Power Conditioner

[John T]

As far as a floating neutral generator (many come that way) not being able to run some furnaces one needs to know how that genset is actually configured be it direct, or via a transfer switch, and whether or not the neutral is switched, or the gensets n and g are attached to the utility n and g, or a typical genset cord plugs into a receptacle on side of house or the genset is a seperate derived system and connected

What I’m saying is even if the genset has a floating neutral that doesn’t necessarily mean the furnace is wired to a floating neutral. Too much to explain here.

That being said I’m not surprised if a furnace or oven doesn’t work wired to a floating neutral but not getting in all the weeds explaining why that’s above this question.

There is to be only one n g bond,,,, there’s all sorts of ways to connect a portable genset, the whole issue of bonding and grounding and seperate derived sources and when or not ground rods are required is complex and no need to open thst can of worms here unless someone has a specific question , it can’t be covered here in a paragraph grrrrr

In short some devices may need to be connected to a bonded service to work and thee are ways to cure that even if the genset is floating Nuff said And not going in the weeds on and on and on lol elec threads are long enough already

John T

 

[will-max dairy]

Short answer?

With these furnace/oven failures, bonding the neutral of a gen set possibly has more to do with just nullifying the noise between ground and neutral from the gen set... than changing the noise in the supplied device. Your computer and any other ITE stuff in the house, unless it was made in the 1980s or before... doesn't care about the little glitches in your generator power. They don't care about power factor. They don't care about little distortions in the sine wave. They just plain... don't care. Matter of fact, they are more likely to distort the sine wave themselves.

The other short answer is... I may have written paragraphs and paragraphs above... but if my house was at 33 degrees, and my furnace needed a neutral-ground jumper in the plug to run off of the only generator available... I'm making that connection and asking questions later. I would then just make sure I shut off the generator before I touch the furnace... or I would ground the furnace before touching it. Otherwise... there is no need to touch the furnace if it's running...

The disclaimer is: We're all adults here. Roll your dice and move your mice. If you want to build a backup generator with a pure sine wave and lightning protection (like a ground rod); beautiful. My technical curiosity is endless... show us how you did it... because I don't have the money to do so for myself, lol.

 

[Earl Grey]

I have seen some cheaper generators that will surge when on a light load, so the HZ fluctuates. By hooking up and electric heater to put a little load on the generator that usually stabilizes it.

 

[John T]

Short answer?

Bonding the neutral of a gen set possibly has more to do with just nullifying the noise between ground and neutral from the gen set... than changing the noise in the supplied device. Your computer and any other ITE stuff in the house, unless it was made in the 1980s or before... doesn't care about the little glitches in your generator power. They don't care about power factor. They don't care about little distortions in the sine wave. They just plain... don't care. Matter of fact, they are more likely to distort the sine wave themselves.

The other short answer is... I may have written paragraphs and paragraphs above... but if my house was at 33 degrees, and my furnace needed a neutral-ground jumper in the plug to run off of the only generator available... I'm making that connection and asking questions later. I would then just make sure I shut off the generator before I touch the furnace... or I would ground the furnace before touching it. Otherwise... there is no need to touch the furnace if it's running...

The disclaimer is: We're all adults here. Roll your dice and move your mice. If you want to build a backup generator with a pure sine wave and lightning protection (like a ground rod); beautiful. My technical curiosity is endless... show us how you did it... because I don't have the money to do so for myself, lol.

Indeed making a bonding plug to insert into one of the gensets NEMA 5-15R if it has a floating neutral but you need it bonded is easy peasey. Just jump n and g of the plug and plug it in done all the time. Of course there are times the genset should be flosting but that’s far beyond this thread if anyone needs more shoot me a private message. This is getting beyond the question but engineers and electricians enjoy this lol. It’s like catnip for us but bores others

John T

 

[wp6529]

As far as a floating neutral generator (many come that way) not being able to run some furnaces one needs to know how that genset is actually configured be it direct, or via a transfer switch, and whether or not the neutral is switched, or the gensets n and g are attached to the utility n and g, or a typical genset cord plugs into a receptacle on side of house or the genset is a seperate derived system and connected

What I’m saying is even if the genset has a floating neutral that doesn’t necessarily mean the furnace is wired to a floating neutral. Too much to explain here.

That being said I’m not surprised if a furnace or oven doesn’t work wired to a floating neutral but not getting in all the weeds explaining why that’s above this question.

There is to be only one n g bond,,,, there’s all sorts of ways to connect a portable genset, the whole issue of bonding and grounding and seperate derived sources and when or not ground rods are required is complex and no need to open thst can of worms here unless someone has a specific question , it can’t be covered here in a paragraph grrrrr

In short some devices may need to be connected to a bonded service to work and thee are ways to cure that even if the genset is floating Nuff said And not going in the weeds on and on and on lol elec threads are long enough already

John T

The main panel should be the N/G bond point in most cases. A transfer switch before, or an approved interlock backfed breaker will both leave that bond intact. Whether the generator has a bond or not will have no impact on anything downstream of that main panel. Whether there is a double bond due to one at the generator as well also has no impact downstream of the main panel. There might be a theoretical shock risk with that second bond allowing the generator frame to be above ground potential due to neutral current, but for any portable home generator the maximum imbalanced current the generator can produce and thus present as neutral current is so low that it is unlikely the voltage would even produce a noticeable tingle unless barefoot in the rain. Very over hyped issue that really only has practical applicability to very large gensets.

 

[buickanddeere]

The main panel should be the N/G bond point in most cases. A transfer switch before, or an approved interlock backfed breaker will both leave that bond intact. Whether the generator has a bond or not will have no impact on anything downstream of that main panel. Whether there is a double bond due to one at the generator as well also has no impact downstream of the main panel. There might be a theoretical shock risk with that second bond allowing the generator frame to be above ground potential due to neutral current, but for any portable home generator the maximum imbalanced current the generator can produce and thus present as neutral current is so low that it is unlikely the voltage would even produce a noticeable tingle unless barefoot in the rain. Very over hyped issue that really only has practical applicability to very large gensets.

What ? Use a proper transfer switch instead of some jimmy rigged cob job to connect the generator ???

 

[John T]

I have seen some cheaper generators that will surge when on a light load, so the HZ fluctuates. By hooking up and electric heater to put a little load on the generator that usually stabilizes it.

Some of that has to do with the quality of the engine, the speed governor and the voltage regulation. There’s a difference in say a Honda or Yamaha versus a super cheap off brand sold at big box stores. I found the same as you a bigger constant load yields better results even with a cheap genset. FWIW I never had a problem with electronic sensitive loads even with a non inverter genset and again if needed I used a bonding plug to convert a flosting genset to a bonded

John T. Retired but ever curious old engineer

 

[zuhnc]

A generator and extension cords to individual equipment is a proper way to power said equipment. Back feeding the dryer or welder outlet is NOT proper nor safe.

The panel manufacturers' approved interlock mechanism and breaker on the main panel is also an acceptable way of powering a panel.

 

[John T]

A generator and extension cords to individual equipment is a proper way to power said equipment. Back feeding the dryer or welder outlet is NOT proper nor safe.

The panel manufacturers' approved interlock mechanism and breaker on the main panel is also an acceptable way of powering a panel.

Speaking of extension cords off gensets to power appliances. It was and I believe still true if a genset feeds tools via its own onboard receptacles no ground rods are required. May have changed since so no warranty consult the nec and trained competent professional electricians and engineers. Note the genset May or may not be bonded from the factory.

Last time I researched osha regarding gensets on construction sites to power tools. They didn’t want the gensets to be earth grounded to a ground rod but did want them bonded. Note OSHA is complicated and not the same as nec do again no warranty on this read osha for yourself don’t. Take my word !!!! This is still in airdabce with the rule no ground rod needed to power via onboard receptacles from gensets so it sounds all well ??

John T. Ever curious engineer who enjoys this if it bored others lol

 

[farmersamm]

Last time I researched osha regarding gensets on construction sites to power tools. They didn’t want the gensets to be earth grounded to a ground rod but did want them bonded. Note OSHA is complicated and not the same as nec do again no warranty on this read osha for yourself don’t. Take my word !!!! This is still in airdabce with the rule no ground rod needed to power via onboard receptacles from gensets so it sounds all well ??

Of course they want the generator bonded. If you're running equipment with a generator that has standard receptacles, there's no other way to clear an equipment ground fault.

 

[John T]

Of course they want the generator bonded. If you're running equipment with a generator that has standard receptacles, there's no other way to clear an equipment ground fault.

X2. Correct farmer sir. !!!
John T

 

[John T]

The main panel should be the N/G bond point in most cases. A transfer switch before, or an approved interlock backfed breaker will both leave that bond intact. Whether the generator has a bond or not will have no impact on anything downstream of that main panel. Whether there is a double bond due to one at the generator as well also has no impact downstream of the main panel. There might be a theoretical shock risk with that second bond allowing the generator frame to be above ground potential due to neutral current, but for any portable home generator the maximum imbalanced current the generator can produce and thus present as neutral current is so low that it is unlikely the voltage would even produce a noticeable tingle unless barefoot in the rain. Very over hyped issue that really only has practical applicability to very large gensets.

Over hyped indeed X2

What non sparkies don’t realize it makes a difference if the transfer switch only switches the hots orrrrr if it also switches the neutral !!!

If it swirches hots and neutral it’s like your own seperately derived system and requires a grounding electrode and there be one ng bond. In a lifetime of practice most transfer methods only switch the hots not the neutral although I have seen some sds in use

However if it as many do only switches the hots and the genny and utility neutrals are connected in that case since there should be only one ng bond and the genny itself should use a floating neutral

That’s the code at least when and where I practiced but as always where fire and life safety are concerned consult the nec and electricians and engineers don’t bet the farm or a life on anything posted here by me included !!!

I fully agree it’s over hyped and things can still work if not wired to code but being trained in snd understanding code my best professional opinion and advice is to wire gensets and transfer methods per the nec it could save a life or prevent a fire !!!!!!!!!

A pleasure chatting with all the sparky gents here we might learn from each other but the non sparkies. May be bored to tears now lol lol

God Bless y’all best wishes

John T. BSEE, JD. Mostly retired still curious and willing to help

 

[John T]

If you want a practical example of how these leakage currents affect things... look at the outlets in a modern hospital room... they will often have a label on them stating that they are isolated or low leakage or something to that effect...

When designing medical electronics and sensors... say... an EKG... these leakage currents have to be taken into account, as well...

In my day I specified isolated grounds in hospitsls as well as many computer rooms. Good engineering g as well as code

John T

 

[John T]

I'm now going to need a moment... as I'm having PTSD from going through iterations of EMI testing... then safety testing... on products over the years. You may add "Y" components to ground... to pass EMI testing... but then fail safety testing... which cycles you back to EMI testing to try something else.... rinse/repeat...

At 1500 dollars a day for testing at a lab four hours away, with new products that were usually a little buggy to begin with, and always being done at the end of new product development, with management breathing down your neck... it was... just a little stressful.

I hear you when it comes to ptsd been there done that myself lol
Best wishes pleasure sparky chatting g with you sir

John T

 

[Stan Coryell]

EXACTLY!

This is TYPICAL of gas furnaces that use a "flame rod" to sense that the pilot or main burner is lit.

A flame sensor generators current when heated. The control board senses current and allows power to the gas valve to remain.

I can’t think of any HVAC equipment, that I have worked on, that uses the equipment case as a neutral reference for 24 VAC. Really the only thing requiring a neutral would be the gas valve or motor operated damper. All other controls are safety interlocks. The transformer neutral is bonded to the case, but it's purpose is over current protection for the transformer.

 

[Dusty MI]

I older generators need to turn a certain constant RPM to maintained 60 cycles, but there are newer ones that make the 60 cycles with electronics, and maintain the 60 cycles no mater the RPM.

 

[wp6529]

A flame sensor generators current when heated. The control board senses current and allows power to the gas valve to remain.

I can’t think of any HVAC equipment, that I have worked on, that uses the equipment case as a neutral reference for 24 VAC. Really the only thing requiring a neutral would be the gas valve or motor operated damper. All other controls are safety interlocks. The transformer neutral is bonded to the case, but it's purpose is over current protection for the transformer.

A thermocouple generates current when heated and is used to power a gas solenoid valve in some gas burners. A "flame rod" is a different sense only thing. There are also optical and UV flame sensors used in better equipment.

 

[farmersamm]

Test post. Something about this site saves a draft forever.........can't get rid of it

 

[will-max dairy]

There has been much verbiage... and I'm pointing a finger right back at myself... but a lot of that has been side discussions and questions... related to the issue at hand, but not directly answering it.

Even myself... I've gone off and talked about obscure standards, EMI suppression design... yada, yada, yada. But, I think the simplest actual answer here is:

"Dirty" power has some quantitative definitions, but even knowing them doesn't really help in the situation at hand. Even in a production/testing environment, the be all and end all is a test.

I think that many of us would agree that, if you have a house full of modern products (I'll say...after 1990), the risk of actual damage to anything from your generator, due to how "dirty" its power is, is very, very small.

Which means that, you could best define "dirty" power, or not, from your generator by a dry run test.

Take a little time to rig up the extension cable(s) or panel hookup that you plan on using (here is where I'm not well versed in NEC, OSHA, etc... depend on others, ideally a local electrician)... and make this connection safe, electrocution-wise to the best of your ability.

Then run a test and see, for instance, if your furnace lights... if your freezer works, If your AC works, if your TV works... if your computer works, etc. etc.

Again, as long as you make the setup safe, electrocution-wise... the risk of damaging any of your appliances is very, very small.. and you'll figure out exactly if your generator is "too dirty"; which is all that really matters. If you do this test, you may also find out just how many, or few, appliances you can run... or if you need to keep a minimum load on to be smooth, etc., etc.

You can always, then, go into sizing up an inverter system, if you don't like the results. If you like the results, look at that... you have a backup plan...

Disclaimer.. if you have someone in your house on some form of actual sensitive life support equipment... all bets are off... it probably won't be damaged by a test... but to test something like that without a backup, is beyond irresponsible... work with a health care provider on that...

In thinking about this, I realize that my own "backup plan" is, more or less, just a thought. I have a 7250Watt Troy Built generator... and I figure that I just have enough knowledge to MacGuyver it to the furnace or meat freezers, if I had to.

Not really a plan, is it?

 

[John T]

I older generators need to turn a certain constant RPM to maintained 60 cycles, but there are newer ones that make the 60 cycles with electronics, and maintain the 60 cycles no mater the RPM.

Hi Dusty, exactly. The later inverter generators just use the raw energy output of a conventional generator and an electronic inverter to produce a sine wave at 60 Hz even if the raw input wasn’t the perfect rpm or 60 Hz or exact voltage. Still I have used several different brands of conventional non inverter gensets never a problem

I didn’t make it to Florida this year due to health issues but had a good fun 16 year run including the time we met

John T