30A A/C disconnect

[scanchain]

I'm putting in a 30A 240V A/C compressor disconnect outside.

I like those Square D disconnect box with a 30A breaker but I can't seem to find them for sale anywhere. What everyone is selling are those fused boxes.

A thought occurred to me that are the breakers or fuses really needed if this is a dedicated circuit, protected by the 30A break at the panel? Would a non-fused disconnect suffice?

 

[slow]

What are you connecting to the disconnect and does it require fuses?

 

[wyliesdiesels]

I'm putting in a 30A 240V A/C compressor disconnect outside.

I like those Square D disconnect box with a 30A breaker but I can't seem to find them for sale anywhere. What everyone is selling are those fused boxes.

A thought occurred to me that are the breakers or fuses really needed if this is a dedicated circuit, protected by the 30A break at the panel? Would a non-fused disconnect suffice?

If this is for an A/C compressor, you need to check the nameplate to see if fuses are required in the disconnect

 

[scanchain]

What are you connecting to the disconnect and does it require fuses?

It will be for an A/C compressor. The one I'm probably buying says

System MCA 23.9A
System MFA 25A

 

[wyliesdiesels]

It will be for an A/C compressor. The one I'm probably buying says

System MCA 23.9A
System MFA 25A

does the nameplate state that fuses are needed?

do you have a picture of the nameplate?

 

[scanchain]

does the nameplate state that fuses are needed?

do you have a picture of the nameplate?

Unfortunately, I haven't bought it yet.

Here's the brand and model Daikin 4MXS36RMVJU

 

[bczygan]

https://www.daikinac.com/assets/DOC/InstallationManuals/Daikin-AURORA-MXL-MXS-Installation-Manual.pdf

Bill

 

[mrobins297aaa]

One of the advantages of having a fused disconnect outside is you can fuse the unit with proper size fuse.... i.e, you have a 30 amp breaker in your panel and #10 copper or #8 alum wire and the unit has a max fuse size of 25 amps you can easily get 25 amp fuses so it will be sized correctly.

I think you would have a hard time finding a 25 amp breaker for your panel.

when I was doing HVAC for a living we always installed fused disconnects outside at the AC condenser

 

[wyliesdiesels]

Lousy manual

 

[wyliesdiesels]

One of the advantages of having a fused disconnect outside is you can fuse the unit with proper size fuse.... i.e, you have a 30 amp breaker in your panel and #10 copper or #8 alum wire and the unit has a max fuse size of 25 amps you can easily get 25 amp fuses so it will be sized correctly.

I think you would have a hard time finding a 25 amp breaker for your panel.

Per 240.6, 25a is a standard breaker size.

 

[mrobins297aaa]

How did I know someone would say that. where did you get the table 240.6?

yeah maybe the new panels out today

I make that comment from experience of doing hundreds of these installs during the 70's 80's and 90's.

A lot of the old panels we were installing new breakers in we were lucky if we could even find a breaker for it let alone a 25 amp.

a lot times we were replacing a old unit which already had a 30 amp breaker and the wire already run.

I can't ever remember reading the instructions on a condensing unit and it said that it required a fused or non fused disconnect, code required the disconnect, I usually looked at the max fused and that's what I fused it at.

 

[mrobins297aaa]

we only carried 2 sizes of disconnects 30 amp and 60 amp
also we only carried 2 wire sizes. #8 al sec (2 wires and bare ground) and #6 al sec
and we fused them as required

 

[Norcal]

we only carried 2 sizes of disconnects 30 amp and 60 amp
also we only carried 2 wire sizes. #8 al sec (2 wires and bare ground) and #6 al sec
and we fused them as required

30A is the smallest size for pull out A/C discos, and safety switches, 60A is the next size up.

 

[scanchain]

I see my local Home Depot carries the Square D QO 25A breaker.

So my choices are

1) 30A breaker in the panel, 25A fuses in the disconnect box
2) 25A breaker in the panel, 25A fuses in the disconnect box
3) 25A breaker in the panel, disconnect box with no fuse

My wires are 10ga copper.

Which would be preferred, and why? Thank you.

 

[Norcal]

I see my local Home Depot carries the Square D QO 25A breaker.

So my choices are

1) 30A breaker in the panel, 25A fuses in the disconnect box
2) 25A breaker in the panel, 25A fuses in the disconnect box
3) 25A breaker in the panel, disconnect box with no fuse

My wires are 10ga copper.

Which would be preferred, and why? Thank you.

Option #1 will be the easiest, as not everyone stocks 25A breakers but 25A fuses should be easy to source.

 

[yatg]

Door #3.

Internet world, qo225s are readily available, assuming you have a sqd qo panel.
If you're a pessimist, just keep a spare on hand and you'll never need it.

I like the sqd 60a disconnects with a switch.
About $14 at my home depot, but maybe not yours.

 

[alfredeneuman]

where did you get the table 240.6

It's new in the 2017 NEC.
In 2014 the breakers were just listed in text 1 by 1, but the information is still the same as is it ever was.

 

[sberry]

I was in a mobile home park,,, lots of the units had AC and the stock in trade was 10 SO or SJO and 30A breakers. I don't recall what the label on the units were? They had about 13 fla or so, they didn't downsize the wire,,, they all got the same and as I recall all the service was SQD maybe. They didn't tailor breakers or fuses, they simply drag a cord under the units and ****** upper.
Its been some time since I really hook up, last time I even worked on one was for a ****** pull out went south.

 

[LS6 Tommy]

I don't see the required HACR rating on that breaker. The unit data plate will tell you if it requires a fused or a breaker disconnect. You must use what it states. If it doesn't require it, then just get a plain disconnect rated for 30A. Most times, non fused is preferred by manufacturers. I have no idea why.

Tommy

 

[wyliesdiesels]

How did I know someone would say that. where did you get the table 240.6?

yeah maybe the new panels out today

I make that comment from experience of doing hundreds of these installs during the 70's 80's and 90's.

A lot of the old panels we were installing new breakers in we were lucky if we could even find a breaker for it let alone a 25 amp.

a lot times we were replacing a old unit which already had a 30 amp breaker and the wire already run.

I can't ever remember reading the instructions on a condensing unit and it said that it required a fused or non fused disconnect, code required the disconnect, I usually looked at the max fused and that's what I fused it at.

table 240.6 was originally just a paragraph and has been in the code for many cycles so....

It's new in the 2017 NEC.
In 2014 the breakers were just listed in text 1 by 1, but the information is still the same as is it ever was.

yeah and it has been in the code for many cycles before that...

 

[sberry]

I am not sure if they prefer non fuse but list the code minimum..

 

[alfredeneuman]

yeah and it has been in the code for many cycles before that...

I've got a 1956 NEC and it's in there

 

[mike93lx]

Most times, non fused is preferred by manufacturers. I have no idea why.

Tommy

less chances for problems, lowering the need for tech support?

 

[mrobins297aaa]

so when I have a unit that requires a 35 amp fuse, how do I do it with a non fused disconnect?, does somebody actually make a 35 amp breaker?

we always fused them all

 

[mrobins297aaa]

table 240.6 was originally just a paragraph and has been in the code for many cycles so....



yeah and it has been in the code for many cycles before that...

I never said it wasn't in the code, I just said it would have been hard to find.

Lets see pretend it's 1985 and tomorrow I have to install a 2 ton ac and it needs a 25 amp fuse, well I'll just pickup my phone and see if the supply house has it while I'm driving home, but wait I don't have a phone, well amazon must have it and I can get it overnight, **** I don't have a computer and what is a amazon..........lol.

the point being it's just a lot easier to stock a bunch of fuses than it is to stock of bunch of breakers from god knows how many manufacturers

anyway that's the way we did it and I don't remember those fuses being a big problem

 

[kaffine]

so when I have a unit that requires a 35 amp fuse, how do I do it with a non fused disconnect?, does somebody actually make a 35 amp breaker?

we always fused them all

If it says it requires fuses then you need fuses, a breaker even if 35 amp isn't acceptable. Some just say the max OCPD and don't specify it needs to be fuses. If it says max OCPD 35 amps you could use a 30 amp breaker but not a 40 amp.

When I did my AC I put in a small subpanel so I could run a 120V outlet as well since there wasn't one nearby and are now code required.

I prefer to stay away from fuses if I can. Breakers can be reset at midnight I know I'm not going to have a spare fuse around.

 

[Jim greengo]

less chances for problems, lowering the need for tech support?

What he said.

 

[Norcal]

35A fuses are pretty common, just use a 60A fusible disco, 35A is the smallest size fuse that fits 60A fuse clips.

 

[Terry D]

One of the advantages of having a fused disconnect outside is you can fuse the unit with proper size fuse.... i.e, you have a 30 amp breaker in your panel and #10 copper or #8 alum wire and the unit has a max fuse size of 25 amps you can easily get 25 amp fuses so it will be sized correctly.

I think you would have a hard time finding a 25 amp breaker for your panel.

when I was doing HVAC for a living we always installed fused disconnects outside at the AC condenser

I install 25 amp breakers a lot, they are available at supply houses. More and more A/C condensers are requiring this size. I should say they are available for newer panels, no idea what you have

 

[3rdgendslmech]

Can you put a 25 amp breaker in the panel while using the 30 amp disconnect outside?
The 25 amp breaker inside should trip before the outside disconnect right?

 

[Terry D]

Can you put a 25 amp breaker in the panel while using the 30 amp disconnect outside?
The 25 amp breaker inside should trip before the outside disconnect right?

I would use a non fusible disconnect, there is no need for overcurrent protection inside and outside. The disconnect is for a service tech, to assure the power is off and remains off.

 

[mike93lx]

I would use a non fusible disconnect, there is no need for overcurrent protection inside and outside. The disconnect is for a service tech, to assure the power is off and remains off.

So even if the manufacturer specs a fusible disconnect, you won't use one because there "is no need"?

 

[Terry D]

So even if the manufacturer specs a fusible disconnect, you won't use one because there "is no need"?

You are reading this wrong, I said there is no reason to double overcurrent protect it. You always have to go with what the name plate says. I don't have that piece of equipment in front of me, so I don't know what it says. It was never stated in here if it needed fuses or not .3rdgendslmech just asked if the breaker would trip before the fuses would blow. I don't wire A/C condensors everyday, but the ones I do state fuses or HVAC rated breakers.
Most breakers now are rated for HVAC, at least the brands I use for services. And it doesn't say the fuses have to be in the disconnect, this circuit could be coming out of a old fuse panel.

 

[TRWham]

less chances for problems, lowering the need for tech support?

I have posted this before, but when I worked for Copeland, the most common problem found with warranty return compressors was NOTHING. Perfectly good compressors were routinely changed out for no good reason other than possibly driving service revenue.

 

[wyliesdiesels]

I don't see the required HACR rating on that breaker. The unit data plate will tell you if it requires a fused or a breaker disconnect. You must use what it states. If it doesn't require it, then just get a plain disconnect rated for 30A. Most times, non fused is preferred by manufacturers. I have no idea why.

Tommy

The HACR rating label was done away with because all breakers are rated HACR now.

 

[grounded-b]

You are reading this wrong, I said there is no reason to double overcurrent protect it. You always have to go with what the name plate says. I don't have that piece of equipment in front of me, so I don't know what it says. It was never stated in here if it needed fuses or not

Yes, it was stated that it required fuses, based on the nameplate....

It says: MFA = 25A

That means "maximum FUSE ampacity".

If it didn't matter, it would say MOCPD = 25A (Maximum Over Current Protective Device) = fuse OR breaker

 

[Norcal]

I have posted this before, but when I worked for Copeland, the most common problem found with warranty return compressors was NOTHING. Perfectly good compressors were routinely changed out for no good reason other than possibly driving service revenue.

Thread drift !!!!
What did Emerson/Copeland do about warranty compressors that had nothing wrong with them, eat it or back charge?

 

[TRWham]

Thread drift !!!!
What did Emerson/Copeland do about warranty compressors that had nothing wrong with them, eat it or back charge?

I'm really not sure, but Copeland was never known for being generous with warranty.

 

[sberry]

The HACR rating label was done away with because all breakers are rated HACR now.

I was a wondrin what happened to that. Seems I looked for it on one. Thought I was missing something. Maybe I was becoming senile,

 

[Terry D]

Yes, it was stated that it required fuses, based on the nameplate....

It says: MFA = 25A

That means "maximum FUSE ampacity".

If it didn't matter, it would say MOCPD = 25A (Maximum Over Current Protective Device) = fuse OR breaker

Didn't see that, Thanks