fuse reducers

[Geoffrey Lyons]

Is the use of fuse reducers an accepted practice or are they not up to par, half a...n it ????

 

[jim dungar]

Is the use of fuse reducers an accepted practice or are they not up to par, half a...n it ????

There are times they are required. For example, if the only available fusible switch in a panelboard is larger than the load you want to protect.

 

[Geoffrey Lyons]

thanx jim that is exact situation Im in just wasnt sure how common it was to use them

 

[barclayd]

I know they're CALLED "Fuse Reducers", but, actually, they are "Fuse Expanders". They make a small fuse BIGGER.
db

 

[iwire]

We used to do work for a large retail chain that specified fusible switch gear and every bucket was ordered one size larger then needed, so in a brand new installation every bucket had fuse reducers in it. :-?

 

[raider1]

We used to do work for a large retail chain that specified fusible switch gear and every bucket was ordered one size larger then needed, so in a brand new installation every bucket had fuse reducers in it. :-?

I have had a certain engineer that I have worked with in the past always oversize disconnects for rooftop A/C units so that it was neccessary to use fuse reduces in all the disconnects. I never felt very confident in using those fuse reduces and I never saw the reason to way oversize the disconnect.:-?

Chris

 

[brian john]

Fuse reducers are used when needed.

 

[Packinaglock]

I have used them quite a bit.

 

[mdshunk]

I wonder if any of the IR guys could say whether there's historically been any problems with the fuse reducer to fuse connection?

 

[iwire]

Well that same retail company I mentioned before required IR scans at the end of the job. I was sent with the IR report to address the issues they found. There was a number of 'issues' with the switchgear all them turned out to be factory buss bar connections that appeared to be connected with rivets. The fuse reducers where not on the report at all.

In the end it was the customers problem as they supplied all the distribution equipment.

 

[infinity]

I would think that a listed product (fuse reducers) when installed properly would work just like the larger size fuse made for the specific gap.

 

[brian john]

I would have to ask our IR guys, but in my days of doing the reports I remember there being an issue with one style, The Bussman reducers all seem to be OK when properly installed.

 

[petersonra]

I would think that a listed product (fuse reducers) when installed properly would work just like the larger size fuse made for the specific gap.

I think they work fine. I know some places prefer larger sized switches, just like many places prefer not to use the smallest NEMA size starters.

The reality of it is that if you buy enough of them, the next size up is about the same price and you stock one less item.

 

[barclayd]

Value Engineering

Value Engineering

Would someone seriously consider using a 400A switch for a 125A circuit?
Or even a 175A? I'm sorry, I do not see any economic benefit to an owner.
Designing to purposely have to use Fuse Reducers for new work would be like designing a new conduit run saying "Don't use a 4-11/16 box, use a 4 sq with an extension."

It does, however, give lots of opportunity for the dreaded "V A L U E E N G I N E E R I N G". BU-WHA-HA-HA-HA
Maybe that's why they do it.

Anyway - Fuse Reducers work great - never had a problem.

 

[petersonra]

Would someone seriously consider using a 400A switch for a 125A circuit?
Or even a 175A? I'm sorry, I do not see any economic benefit to an owner.
Designing to purposely have to use Fuse Reducers for new work would be like designing a new conduit run saying "Don't use a 4-11/16 box, use a 4 sq with an extension."

It does, however, give lots of opportunity for the dreaded "V A L U E E N G I N E E R I N G". BU-WHA-HA-HA-HA
Maybe that's why they do it.

Anyway - Fuse Reducers work great - never had a problem.

OTOH, if you are not sure of the exact size of your load at the time you have to submit a plan, oversizing it makes some sense.

And as I mentioned earlier, if you buy in quantity, you can often purchase a larger size of something for about the same price. And it is one less thing to have to worry about having in stock. Probably more true for 100A and smaller switches than larger ones though.

 

[barclayd]

If you don't know the loads by the time you get submittals, there just might be some other problems with the entire project.

30 to 60 - maybe/maybe not.
Anything else - (I'm not really from Missouri) I'm from Missouri, show me.

Just curious, though - would you also have to upsize your conduit to take advantage of the larger switch?

"OTOH" I had to look that up - it's from 'Fiddler on the Roof'
I thought it meant 'Only Throw Over Hand' (had the Hand part right)
db

 

[petersonra]

If you don't know the loads by the time you get submittals, there just might be some other problems with the entire project.

30 to 60 - maybe/maybe not.
Anything else - (I'm not really from Missouri) I'm from Missouri, show me.

Just curious, though - would you also have to upsize your conduit to take advantage of the larger switch?

"OTOH" I had to look that up - it's from 'Fiddler on the Roof'
I thought it meant 'Only Throw Over Hand' (had the Hand part right)
db

A lot of specs handle this by not allowing < 3/4" conduit to be used (for 30 to 60).

 

[augie47]

I've seen many jobs where the exact requirements for the fuse size on HVAC units is unknown until the units are set and often 60 amp or 100 amp disconnects are speced only to find the max fuse won't match. I have always detested fuse reducers thinking they were a "weak link", but, as often happens, the forum has taught me differently.

 

[jerm]

I've used them, 30 to 60 when we didn't know up front, no problems to date.

 

[charlie]

It is no problem to use them and they are listed under FITTINGS FOR FUSEHOLDERS (IZZR) in the UL White Book. :smile: