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post #21 of 31 Old 04-13-2012
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Re: Wiring up electronics to a switch?

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Originally Posted by SanDiegoChip View Post
See any flaws in this?
L

Older pics but you get the space picture, less space now

Temps sensors should go to the battery with the most potential to get warm and to the NEG terminal NOT the hot... How you going to fuse a temp sensor...
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post #22 of 31 Old 04-13-2012 Thread Starter
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Re: Wiring up electronics to a switch?

Hi,
Thanks for the suggestion on the relay. I am going to check them out. We have a toggle switch for our wind generator (also yet to be installed - the toggle switch) and it is a $30-50 item I think. Also it does not fit in the inch plywood without cutting some of the plywood out. The plywood at the nav station is too thick for a toggle switch. The push pull switch is in a hard to get at spot from behind and making it toggle switch friendly by routering out some plywood would be difficult. Darn boats, there is always something to consider.
Thanks,
Chip
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Re: Wiring up electronics to a switch?

Hi,
Looks like another test call is going to be made to Xantrax support on the Temps sensor

From pg 7 in the manual.


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post #24 of 31 Old 04-14-2012
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Re: Wiring up electronics to a switch?

Just follow the instructions, the BMS unit Redarc make for motorhome's is also done via the positive terminal.

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post #25 of 31 Old 04-14-2012
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Re: Wiring up electronics to a switch?

When the instructions are wrong it is usually not a good idea to follow them. Temp sensors measure temperature and the temp is the battery temperature. The neg terminal will have the same temp, or within a couple degrees, as the positive terminal. The neg terminal however will not cause a fire, or cause your electronics to fry, if it chafes and shorts.

By ABYC standards anything connected to the + terminal needs to be fused and you can't fuse a temp sensor or it won't work. It will work fine however when placed on the neg terminal and will be far safer... Temperature is temperature....

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Re: Wiring up electronics to a switch?

A short requires a completed circuit, not many boats run an "earthed hull" not a good idea.

Positive and negative if shorted will both spark, negative terminals will spark, if you don't believe me disconnect the earth terminal and tap it on the battery terminal, note the sparks. A short requires both positive and negative so neither is more likely to short than the other as it requires both of them to happen.

Two seperate manufacturers disagree with you, and If you fail to follow their installation instructions and it doesn't work/gets damaged it will be on your own head.

As a side not whilst the negative terminal will indeed also allow detection of heat the positive will be warmer and therefore give a more accurate temp sense.

I agree a fuse would be best but in the case it can't, by the way the starter motors in almost every single vehicle are not fused with heavy canling and longer runs.

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Re: Wiring up electronics to a switch?

Quote:
Originally Posted by JustinCook View Post
A short requires a completed circuit, not many boats run an "earthed hull" not a good idea.

Positive and negative if shorted will both spark, negative terminals will spark, if you don't believe me disconnect the earth terminal and tap it on the battery terminal, note the sparks. A short requires both positive and negative so neither is more likely to short than the other as it requires both of them to happen.

Two seperate manufacturers disagree with you, and If you fail to follow their installation instructions and it doesn't work/gets damaged it will be on your own head.

As a side not whilst the negative terminal will indeed also allow detection of heat the positive will be warmer and therefore give a more accurate temp sense.

I agree a fuse would be best but in the case it can't, by the way the starter motors in almost every single vehicle are not fused with heavy canling and longer runs.
Yes a short does require a completed circuit. A loose positive is dangerous because there are many unprotected negative items on a boat - like the engine block. A loose negative on the other hand is not an issue as all positive connections should be covered - both by ABYC and common sense.

ABYC calls for the fusing of every positive wire with the exception of dedicated starting circuits. I fuse those as well without problems.

Manufacturers and their manuals are not always correct and some make more mistakes than others.

Brian
Living aboard in Victoria Harbour
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Re: Wiring up electronics to a switch?

Justin, you won't find many "earthed" hulls in fiberglass boats simply because the fiberglass hull is an insulator and that makes earthing it impossible.

Likewise, automobile industry standards should be taken with a grain of salt. They are largely based on "what's the cheapest way we can do this" and not on anything else. Consider that virtually all cars were built with fusible link wires until recently, and these were used for boat alternators as well. Except there were a number of fires from those fusible link wires and they've now been largely phased out in favor of more expensive proper fusing.

Similarly, all US cars are built with SAE-spec wiring. Those of us who don't work for Detroit use AWG-spec wiring, where "the same" gauge is actually about two sizes larger and significantly more expensive. SAE spec for carrying capacity and "proper" wire sizes just doesn't cut it on boats.

And while there may always be ground loops and differential voltages, the overwhelming odds, and safer practice, show that if you have a crowbar short between a hot wire and any random part of a system, versus a ground wire and some random part of the system, the crowbar short to the hot wire will be far more spectacular, far more often. The ground side differentials usually are insignificant.

If you don't believe that, take a voltmeter (come on, be brave, use a real crowbar) and see what the voltage from the engine ground point or battery negative is, to any other bare metal within reach. Now repeat the measurement from that same point to a hot lead.

Specs are all well and good, and there's usually a good reason for them. But adopting those specs without understanding how or why they may or may not be proper for your situation, isn't best policy either. Beats nothing, true, but still isn't always a great idea.
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Re: Wiring up electronics to a switch?

Thank you for making my point. Boats are rarely earthed, biggest risk is obviously in a steel vessel that may have an accidental earth (eg motor to hull bolt through engine mount is now earthing due to wear/poor alignment etc)

All wires should be protected and secured, saves issues.

If you can put a volt meter between any combination of hot wire/battery feed/engine block/earth point and get different readipngs then you in fact have a voltage issue, they should all be almost exaclty the same, even at the other end of the vessel (within reason). if not you have an issue that needs to be addressed.

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post #30 of 31 Old 04-14-2012
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Re: Wiring up electronics to a switch?

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Originally Posted by JustinCook View Post

Two seperate manufacturers disagree with you, and If you fail to follow their installation instructions and it doesn't work/gets damaged it will be on your own head.
They are not disagreeing with me they are incorrect and disagreeing with the ABYC and current US accepted safety standards.. On boats the temps sensors should be wired to a neg battery terminal. In a land based solar system that does not move and vibrate running to the + terminal is more acceptable. These inverters are installed in off grid nearly as much as marine.

Xantrex is one of the worst manufacturers for poorly written manuals. I have a full list of changes that need to be made to the manual of just one of their products. They have agreed these changes need to be made, in writing, (Marina head of technical support per 2010 correspondence) yet they do nothing.


Here's a manufacturer, Balmar, who actually has a clue..


Battery Temperature Sensor (MC-TS-B)

In addition to its ability to completely discontinue charging when a thermal runaway condition is detected at your battery, the regulator can also modify charging voltage to compensate for smaller changes in ambient battery
temperatures.

In addition to shutting down charging in a catastrophic over-temperature
condition, the regulator will send the Dash Lamp terminal to ground,
allowing the operator to identify a potential system problem if a dash
warning light or audible alarm are used in conjunction with the Dash Lamp
circuit.

To install the Battery Temperature Sensor:


1.Attach the thermister lug to the battery's negative post as shown in the
image at right. If the bank has multiple batteries connected in parallel,
mount the lug on the negative terminal closest to the center of the
battery bank. "


And another one. ProMariner:

"Remote Temperature Sensor Probe

Probe Connections:
Battery End (ring terminal) – Connect to the NEGATIVE terminal of the battery."


(the all caps on the word NEGATIVE were done by ProMariner in the manual not me..)

And another one, Sterling Power:

"Battery Temperature Sensor

Connect the sensor end to the negative stud terminal on one of the batteries you think will be in the hottest environment."




Some manufacturers do abide by current safety standards and do give proper instructions for wiring temp sensors...

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Last edited by Maine Sail; 04-15-2012 at 07:36 AM.
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