|
| Author |
Message |
Borrego
Member
|
# Posted: 20 Feb 2017 01:17pm
Reply
I actually want to install (2) transfer switches...1 at my regular residence which is on-grid to use for temporary power outages, and 1 for our cabin which is off-grid.
The on-grid one would be used to run a fridge, couple light circuits, that all, in the event of emergencies.
The cabin would be tied into the generator/solar setup.
Do I need a different type for each application? Or can I just buy two of the same? And any recommendations are welcome!
|
|
MtnDon
Member
|
# Posted: 20 Feb 2017 02:09pm
Reply
If the cabin is not grid tied and is not subject to inspections you can likely get away with using one of the RV type transfer switches as long as the 30 or 50 amp capacities will cover the loads.
The grid tied home will need a code approved transfer switch. And it will need to have capacity to transfer the entire service capacity of 100 to 200 amps even if the generator can only supply 16 amps. Then the problem becomes ensuring that no big loads are turned on when the tiny output generator is connected.
|
|
Steve_S
Member
|
# Posted: 20 Feb 2017 02:45pm
Reply
Borrego, for your cabin, what kind of Charger Controller & Inverter do you have ? Does either monitor the battery bank and does it have capacity to send a low signal to an ATS ? Some do, some don't. Might be worth checking as that would affect your choice of ATS.
|
|
bldginsp
Member
|
# Posted: 20 Feb 2017 03:14pm - Edited by: bldginsp
Reply
Quoting: MtnDon And it will need to have capacity to transfer the entire service capacity of 100 to 200 amps
I don't believe that's true. You can run a set of feeders off the main service at whatever size you want with the correct breaker ahead of the feeders. Say 30 amp if it's just reefer and lights. The transfer switch is in those feeders before the small subpanel that has breakers for the individual circuits. If you run too much load the breaker in the generator breaker will throw. A smaller transfer switch will cost a lot less.
As to what type of transfer switch you use, you can use anything you want so long as it's listed (approved) and you are using it within its capacity and correctly connected. They make all kinds- you may choose an automatic transfer switch for the grid tie, and if your generator has a starter it can be set to start up automatically. At the cabin a simple manual transfer switch would probably be enough. Locate it near the genset and throw it when you start the generator.
To maintain your circuit breaker safety system, be sure you don't disconnect the bond of ground to neutral, wherever it is located.
|
|
MtnDon
Member
|
# Posted: 20 Feb 2017 06:40pm
Reply
Yes, that is correct about the transfer switch, bldginsp, although that may mean chopping into the wiring to isolate only those circuits that are to be generator powered.
|
|
Borrego
Member
|
# Posted: 20 Feb 2017 09:11pm
Reply
Quoting: MtnDon although that may mean chopping into the wiring to isolate only those circuits that are to be generator powered.
That is what I intend to do. This will not be inspected. At either property.
|
|
toyota_mdt_tech
Member
|
# Posted: 20 Feb 2017 09:26pm
Reply
https://www.interlockkit.com/
|
|
bldginsp
Member
|
# Posted: 20 Feb 2017 09:51pm
Reply
"Chopping" is not necessary. The transfer switch goes next to the service panel or sub panel, you disconnect as many circuits as you need to at the breakers, remove those breakers, put in a single breaker for the transfer switch then connect the circuits to the switch. In effect it's just a separate sub panel for those circuits, with an alternate power source. Here's a common one:
http://www.homedepot.com/p/Generac-30-Amp-Indoor-Generator-Transfer-Switch-Kit-for-6- 10-Circuits-6294/203835641
There's nothing illegal or untoward about this, you're just installing another piece of equipment. But with all transfer switches if not wired correctly there are dangers- particularly retaining the main bonding jumper- so it's a good idea to have an experienced pro do it if you are not sure.
|
|
|
razmichael
Member
|
# Posted: 20 Feb 2017 10:09pm
Reply
Can't you just use a generator subpanel like
subpanel
"The generator panel features 2 factory-installed main circuit breakers and a mechanical interlock to help ensure that only 1 main circuit breaker is in the on position at any time".
We have one installed at our house along with an outdoor generator socket. Lot cheaper although it is a manual system.
|
|
creeky
Member
|
# Posted: 20 Feb 2017 10:38pm
Reply
For off grid I liked the powermax. The one I have has worked well for years. I don't use it often tho. Maybe 50 times a year during the cold/dark early winter.
Not at all this year. Lithium batteries rule.
|
|
bldginsp
Member
|
# Posted: 20 Feb 2017 11:06pm
Reply
Quoting: razmichael Can't you just use a generator subpanel
That is a transfer switch
|
|
Mike 870
Member
|
# Posted: 21 Feb 2017 08:56am
Reply
I did mine the way bldginsp describes. I got a separate subpanel, put it right next to my main load center. Removed the circuits I wanted to be able to run on backup power and put them into the new subpanel. In the new load center there are two breakers with a tie so that when one is off the other is on. This is the low tech manual transfer switch. One brings power from the main load center, the other from the generator. Neither can be on at the same time so back feeding is prevented. I used QO-D breakers.
|
|
bldginsp
Member
|
# Posted: 21 Feb 2017 09:11am
Reply
There are many such smaller transfer switches for the purpose, because it is the primary reason people would use a transfer switch- to power just a few circuits in a power outage. Hospitals don't transfer just a few circuits though, so they have huge switches to connect to large generators. Different ballpark.
Most such switches do not switch the neutral. Such a switch should be used with a generator that does not bond ground and neutral. Otherwise, you have two bonds to ground and neutral, one at the service and one at the generator. This can energize the ground system on the generator with neutral current when the generator is not being used, or energize the ground system on the service with neutral current when the generator is being used. Neutral current has high amperage, but low voltage, and can still kill you.
Rules of thumb-
-if the transfer switch does not switch the neutral, disconnect the ground/neutral connection at the generator, but keep the ground system connected to the frame of the generator.
-if the transfer switch does switch the neutral (rare), connect the ground and neutral at the generator (and service) and keep everything metal connected to the ground system (always).
If you don't understand this, hire an electrician who does. (not a handiman who has never done it).
|
|
Borrego
Member
|
# Posted: 21 Feb 2017 09:35am
Reply
Quoting: toyota_mdt_tech https://www.interlockkit.com/
Thanks!
Quoting: bldginsp If you don't understand this, hire an electrician who does. (not a handiman who has never done it).
Good advice!
|
|
Atlincabin
Member
|
# Posted: 21 Feb 2017 12:08pm - Edited by: Atlincabin
Reply
So, any reason one couldn't just wire in a double-pole, double-throw switch (with inline breakers as necessary)? I'm assuming a fairly light (20A or less) load).
|
|
bldginsp
Member
|
# Posted: 21 Feb 2017 02:20pm - Edited by: bldginsp
Reply
Yes I suppose you could. A transfer switch is a double throw double pole switch. But many DPDT switches are made for electronics applications and don't have very high ratings. Saw a bunch rated at 32a on eBay, never heard of the brand, cheap as could be. A few recommendations-
-mount the switch in a separate box and cover, and use it to feed a small sub panel.
The size of the load doesn't matter, what matters is that all components are rated for whatever load they will take.
Be sure you have breakers at the source of each power source.
Have a main disconnect on the sub panel, before the other breakers.
Make sure all your wire sizes are correct given your breakers
Make sure the switch you are using has been listed by UL or other American listing agency. There is a lot of foreign junk out there that is not safety inspected.
Ground everything as usual- neutrals isolated in the subpanel.
Get a permit and have the inspector help you out
Hire an electrician.
Everything I said above about grounding and bonding still applies
|
|
low277
Member
|
# Posted: 21 Feb 2017 07:06pm
Reply
Quoting: bldginsp Most such switches do not switch the neutral. Such a switch should be used with a generator that does not bond ground and neutral. Otherwise, you have two bonds to ground and neutral, one at the service and one at the generator. This can energize the ground system on the generator with neutral current when the generator is not being used, or energize the ground system on the service with neutral current when the generator is being used. Neutral current has high amperage, but low voltage, and can still kill you.
Separately Derived vs Non Separately Derived. 
|
|
|
