Power Conditioner

[farmersamm]

While it may just be "lawyer speak"..................most engine drive welders will state in the manual how they can be used when utilized as a generator. My 250GXT manual states that it cannot be used to power sensitive electronic stuff like the computer. Can't speak to other models, but I'm sure there are welders that produce cleaner power. The lights will flicker when the welder powers the house.

One problem with my welder is RPM. The Hz depends on a steady, proper, RPM. If the governor hunts, you can see the variance in voltage. Being a carbureted setup, I'd be pretty sure that a fuel injected motor would maybe do a better job?

I don't run anything by patching at the disconnect. I run only with extension cords. You can't backfeed the utility.......it can hurt someone.

We run our house on Propane. This is a life saver when there's a power outage. You don't lose your heat. I keep a pigtail in the heater cabinet. When the power goes out, I simply disconnect the house wiring that feeds the heater, and put the pigtail in its place.......which hooks to the extension cord. Lot of newer homes around here are built with electric heat..........A huge mistake IMHO.

 

[farmersamm]

Dunno about floating neutrals. This Armstrong has a circuit board, and it runs fine when you bypass the house wiring(shrug).

 

[wp6529]

EXACTLY!

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

I classify this as a poor design issue and not a legitimate technical reason. Good design would use differential sensing as that is what you are looking to measure, why would you reference to neutral if the signal is referenced to ground? Probably saved $0.05 in components on the control board with the poor design.

 

[will-max dairy]

The grounding of gas furnaces has a wildcard, the gas supply itself. Depending on whether the gas comes from a buried line, or a propane tank... and whether there are any dielectric unions involved... who did the gas plumbing... and did they even think of using dielectric unions... and if they didn't... there could be a teeny tiny ground to chassis voltage setup from that...

Then... if you think about the fact that your pilot/flame sensor could be just a lowly thermocouple with a few milliamps of output...

Seems as though whether you need to bond or float the neutral should be tested with your generator/backup system of choice on a warm, sunny day...

Modern computers and stuff shouldn't give the proverbial rat's behind about variations from about 47 Hz to 63 Hz.... or 90VAC to 264VAC...they are also tested for millisecond-duration brownouts and interruptions (the standard used to be... IEC 61000-4-11 that specified the "dip and interrupt" hardening of modern electronics)

 

[John T]

Oli great question and of course being it’s electrical you may get a ton of responses. My approach is to lay out some basics to hopefully educate and not confuse you

1. Its true certain sensitive electronic devices may not perform well if subjected to let’s call it dirty power
2 it’s true many devices convert raw or dirty ac into dc and still work fine even if dirty power is applied
3 conventional non inverter generators if high end produce good quality ac snd 60 Hz provided the engine runs and stays at the correct rpm. They are not necessarily dirty power producers and csn power most anything including sensitive electronics no problem. Besides as posted above certain devices just convert the incoming ac to dc snd can still work with dirty power
4 now let’s talk inverter generators. One advantage is they take raw ac generated power even if frequency or voltage isnt perfect and electronically produce 120 vac
5 however a cheap inverter might produce a modified sine wave at 120 and for sure many devices don’t work well ir at all if subjected to a msw
6 however a better inverter produces a near pure sine wave even if its generator isnt working perfect
7 yes they make power conditioners thst could protect high or low voltage or other imperfections but with a quality inverter they aren’t badly needed
8 they also make uninterrupted power supplies that could use quality say 12 vdc to 120’ac inverters with internal batteries and built in battery chargers so you never run out of output so long as the batteries are charged and there’s never any switching or delays because you’re constantly fed quality inverter power
9 they could make cheaper ups thst switch from utility to battery snd inverter if power goes off but I was never a fan if those

Bottom line if your genset has quality voltage regulation snd runs at the correct stable rpm I would not be afraid to use it for home backup power even with sensitive electronics.

No warranty in a retired EE so see what other professional engineers and electricians have to say

PS it makes a difference if your genset should have a bonded or floating neutral and if you need a grounding electrode like a ground rod , but that’s another whole issue I could address as needed enough said for now

Best wishes God bless all here

John T. BSEE , JD

 

[farmersamm]

I've been thinking about this "floating neutral" thing, and how it affects a furnace. And why it might not work without a bonded neutral.

If you're powering the furnace with a standalone generator, not hooked into the home system via a transfer switch, it has to to have a bonded neutral. It's a SDS. Without the bonded neutral, there's no way for fault current to find its way back to the source. THE GROUND WIRE IS NORMALLY A NON CURRENT CARRYING CONDUCTOR. So.................what's furnace operating current doing on that wire???

 

[zuhnc]

I have been doing electrical stuff and working with generators of all types for about 50 years. I have yet to find a definition of "dirty power". Can anyone enlighten me? Does this type of power need "washing" prior to use? Clorox or just detergent?

Or is "dirty power" just subjective and no one knows what it really means, quantitatively. Not hearsay or conjecture.

 

[will-max dairy]

I have been doing electrical stuff and working with generators of all types for about 50 years. I have yet to find a definition of "dirty power". Can anyone enlighten me? Does this type of power need "washing" prior to use? Clorox or just detergent?

Or is "dirty power" just subjective and no one knows what it really means, quantitatively. Not hearsay or conjecture.

Anything with a CE mark has been tested to:
IEC 1000-4-4 (Electrical Fast Transients)
IEC 1000-4-5 (Surge)
IEC 1000-4-11 (Dips and Interruptions)

And, it has to meet the Total Harmonic Distortion and Flicker limits of IEC 1000-3-2

Any power source that exceeds the limits in the top three standards could be considered "dirty"

Any product that exceeds the Harmonic Distortion and Flicker limits could be considered as "dirtying" the circuit that it's connected to.

For the last thirty years, products have been built and tested to these limits to the extent that we are becoming blissfully ignorant of both how "dirty" things used to be and how sensitive to "dirt" things used to be.

 

[farmersamm]

https://blog.se.com/infrastructure-and-grid/power-management-metering-monitoring-power-quality/2023/11/30/dirty-power-what-it-is-and-why-you-need-to-clean-it-up/

Near as I can tell, it's corruption of the sine wave.

 

[redtom]

It's true. I have a 5kw generator I bought in 2000. I use for power outage. It runs my fridge etc. My gas stove will NOT light the electronic oven with this generator. Even if it's the only thing on at the time. It tries but cycles off before lighting. I've never checked the output voltage or cycles but I believe and net research yields the output is too "dirty".

 

[TerryfromSWIowa]

I don't know about dirty power, but I always thought it was the surge from generator that caused issues with electronics. That is why I always ran a few lights or a coffee pot if I had to run furnace or a television during an outage.

 

[John T]

I have been doing electrical stuff and working with generators of all types for about 50 years. I have yet to find a definition of "dirty power". Can anyone enlighten me? Does this type of power need "washing" prior to use? Clorox or just detergent?

Or is "dirty power" just subjective and no one knows what it really means, quantitatively. Not hearsay or conjecture.

Over my life’s practice I’ve heard electricians engineers and lay gents use the term dirty power and never asked any for their definition either lol it’s become a term thrown around too loose and I don’t recall any precise definitions even in many nec seminars. So dont ask me I dont have the answers my bad grrrr on me

John T

 

[John T]

It's true. I have a 5kw generator I bought in 2000. I use for power outage. It runs my fridge etc. My gas stove will NOT light the electronic oven with this generator. Even if it's the only thing on at the time. It tries but cycles off before lighting. I've never checked the output voltage or cycles but I believe and net research yields the output is too "dirty".

I can’t know your genset and how it’s configured and feeds your furnace I can only say many small portable gensets come from the factory with a floating non bonded neutral. In cases where a bonded neutral is needed to operate properly many just use a bonding jumper of a NEMA 5-15 plug with its n and ground jumped together and plugged into one of the gensets receptacles.

If for some reason your furnace requires a bonded neutral and your somehow ?? powering it with a floating neutral it could make a difference I can’t know just saying

Ps some of my furnaces use a flame sense mechanism which detects the small Millivolt difference dependent on if a flame is present.

Again I have no idea about your genset, how it’s wired and used and your furnace so this is only info about how many gensets. Come from the fsctory

John T

 

[redtom]

I can’t know your genset and how it’s configured and feeds your furnace I can only say many small portable gensets come from the factory with a floating non bonded neutral. In cases where a bonded neutral is needed to operate properly many just use a bonding jumper of a NEMA 5-15 plug with its n and ground jumped together and plugged into one of the gensets receptacles.

If for some reason your furnace requires a bonded neutral and your somehow ?? powering it with a floating neutral it could make a difference I can’t know just saying

Ps some of my furnaces use a flame sense mechanism which detects the small Millivolt difference dependent on if a flame is present.

Again I have no idea about your genset, how it’s wired and used and your furnace so this is only info about how many gensets. Come from the fsctory

John T

Please note, it was my oven that wouldn't light. Oven-furnace, same principle, sorta.

 

[farmersamm]

Well.................looked high, and low, and still haven't come up with an answer

From a Rheem diagnostic PDF https://my.rheem.com/pts/FAQ/FAQ_Gas_Furnace.asp

I've found reference to modern furnaces somehow checking for equipment ground, and not operating if none is detected. I have no idea whether this is true.

Other discussions relate to the EGC as a 0 voltage reference point for the control circuit. This is beyond my understanding.

In the same vein, I've seen a discussion that claims the earth ground removes spurious signals from the control circuit. This is beyond my understanding.

Anyways..........without a bonded neutral, the equipment ground is an open circuit as far as the circuit breaker is concerned. This applies to using an extension cord..........none of this is meant to apply to the use of a transfer switch. It's about plugging into a welder/generator, or a plain generator.

So.......................using an extension cord with a generator that has a floating neutral won't provide a path to source for clearing a fault, unless you bond the neutral. Welders have a bonded neutral, so they're safe for use with an extension cord. And, does this explain why my furnace runs on the welder?

But this doesn't answer the question as to why you need a bonded neutral to run a furnace. I can't imagine any current, other than fault current, running on a ground wire. I'm at a loss.

 

[Watthour]

For some snooty installations . A 1:1 ratio transformer is used . The load is not electrically or mechanically connected , only magnetic coupling .
The impedance in the transformer windings filters out the most of high frequency harmonics and smooths out some of the distorted sine waves .

About the same solution can be accomplished with a line-side reactor (like TCI) if you know the approximate load.

 

[will-max dairy]

Well.................looked high, and low, and still haven't come up with an answerView attachment 103809

From a Rheem diagnostic PDF https://my.rheem.com/pts/FAQ/FAQ_Gas_Furnace.asp

View attachment 103810

I've found reference to modern furnaces somehow checking for equipment ground, and not operating if none is detected. I have no idea whether this is true.

Other discussions relate to the EGC as a 0 voltage reference point for the control circuit. This is beyond my understanding.

In the same vein, I've seen a discussion that claims the earth ground removes spurious signals from the control circuit. This is beyond my understanding.

Anyways..........without a bonded neutral, the equipment ground is an open circuit as far as the circuit breaker is concerned. This applies to using an extension cord..........none of this is meant to apply to the use of a transfer switch. It's about plugging into a welder/generator, or a plain generator.

So.......................using an extension cord with a generator that has a floating neutral won't provide a path to source for clearing a fault, unless you bond the neutral. Welders have a bonded neutral, so they're safe for use with an extension cord. And, does this explain why my furnace runs on the welder?

But this doesn't answer the question as to why you need a bonded neutral to run a furnace. I can't imagine any current, other than fault current, running on a ground wire. I'm at a loss.

Samm,

In modern electronics the ground conductor isn't just there to shunt away fault current. It's also the reference for noise filtering and what are called "spurious signals."

In modern electronics, there are often a mix of capacitors (Read about "X capacitors" and "Y capacitors") and diodes/MOVs (Metal Oxide Varistors) that connect both line to line and line to ground.

Just about any given product will always have a tiny bit of what's called "leakage current" riding on the ground wire... which comes from AC currents going to the green wire ground, through these line to ground ("Y"-type, jargon-wise) components. It's usually on the order of a few milliamps. I think the limit for safety testing (see IEC 60950 or IEC 61010-1 for example) is around 3 to 5 milliamps.

If you are depending on a sensor that is delivering a few milliamps between chassis and a working circuit... these leakage currents and how they change when ground/neutral bonding changes... could futz up your readings.

 

[will-max dairy]

There is a tradeoff with these EMI (ElectroMagnetic Interference) filtering components. Consider a TVS (Transient Voltage Suppressor) diode or a MOV (Metal Oxide Varistor) that is connected from hot to ground and/or neutral to ground... they prevent damage to a product in the case of a lightning surge, or from an ESD (Electrostatic Discharge), or from switching transients (for instance, those nasty arcs that happen if you unplug a running vacuum cleaner).... but by protecting the products from damage... they setup a certain ground/neutral relationship that internal circuits rely on.

Usually, as you've read, circuits in a product have a working 0 Volt reference... as in... if you have a microprocessor running on 5VDC... that 5VDC is referenced to a plane on the circuitboard that is considered 0 Volts DC...

That 0 Volt plane may... or may not be connected to Neutral (almost never) or the green wire Earth (sometimes)... or sometimes, there will be a controlled impedance, like a 1000pF capacitor, between that 0 Volt and Earth ground... to allow high frequency stuff, like ESD, transients and stuff... to "drain away" to Earth, while acting like a nearly infinite resistance to DC currents and voltages. ESD test benches put about 1 Megaohm between 0Volt and Earth... to allow charge to slowly drain away over time; while still allowing ESD events to reach 8KV... or whatever test threshold is needed.

If you have a very sensitive circuit in that 5VDC microprocessor circuit...for a high end sensor... there will be all sorts of noise reduction and filtering circuits, such that you can pick off signals in the microvolt level. This costs money. (isolated power supplies...bulky zero volt reference planes... differential signal amplifiers...controlled impedances to ground... sometimes digital post-processing to digitally filter "60 Hz hum" out of your sensor signal)

If you have a gas valve with a flame sensor... it might be trying to work with the same levels of noise and susceptibility... but instead of spending the money to make it really noise immune... you just leave the circuit cheap and simple, and err on the side of caution and shut off the gas.

I've never done the UL testing on a gas appliance flame sense circuit, and I don't gamble... but I bet that one of the hard and fast requirements of getting a gas appliance through UL is "fail safe"... as in... if in doubt? signal is noisy? shut off the gas.

 

[will-max dairy]

Well.................looked high, and low, and still haven't come up with an answerView attachment 103809

From a Rheem diagnostic PDF https://my.rheem.com/pts/FAQ/FAQ_Gas_Furnace.asp

View attachment 103810

I've found reference to modern furnaces somehow checking for equipment ground, and not operating if none is detected. I have no idea whether this is true.

Other discussions relate to the EGC as a 0 voltage reference point for the control circuit. This is beyond my understanding.

In the same vein, I've seen a discussion that claims the earth ground removes spurious signals from the control circuit. This is beyond my understanding.

Anyways..........without a bonded neutral, the equipment ground is an open circuit as far as the circuit breaker is concerned. This applies to using an extension cord..........none of this is meant to apply to the use of a transfer switch. It's about plugging into a welder/generator, or a plain generator.

So.......................using an extension cord with a generator that has a floating neutral won't provide a path to source for clearing a fault, unless you bond the neutral. Welders have a bonded neutral, so they're safe for use with an extension cord. And, does this explain why my furnace runs on the welder?

But this doesn't answer the question as to why you need a bonded neutral to run a furnace. I can't imagine any current, other than fault current, running on a ground wire. I'm at a loss.

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...

 

[will-max dairy]

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.