Multi head ductless unit; nameplate marking 440.4(B)

[electrofelon]

Then someone would be wasting a lot of money when they could buy a system with the number of indoor units they actually need.

-Hal

I am not an expert on these, but I don't think that is necessarily how it works. The outdoor unit has a certain number of BTUs which is shared among the indoor units. It may be that you do not need the quantity of indoor units provided but you need the total BTUs.

 

[WD40]

Daikin has already determined the inside units that will work with the outside units. They have done the work for you, just follow their requirements. The outside and inside units work on D.C.

The indoor units may be DC motors internally but the Daikin I just installed runs the regular 240 VAC from a terminal strip on the outdoor unit to the indoor unit, with a DC signal wire that is a 'Class 1' circuit that uses the 3rd wire in the tray cable. Each indoor unit has its own power rectifier.
If you look at the terminal strip its just jumpers from the incoming power to the indoor units.
No fuse, overloads or contactor just a splice block.

 

[electrofelon]

Expanding the topic a bit, but I think these things need better clearer labeling.
As we are discussing, they could be clearer about the indoor units and the numbers for that, but also I think the indoor unit should be labeled that it is meant to be powered from another component. I say this because of an interesting experience I had recently. This was a split system with a typical outdoor unit but it had a air handler in the Attic. The homeowner relayed to me that the HVAC guy said it needed 240V to the air handler. I looked at the thing, and it seemed to me that's what it needed. It had a label that had MCA and OCPD on it. It said 240 volts. So I wire it up and give it 240 volts to what look to be clearly the terminals on the control board. Well turns out those were some low voltage terminals and it's powered from the outdoor unit. Fortunately I didn't heat it up and the HVAC guy caught it but I found that label to be very deceiving. I think there should be some industry standard term for when a unit is powered from another component and it should be on the label.

 

[tortuga]

Expanding the topic a bit, but I think these things need better clearer labeling.
As we are discussing, they could be clearer about the indoor units and the numbers for that, but also I think the indoor unit should be labeled that it is meant to be powered from another component. I say this because of an interesting experience I had recently. This was a split system with a typical outdoor unit but it had a air handler in the Attic. The homeowner relayed to me that the HVAC guy said it needed 240V to the air handler. I looked at the thing, and it seemed to me that's what it needed. It had a label that had MCA and OCPD on it. It said 240 volts. So I wire it up and give it 240 volts to what look to be clearly the terminals on the control board. Well turns out those were some low voltage terminals and it's powered from the outdoor unit. Fortunately I didn't heat it up and the HVAC guy caught it but I found that label to be very deceiving. I think there should be some industry standard term for when a unit is powered from another component and it should be on the label.

Yeah something got lost in translation when these went from being a simple split system with one outdoor unit and one wall mount indoor unit (listed together), to one outdoor unit thats a mini circuit distribution center distributing several 'motor branch circuit taps' (for lack of a better word) to a matrix of possible different indoor equipment, not just the typical wall units, and on top of that they add on condensate pumps and 'defrost heaters' of yet another brand. Even the indoor units may be a different brand.

 

[electrofelon]

Yeah something got lost in translation when these went from being a simple split system with one outdoor unit and one wall mount indoor unit (listed together), to one outdoor unit thats a mini circuit distribution center distributing several 'motor branch circuit taps' (for lack of a better word) to a matrix of possible different indoor equipment, not just the typical wall units, and on top of that they add on condensate pumps and 'defrost heaters' of yet another brand. Even the indoor units may be a different brand.

Yeah. Now I am wondering about the one I hooked up wrong, and if the branch circuit to the outdoor unit is adequate. The attic unit wasn't A huge load, but larger than the typical wall mount indoor units.

 

[mtnelect]

As Electricians, you are only interested in providing power to the outside unit(s), so just follow the label on the outside unit. Don't install a "GFCI" they are exempted per NEC 210.8(F), until September 1, 2026. The NFPA has a task force on this tripping problem(s)

As for me and other installers, this is the steps to follow:
1) Complete a "Heat Load" engineering study of the structure, this will tell you how much tonnage each room will need. Don't use the "Rule of Thump" per square foot, that is just an estimate.
2) Install the outside & inside unit(s).
3) Run the cable(s) from the outside unit(s) to the inside unit(s) and refrigerant line(s). Use the Daikin Matrix below
4) Most homes require two outside units, maximum four inside units per unit.
5) File a permit.

 

[hbiss]

As Electricians, you are only interested in providing power to the outside unit(s), so just follow the label on the outside unit.

-Hal

 

[tortuga]

As Electricians, you are only interested in providing power to the outside unit(s), so just follow the label on the outside unit.

The calculated load on a branch circuit has to include all the connected loads if the inside units are not included in the MCA of the outside unit are you saying the person responsible for the electrical permit need not consider that load?

 

[mtnelect]

The calculated load on a branch circuit has to include all the connected loads if the inside units are not included in the MCA of the outside unit are you saying the person responsible for the electrical permit need not consider that load?

Daikin has done the engineering on what inside unit(s) will work with the outside unit(s) and provided the matrix for the installer to select from. The Electrician just needs to follow the label on the outside unit(s).

 

[electrofelon]

Daikin has done the engineering on what inside unit(s) will work with the outside unit(s) and provided the matrix for the installer to select from. The Electrician just needs to follow the label on the outside unit(s).

We seem to be going around in circles. So are you saying the MCA on the outdoor unit includes the indoor units? Yes or no? If yes, can you explain where it is in the nameplate shown in post #6. If no, can you explain which code section allows us to ignore the load of the indoor units?

 

[hbiss]

So are you saying the MCA on the outdoor unit includes the indoor units?

YES!! They are included in the numbers given on the outdoor unit which also powers the indoor units which are part of the complete manufactured package.

If yes, can you explain where it is in the nameplate

Why would it be itemized separately on the nameplate? The outdoor unit and indoor units are a package.

Why is this so difficult to understand??

 

[electrofelon]

YES!! They are included in the numbers given on the outdoor unit which also powers the indoor units which are part of the complete manufactured package.

Why would it be itemized separately on the nameplate? The outdoor unit and indoor units are a package.

Why is this so difficult to understand??

Actually no, they are not a package. You buy the components separately, and there are multiple different ways to configure a complete system.

Also note Tortuga said that Daiken said the indoor units were not included. You seem to be very adamant about your position. I really don't care either way, I just want clarification on which it is. Based on the wording of the data plate, and what Tortuga said it appears to me they are not included.

 

[wwhitney]

So are you saying the MCA on the outdoor unit includes the indoor units? Yes or no? If yes, can you explain where it is in the nameplate shown in post #6.

If the indoor units are fed 240VAC taken straight from the terminals on which the outdoor unit's supply conductors are landed, then it is clear to me that the MCA on the outdoor unit does not include the indoor units for the unit discussed in post #6, per the accounting there.

But it is possible that the power for the indoor units comes from the output side of the "Compressor Drive" (which I assume is a VFD), in which case the MCA on the outdoor unit does include the power for any approved set of indoor units.

Cheers, Wayne

 

[electrofelon]

If the indoor units are fed 240VAC taken straight from the terminals on which the outdoor unit's supply conductors are landed, then it is clear to me that the MCA on the outdoor unit does not include the indoor units for the unit discussed in post #6, per the accounting there.

But it is possible that the power for the indoor units comes from the output side of the "Compressor Drive" (which I assume is a VFD), in which case the MCA on the outdoor unit does include the power for any approved set of indoor units.

Cheers, Wayne

Or it could be included in "fan motor drive"

 

[tortuga]

I really don't care either way, I just want clarification on which it is. Based on the wording of the data plate, and what Tortuga said it appears to me they are not included.

Same here, I don't really have any more to add than post 6 &7, i appreciate the feedback that I am not the only one confused.
And all those numbers sure just don't add up for me with the largest options, I'd just love to see how they arrived at 18.1 Amps with all that equipment, admittedly its a academic question as its only off by an amp or less.

YES!! They are included in the numbers given on the outdoor unit which also powers the indoor units which are part of the complete manufactured package.

Thats what I was always taught also what I expected to see and I do appreciate the feedback Hal confirming that's what you expect also.
Obviously thats not the case on every HVAC system just theses mini splits, a ducted forced air system where the indoor (air handler / filter / condensate pump) and outside heatpump are on two separate 240V circuits, with 24V controls between.
I even see mix and match different brands heatpump with older air handlers that were previously oil or something.

 

[mtnelect]

We seem to be going around in circles. So are you saying the MCA on the outdoor unit includes the indoor units? Yes or no? If yes, can you explain where it is in the nameplate shown in post #6. If no, can you explain which code section allows us to ignore the load of the indoor units?

Attached is the Installation Manual for Daikin, showing the electrical wiring between the outside unit and the two inside units. Only one 240-volt dedicated circuit is required to the outside unit and the two cables feeding the inside units. This is the same, whether there is one or four inside units.

Other manufacturers of ductless systems could be different, and that is why reading the Installation Manual first is very important.

 

[pipe_bender]

Gotta love the detail in that one seen it many times LOL
For the supply to the outdoor unit:
"Safety devices in accordance with local and national codes, i.e. a circuit breaker"

Huh I need a circuit breaker wow! Thanks for the tip.

Connections between indoor and outdoor units:
"Recommend using AWG 14, stranded and insulated wire for connections between indoor and outdoor units. Local code always supersedes recommendation."

Ok fascinating so 14 AWG and insulated wire great info lots of detail worth the read glad we checked boss.

 

[hbiss]

Thats what I was always taught also what I expected to see and I do appreciate the feedback Hal confirming that's what you expect also.
Obviously thats not the case on every HVAC system just theses mini splits, a ducted forced air system where the indoor (air handler / filter / condensate pump) and outside heatpump are on two separate 240V circuits, with 24V controls between.

Well, mini splits are what we are talking about here.

The ducted systems you mention are the conventional systems that we have installed forever. Supply power with disconnect to the outdoor unit according to the MCA/MOP on the label. Supply power with disconnect to the indoor air handler according to its label. Provide 24V control wiring between them and a thermostat.

Heat pumps vs straight AC just have reversing valves in the outdoor unit that change over from AC to heat. Nothing for us to be concerned about.

But of course, if the installation is outside of these two general categories especially, read the manuals.

-Hal

 

[electrofelon]

Attached is the Installation Manual for Daikin, showing the electrical wiring between the outside unit and the two inside units. Only one 240-volt dedicated circuit is required to the outside unit and the two cables feeding the inside units. This is the same, whether there is one or four inside units.

Other manufacturers of ductless systems could be different, and that is why reading the Installation Manual first is very important.

Thanks, but You didn't answer my question.

 

[wwhitney]

One data point: I looked at the Technical and Service Manual for Mitsubishi MXZ-SM??NAM-U1, where ?? is 36, 48, or 60 (3-5 tons). These outdoor units support 2-4 to 2-8 indoor units (depending on tonnage). The MCA in the manual is specified as:

29 A (When power is supplied separately)
35 A (When power is supplied from the outdoor unit)

Presumably that refers to power to the indoor units.

https://hvacdirect.com/media/pdf/Mitsu-Condenser-Service-Manual.pdf?srsltid=AfmBOoq1UhRFdXRTtcBSnfb6zCNpmf3IKRwXdWpaiQHwAAY4e-qwj0eO

Cheers, Wayne