Board logo

Fuse rating for bike petrol pump?
David Jenkins - 9/1/08 at 09:21 PM

I've just finished wiring up the bike pump - it's running OK on a 5A fuse, but I don't know if that's big enough.

What have other people used? I don't want to run it with too small a margin, e.g. if it's using 4.8A!

David
(Yes, I know I could put a meter on it, but there's no fuel in the tank and I'd rather not run it dry for more than 2 or 3 seconds at a time)

[Edited on 10/1/08 by David Jenkins]

flak monkey - 9/1/08 at 09:39 PM

You put a fuse in to protect the wiring, not the component. So whats the current carrying capacity of the wires? At a guess it will be on 1mm^2 cable, so about 16amps.

Stick a 10amp fuse in and it will be fine.

David

dave1888 - 9/1/08 at 09:42 PM

Agreed id go with 10amp iirc bike pumps draw about 5amps under full load.

Mark G - 9/1/08 at 10:54 PM

Generally speaking the way to work out what fuse to use is to run the component with an ameter in the circuit to find the current draw and then add 1/3 of that again and you have your fuse rating.

So if you're pump is running on around 5 amps then I'd use a 7 amp fuse.

tks - 9/1/08 at 11:10 PM

just pull the fuse place the am meter in place..

and let someone turn on the ignition pump will prime you read value. you turn off ignition..

as easy as dell..

Tks

p.s. 5seconds without fuel wont harm the pump. (it isn't made from butter)

David Jenkins - 10/1/08 at 08:56 AM

quote:
Originally posted by tks
just pull the fuse place the am meter in place..
<snip>
p.s. 5seconds without fuel wont harm the pump. (it isn't made from butter)


Doh! It was late last night when I posted my question, and I didn't have my thinking head on...

I was considering how I could maybe disconnect the pump's earth lead and put the ammeter in-line, and other such nonsense. Pulling the fuse was the easy option that didn't occur to me...

I know the pump will stand a few seconds of running dry - it could happen in real life - but I don't want to push my luck with a pump that hasn't seen any petrol for years.

Looks like a 10A will be good-enough protection.

cheers to all,
David

02GF74 - 10/1/08 at 09:53 AM

remove the hose from inlet, fit another hose with funnel at end and fill with petrol, run pump as above.

but 10 A is fine.

David Jenkins - 10/1/08 at 11:40 AM

quote:
Originally posted by 02GF74
remove the hose from inlet, fit another hose with funnel at end and fill with petrol, run pump as above.


No hoses! (yet)

Mark G - 17/1/08 at 10:17 PM

One thing to remember when measuring current in circuits is that most mulitmeters have and internal fuse of 10amps for current, so if you're expecting to see a current greater than 10 amps then you'll need to use an amp clamp or you'll blow the fuse in your meter.