electrical oddity and I am stumped

powerboatr · 01-29-2009, 07:55 PM

Last week i had to replace my converter because it gave up the ghost and would not produce 12volts, sooooo
i replaced it with a nice xantrex unit and upgraded a few other elctrical items

i also installed a real analog voltmeter so in the future i would know when things are going south
I estimate we ran 3-4 days before the batteries dropped off enough to make the heater fan sound slower than normal

my question is now when the water pump comes on a get a quick voltage drop from 13.5 to 12.5 and it quickly regains to 13.5 to 14
but when the pumps kicks off the voltage goes WHAM down to 8 to jumps back to 14 to 16 and then you can hear the pump sort of do a soft rollover and then fianlly stops, like its doing the charging.
but the gauge will fluctuate 8-14-16 a few times then stabilize at 13-14 and everything is good

last night ti did it again and when the volts dropped below 8 the converter went into self protect and dropped all 12v power for a few seconds ( 5-6)
then everything was normal.
so today i though i would soften those voltage spike and put in a set of diodes, one for the positive and one for negative at the pump to stop any back wash of voltage,
i ran the pump and it still did the fluctuate thingy.

i checked my surge tank for proper air charge, thinking it was causing a reverse hammer to drive the pump.
i also thought maybe the pressure fluctuations were causing the pressure switch to open and close real fast and this may cause the voltage spikes of start and stop

so i am stumped,

aintgotnun · 01-30-2009, 08:52 AM

It does sound like you are gettin a DC surge. While it's been a bit since my electronic days... I would seem that you may need a "Bypass Capacitor" in your circuit to help dampen the AC like effects in your DC circuit. Here's a link explaining what their purupose in circuits. clicky For your application you would need a pretty large one I wouldn't even begin to guess as I haven't done this in so long.

**KyDan** · 01-30-2009, 08:59 AM

That's really odd, I wonder if your pump check valve is not holding??

Try this, and I admit I'm not sure exactly what it will prove.....
Station yourself near the water pump wall switch.
Have a helper run the water until the pump goes on and then when you
think it's about ready to cycle off, flip the water pump switch to off.
See if your power center acts up or does it just resume normal operation?
Listen to the pump, does it continue to make noises after you flip the switch to off?

If the power center still does it's voltage drop and kick out then you have a problem
in the power center or wiring.
If it's perfectly normal you can narrow it down to the pump..... especially if the
pump noise continues after you've flipped it off.

Worth a try??
Let us know what happens.

**Bama Rambler** · 01-30-2009, 09:57 AM

Well, let me throw my 2 cents in.

I'm going to assume that you have a regular switched pump and not a variable speed model.

It seems to be pointing to the converter. Here's why I say that. When the pump starts the voltage sags and the converter compensates by raising the voltage back to normal levels. The pump runs drawing a good deal of amperage and pumps fine. Now the pump reaches set pressure and the switch disconnects causing a high spike on the line because all that high current flow just stopped. The converter sees this spike and trys to compensate but overshoots because the spike is so short in duration thereby causing the 8 volts you see. Since the converter now sees a low voltage it kicks out for a few seconds.

A capacitor at the output of the converter may solve this problem, but in reality it should already have one.

Be sure to check all your connections if you haven't already because a loose one could amplify the problem.

aintgotnun · 01-30-2009, 11:02 AM

or use a really big hammer

just sayin

**KyDan** · 01-30-2009, 11:42 AM

I wonder if a loose connection at the house battery might cause this???
IE- the inverter is working extra hard to run the pump because the house battery
is not helping.

powerboatr · 01-30-2009, 04:14 PM

Quote:

Originally Posted by KyDan

That's really odd, I wonder if your pump check valve is not holding??

Try this, and I admit I'm not sure exactly what it will prove.....
Station yourself near the water pump wall switch.
Have a helper run the water until the pump goes on and then when you
think it's about ready to cycle off, flip the water pump switch to off.
See if your power center acts up or does it just resume normal operation?
Listen to the pump, does it continue to make noises after you flip the switch to off?

If the power center still does it's voltage drop and kick out then you have a problem
in the power center or wiring.
If it's perfectly normal you can narrow it down to the pump..... especially if the
pump noise continues after you've flipped it off.

Worth a try??
Let us know what happens.

ok folks i think i have it narrowed down
one hammer almost was used, but luckily it talked me out of beating the snot out of the pump

this being said, i followed the above idea and i think i have a pressure wave of water causing the pressure switch to sens high pressure cut off, then when it stops there is a drop in pressure and it fires back on, only it takes a split second to come online and by the the pressure wave has subsided and the pressure is back to normal
so i am going to by pass my accumulator and see if the wave subsides.
the reason i feel this way, is last night after, draining the system and then bleeding all the air out of the line, i was in the basement cleaning up my mess and my wife was running hot water in the sink, when she shut off the faucet the little noisy check vale in the water heater made noises like it was going backwards and open close open. i am going to pull that one out later this afternoon and see if it bad as well. could just be the whole hydraulic hammer effecting everything
thanks for the ideas

LadyWindrider · 01-31-2009, 12:53 AM

All the above info is good stuff, but I would go with KyDan. As for the capacitor, that's what the battery or batteries are, big capacitors. They should smooth any spike.
The first thing to try is disconnect shore power, and retest. If you still get this spike, you have a bad battery or a bad connection. You mentioned you pulled your house battery down before you noticed the converter was out, so, make sure you are charging the house battery back up. To see the voltage spike you are talking about would take around 200 amps on a 500 amp battery that is fully charged. The other thing to remember is, don't trust a $5.00 meter. Might want to move your meter connection straight to the battery and retest pump with shore power disconnected. Make sure to test cable at the battery, and then test on the battery post. If the readings aren't the same, you have found your bad connection. Good Luck.

powerboatr · 01-31-2009, 07:24 PM

after much toying around with my voltmeter at the pump. i discovered two things
1. if you accidentally crack open the valve to winterize the water system it causes the pump to suck air and water, and since air is less dense it sucked it a lot, caused some rumblings in the pump as it kept loosing prime
2. the pressure switch is way to sensitive, i tried adjusting the cut off pressure to no avail it would find its mark then kick on a off a few more times,
it must just be worn out,
i think i will get a variable speed smart pump, and be done with it
thanks folks for the guidance

**KyDan** · 02-01-2009, 07:33 AM

I'm glad it wasn't your new power center!!!

**Bama Rambler** · 02-01-2009, 08:25 AM

that's good investigative work. I'm glad it wasn't your converter too. I've ben wanting to try one of the variable speed pumps. Let us know how it works for you once you get it replaced.

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