swamp cooler (fuse sizing)

[godsquadgeek]

It's not a biggy, but it bugging me.

I was wondering if I go with the 170% overcurrent protection as per article 430.

or what?

I have a .6 amp 240v swamp cooler pump, that i need to fuse.

it was blowing a 1 amp, so I was double checking.

I thought for a second on fractional horse it was higher like 270%, but maybe i was thinking of the 170.

.6X1.7= 1.02amp

so a 1 amp is close, i know you are supposed to go to next higher, which would be a 2, which we don't carry.

so 3 is next size up,

and thats what I put in it.

I was just curious though.

 

[david luchini]

It's not a biggy, but it bugging me.

I was wondering if I go with the 170% overcurrent protection as per article 430.

or what?

I have a .6 amp 240v swamp cooler pump, that i need to fuse.

it was blowing a 1 amp, so I was double checking.

I thought for a second on fractional horse it was higher like 270%, but maybe i was thinking of the 170.

.6X1.7= 1.02amp

so a 1 amp is close, i know you are supposed to go to next higher, which would be a 2, which we don't carry.

so 3 is next size up,

and thats what I put in it.

I was just curious though.

3A is the next standard size fuse above 1A.

 

[godsquadgeek]

still confused.

still confused.

what they had was a KLDR rated fuse, time delay, current limiting.

but it was for inductive loads like XFRMers and solenoids.

this was a mini pump/motor, so I am thinking a standard CCMR rated motor fuse.

that may have been the issue.

but all the charts I see online are saying to give these small motors, a small fuse.

like 8/10th of an amp.

http://www.littelfuse.com/~/media/electrical/application-notes/littelfuse-motor-protection-guide.pdf

so it is those places that confuse me, I thought minimum o.l. protection for motors was 1.15-1.4.

I looked at the chart above, and it mentions single phase 240 with a 1.135 multiplier at the lowest fractional horse which was i think 1/8.

So anyway, .7 at 1.15 is about .8, or 8/10th of an amp.

 

[godsquadgeek]

3A is the next standard size fuse above 1A.

i think little fuse, KLDR series and CCMR series does have 2 amp, as well as fractions between 1 and 2.

and sub 1, like 6/10, or 8/10.

 

[david luchini]

i think little fuse, KLDR series and CCMR series does have 2 amp, as well as fractions between 1 and 2.

and sub 1, like 6/10, or 8/10.

See 240.6(A). As far as the NEC is concerned, 1A and 3A are standard fuse sizes, 2A, 6/10A, etc. are non-standard fuse sizes. So, the next standard fuse size above 1A is 3A, The use of non-standard sizes is permitted, but not required.

 

[jim dungar]

i think little fuse, KLDR series and CCMR series does have 2 amp, as well as fractions between 1 and 2.

and sub 1, like 6/10, or 8/10.

Look at section 240.6(A). These are the sizes to be used when other sections of the code say you can 'go up in to the next size', like in 430.32(C).

2Amps is not a standard fuse size however you may use one if you want to, but that becomes a design choice.

 

[cowboyjwc]

Never seen anyone fuse a swamp cooler. Usually just see a switch on it.

 

[godsquadgeek]

Never seen anyone fuse a swamp cooler. Usually just see a switch on it.

they have buck transformers on them,

so we fuse the secondary to protect the branch ckt. (usually an in line fuse)

480 bucked to 120 or 240 for the pumps.

Other buildings have a relay that has a 480v coil.

and it closes when the cooler is remotely started.

because the coil is in parallel with the main fan motor L leads.

, those have a separate wire pulled (110 circuit), GFCI, usually,

that passes through the above contactor,


other wise the pumps run dry when the fans are off or not in use.

(but you probably know all thats stuff anyway).

 

[godsquadgeek]

See 240.6(A). As far as the NEC is concerned, 1A and 3A are standard fuse sizes, 2A, 6/10A, etc. are non-standard fuse sizes. So, the next standard fuse size above 1A is 3A, The use of non-standard sizes is permitted, but not required.

nice to know that there are standard versus permitted fuses, thankx.

 

[godsquadgeek]

Look at section 240.6(A). These are the sizes to be used when other sections of the code say you can 'go up in to the next size', like in 430.32(C).

2Amps is not a standard fuse size however you may use one if you want to, but that becomes a design choice.

it becomes conviluted in control cabinets

when we have a .5kva control transformer.

and we need to fuse the transformer.

500VA/480V

500/480

=1.25A or a 2Amp fuse for primary.

and I think we were using 5 amp fuses for secondary.

I would not feel comfortable putting a 3 on something rated 1.25A.

but thats just me.

 

[jim dungar]

and I think we were using 5 amp fuses for secondary.

I would not feel comfortable putting a 3 on something rated 1.25A.

but thats just me.

There is no way I would fuse a control power transformer at only 125%, the inrush on these is extremely high. 5A fuse is absolutely okay.
This fuse is there only to remove a faulted transformer from the power system. If you want to keep the the CPT from being overloaded, then add secondary fuses.