JJWalecka
Senior Member
- Location
- New England
Heat pump disconnect question
- Thread starter JJWalecka
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You'll need to change the 30 amp CB to a 25 amp if you don't want to use a fused disconnect.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I wonder why they specify a different size fuse than the breaker? I've never seen a nameplate list it like that.
The 26 would allow you to round up to a 30A fuse since 26 is not a standard size.
Perhaps its a mistake, or perhaps the trip curve of a 30A fuse is similar to a 25A breaker.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Where is it stated that you can round up OCPDs to the next standard size?
cashpoppper
Member
- Location
- usa
- Occupation
- hvac
@tortuga theory and the name plate are both weird.
use a 25, 1 amp won't make a difference with inrush current.
if you're that worried use a 30amp OCPD (more common) and find some non-time delay fuses and see how good your luck is.
use a 25, 1 amp won't make a difference with inrush current.
if you're that worried use a 30amp OCPD (more common) and find some non-time delay fuses and see how good your luck is.
Square D QO 25 Amp 2-Pole Circuit Breaker QO225CP - The Home Depot
Bring the best and essential addition to your electrical application by selecting this Square D QO 2-Pole Circuit Breaker. Made of durable material.
www.homedepot.com
240.4(B)
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
I don't know if the rules for HVAC equipment have a similar 'round up' allowance, but 240.4(B) applies to conductor protection, not equipment protection.
cashpoppper
Member
- Location
- usa
- Occupation
- hvac
inspector shot down my equipment protection. i ran 10ga on a double 30, and the equipment was only rated for 15. Fail. had to pull the 30amp and install the 15.
which i thought was weird. it's not inside the house, who cares if it catches fire inside the metal box, that's 3ft away from the house.
which i thought was weird. it's not inside the house, who cares if it catches fire inside the metal box, that's 3ft away from the house.
rc/retired
Senior Member
- Location
- Bellvue, Colorado
- Occupation
- Master Electrician/Inspector retired
If you installed a 30 amp breaker for a unit that has 15 max requirement, the inspector should fail you. I would.
who cares if it catches fire inside the metal box, that's 3ft away from the house.
[/QUOTE]
I care. A neighbor had a fire in his main disconnect and sparks ignited the growth below the disconnect. It burned about 100' feet along the fence line.
Just saying.
Ron
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
This might help to explain.
- Location
- Illinois
- Occupation
- retired electrician
It states maximum size so you cannot round up. You either find a 26 amp fuse or round down to 25 amps.
Don do you have a code reference for that? I am looking at 440.22(A) Exception 1. [2023 NEC]
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
I would think 110.3(B). Neither 240.4(B) nor 440.22 give you license to ignore the manufacturer's max fuse or circuit breaker marking. (Especially not 240.4, which is titled 'Protection of Conductors' and does not apply to equipment.)+
At least the nameplate on this heatpump actually makes clear you can use a breaker.
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
I agree ... That's why the NEC created a special section for refrigeration, follow the Nameplate Exactly. I go a step further and always read the Installation Manual on each unit.
Then what is 440.22(A) exception #1 for? What is that exception for if not rounding up to the next standard size?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Motors that don't come with a max fuse marking?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
440.22(A) does not apply directly to the equipment shown in the OP. It applies only to an individual motor compressor without any other loads present. The equipment in the OP also includes a fan, so it falls under 440.22(B).
Now when the motor compressor is the largest load (typical case), 440.22(B)(1) applies and it refers to the "value specified in 440.22(A)" plus the sum of the other loads. Presumably the maximum fuse size is the result of the manufacturer doing that 440.22(B) calculation. Which calculation may already include the use of the 440.22(A) exceptions. The installer doesn't get to apply those exceptions again.
Cheers, Wayne
Okay I see the rounding up does not apply to the OP's unit. It would apply to an individual motor compressor without any other loads present and possibly only if your under the 2023 NEC. I am not sure if that exception is new to the 2023 or they re-worded it, I suspect its new.