Inverter Location

Discussion in 'Electrical Systems' started by The Boatyard, Jan 7, 2015.

  1. The Boatyard
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    The Boatyard New Member

    We currently remodel/build houseboats. A question came up regarding the proper location for an inverter. While I am aware that an inverter cannot be installed in the engine compartment unless it is ignition protected. Can an inverter be installed in the same hatch compartment as batteries? Thanks for all the help.
     
  2. CDK
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    CDK retired engineer

    The preferred location for an inverter is close to the batteries as this keeps cable losses low. For safety reasons the device should be on the same level or below the batteries and the compartment must be vented to prevent buildup of an explosive mixture.
     
  3. daiquiri
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    daiquiri Engineering and Design

    CDK, where does this requirement come from? I couldn't find any rule requiring inverter to be placed below batteries.

    The above situation is hardly achievable in case of small boats, because it would be in contrast with the ISO 13297, which requires the inverter to be placed at least 500 mm above the bilge water level (15.1 of the ISO 13297). At the same time, the ISO 10133 simply requires batteries to be placed above the anticipated bilge water level (5.1 of the ISO 10133). For small boats with limited space under the main deck and in the technical compartments, these requirements imply that the inverter has to be placed above batteries, because batteries are kept as low as possible due to their weight.

    This pic shows what might be a typical resulting arrangement: http://solarandalucia.net/wp-content/uploads/2009/09/IMG_0373.JPG

    Cheers
     
  4. michael pierzga
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    michael pierzga Senior Member

    Yah, close to the batteries. Naturally the batteries are in thier own airtight ventilated box.

    Inverters generate heat so the location needs to be ventilated.

    When inverters are mounted up high near the ceiling , heat rises and they suffer.

    Inverter fans pull a lot of air.

    Make sure the inverter is in a clean space that is free from salty air and dust. An air filter protecting the compartment is a good idea.
    Inverters make noise so not to close to people .
     
  5. CDK
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    CDK retired engineer

    I believe you immediately, but I don't think in terms of rules.
    Batteries are normally harmless objects, but there are circumstances (regulator defects) that cause them to expel hydrogen and oxygen in a 2:1 mixture that is highly explosive and lighter than air.
    Inverters also are harmless objects, until an external event like excessive DC voltage causes a short circuit or overload and parts in the inverter blow up.

    With the inverter mounted above the batteries a regulator failure can trigger a chain reaction ending in a big bang. So I would not install it above a battery.
     
  6. daiquiri
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    daiquiri Engineering and Design

    Yes, that makes sense. Thanks.

    But, as said before, placing the inverter below the level of batteries is not easy to accomplish, while at the same time observing the requirements by the ISO rules.

    Since hydrogen is a very lightweight gas, it will probably tend to stratify at the ceiling of the battery compartment. So placing the batteries and inverter just above the level required by the ISO, and the inverter far from the ceiling and not directly above the batteries (in the path of a possible H2 leakage) should make all the requirements (both rational and formal) satisfied, right?

    The problem is that the hydrogen stratification is a situation of a fragile dynamic equilibrium and should not be taken as granted. So keeping batteries in a separate compartment (as M. Pierzga noted), sealed towards other electrical systems and ventilated by an ATEX fan sounds like an ideal situation which would eliminate nearly any risk associated to the hydrogen leakage.

    Cheers
     
  7. rxcomposite
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    rxcomposite Senior Member

    Agree with Michael. Class Rules require batteries in their own airtight ventilated box. Most of the time this airtight box leaves very little space to snuggle anything in between. Outside the box would be a good idea to start with.

    Some inverters uses relays, which could cause sparking. I have seen inverter capacitor blew up. Now isn't that explosive?
     
  8. michael pierzga
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    michael pierzga Senior Member

    And no cheating on DC input wire cross section , cabling or terminal craftsmanship.

    An appropriate knife fuse for input , breakers on the output circuit, .

    Inverters are a fire hazard.
     
  9. The Boatyard
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    The Boatyard New Member

    Thanks for all the help. These were the thoughts that we have been tossing around. In our ABYC book, it only states that the inverter cannot be directly above the batteries. Our dilemma was that unless an inverter was igntion protected it could cause a spark and potentially cause an explosion if there was hydgrogen gas trapped in the hatch compartment. We would like to keep the inverter in the same hatch compartment as the batteries because of the close proximity.
     
  10. Ike
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    Ike Senior Member

    Battery compartments are required by Fed Regs and ABYC to be ventilated to allow Hydrogen gas to easily escape. This does not require anything on the scale of engine room ventilation. Hydrogen dissipates so rapidly that even a small hole (1/4 inch even) will allow hydrogen to escape. The hydrogen needs to be allowed to escape without encountering other equipment in the compartment. The ABYC standard is also based on the fact that batteries, particularly lead/acid batteries also emit corrosive gas that will over time attack the inverter or any other equipment mounted above them. So inverters should not be above the batteries and placing the inverter near and at the level of the batteries shortens cable lengths, reduces voltage drop and possibility of wire overheating.
     
  11. missinginaction
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    missinginaction Senior Member

    I spent a lot of time researching before I designed my electrical system, it ended up like this:

    1. Sealed AGM batteries securely installed in dedicated compartment below cabin sole. They are adjacent to the engine room but separate from it. Since AGM's are sealed I've had no issues with any explosive gasses. The compartment isn't sealed so in the event of a malfunction gasses would escape.

    2. Inverter, charger, and main panel installed in separate cabinet adjacent to batteries in main cabin, above the batteries but not directly above. 2/0 cables from batteries to DC main panels sized to inverter and starter loads. 4 feet from inverter to house bank.

    3. Marine Rated Battery Fuses installed on all positive battery terminals. Size fuses to anticipated load. This includes starter, inverter, cable to main panel and cables to charger.

    4. Class T fuse installed between inverter cut off switch and house bank.

    I keep a large computer case fan running in the electrical cabinet just to keep a little air moving in there.

    My goal was to be safe. Every cable is fused. Even the starter.

    Believe it or not, fusing the starter cable saved me some major engine damage. When I was getting this boat ready to go I foolishly (don't ask me how, it's too involved) introduced some water into the cylinder(s) of my engine. A short time later I attempted to start the engine. The $11.00 MRBTF blew instantly. A little while later I determined the problem. I pulled the plugs, installed my spare fuse and prayed. After I got the water out of the cylinder(s), I reinstalled the plugs and she started right up. That terminal fuse blew when the starter current rose saving me potential catastrophic engine damage from a hydraulic.
     
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  12. sdowney717
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    sdowney717 Senior Member

    I installed my inverter under the galley sink on a shelf. This is separated from the engine room by a plywood bulkhead. The batteries are in a box in the engine room. Round trip wire length is about 10 feet of 2/0 wire and it seems to work fine and keeps the inverter in a high dry isolated area away from the bilge and engine room and batteries.
     
  13. sdowney717
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    sdowney717 Senior Member

    I have cranked several engines (v-8) that were hydraulically locked either by gasoline or water and they just stop turning and were not damaged. I would be surprised if an engine starter has enough torque to damage the engine.
    They were not diesels, maybe diesels will break.

    After spinning up against the lock, they will then just click the solenoid on and nothing happens except a lot of current draw and maybe some small noises and a tiny bit of movement.

    I was most concerned when one time my prop grabbed a buoy channel chain and it was idling and instantly was forced to stop.
    I had to unwind the prop shaft and it then restarted and ran ok.
     
  14. CDK
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    CDK retired engineer

    A starter motor usually is 2.5-4 hp, by itself not enough to cause engine damage. But if the flywheel can get some momentum before a piston starts to compress water I think damage is possible!
     

  15. missinginaction
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    missinginaction Senior Member

    Thanks for the responses guys. You might be right about the starter not damaging things. I'm still glad I have those terminal fuses installed. All those fuses help me sleep better.

    MIA
     
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