Generator sizing question

[Thezapper]

Hello fellow members I have some questions before I buy my next generator. I am looking at buying a Honda eu2000 to power my home furnace. I already have a Honda eu6500is and I love it, but I wanted another gen set to specifically run a single furnace. The furnace in question is a Trane xv90 natural gas unit with a 2 stage blower. Here are the specs on this unit.

Here are the specs on the Honda eu2000

I understand I can get bigger, cheaper generators but I wanted to know if this little champ will run my Trane furnace.

 

[R.Anderson]

Yes it will. Furnace 11.1 amps Generator 13.3 amps

 

[theoldwizard1]

Honda 2000 have "different" grounding. You may have to use a bonding plug.

 

[Thezapper]

The only thing I'm worried about is the amperage spike when the motor first turns on, some people say it's twice as much the running amps. If I only had a friend that had one so I can try it out before I buy my own, or I could measure the current with a amp clamp?

 

[theoldwizard1]

Not all "amp clamps" will measure "start up" current.

You could get a Champion 2800/3100 watt inverter generator for less than the Honda EU2000. Yeah, it's not a Honda, but IMHO the Honda's are overpriced.

 

[bjcouche]

I wouldn't be so sure that that generator will work. That little Honda is rated for 2,000W peak, which is often the maximum surge current, like for motor starting, that the generator can handle. And even then, this might be only for 0.5 seconds. Furnace blower motors spin large fans with significant inertia, and take several seconds to spin up to full speed. Before I spent money on a generator, I'd want to be more sure it will work. Can you rent one from a rental place to try it?
AC induction motors, single phase, can take 2-3X rated current for startup. That being said, your furnace does call for a 15A circuit breaker, but then still, a 15A breaker will pass more than 15A for a few seconds....

Your furnace lists the blower as "variable" speed. Do you know if the blower is controlled by a variable speed inverter controller? If so, then there is likely little to no inrush current for motor starting. However if it's inverter controlled, many inverters have non sinusoidal input current waveforms, which can cause significant voltage distortion to the generator.

If you can't locate the exact generator to rent or borrow for testing, then renting a different 1500-2000W generator would at least give you some more confidence that the generator you want to use will work.

I've been through this before. A 5KW generator will not run my well pump even though the well pump is only about 2HP. The startup current stalls the generator. I ended up using an 8KW generator, and that one is able to provide the surge current to get the pump started.

Brian

 

[theoldwizard1]

However if it's inverter controlled, many inverters have non sinusoidal input current waveforms, which can cause significant voltage distortion to the generator.

I would no longer use the word "many" especially in this context. I would be doubtful that any furnace fan speed inverter drives were non-sinusodial, unless the motor was DC.

 

[goodwrench]

I think Home Depot might rent the little Honda. would definitely try to rent before buying. inverter generator don't have a lot of surge capacity

 

[Thezapper]

The only place that rents one is about 100 km away, I guess that is the safest bet. Thank you guys for your input

 

[bjcouche]

Operating equipment on a generator is lot different than running it on grid power. This is due to both the maximum current capacity and the source impedance. Generators have much higher impedance (think of it as series resistance) than the power coming from the power company.

Technical info:
Most electronic devices these days use electronic power supplies, instead of the old style transformer type power supplies. This is cost driven. The electronic power supplies take the 120V, run it through a bridge rectifier to make DC, then step it down to the required voltages, 5V, 12V, 24V, etc. The bridge rectifier only draws current near the peaks of the AC voltage waveform. For easy math, say it draws current for 25% of the waveform time. The other 75% of the time it is drawing no current, however the average power must be maintained, thus during that 25% time, the current is 4X what it would be if it was drawing current 100% of the time. This causes high peak currents, even though the average current is low. High peak currents cause voltage distortion on the power source, and the higher the source impedance, the more the voltage is distorted.
More modern electronic equipment has PFC (Power Factor Corrected) power supplies. These use more sophisticated (and more costly) electronics to draw power throughout the entire sine wave. This is becoming common in consumer electronics due to UL and European requirements. From my experience, it is rare to find variable speed motor drives (at least in the US) that have a PFC front end. Having a PFC front end nearly doubles the cost of the speed controller.
The OP has an AC motor, so if it's variable speed, then the speed controller takes the 120V, converts it to DC, then inverts it back to the required voltage and frequency to achieve the proper speed.

Attached are some pictures of scope measurements of a 3500W briggs generator purchased from a big box store. One shows the voltage unloaded. Another shows it loaded with a resistive load to 4.87A (584W). The next shows fairly bad voltage distortion when powering a 12Vdc power supply at 7.36A (854W). This demonstrates the problems that can occur when operating NON power factor corrected electronic loads on a generator. The last file shows the same 12V power supply plugged into grid power with the load now 9.1A (1101W). For a more detailed discussion, we should probably move this to a new thread.

 

[wyliesdiesels]

The only thing I'm worried about is the amperage spike when the motor first turns on, some people say it's twice as much the running amps. If I only had a friend that had one so I can try it out before I buy my own, or I could measure the current with a amp clamp?

In-rush current as its called is anywhere from 4x-8x the FLA of the motor for approx 100ms.

And u will need a clamp meter that measures in-rush. Not all clamp meters can....

 

[ishiboo]

The Honda's compare very favorably to the cheap inverter generators in terms of being able to handle larger loads when it comes to start current. If it didn't work, adding a soft start capacitor would probably solve the problem, and they're not expensive. People with boats/RVs do it all the time to be able to run bigger ACs on the smaller Hondas.

 

[tldavis]

Not all "amp clamps" will measure "start up" current.

You could get a Champion 2800/3100 watt inverter generator for less than the Honda EU2000. Yeah, it's not a Honda, but IMHO the Honda's are overpriced.

As someone who works for the power equipment division of Honda, you get what you pay for

 

[theoldwizard1]

Attached are some pictures of scope measurements of a 3500W briggs generator purchased from a big box store. One shows the voltage unloaded. Another shows it loaded with a resistive load to 4.87A (584W). The next shows fairly bad voltage distortion when powering a 12Vdc power supply at 7.36A (854W). This demonstrates the problems that can occur when operating NON power factor corrected electronic loads on a generator. The last file shows the same 12V power supply plugged into grid power with the load now 9.1A (1101W). For a more detailed discussion, we should probably move this to a new thread.

Not that I want to get into a "deep dive" discussion, those images don't look at bad to me !

The first one make me think there is some kind of "voltage regulation" in the generator "clipping" the peak voltage which is actually a good thing. 2 of course is very normal. 3 really is not unusual (E lead I in an inductive load).

 

[theoldwizard1]

As someone who works for the power equipment division of Honda, you get what you pay for

I still say they are overpriced !

There have been HUGE advances in electronic (and inverters specifically) since the EU2000 was introduced. A 3000W inverter (assuming a high voltage DC source) now costs <$100 !

Common on Honda, how about an update and a more "realistic" price !

 

[Thezapper]

I know what you mean they are expensive and I've been looking at other alternatives. Ive been looking at this guy Hyundai 2800 inverter generator.

Here is the link to the picture http://www.hyundaipower.ca/hy2800.php . It has more power than the Honda , but the reviews are hit and miss.... There good, there ****, there great, there horrible, my head is spinning..... I actually called their 1-800 number and someone picked up.... I left a email for a couple of parts to test them out and they replied within 4 hours, so that's important too isn't it? It's 800 cdn with a 2 year warranty, what do you guys think about this unit?.