First split a/c install

[mark32]

A buddy changed his mind from installing a spa to a Mitsubishi split a/c unit. The a/c will be set about 15' from the house, I already have 1"pvc running out there which lb's into the house and into the panel a short distance from there. So what are you guys doing out there as far as powering the blower unit? I've read bits and pieces on here but nothing too complete on the topic. Maybe swap out the lb for a j-box and pipe up the wall with the blower power (Coming from the a/c unit). What about the t-stat cable, I could just reclassify the control circuit and use thhn when I pull it from the house to the condensing unit, right?

 

[Dennis Alwon]

It really depends alot on the units. Many of the units we just power the outdoor a/c and the heating guys run thermostat wire to the blower. These units are a 24V DC motor. Some of the units have backup heat in which case you need to power the unit inside as well. I would call the a/c guy and get the info on the unit.

The t-stat is usually a part of the remote control

 

[stickboy1375]

Depending on the unit you get to wire, The ones I have been doing require a feed to the outside unit, disconnect, etc... then a 3 wire interconnect wire... I supply 14-3 UF with ground for this connection. and I generally just follow the line set to the indoor unit, and the remote is the Tstat, no other wiring is involved. almost forgot disconnect is required at the indoor unit as well.

 

[mark32]

Thanks Dennis and Stickboy, yeah I was wondering about a disc for the indoor unit. I've seen a number of these installed but I don't recall seeing a shut off for one.

 

[stickboy1375]

Thanks Dennis and Stickboy, yeah I was wondering about a disc for the indoor unit. I've seen a number of these installed but I don't recall seeing a shut off for one.

All the units I've installed have only required a 2 pole disconnect even though 3 wires are present, two of the wires are 240volts, I really have no idea what voltage is on the control part of the circuit, if any....

 

[hbiss]

The ones I've seen call for all three wires to be disconnected "if required". (If you only did two how would you know which ones? From what little I can tell they are all hot.) All indoor units operate with the same voltage as the outdoor supply. Try to find a 3 pole switch that doesn't look like a manual starter so that's not going to happen on a living room wall. That's why disconnects for the inside units are not enforced around here. I would also read the instructions because at least one manufacturer prohibits the 3 wire from the outdoor unit to the indoor unit from being run with the supply. Not because of different voltages but because there is also some kind of communications on it in addition to the power for the indoor unit and they are worried about inteference. So use separate conduits. There is no thermostat or thermostat wire, temperature control is built into the indoor unit and you control it with an infrared remote like your cable box. Heating mode is a heat pump, there are no heating elements.

-Hal

 

[stickboy1375]

The ones I've seen call for all three wires to be disconnected "if required". (If you only did two how would you know which ones? From what little I can tell they are all hot.)
-Hal

Simple, I read the instruction manual. Only a 2 wire disconnect was required, the third conductor was spliced through, they are labeled 1, 2, (240volts) and 3... The number 3 terminal turns the outdoor unit on and off with a call for heat/AC, I as stated, I don't know what voltage is on this 3rd terminal if any.


Here... page 16 http://us.sanyo.com/dynamic/product/Downloads/30.36KHS82 Installation Instructions-39363246.pdf

 

[renosteinke]

While the blower unit can be powered separately, it is usually powered from the outside unit. That's why so many of thise little fans are 230 volts- just like the outside unit.

That is, you run a power cable and a thermostat cable from the outside unit to the inside of the house. Whether the thermostat cable goes to the thermostat, or to the blower unit, depends on the specific equipment. Read the instructions - they're probably on the manufacturers' site.

One detail to keep in mind is: what happens to the condensate from the indoor unit? While the AC guy can usually just run a drain line, sometimes he also needs to instal a condensate pump, andyou'll need to provide power for that.

 

[mark32]

Thanks again guys. Finally found the install manual and it does show all three lines for the inside unit being disconnected if *required*. There's nothing about running separate raceways for the condenser unit feed and the blower feed which is good because they'll both be in the same pipe on this one. Guess I'll have to find a single throw triple pole switch now. Thanks for the heads up on the condensation issue, I'll have to ask my buddy if he has any plans for that.


Found it:

http://www.amazon.com/Leviton-MS303-DS-Three-Pole-Disconnect-Non-Grounding/dp/B002MPPT3Y

 

[iwire]

Guess I'll have to find a single throw triple pole switch now. Thanks for the heads up on the condensation issue, I'll have to ask my buddy if he has any plans for that.


Found it:

http://www.amazon.com/Leviton-MS303-DS-Three-Pole-Disconnect-Non-Grounding/dp/B002MPPT3Y

Exactly the kind we use for these indoor units, we install a 4" square box with a single gang mud ring and when it is all said and done it looks almost like a regular switch, much better looking than a non-fused disconnect etc.

 

[hbiss]

Those are what I was talking about too. I think we would get plenty of flack if we put that on the wall below the indoor unit with the rest of the room Decora. Really, I can't see why the manufacturer can't incorporate a disconect under the cover. Could be as simple as a connector.

-Hal

 

[stickboy1375]

Thanks for the heads up on the condensation issue, I'll have to ask my buddy if he has any plans for that.


F

The indoor unit is always mounted high, but regardless, they just hard pipe a 3/4 pvc drain out with the line set... not a big deal.

 

[stickboy1375]

Those are what I was talking about too. I think we would get plenty of flack if we put that on the wall below the indoor unit with the rest of the room Decora. Really, I can't see why the manufacturer can't incorporate a disconect under the cover. Could be as simple as a connector.

-Hal

I've been questioning this for awhile... just use a molex connector and be done with it... I love how plumbers insist a disconnect isn't required simply because they have never seen one installed to code before. :roll:

 

[KWH]

Split System

Split System

I have done 2 ( Mitisbushi ) that just required a 3wire m/c cable between inside and out. The third one ( brand unknown ) the Hvac installer had me install #14 stranded conductors for control which was d/c saying any other wire size or solid would not work right. The job was time and material just not sure why the difference.

 

[hbiss]

HVAC guys, like plumbers are not known for their electrical expertise.

-Hal

 

[Dennis Alwon]

I have not seen a disconnect required for the DC motors as they are quite small. However, I have taken a feed to an inside switch by the unit, run the switch leg to the outside disco and then a 3 wire back to the inside unit from the outdoor unit. Basically you have 2 DP switches in parallel. either one will disconnect the units.

 

[mark32]

After going through the install manual for the outdoor unit I see it says "max fuse 20a" for the ocp. Initially I was just going to use a non fusible disc but I recall reading somewhere that if the instructions say fuse you must use a fuse, forcing me to use a fusible disc in this scenario. Can anyone confirm this?

 

[stickboy1375]

After going through the install manual for the outdoor unit I see it says "max fuse 20a" for the ocp. Initially I was just going to use a non fusible disc but I recall reading somewhere that if the instructions say fuse you must use a fuse, forcing me to use a fusible disc in this scenario. Can anyone confirm this?

Generally they say max fuse OR breaker, I would look at the actual unit for this info.

 

[mark32]

Good call Stickboy, I'll just bring both disconnects when I go do the job. Perhaps the unit itself with say fuse OR breaker as you've stated.

 

[mark32]

Well I finished the job, here's a summary. First the 3 pole sw for the inside unit. After some thought, prior to installation, I was going to run #14 from the condensing unit to the indoor unit as was stated elsewhere here, but why I thought, there's no internal ocpd for the conductors feeding the indoor unit so I must run #12 right? So I look at the largest single gang cut in box and it's only rated for 8 #12's, I needed 9 so I had to cut in a two gang Second, as you'll see in one of the pics, I could have used a fused disc or a hacr breaker, however, I didn't see such a rating on the CH breaker I was to install so I went with the fused disc. Lastly, the install came out quite nicely, but here's what happens when you lose your focus as you'll see in the pic below. I had purposely pulled into the disc extra wire for the indoor unit so I could pass them right through the disc and into the condensing unit. Well an hour later I go to finish off the disc and I look at my watch. Hmmm, I'm suppose to pick up my son from daycare. I was running a bit late and I instantly had the image my wife would be calling me at any moment saying I had to pick him up and what was taking so long, blah blah. At that point I cut the wires short and had to splice them, doh. Bonus pic of some screws (Three seen in the photo) my buddy had unintentionally and unknowingly screwed right into the back of the panel from the outside wall where he mounted a piece of wood. Question, could I have used #14 for the indoor unit?