Electrician Talk banner

Demand factors/ feeder size: small cabins

894 Views 20 Replies 11 Participants Last post by  electricguy
Hey y'all, I'm trying to determine the feeder sizes for a couple of tiny cabins that a client is putting on their property. They are incredibly small- like 100sq', but they plan to rent them out. (Not a tiny house on wheels)

I'm not sure how to classify them: dwelling unit? apartment?

They have a 500 watt heater, LED lights, 20 amp/120 volt circuit for a kettle/ hot plate, and a bar fridge. No hot water, no other appliances.

Basically just a shed, but since someone will sleep in there, is it considered something else?
Can I just feed it with 20 amps,120/240? and calculate for voltage drop?

I appreciate your feedback. Thanks
1 - 20 of 21 Posts

· Registered
Power distribution and controls
Joined
·
2,932 Posts
It does not matter what we choose to classify them as. It matters to the AHJ.

I would never do an assumed underground feed for more than one of anything and do it at 120v.
Why would you deliberately imbalance the owners service.?

No hot water, no place to take a shower. Not even on my list of places that I would stay unless the owner was paying me to stay there. What about a toilet?

Rental, fire code? Bet the FA system will cost a bloody fortune to pass the local fire code, then there are fire sprinklers which could be mandatory. They are here for human rental spaces.
 

· Conductor Protector
Joined
·
267 Posts
Discussion Starter · #3 ·
It does not matter what we choose to classify them as. It matters to the AHJ.

I would never do an assumed underground feed for more than one of anything and do it at 120v.
Why would you deliberately imbalance the owners service.?

No hot water, no place to take a shower. Not even on my list of places that I would stay unless the owner was paying me to stay there. What about a toilet?

Rental, fire code? Bet the FA system will cost a bloody fortune to pass the local fire code, then there are fire sprinklers which could be mandatory. They are here for human rental spaces.
 

· Conductor Protector
Joined
·
267 Posts
Discussion Starter · #4 ·
Oh for five cents, I wasn't looking for whether or not it's a place you would like to stay- I wouldn't either...
As for the owner's insurance and how basic it is- that is up to them.
said I'd be feeding them with 120/ 240, not 120- system stays balanced. Heater is 240.
I'm just looking for how to classify this type of structure as per the CEC, so as to feed it appropriately/ minimally.
I can ask the inspector tomorrow, but it's a holiday today and I'm trying to price this out, so I'd love helpful input.
Cheers and happy thanksgiving to the Canadians
 

· Light Bender
plumber
Joined
·
7,520 Posts
I don’t think one 20 amp circuit is enough.
Maybe two 15 amp circuits to each would be better. (Heater separate of course)

arc fault does not apply here, it’s not a dwelling unit, so you can run a mwbc. (Technically is a residential occupancy)

smoke detectors for sure as people will be sleeping in there.
 

· Hackenschmidt
Joined
·
14,409 Posts
I thought the OP said 120/240 meaning a three wire multiwire branch circuit to the cabin. By the NEC I believe there's nothing stopping you from putting 240V and 120V outlets on that circuit. With a 500w baseboard heater using 2A I would think you could install one or more split receptacles with top on A and bottom on B.

@eddy current is right - I'd want a smoke and carbon monoxide detector, people do stupid things with CO when camping. I'd also put a receptacle outside to discourage running cords through the door.

It would be nice if they could reset their own breakers.
 

· Conductor Protector
Joined
·
267 Posts
Discussion Starter · #7 ·
Thanks Eddie, I was hoping you might be on. I should have said the cabins will each have a MLO load centre. A circuit for heat, 20 amp plugs (2 on 1 cct.) fridge (mini), and lights/ 15 amp plug (1)- I was planning to do AFCI. Smoke- yes.

Just wondering if ok to feed with 20 amps on MWBC/ 12/3 Teck considering v.drop.

What makes it not a dwelling unit? no kitchen? Reading the definitions of dwelling unit/ residential occupancy does make it seem more like the latter, so thanks for that and whatever else you might add. I appreciate it.
Cheers.
 

· Registered
Joined
·
1,261 Posts
I think you need a frank discussion with your AHJ if this is even a viable job.

What you're describing is becoming popular in my area because there's a housing problem. 100sqft often avoids building permits. Accessory dwellings may not even be legal per zoning. They probably have to be treated like garden sheds.
 

· Registered
Master Electrician - Ontario
Joined
·
4,181 Posts
If anything, I think I would run a 100 amp exterior panel somewhere convenient and treat them as a portable structure. I would have an RV type receptacle, probably 30 amps (except 120/240) male on the building and some sort of receptacle that matches near the 100 amp panel. I would just plug the building in an out as they are being used since you have an MLO panel inside.

Failing that as a viable option, I would still run the 100 amp out there, then feed UG with a 30 amp 120/240 to the MLO. In Ontario you would need a disco in that case, that is why I suggested the cord option previously.

Plus 1 on the smoke / CO. I might also consider putting some sort of horn on the exterior so if the smoke does go off, people in the house are alerted. and can render assistance if needed.

I forgot to answer the part about the load... I would just do a square footage and known loads and be done with it... there is no way it will use more then 30 amps.

Cheers
John
 

· Registered
Joined
·
359 Posts
I thought the OP said 120/240 meaning a three wire multiwire branch circuit to the cabin. By the NEC I believe there's nothing stopping you from putting 240V and 120V outlets on that circuit. With a 500w baseboard heater using 2A I would think you could install one or more split receptacles with top on A and bottom on B.

@eddy current is right - I'd want a smoke and carbon monoxide detector, people do stupid things with CO when camping. I'd also put a receptacle outside to discourage running cords through the door.

It would be nice if they could reset their own breakers.
Our code requires heating to be on separate circuit.
 

· Conductor Protector
Joined
·
267 Posts
Discussion Starter · #12 ·
I guess maybe I was not clear. All circuits in cabin on breakers in panel inside cabin. The baseboard heater would be on it's own circuit. 2 pole breaker. MLO panel, so no main disco. Will be fed from outdoor 3R panel approx 60' away. Where does it say this needs a main?

It kind of is a portable structure, but since it's not on wheels it's ok in BC to connect to power. It will sit on blocks or something. Our AHJ for electrical is totally separate from the building department. I don't care about building codes etc- that's the client's problem- I only need to meet our code with TSBC.

I thought about doing what Navy guy suggested, but I didn't want to go 30 amp 120V RV receptacle due to wire cost/ balancing of load, and 50 amp 120/240 is overkill. More power available at 20 amps 120/240 than [email protected] 120 anyway.

I guess I'll wait and see what the inspector says, but hope to see more constructive comments.
Thanks
 

· Registered
Rezy jman
Joined
·
168 Posts
I would be tempted to go to 30a if I were you, someone has a kettle on and turns on the hot plate your going to be pushing 20a without considering the heater. They are both probable 1200 - 1500w each so if both are on your pushing that 20a breaker. For peace of mind I'd probably go 30a and not worry about voltage drop if it's only 60' away from main panel.

Also I would consider it a Dwelling unit if it has sleeping and cooking appliances.
 

· Super Moderator
Florida, USA
Joined
·
9,245 Posts
I wouldn't worry about classification unless it comes up. The load is the load, right?
Hunting camp? Fishing camp? Missionary retreat? Who knows and who cares? Sounds like you have a plan.
Run off a 2 pole 30A breaker w/ 10-3 to that MLO panel and they'll be fine, right?

I like the outdoor receptacle plan. Need to power that leaf blower on the campfire, right? A radio, who knows...
 

· Registered
Master Electrician - Ontario
Joined
·
4,181 Posts
I thought about doing what Navy guy suggested, but I didn't want to go 30 amp 120V RV receptacle due to wire cost/ balancing of load, and 50 amp 120/240 is overkill. More power available at 20 amps 120/240 than [email protected] 120 anyway.
I agree, that is why I suggested an RV type receptacle at 120/240. A standard RV receptacle is only 120 volts. Maybe I should have said a generator type instead (L14-30). On my trailer (18' tandem axle) for job sites I have a 30 amp 120/240 volt twistlock (L14-30) receptacle male and a cord that is used to plug into a 30 amp 120/250 volt female receptacle located on the site. This runs my lights and my 240 volt heater.

Cheers
John
 

· Super Moderator
Florida, USA
Joined
·
9,245 Posts
Inspector says no built in appliances, not a dwelling unit. No minimum amps. No need to use RV receptacle and cord. I'm going with 30 amps 120/240. thanks guys
Sounds like you made out real good with the inspector.

Are you going to do smoke/ CO since they're sleeping in there? Can't see the owner arguing over that cost.
 
1 - 20 of 21 Posts
Top