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ContinuousWave: Small Boat Electrical
Can't find 6 amp blade fuse
|Author||Topic: Can't find 6 amp blade fuse|
posted 07-26-2009 01:00 PM ET (US)
I am trying to eliminate all of the in-line fuses and wires by going to a distribution panel that uses blade fuses. The Horizon marine radio has an in-line 6 amp glass tube fuse but I can't find a 6 amp blade fuse. Would you go with a 5 amp or 7.5 amp?
posted 07-26-2009 02:05 PM ET (US)
Fuses are for protecting the wire from overheating. I would think you would be safe to use the 7.5 amp fuse.
posted 07-26-2009 02:30 PM ET (US)
I'd use the 5.
posted 07-26-2009 03:04 PM ET (US)
Check the spec sheet on the VHF to see what max amperage is. If it is 6 amps or less the 5 amp fuse will be blowing frequently. Remember that fuses protect wiring from overheating. I'm sure that the wiring is 16 gauge or larger.
posted 07-26-2009 09:00 PM ET (US)
Go with a 5. NEVER insert a greater amperage fuse than what is specified.
posted 07-27-2009 03:23 AM ET (US)
Before you go any farther, check your specs in the manual. If the manual is lost, you can usually download one from the Horizon site. I looked at the specs on one and in low power mode(1 watt) the VHF pulls 1.5 amps. In high power mode(25 watts) the VHF pulls 5 amps.
You have a few choices if indeed your VHF has the same specs.
1. leave the in line fuse with the 6 amp fuse.
2. reduce to 5 amps and run the risk of losing communications when you really need it from a blown fuse while transmitting on "HIGH".
3. increase to 7.5 amps and "maybe" run the risk of damaging the VHF just to be able to convert to blade fuses.
Using the 7.5 amp blade fuse will increase the current capable of entering the power supply of the VHF by 20%. If the VHF is operating properly, I don't feel that this will be of any danger. Others will disagree but this is something that you will need to decide.
posted 07-27-2009 12:48 PM ET (US)
Thanks for the help. All of this makes sense. I agree with seaBob's general assessment, but HappyJim is correct. My unit, on high power draws 5.5 amp's and would likely blow a 5 amp fuse. I suspect that might happen the one time I actually needed to have a radio. The decision to go to the blade fuse distribution panel has already been made, but I had no idea I would have trouble matching fuse amperage. This isn't the only example. I had no idea. I may just go with the in-line glass fuse (something I had hoped to eliminate) and then run it through the distribution panel with a 7.5 amp fuse.
posted 07-27-2009 06:09 PM ET (US)
Here is the response I received from Blue Sea Systems:
Thank you for choosing a Blue Sea Systems ST-Blade fuse block. It will indeed be a great asset as you clean up a mess of wires!
Remember that the fuse exists to protect the wire, not the device; the inherent resistance of your radio is what limits current flow. The fuse is there to prevent a fire if your radio suffers some sort of a failure and does not limit the current flow. Most wiring in situations like yours would be adequately protected with a 15A fuse, so a 7.5A fuse is adequately conservative for the purpose.
Thank you for your email, and happy wiring!
Blue Sea Systems
posted 07-28-2009 12:19 PM ET (US)
I don't believe Erin Morey, Technical Writer, Blue Sea Systems understands the difference between circuit protection and electronic device overload protection.
posted 07-28-2009 01:33 PM ET (US)
That's ridiculous. No surge in power that would blow a 6amp fuse but wouldn't blow a 7.5amp fuse is going to damage a VHF radio. I'm not even sure where such a surge would come from on a small, closed, 12vdc system like a boat.
The expert is right, 7.5amps is more than adequate protection for the circuit.
posted 07-28-2009 08:42 PM ET (US)
I have installed the Blue Sea System 6 fuse box on my 170 Montauk and have never had a problem. Here are pics of the install.
posted 07-29-2009 06:41 AM ET (US)
"The expert is right" ?? From my experience a "Technical Writer" does not necessarily equate to being an expert. Their job function depending upon position is to write user manuals, assembly instructions, procedures manuals and sometimes offer online help. Many have tech writing skills but lack knowledge and experience, Material for reproduction is often reviewed by an expert prior to publication. Not knocking the product, just that bit of advice given.
"such a surge would come from" a internal failure of the electronic device or possibly a spurious fault. In the case of internal failure a fuse of the proper rating is designed to limit or prevent further damage. Believe it or not some items today are still easily repairable. The inline fuse of external electronic power cables is not there to protect the wiring, external circuit or the power cable as the Blue Sea Systems "expert" stated.
The Bussmann glass fuses of that type and range also come in 5, 7 & 8. Standard Horizon obviously chose the 6 for a reason. Typically manufacturerers choose the fuse rating just high enough to avoid nusance blows that the particular product may encounter. By putting it inline it is usually more accessible for replacement. Some electronics have chassis mount fuses that are accessible externally or internally. Warranty coverage for the VHF could be denied if the fuse holder is removed from the power cable. Granted the VHF mentioned is probably a throw away non-repairable item. The 1.5 difference may not cause any problems but why risk it and possibly fry a radio or other electronics.
posted 07-29-2009 11:32 PM ET (US)
To further support the folks at Blue Sea, here is what Devin Massens at Standard Horizons Marine Electronics had to say:
"Thank you for contacting Standard Horizon Marine Electronics. We appreciate the opportunity to be of assistance to you.
You shouldn't have any complications by using the 7.5 amp fuse. 6 amp fuses can be difficult to find, when this is the case for customers we will typically recommend the 7.5 amp fuse.
If you have further inquiries, please feel free to contact us at:
Phone: (800) 767-2450
posted 07-30-2009 07:27 AM ET (US)
Contacting Standard Horizon was a good idea and glad the installation is going to work for you.
The power cord on my Icom M602 is 14 AWG, it has a 10 amp inline fuse to protect the radio. In a non-bundled run wire max. capacity is 35A. According to the reply from BSS I should be fat, dump and happy using a 25A fuse.
BSS replied to you by saying, "Remember that the fuse exists to protect the wire, not the device...Most wiring in situations like yours would be adequately protected with a 15A fuse, so a 7.5A fuse is adequately conservative for the purpose." Basically what they said was use a 15A fuse if you so desire.
"The fuse is there to prevent a fire if your radio suffers some sort of a failure and does not limit the current flow."
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