TWL: Re: TWL Electrical Disconnects
At 09:19 AM 07/14/2000 -0700, Murray Birch wrote:
Small point - always check the amperage rating of 1-2-BOTH switches - they
can vary greatly. Some of them are designed for VERY light loads while
others can take the full amperage of the starting circuit. Some people may
not be aware that these switches even have an amperage rating. If you push
high amperage through the wrong 1-2-BOTH switch it could literally melt or
worse, cause a fire.
Murray Birch
Alaska Spirit
50' Puget Trawler
Arild replies:
With respect to inverters, I should like to point out that such a
disconnect switch could in fact cause malfunction of high capacity
inverters.
The contact resistance in the disconnect switch will result in a voltage
drop. this drop may be interpreted as a "too low battery voltage" and the
inverter will either not put out full wattage or it may shut down
entirely.
This is why we always recommend using large diameter wire with a T-tron
fuse installed in line and mounted right next to the battery.
In the event of a problem with either the wire or inside the inverter;
any short circuit will blow the fuse before any damage such as a fire
occurs. A failure which simply goes open circuit, does not need a fuse
for protection.
The fuse can be removed as a disconnect means for service work.
Regards
Arild
Small point - always check the amperage rating of 1-2-BOTH switches - they
can vary greatly. Some of them are designed for VERY light loads while
others can take the full amperage of the starting circuit. Some people may
not be aware that these switches even have an amperage rating. If you push
high amperage through the wrong 1-2-BOTH switch it could literally melt or
worse, cause a fire.
Murray Birch
Alaska Spirit
50' Puget Trawler
Arild replies:
With respect to inverters, I should like to point out that such a
disconnect switch could in fact cause malfunction of high capacity
inverters.
The contact resistance in the disconnect switch will result in a voltage
drop. this drop may be interpreted as a "too low battery voltage" and the
inverter will either not put out full wattage or it may shut down
entirely. --- snip
As in my previous post about starter battery switches, I believe in switches
because of the control you acquire as well as safety. My house bank is fused at
300 amps for disasters, but I also have a Blue Seas heavy duty (300 amps) rotary
switch in the line to the inverter.
Voltage drop due to the switch in the charge cycle will be made up by the
charger, which senses voltage at the battery. Voltage drop in the inverting
cycle is unavoidable, but has no noticeable effect on the AC voltage produced
because that output is regulated by the inverter. The switch is rarely thrown,
so wear-and-tear is not a problem.
The simple key to problem searching with high currents is that the switch
doesn't get warm, so my switch's resistance must be very small. My cables will
get warm after charging at 120 amps for an hour, and I've estimated the wattage
lost there via a temperature guess, and then calculated what the resistance must
be. It's about 0.2 ohm, as I remember, which is as small as you can expect from
3/0 cables with a connector at each end, and is also harmless.
The boat was wired with such a switch to the inverter before and had no
failures, and the senior marine electrician who approved my upgrade plan
recommended the new switch for the larger inverter, and I agreed. A good switch
isn't a voltage drop problem, and I'm glad mine is there.
--
Regards --- Don Dement
M/V Merrymar -- DeFever 48 -- Annapolis
Where does one obtain a T-tron in-line fuse holder of the required capacity?
At 11:34 7/14/2000 , you wrote:
... snip ...
This is why we always recommend using large diameter wire with a T-tron
fuse installed in line and mounted right next to the battery.
In the event of a problem with either the wire or inside the inverter;
any short circuit will blow the fuse before any damage such as a fire
occurs. A failure which simply goes open circuit, does not need a fuse
for protection.
The fuse can be removed as a disconnect means for service work.
Regards
Arild
Jack Haring
WhoopeeWagen
At 04:54 PM 07/14/2000 -0400, Jack Haring wrote:
Where does one obtain a T-tron in-line fuse holder of the required capacity?
West Marine has them listed in the caqtalog.
If your localWEST store doesn't have stock try a local electrical jobber.
Arild
At 18:52 7/14/2000 , you wrote:
At 04:54 PM 07/14/2000 -0400, Jack Haring wrote:
Where does one obtain a T-tron in-line fuse holder of the required capacity?
West Marine has them listed in the caqtalog.
If your localWEST store doesn't have stock try a local electrical jobber.
Thanks Arild; the manufacturer has great technical information on their Web
site:
http://www.bluesea.com/products/FB/FB.html
What the West Marine catalog doesn't tell you is that the "ANL"s are
slow-blow fuses, while "T" fuses are faster.
Jack Haring
WhoopeeWagen