Select circuit transfer switch vs. Interlock kit

Hello fellow electricians, I am one of you now!

• Warning
• This will probably be a long winded post for a simple question.

My father asked me to set him up with a generator in case of power outage, so I told him my favorite way to do this is with a back feed breaker / interlock kit. Because I just recently got my Masters license and am looking to potentially start targeting work in their area (Northern NH) I decided to call a few electricians just for s

While it may be easy to overload a small generator I feel like his stated repercussions would be very unlikely due to the fact that with an interlock you would have the OCP on the unit itself and on the back feed breaker. So unless both of those devices failed and the generator was severely underpowered, the danger is very small.

SOO! IN YOUR OPINION...am I am idiot and should I feel bad about having installed many interlocks in the past or was this guy just being overly cautious?

I HATE select circuit transfer switches because they suck to install and are severely limiting if you have even the most vague understanding of loading. Should I drop this notion or keep doing what I am doing?

Hello fellow electricians, I am one of you now!

My father asked me to set him up with a generator in case of power outage, so I told him my favorite way to do this is with a back feed breaker / interlock kit. Because I just recently got my Masters license and am looking to potentially start targeting work in their area (Northern NH) I decided to call a few electricians just for s

While it may be easy to overload a small generator I feel like his stated repercussions would be very unlikely due to the fact that with an interlock you would have the OCP on the unit itself and on the back feed breaker. So unless both of those devices failed and the generator was severely underpowered, the danger is very small.

SOO! IN YOUR OPINION...am I am idiot and should I feel bad about having installed many interlocks in the past or was this guy just being overly cautious?

I HATE select circuit transfer switches because they suck to install and are severely limiting if you have even the most vague understanding of loading. Should I drop this notion or keep doing what I am doing?

I’ve installed a lot of portable generator connections with interlocks and I’ve never had an issue.

One thing I noticed about interlocks is that older electrician sometimes hate them, it seems to be something about how such a simple thing could give such a great reward. It’s like they feel that it’s cheating and it can’t possibly be code compliant.

There’s absolutely no point in installing one of those six or 10 circuit transfer panels. I put red stickers on breakers that I want the customers to shut off before switching over the interlock, such as hot tubs and central air conditioners.

if those ignorant companes don't install the interloc , then there's more work for you. I personally have one with B&S Q6500 inverter generator and had to use it for two-3 days and most of the time the generator was at low speed because the load was so low. Installed them for several people and never heard anything bad.

I like 3 pole transfer switches, prefer them over interlocks 1000%. Gets away from all that nasty neutral issues and some of the grounding issues when doing this kind of work.

I never use "back f_ _ ding" as a term. A lot like "dirty power". The meaning can be so vague as to create problems. Or it is just technically wrong.

Your in charge of the job so you get to choose how it is going to be done. If interlocks are available and approved by your AHJ and POCO then go for it.

As for using portable generators I despise those for a home. First they are 3600 rpm, second there is no voltage or HZ controls until you get to 3600 rpm. As for having a portable fry electronics because of a low voltage condition I guess it is possible.

I use an old Onan 6.5kw, 1800 rpm machine for my home. A WHOLE lot less noise.

Choosing the right machine is extremely important relative to your loads. Something most people fail to deal with. I have UPS's for my sensitive equipment.

People repeat what works for them. If they have done it a couple of times then it becomes easy. Connecting a portable generator to a home is doable. I caution people a lot on how it works and how it has to to work. Picking up a load with a portable generator can be a bit harder if you have motors like pumps, or a clothes washer to consider.

I like 3 pole transfer switches, prefer them over interlocks 1000%. Gets away from all that nasty neutral issues and some of the grounding issues when doing this kind of work.

I never use "back f_ _ ding" as a term. A lot like "dirty power". The meaning can be so vague as to create problems. Or it is just technically wrong.

Your in charge of the job so you get to choose how it is going to be done. If interlocks are available and approved by your AHJ and POCO then go for it.

As for using portable generators I despise those for a home. First they are 3600 rpm, second there is no voltage or HZ controls until you get to 3600 rpm. As for having a portable fry electronics because of a low voltage condition I guess it is possible.

I use an old Onan 6.5kw, 1800 rpm machine for my home. A WHOLE lot less noise.

Choosing the right machine is extremely important relative to your loads. Something most people fail to deal with. I have UPS's for my sensitive equipment.

People repeat what works for them. If they have done it a couple of times then it becomes easy. Connecting a portable generator to a home is doable. I caution people a lot on how it works and how it has to to work. Picking up a load with a portable generator can be a bit harder if you have motors like pumps, or a clothes washer to consider.

SWDweller said : I like 3 pole transfer switches, prefer them over interlocks 1000%. Gets away from all that nasty neutral issues and some of the grounding issues when doing this kind of work.

I never use "back f_ _ ding" as a term. A lot like "dirty power". The meaning can be so vague as to create problems. Or it is just technically wrong.

Your in charge of the job so you get to choose how it is going to be done. If interlocks are available and approved by your AHJ and POCO then go for it.

As for using portable generators I despise those for a home. First they are 3600 rpm, second there is no voltage or HZ controls until you get to 3600 rpm. As for having a portable fry electronics because of a low voltage condition I guess it is possible.

I use an old Onan 6.5kw, 1800 rpm machine for my home. A WHOLE lot less noise.

Choosing the right machine is extremely important relative to your loads. Something most people fail to deal with. I have UPS's for my sensitive equipment.

People repeat what works for them. If they have done it a couple of times then it becomes easy. Connecting a portable generator to a home is doable. I caution people a lot on how it works and how it has to to work. Picking up a load with a portable generator can be a bit harder if you have motors like pumps, or a clothes washer to consider. Click to expand... I have a 3kW inverter portable that I've used for many years in multiple houses as backup - never a problem, and is nice and quiet. I see no reason to have a stationary generator being wasted for the infrequent need, when the portable works fine AND can be used for far more (job sites, rv, etc).

Generally, those panels that have all the individual ckt transfer switches just suck. They are junk. They are aimed at a low market consumer. Not a good quality product.

I have the generac 6853 on my own home as i am probably not going to be there during a storm and i needed something simple for the wife to use.

1 / It switches neutral so i can leave the generator plugged in (generator has remote start / stop so she can start it from inside the house).

2 / she doesn't have to select anything just press the transfer button

3 / the stove (not on transfer) sings a song when power is restored and the main ac unit will restart so no guessing if power is back

4 / i needed extra breaker space and this gave me 6 extra spaces

5 / i flush mounted it so it looks pretty good next to the main panel

If it wasn't for the wife i might have gone with a simple interlock kit but when i did pro's and con's this just seemed a better idea especially as labor was free.

I've had a house subpanel in each of my homes that has held all the vital loads, so i just put a separate interlock panel between the service panel and the house panel to cut it over to the generator inlet.

Some people, I myself, do not like the panel mount interlock kits. I believe they are not allowed in Canada. If the cover is off then there is no interlock. What happens if the main breaker does not fully open internally? Or the generator breaker? There is no way to see the load on the generator unless you install power meters for the generator. I will install the interlock bracket that is fixed to the breakers and cannot be removed but only for people I know and they understand how it works. They also sell for under $100.00 a meter that tells how many watts are being used. Obviously a true transfer switch and a small panel is the much safer way to go but it more labor and costs more.

Interlock kits are OK subject to AHJ / POCO bias.

Some manufacturers, like Square D, have listed interlock kits. Home owners should not ever remove the panel cover, so what is the problem?

If you really want to mitigate this offense, you could use anti-tamper screws to secure the panel cover and add a few nasty warning labels.

The transfer switch is the most robust, but more expensive.

For both of the above, adding those cheap power monitor meters is a great idea. Educated homeowners know to watch those meters and shed loads as needed; no curling irons, pedicure heat baths, avocado toast, or Toto butt washers when the genny is running please.

Separate breaker panels for "emergency power" in residential is not all that great for two reasons :

Do you really want to prevent someone from turning on a light in the middle of the night so they don't trip on the way to the WC?

Most of those ready-made back-up panels do not accept GFI breakers, or the now mandated Arc-fault breakers.

I have a standby at home, partial coverage. May cobble something together from the boneyard into a full house set up eventually. I've done interlocks, partial panel and three pole switches. Dealing with AFCI, no more of the three way switch setups and only subpanel type with real breakers. Three pole really solves a lot of worries but is large and expensive. Portables are fine as long as maintained and used regularly.

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