dcsimg
Self Help Forums

Go Back   Self Help Forums > Repair > Electrical - Existing Home
Register FAQ Members List Calendar Today's Posts

Electrical - Existing Home Electrical Repair / Remodeling Ideas / Problem Solving Solutions

Reply
 
Thread Tools Display Modes
  #1   IP: 68.95.197.193
Old August 31st, 2011, 10:09 AM
bobm bobm is offline
Senior Member
 
Join Date: Oct 2004
Posts: 213
Default Which manual Transfer switch for generator

Hello All,

I would like to install a generator safely in my home and looking for recommendations for an reliable manual transfer kit. My needs are small, 1-220 (Well pump) and 4-110(furnace, Fridge, lighting) circuits would be all I need. The GenTran-KIT3026 (link below) look promising. It seems to have replaceable breakers and hooks into the main box like a subpanel which makes installation very standard. Am I correct in assuming that I would wire the 5 circuits to be covered by the generator into this box like I would any sub panel and there will be a switch that controls power input from either the main panel or the generator? Are there any manual transfer switches that will accept Square D QO?

http://www.amazon.com/GenTran-KIT3026-Prewired-Generators-7500-Watt/dp/B002PHLVSQ%3FSubscriptionId%3D11D6133PXVDXT304BJ82 %26tag%3Dportable-power-generator-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165 953%26creativeASIN%3DB002PHLVSQ

Thanks Bob
Reply With Quote
  #2   IP: 130.76.32.197
Old August 31st, 2011, 12:21 PM
suemarkp suemarkp is offline
Super Moderator

 
Join Date: Dec 2003
Location: Kent, WA
Posts: 8,325
Default

This will work for you, but it is marginal and will be maxed out (assuming the photo is accurate). The top two double pole breakers are the switch part of the transfer switch. One wires to your main panel and the other wires to your generator (or the inlet receptacle).

That leaves 4 breaker slots left for your circuits. You'll need a double pole for the well pump. You'll have to use twin breakers in the last 2 slots to supply your other 4 circuits (hopefully that panel is listed for twins...). If code requires those 120V circuits to be AFCI protected, you won't be able to do that with a twin breaker.

You could just buy a manual transfer switch, a Square D QO subpanel of however many slots you want, and a power inlet box. Cost will be about the same, but you'll lose the power meters.

http://www.northerntool.com/shop/too...6624_200196624
http://www.northerntool.com/shop/too...6574_200196574
http://www.northerntool.com/shop/too...Product%20Page
< didn't choose a link for a Square D subpanel -- shop your local home center >

Have you picked the generator? Make sure you can get one that can have its neutral unbonded from its ground. Also, try to get one that has its GFCI protection after some point where you can access the wires. You can't feed a house from a GFCI equipped generator unless you spring for a transfer that switches the neutral, and those are very hard to find and very expensive.
__________________
Mark
Kent, WA
Reply With Quote
  #3   IP: 68.95.197.195
Old August 31st, 2011, 08:00 PM
bobm bobm is offline
Senior Member
 
Join Date: Oct 2004
Posts: 213
Default

I like the idea of a simple switch and I suspect the power meters are not that big of a deal. I wonder if these can be found on the generator anyway.

Thanks for the tip on the separation of the ground and neutral on the generator. Does the transfer switch isolate the neutral between the main panel and the neutral of the generator? I assume the grounds will not be isolated between the two?

Any recommendations for small generator that will meet my needs? I am thinking that an LP model might be best and possibly less maintenance?

Thanks Bob
Reply With Quote
  #4   IP: 71.231.114.210
Old August 31st, 2011, 08:29 PM
suemarkp suemarkp is offline
Super Moderator

 
Join Date: Dec 2003
Location: Kent, WA
Posts: 8,325
Default

In most cases, a residential generator will NOT be a separately derived system. In this case, the neutral is not switched in the transfer switch (it is called a solid neural which means all the neutrals go to the same bus bar), and there must be a 4-wire feed between the generator and transfer switch (H-H-N-G). The neutral will be isolated from the switch chassis (on plastic stand offs) and the ground should have its own bar directly bolted to the chassis.

The main panel in the house will connect your neutral and ground. That is why you can't have GFCI output on your generator as that main bonding jumper in the house will cause it to trip at the N-G connection.

I'm not all that familiar with the LP ones. I was looking at a propane weed wacker and it actually had some surprising maintenance requirements (valve adjustments). In order to start your well pump, and have some headroom, I'd look for a generator in the 7000KW range (30A at 240V). Finding one with a floating neutral can be difficult, as most manufacturers don't tell you in the specs whether it floats or not. Some are labeled. I'd pick your candidates and then do a detailed search to see if the N can be unbonded or if it floats from the factory.

A generator designed for home powering will most likely have what you need. But these look like a box that sits on a concrete pad. The ones on wheels can be done many different ways.
__________________
Mark
Kent, WA
Reply With Quote
  #5   IP: 68.95.197.195
Old August 31st, 2011, 08:45 PM
bobm bobm is offline
Senior Member
 
Join Date: Oct 2004
Posts: 213
Default

>The main panel in the house will connect your neutral and ground.<
I understand this and at the sub panel and the tranfer switch these will be isolated. I am with you so far?

> That is why you can't have GFCI output on your generator as that main bonding jumper in the house will cause it to trip at the N-G connection. <
I lost you here, I thought GFCI montiors current imbalence between H-N I did not think it looked at the ground?

Thanks
Bob
Reply With Quote
  #6   IP: 71.231.114.210
Old September 1st, 2011, 07:17 AM
suemarkp suemarkp is offline
Super Moderator

 
Join Date: Dec 2003
Location: Kent, WA
Posts: 8,325
Default

The GFCI does just monitor H and N, but the G gives the current another path to take thereby reducing what is in the N.

Connecting the N-G together at the main panel gives the neutral current two paths back to the generator if the G is bonded to the N at the generator. So if you had 10 amps in a hot, you would have 5 amps in the N and 5 amps in the G. The mismatch between the N and H will trip the GFCI.

This is one of those cases where if you turn the generator on, the GFCI will hold. But as soon as you turn on a load (e.g. switch on a light), then current flows and a mismatch will occur tripping the GFCI.

The only way to prevent this it to make sure the N and G are not connected at the generator. You can measure with a meter by just sticking an ohm meter between the N and G pins in a receptacle with the generator off. If you see a low resistance connection, it is bonded.

Recent rules by OSHA and perhaps others are causing more and more receptacles on a generator to be GFCI protected. It used to just be the 15 and 20 amp 120V ones.
__________________
Mark
Kent, WA
Reply With Quote
  #7   IP: 68.95.197.193
Old September 1st, 2011, 10:23 AM
bobm bobm is offline
Senior Member
 
Join Date: Oct 2004
Posts: 213
Default

>Connecting the N-G together at the main panel gives the neutral current two paths back to the generator if the G is bonded to the N at the generator.<
Ok that make sense now. I assume the reason they bond the N and G in a portable Generator is to prevent any potential voltage between the N and G when running in the field?

I noticed the switch box below is designed for GFI generators or where you need a separate derived system. Why would you ever want a separate system? Is this the switch to get so you are covered with any type of generator?


http://www.electricgeneratorsdirect....03D/p3717.html



>Make sure you can get one that can have its neutral unbonded from its ground.<
Curious, what is the safety issue with having the neutral and ground bonded at the generator? Let assume GFI is out of the picture and we are using a transfer switch which does not switch the neutral?

Thanks for your help on this,

Bob

Last edited by bobm : September 1st, 2011 at 12:18 PM.
Reply With Quote
  #8   IP: 130.76.32.213
Old September 1st, 2011, 03:20 PM
suemarkp suemarkp is offline
Super Moderator

 
Join Date: Dec 2003
Location: Kent, WA
Posts: 8,325
Default

Hey, that's a pretty cool transfer panel. I had never seen a 3 pole switch that was affordable. Perhaps the new GFCI requirements are making the manufacturers realize we really need these now.

That transfer switch will save you a lot of headaches (although I might step up to the 60A Util / 50A Gen model as it is only a few dollars more and lets you upgrade to a larger generator should the need arise). The separate derived -vs- not is a design decision. The transfer switch was always the main issue. But you solved that. With a 3 pole transfer switch, you feed the house with only 3 wires (H-H-N), you bond neutral and ground at the generator, and you must have a ground electrode (rod, or probably 2 rods) connected to the ground wire at the generator.

Personally, I think unbonded generators are safer for portable use. Because they are not bonded, you can't be shocked by just touching the hot wire. So they are safer for portable use, as you have to touch both wires to get shocked. But your house is required to be bonded and grounded. So you end up bonding the generator and now it is just like utility power. But bonding is much easier to do than unbonding depending on how hard the bonding strip is to remove. You can always bond the generator with a plug that has in internal jumper from H to G -- just plug it into one of the larger receptacles and label it "bonding plug". But I don't know why you'd want to bond it...I think people are too used to thinking about grounded utility systems and why that forces you to have to bond your house.

The GFCI is just an added safety measure. Seems like more of a hassle when powering the house from one, and rather unnecessary if you're using an unbonded generator. But someone decided that larger generators should be bonded and that GFCI's make them safer. While true, it causes more headaches, especially for people who installed a solid neutral transfer switch a few years ago and now want to replace the generator. The GFCI's can also nuisance trip at construction sites if you have real long extension cords or they are getting worn out.

If you have a solid neutral transfer switch and a bonded generator, you've created a parallel path for the neutral current in the feeder between the main panel and the generator panel as long as the generator is plugged into the transfer switch. This isn't a huge hazard, but NEC 250.142 prohibits N-G connections on the LOAD side of the service disconnect.

It is the same technical issue as running a feeder to a detached building and why range/dryer plugs have changed from 3 wires to 4. Prior to 2008, you could run a 3-wire feeder to a detached building and establish a new grounding system there with new equipment grounds. In 2008, they forced you to run 4 wires to the detached building. That increases the integrity of the fault path, since it is never carrying current in normal conditions. Using the neutral as a combination neutral/ground/bond is something the NEC doesn't like. I'm sure they'd make the power company bring 4 wires to your house to make that safer too, but there is just too much installed base and resistance from the power company to make that change.
__________________
Mark
Kent, WA
Reply With Quote
  #9   IP: 24.147.89.33
Old September 1st, 2011, 10:53 PM
bobm bobm is offline
Senior Member
 
Join Date: Oct 2004
Posts: 213
Default

I do enjoy understanding the theory so thanks for explaining all of this. Currently my main 200 amp panel is maxed, old and difficult to work in. I am thinking of hiring and electrician, if I can find the right one to help me with an upgrade. Let consider swapping out the main panel for a larger enclosure, would the ideal installation entail a transfer switch feeding the main panel? I did look for a 200 amp transfer switch but could not find one at a reasonable price. Curious as to your thoughts?

One reason I like this approach is I am always hesitant working in the main panel even with the main breaker off. If I had an external transfer switch it would be like working in a sub panel when I moved the switch over to generator. Should this approach prove not feasible, can I ask the Electrician to install a 200 amp disconnect upstream from the main panel? When swapping out the main panel will the Electrician ask for the power company to turn off the power, seems reasonable to me but I have heard stories of electricians doing this live.

Thanks Bob
Reply With Quote
  #10   IP: 130.76.32.209
Old September 2nd, 2011, 11:34 AM
suemarkp suemarkp is offline
Super Moderator

 
Join Date: Dec 2003
Location: Kent, WA
Posts: 8,325
Default

Using a whole house transfer switch gives you the most flexibility -- you can run anything in the house, but you just have to switch things on or off manually to keep from overloading the generator.

You can get a 200A manual transfer switch (2 pole) for $400 here:
http://www.harborfreight.com/200-amp...tch-42163.html

They used to sell them online, but it appears to be instore only. Could be a problem if you don't have one close.

I'm not too keen on the 200A ones electricgeneratorsdirect has (they use the mickey mouse sliding bracket). But they do have circuit breakers so your inside panel could be located anywhere and not have to be adjacent to the transfer panel.

This transfer switch is 2 pole, so you have the same issues as before -- can't use a GFCI'd generator and may need a floating neutral (floating or not may be OK if it connects to the main disconnect panel). The transfer switch would be your main disconnect, but since it has no overcurrent device in it, it must be installed immediately adjacent to your 200A main breaker panel. If you buy a generator meant to power a house, it won't have the GFCI. It is the portable ones with receptacles that will have that "feature".

A 200A transfer switch would allow you to totally kill power to the 200A interior panel, so working on it would be easy.

You can't replace your main panel without killing power to it. Generally, all you have to do is pull the meter to do that. Usually, pulling the meter requires coordination with the power company, because you'll breaker their meter seal. How that is handled is different with each power company.

Changing your service will require that the Service meet current codes and is inspected. So you'll want to get the power company requirements manual to see if you'll have any issues under current rules. Not much has changed in the NEC for Services, but if you only have a water pipe and ground rod, you'll most likely need a second ground rod installed. You'll also need a intersystem grounding block (a grounded bar that phone, CATV, etc can use to ground their stuff).

Installing any disconnect or transfer switch in front of your main panel will cause that panel to become a subpanel. This means separation of grounds and neutrals, and moving the ground electrode conductor to the new disconnect or switch enclosure. That can be a pain in an older panel with wires already cut to size and limited neutral/ground bar space (but splicing wires is allowed in panels). Replacing the panel with a new one and putting in the upstream disco/switch will make it all clean.
__________________
Mark
Kent, WA
Reply With Quote
Reply






Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 02:08 PM.


Powered by vBulletin® Version 3.6.7
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
© 2002 - QuinStreet, Inc.
http://www.selfhelpforums.com