with proper and even oversized diameters can be suggested.
The wear out of the brushes (but I dont think its this problem) and the emitted rf interference / back EMF of the pump can be affected by an external cap bank placed at the motor connectors - a bank of 10 x 470n / 63 V ceramic caps may help here.
If its a thermoswitch thing - cooling might help to extend the operating periode...

Offline Groundloop

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Re: System spikes 12vdc
« Reply #3 on: June 08, 2009, 02:16:08 PM »

Let us see, you pump is a 12 VDC 6 AMPERE pump. You must use a 12 VDC 10 AMP fuse. A normal car fuse for 10 ampere will do fine. Your pump has a thermal protection system built into it to protect against over heating. The pump needs air to cool down. If your pump is mounted into a closed compartment without circulating air, then it will shut down when it gets warm. Make sure that the pump has enough cooling. If there is a lot of noise on your 12 volt system (because of inverter load etc.) then use a 10000uF 25 Volt electrolytic capacitor mounted close to the pump terminals. + on capacitor goes to + on pump and - on capacitor goes to - on pump.

So, good cooling by using circulating air and one electrolytic capacitor for noise suppression.

Data sheet for you pump can be found in the download section of this forum:;sa=view;down=284


Offline Thaelin

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Re: System spikes 12vdc
« Reply #4 on: June 08, 2009, 07:49:23 PM »
   OK, my bugger there. DC. I did a external heat sink on a dc motor by wire tieing aluminum to the body with a dab of gel under it. Helped it a lot.