Is this "normal" or unusual ?

In my cruisers cabin, the dc system consists of 1 light, pump for
demand water, and cd player. There is a separate 12 ga line back to
the battery for the cd player (installed by previous owner) and the
light and pump are wired I assume as original.

I replaced the small 12v fixture with a 18w fluorescent fixture. cd is
hooked up as before. however, when the pump is turned on the light
dims and the voltage drops to 10.5 or 11 vdc.

Is this indicative of a short or too many things on that circuit or
does this demand pump really draw that much ? I think, from looking at
the pump switch, that you only turn it off in "emergency" and leave it
on all the time to keep the system pressurized ? Is that right ? When
the switch is off there is no running water. Does that mean it is not
working right , (keeping the system under pressure) or is that really
the way it works ? If you are supposed to only turn it on when you
need water, then it makes sense that it draws so much on that circuit
since it is only used "on demand" and not always on.

What am I missing ?

Thanks for tapping your collective experience.

wrote:
Is this "normal" or unusual ?

In my cruisers cabin, the dc system consists of 1 light, pump for
demand water, and cd player.

There should be a bit more...nav lights, anchor light, and bilge pumps,
if nothing else.

Your water pump is electric...like any electric device, the breaker must
be on for it to work. However, it should not draw any power unless it's
running...and it shouldn't run except when you open a faucet.

So, yes...I'd say there's definitely a problem with your 12v wiring.

Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/html/get_ri...oat_odors.html


There is a separate 12 ga line back to
the battery for the cd player (installed by previous owner) and the
light and pump are wired I assume as original.
I replaced the small 12v fixture with a 18w fluorescent fixture. cd is
hooked up as before. however, when the pump is turned on the light
dims and the voltage drops to 10.5 or 11 vdc.

Is this indicative of a short or too many things on that circuit or
does this demand pump really draw that much ? I think, from looking at
the pump switch, that you only turn it off in "emergency" and leave it
on all the time to keep the system pressurized ? Is that right ? When
the switch is off there is no running water. Does that mean it is not
working right , (keeping the system under pressure) or is that really
the way it works ? If you are supposed to only turn it on when you
need water, then it makes sense that it draws so much on that circuit
since it is only used "on demand" and not always on.

What am I missing ?

Thanks for tapping your collective experience.

Something's wrong.

There are two ways to wire a water pump to deliver water when you turn
the faucet. In either case the breaker or panel switch is on all the
time:

1)The pump has a pressure switch that closes when the pressure goes
down and opens when the pump raises it 5-15 psi. If there are no
leaks, this works well. The pump will begin to run a little after you
open a faucet and stop after you close it, unless you run the faucet
very slowly, in which case it will stop sooner. With this setup, you
will get some water flow even if the pump switch is turned off,
particularly if there's an accumulator tank in the system.

2) Each faucet has a built in switch, which turns the pump on when you
open a faucet. These are typically used only on single sink boats.
There's water flow only when the pump is running.

It's also possible to have a water pump that doesn't operate on demand
-- where the switch on the panel would be the only way to turn on the
pump. This is a nuisance, but it's cheap.

In any case, the pump will pull down the voltage a little, but not as
far as 10.5 or 11 volts. This suggests one of the following:

1) A dead or dying battery. This is unlikely if the battery starts the
engine OK.

2) A pump that is clogged or otherwise not running freely, that is
therefore drawing a lot of current.

3) A loose wire at the battery or on the battery side of the panel.
This would show low voltage even though the battery is fine.

4) A short somewhere.

#2 or #4 should blow the fuse or circuit breaker -- in fact, enough
draw to pull a good battery down that far had better blow the
protection, because it will otherwise cause a fire.

The basic diagnostic tool is a voltmeter (a cheap DVM from Radio Shack
will do fine). Measure from plus to minus (usually red to black on
older boats, red to yellow on very new ones), with the pump running,
at the pump, on both sides of the pump switch, at the panel, and at
the battery (actually stick it on the terminals, not on the wires).

Jim Woodward
www.mvfintry.com


wrote in message . ..
Is this "normal" or unusual ?

In my cruisers cabin, the dc system consists of 1 light, pump for
demand water, and cd player. There is a separate 12 ga line back to
the battery for the cd player (installed by previous owner) and the
light and pump are wired I assume as original.

I replaced the small 12v fixture with a 18w fluorescent fixture. cd is
hooked up as before. however, when the pump is turned on the light
dims and the voltage drops to 10.5 or 11 vdc.

Is this indicative of a short or too many things on that circuit or
does this demand pump really draw that much ? I think, from looking at
the pump switch, that you only turn it off in "emergency" and leave it
on all the time to keep the system pressurized ? Is that right ? When
the switch is off there is no running water. Does that mean it is not
working right , (keeping the system under pressure) or is that really
the way it works ? If you are supposed to only turn it on when you
need water, then it makes sense that it draws so much on that circuit
since it is only used "on demand" and not always on.

What am I missing ?

Thanks for tapping your collective experience.

I'd put my money on a corroded (or loose) connection common to the pump
and the light. Don't forget to check the ground as well as the "hot"!

Lloyd

On Wed, 13 Aug 2003 14:24:58 +0000, Jim Woodward wrote:

Something's wrong.

There are two ways to wire a water pump to deliver water when you turn
the faucet. In either case the breaker or panel switch is on all the
time:

1)The pump has a pressure switch that closes when the pressure goes
down and opens when the pump raises it 5-15 psi. If there are no
leaks, this works well. The pump will begin to run a little after you
open a faucet and stop after you close it, unless you run the faucet
very slowly, in which case it will stop sooner. With this setup, you
will get some water flow even if the pump switch is turned off,
particularly if there's an accumulator tank in the system.

2) Each faucet has a built in switch, which turns the pump on when you
open a faucet. These are typically used only on single sink boats.
There's water flow only when the pump is running.

It's also possible to have a water pump that doesn't operate on demand
-- where the switch on the panel would be the only way to turn on the
pump. This is a nuisance, but it's cheap.

In any case, the pump will pull down the voltage a little, but not as
far as 10.5 or 11 volts. This suggests one of the following:

1) A dead or dying battery. This is unlikely if the battery starts the
engine OK.

2) A pump that is clogged or otherwise not running freely, that is
therefore drawing a lot of current.

3) A loose wire at the battery or on the battery side of the panel.
This would show low voltage even though the battery is fine.

4) A short somewhere.

#2 or #4 should blow the fuse or circuit breaker -- in fact, enough
draw to pull a good battery down that far had better blow the
protection, because it will otherwise cause a fire.

The basic diagnostic tool is a voltmeter (a cheap DVM from Radio Shack
will do fine). Measure from plus to minus (usually red to black on
older boats, red to yellow on very new ones), with the pump running,
at the pump, on both sides of the pump switch, at the panel, and at
the battery (actually stick it on the terminals, not on the wires).

Jim Woodward
www.mvfintry.com


wrote in message . ..
Is this "normal" or unusual ?

In my cruisers cabin, the dc system consists of 1 light, pump for
demand water, and cd player. There is a separate 12 ga line back to
the battery for the cd player (installed by previous owner) and the
light and pump are wired I assume as original.

I replaced the small 12v fixture with a 18w fluorescent fixture. cd is
hooked up as before. however, when the pump is turned on the light
dims and the voltage drops to 10.5 or 11 vdc.

Is this indicative of a short or too many things on that circuit or
does this demand pump really draw that much ? I think, from looking at
the pump switch, that you only turn it off in "emergency" and leave it
on all the time to keep the system pressurized ? Is that right ? When
the switch is off there is no running water. Does that mean it is not
working right , (keeping the system under pressure) or is that really
the way it works ? If you are supposed to only turn it on when you
need water, then it makes sense that it draws so much on that circuit
since it is only used "on demand" and not always on.

What am I missing ?

Thanks for tapping your collective experience.