Mini Split Wiring

[depawl52]

I know this issue has been addressed previously/elsewhere, but it keeps coming up on projects I've been involved with. Most of the mini splits I've seen have a "Max Fuse" amperage listed on the name plate. I'm of the opinion that this requires a fuse to be installed somewhere in the circuit (normally at the disconnect at the outdoor unit), as opposed to a breaker of the listed amperage. For example, if the mini split name plate lists a Minimum Circuit Ampacity of 15 and a Max. Fuse of 15, my take would be a minimum 15 amp breaker at the main panel, and a 15 amp fused disconnect. Is this correct?
Thanks.

 

[Dennis Alwon]

You are correct but most units say max fuse or Hacr breaker, in which case a fuseless disconnect is used.

 

[AC\DC]

Like Dennis said it has to be a hacr breaker if it’s like a zinsco or for breaker then you have to use fuses. Unless they are hacr but I have not seen them rated for that.

 

[Dennis Alwon]

Like Dennis said it has to be a hacr breaker if it’s like a zinsco or for breaker then you have to use fuses. Unless they are hacr but I have not seen them rated for that.

You can use the Hacr breaker only if the unit states breaker. Some of the larger rooftop units say fuses only. I doubt the mini split says that

 

[augie47]

I just wired a mini-split for my son... it had MAX FUSE; no mention of "overcurrent device" or "breaker"
(I was shocked to see the price of a FRN-R-30 fuse at big box))

 

[Dennis Alwon]

I just wired a mini-split for my son... it had MAX FUSE; no mention of "overcurrent device" or "breaker"
(I was shocked to see the price of a FRN-R-30 fuse at big box))

That is new to me.... What brand is it? Do you remember?

 

[augie47]

Senville LITO (Amazon)

 

[depawl52]

Yes indeed, the unit in question is a Senville LITO. It says that the MAX Fuse = 15 Amps. But this is a 240 volt circuit, and the the Eaton disconnect says it accepts Class H cartridge fuses. So I'm stumped as to which fuses to use?

 

[mtnelect]

I only install Daikin. When you connect a GFCI breaker, it would trip immediately.
1) So, a TIA-1668 was implemented until September 1, 2026.

 

[mtnelect]

Wrong TIA !

 

[Fred B]

Issue happening with the mini splits I've seen is that there is no neutral connection inside the exterior main unit that is only 240V (normal on original type hvac) yet the interior power heads are 120V, powered from the main unit. This forces the neutral current onto the ground, thus tripping the gfci.

 

[winnie]

Issue happening with the mini splits I've seen is that there is no neutral connection inside the exterior main unit that is only 240V (normal on original type hvac) yet the interior power heads are 120V, powered from the main unit. This forces the neutral current onto the ground, thus tripping the gfci.

Woah! If that is the problem then the fix is trivial. Don't build garbage.

My understanding that in many cases the problem is capacitive coupling from the inverter system.

I've only installed a few Fujitsu units. The interior heads were powered at 240V from the external unit. I noticed that the supply EGC landed on an insulated terminal, and then the bonding jumper to the case went through a ferrite core.

I did not attempt to use a GFCI.

Jon

 

[Dennis Alwon]

There has been a change on this issue so no gfci is needed until 2026. This is from the 2020 Nec. I believe there was a Tia on this also.

Exception No. 2:
Ground-fault circuit-interrupter protection shall not be required for listed HVAC equipment. This exception shall expire September 1, 2026.

 

[depawl52]

Update:
So I called Senville Tech Support today and the rep I talked to told me that a 15 amp breaker at the main panel is all that's requred. Not sure what (or where to find) the NEC has to say about this, I assumed it was a Manufacurer's requirement (fuse in addition to breaker), but Senville says not. So now I'm perplexed, and still haven't been able to find 15 amp Class H fuses to use in the disconnect that was already purchased for this project.

 

[winnie]

The NEC basically says to follow manufacturer's instructions.

The manufacturer's instructions should be correctly expressed on the nameplate.

If the manufacturer requires either HACR breakers or fuses, but the nameplate says 'fuses', then the nameplate is defective. Of course the support rep might be wrong.

Jon

 

[Dennis Alwon]

I don't know what a class H fuse is but does it say class H fuse only? I would use a standard 15 amp fusetron (time delay)

 

[depawl52]

The disconnect is an Eaton DPF221RP, Outdoor 240 VAC Fusible Pullout, and it says: "Use when local fuse protection is required, accepts Class H fuses."
Seems odd, I would think this would be a pretty common item that takes common fuses.
In any event, I'll probably go with the fuses you mentioned, and a 15 amp breaker in the panel.

I was also thinking that the tech support person I talked to was not fully up to speed on this issue of breaker vs. fuse.
Thanks again to all for the input and advice.

 

[David Castor]

Class H is a non-current limiting fuse rated for max of 10,000 interrupting. Sometimes referred to as "NEC" fuses.

 

[scrubbin]

From Graingers website :
Fast-acting, nonindicating UL Class H and K5 fuses are for general purpose use in existing installations that require a high-sensitivity, fast-blow fuse. These fuses are highly sensitive to changes in current flow and don't tolerate temporary overload currents or power surges, so they open within seconds of being exposed to overloads and short circuits. UL Class H and K5 fuses are used as replacement fuses for overcurrent protection in older HVAC installations. Like Bussman NON fuses.
Item 4XF90
Mfr. Model NON-15
$2.86