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While on and off is all that is needed I have seen a lot more provided such as fault codes and stutus of the other unit.
Disco, Mitsubishi mini splits.
- Thread starter chris kennedy
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Thank you for your efforts, gar!
If the only information there is a contact closure, then making the open condition the OFF state will allow a "wired OR" logic so that any one indoor unit can command the outdoor unit to turn on. But if the system is set up for heating and cooling (heat pump) then there would have to be additional information, since the reversing valve would have to be at the compressor end. No way to put it at the inside unit only.
And, of course, there is no way to have one inside unit heating and another one cooling. They all have to operate in the same mode at one time.
If the only information there is a contact closure, then making the open condition the OFF state will allow a "wired OR" logic so that any one indoor unit can command the outdoor unit to turn on. But if the system is set up for heating and cooling (heat pump) then there would have to be additional information, since the reversing valve would have to be at the compressor end. No way to put it at the inside unit only.
And, of course, there is no way to have one inside unit heating and another one cooling. They all have to operate in the same mode at one time.
goldstar
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kwired
Electron manager
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Only one side of the relay coil (located in the outdoor unit) is opened the other one is backfeeding 120 volts to ground coming from the opposing input line of the supply.
Gar explained it fairly well.
Psychlo
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Thanks to everyone for all of the varying points of view and different angles on this topic. I've read through all of the posts here and have emerged with the following questions:
Doesn't 440.3(B) tell us to refer to articles 422, 424, and 430 specifically for "fan coil units", etc.? IMO, this paragraph is directly relevant to these indoor mini split units.
So if we are directed to 430, then I must assume that 430.109(B) applies - since these units (at least all of the ones I've encountered) are well below 1/8 hp. Isn't that the whole point of 430.109(B) - to eliminate the disconnect requirement for small motors? For our purposes, these indoor units are simply small fan motors.
To me, it's not much different than having an inline duct fan installed to boost the air flow in a ducted system. Would someone insist on having a disconnect within sight of a (<1/8 hp) inline duct fan? It's still part of the overall HVAC system. In fact, it may even derive its power from the air handler circuit. But it has nothing to do with any compressor motors. (also, as an aside, consider a motorized damper -need a disco?)
Well, same with the mini split indoor units. They simply blow air, and have nothing to do with a compressor motor. Why would 440 apply to them at all? It wouldn't, necessarily. Hence 440.3(B), which refers us elsewhere for such units, namely to Appliances (422) and Motors (430). If all other <1/8 hp motors are exempt from requiring a disconnect, why not these, too?
The way I see it, the intent is safety. A lockable disconnect (if it is used!) at the outdoor unit is totally adequate to ensure the desired safe conditions for servicing the indoor unit.
Doesn't 440.3(B) tell us to refer to articles 422, 424, and 430 specifically for "fan coil units", etc.? IMO, this paragraph is directly relevant to these indoor mini split units.
So if we are directed to 430, then I must assume that 430.109(B) applies - since these units (at least all of the ones I've encountered) are well below 1/8 hp. Isn't that the whole point of 430.109(B) - to eliminate the disconnect requirement for small motors? For our purposes, these indoor units are simply small fan motors.
To me, it's not much different than having an inline duct fan installed to boost the air flow in a ducted system. Would someone insist on having a disconnect within sight of a (<1/8 hp) inline duct fan? It's still part of the overall HVAC system. In fact, it may even derive its power from the air handler circuit. But it has nothing to do with any compressor motors. (also, as an aside, consider a motorized damper -need a disco?)
Well, same with the mini split indoor units. They simply blow air, and have nothing to do with a compressor motor. Why would 440 apply to them at all? It wouldn't, necessarily. Hence 440.3(B), which refers us elsewhere for such units, namely to Appliances (422) and Motors (430). If all other <1/8 hp motors are exempt from requiring a disconnect, why not these, too?
The way I see it, the intent is safety. A lockable disconnect (if it is used!) at the outdoor unit is totally adequate to ensure the desired safe conditions for servicing the indoor unit.
I approached that subject at an IAEI meeting and the consensus of opinions was that 430.109(B) did allow the branch circuit OC device to be the disconnecting means but that was the "type" of disconnect and did not remove the requirement of 430.102 for the location to be in sight from the motor.
Psychlo
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I'm not quite following. If the disconnect isn't required at all, as per 430.109(B), then there is no "within sight" rule to apply, correct?
I fail to see where 430.109(B) tells that a disconnect is not required. As I read it, 430.109(B) simply allows the branch circuit overcurrent device to serve as the disconnecting means.
430.102 still requires to 430,109 disconnect to be within sight whether it be a type (B)(C)(D) etc..
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I agree.
wwhitney
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I agree that is how it reads. But with that interpretation of 430.109(B), what section provides relief for the "in sight" requirement of 430.102(A) for, say, the snap switch controller of a bath fan?
Cheers, Wayne
IMO, the snap switch qualifies as a disconnect under 430.109(C)(2) but would still need to be "in sight from". In the event the snap switch (or any other 430.109 disconnect) is not in sight then another disconnect means would be needed. In the case of the small bath fan, many of them actually plug in within the housing (in sight from the motor) so 430.109(F) applies also.
wwhitney
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I guess I was thinking that the snap switch is the motor controller under 430.83(C), and as such would require its own disconnect under 430.102(A).
Cheers, Wayne
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Yeah we always used DP snap switches. They look much neater than a pullout or other type of switches.
wwhitney
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OK, on the topic of 430.109(B) , what is wrong with the following logic:
1) A dumb bath fan is wired with a single switched supply controlled by a snap switch.
2) That snap switch clearly meets the definition of 'controller' at the beginning of Article 430.
3) 430.102(A) requires an in-sight disconnect for a motor controller.
4) Nobody installs a separate in-sight disconnect for such a snap switch.
5) So some other section in 430 provides relief from the 430.102(A) requirement in this situation.
6) 430.109(B) is the only section that could do the job.
7) Therefore 430.109(B) negates the "in-sight" requirement of 430.102(A).
8) 430.109 applies to both motor and controller disconnects, which means 430.109(B) also negates the "in-sight" requirement of 430.102(B)(1).
I don't really have an opinion on this matter, the above was just my understanding of 430.109(B) before posts 69 and 70 in this thread.
Cheers, Wayne
1) A dumb bath fan is wired with a single switched supply controlled by a snap switch.
2) That snap switch clearly meets the definition of 'controller' at the beginning of Article 430.
3) 430.102(A) requires an in-sight disconnect for a motor controller.
4) Nobody installs a separate in-sight disconnect for such a snap switch.
5) So some other section in 430 provides relief from the 430.102(A) requirement in this situation.
6) 430.109(B) is the only section that could do the job.
7) Therefore 430.109(B) negates the "in-sight" requirement of 430.102(A).
8) 430.109 applies to both motor and controller disconnects, which means 430.109(B) also negates the "in-sight" requirement of 430.102(B)(1).
I don't really have an opinion on this matter, the above was just my understanding of 430.109(B) before posts 69 and 70 in this thread.
Cheers, Wayne
kwired
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If a component meets definition of both controller and disconnecting means it can serve both purposes.
A motor with internal overload protection can be controlled by the branch circuit device, same device can also be the disconnecting means if within sight (or if any exceptions allowing it to be remote are met).
wwhitney
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430.102(B)(2) allows the controller to be the motor disconnecting means, with conditions. But the controller still needs its own 430.102(A) disconnecting means, doesn't it?
Are you suggesting that the branch circuit OCPD is the bath fan motor controller, and the snap switch is just the bath fan motor disconnect? The snap switch clearly meets the definition of motor controller:
NEC 2011 Article 430 said:
Cheers,
Wayne
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kwired
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I see the source of your confusion - you are using 2012 NEC, which NFPA doesn't have such edition:happyyes:
But seriously, I think a switch can be both controller and disconnect in some instances - and not need an additional controller disconnect.
wwhitney
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In case post 75 was too long, here's my question in an nutshell. A common residential installation is:
Branch OCPD -- Branch circuit -- Snap switch -- Switched Power -- Bath Fan
The snap switch is the motor controller [430.83(C)(2)] and the motor disconnect [430.109(C)(2)]. The motor controller requires its own disconnect under 430.102(A). The only disconnect provided is the Branch circuit OCPD, which is probably not in sight of the motor controller. So what section provides relief from the "in-sight" requirement of 430.102(A)?
The relevance of this question is that I thought it was 430.109(B). But per posts 69 and 70, it does not. In which case what does?
Thanks,
Wayne
Branch OCPD -- Branch circuit -- Snap switch -- Switched Power -- Bath Fan
The snap switch is the motor controller [430.83(C)(2)] and the motor disconnect [430.109(C)(2)]. The motor controller requires its own disconnect under 430.102(A). The only disconnect provided is the Branch circuit OCPD, which is probably not in sight of the motor controller. So what section provides relief from the "in-sight" requirement of 430.102(A)?
The relevance of this question is that I thought it was 430.109(B). But per posts 69 and 70, it does not. In which case what does?
Thanks,
Wayne
wwhitney
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Thanks, I fixed it. I was looking at the 2012 UPC and IBC earlier today.
Agreed, per 430.111. I assume a snap switch is an air-break switch under 430.111(B)(1)?
This is my sticking point--430.111 does not explicitly say that. Is there some other reference?
Thanks, Wayne
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