MEP802 on the House. What's going on here...

[98G]

I've got an 802 and hooked it up to the house. Manual transfer switch. 50 amp 14 50 NEMA plug, 40 amp breaker. 6/4 copper cable.

Red and black to legs 1 and 3, green to ground, white to neutral. Phase and voltage set to 120/240 single phase.

Power on, contactor closed, switch the house to the genset from the grid. Lights are on, a few fans are on, washer is running, percentage of load shows ~25%. Genset is happy so far as i can tell.

Drop the AC thermostat to 60*, AC kicks on and runs. Percentage of load shows ~50%. Everything electrical in the house is running sluggishly.

Hz spot on at 60. Voltage spot on at 240V. Genset seems happy, no black smoke, no stumble. But electrical appliances running slowly.

What should i know that I obviously don't?

This is non-emergency testing before any potential power outages. Learn now while there's no pressure...

Thanks for any education you may provide...

 

[WWRD99]

I'd bet your ac compressor pulls more than 40 amps to start up...pop a soft start on it then it should be able to handle it better. Until then I wouldn't run the ac...might pop the capacitor on the power input of the compressor. If you haven't already do a basic load test by adding a little at a time too if it's a new machine.

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[WWRD99]

How far away is the genset from the house? Is 6 4 big enough for the distance?

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[rickf]

Central air is a pretty heavy load for a 5K genset. How many ton is your compressor? I am sure it is overloading on startup and may not be catching up. I never go by those percentage meters, I have never seen an accurate one yet. I will bet that A/C compressor draws at least half of the capacity of the genset in running mode and then add that to all the other stuff you have going in the house. I think with a 5K genset the A/C would be a non essential item. If you run that compressor too many times on low voltage you WILL burn up the compressor. VERY pricy repair!!

 

[Evvy Fesler]

What do you mean by electrical running slow?

 

[98G]

How far away is the genset from the house? Is 6 4 big enough for the distance?

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15' of 6/4 cable going into the transfer switch and the breaker on the power pole that feeds the house. From the pole to the house it's the same thing that grid power uses, whatever that is. #6 AWG should not be the weakest link.

 

[98G]

What do you mean by electrical running slow?

Turntable on the microwave, and outdoor cooling fan on the AC unit turning slowly.

 

[WWRD99]

15' of 6/4 cable going into the transfer switch and the breaker on the power pole that feeds the house. From the pole to the house it's the same thing that grid power uses, whatever that is. #6 AWG should not be the weakest link.

Ok that's definitely not to much distance then!

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[98G]

Central air is a pretty heavy load for a 5K genset. How many ton is your compressor? I am sure it is overloading on startup and may not be catching up. I never go by those percentage meters, I have never seen an accurate one yet. I will bet that A/C compressor draws at least half of the capacity of the genset in running mode and then add that to all the other stuff you have going in the house. I think with a 5K genset the A/C would be a non essential item. If you run that compressor too many times on low voltage you WILL burn up the compressor. VERY pricy repair!!

I honestly didn't expect it to run the AC. I expected it to overload and shut off. What I'm seeing isn't what I expected to see.

And yeah, AC is nonessential. Refrigerator and lighting during the summer months, and lighting and furnace blower during the winter months and I'd consider it adequate.

My goal today was load it to 75% indicated and see what 75% looked like in terms of what was on. I didn't really expect the AC to be included in the 75%, but tried it as a test and got a result I didn't anticipate.

I didn't know how much to trust the percentage meter. "Not at all" seems like a reasonable answer.

 

[rickf]

Have you checked the voltages in the house at the panel with a meter? I don't care what the genset says, you need to check the voltages in the house!!! There are things that need to be checked and followed up on when installing and checking out a genset for the first time. When you tied in the transfer switch did you change any of the wiring in the main box? If so are the loads all balanced? Have you checked the balance on the leads coming in from the genset, L1 to neutral and L2 to neutral should both read 120 volts under load and 240 from L1 to L2. If that AC fan is running slow you had better cut it off or you are going to lose it.

 

[98G]

I'd bet your ac compressor pulls more than 40 amps to start up...pop a soft start on it then it should be able to handle it better. Until then I wouldn't run the ac...might pop the capacitor on the power input of the compressor. If you haven't already do a basic load test by adding a little at a time too if it's a new machine.

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I thought the same. I'd expect the breaker to pop rather than what I'm seeing.

 

[DieselAddict]

+1, check your voltages and frequency in the house. Don't blindly trust the meters on the generator.

 

[98G]

Have you checked the voltages in the house at the panel with a meter? I don't care what the genset says, you need to check the voltages in the house!!! There are things that need to be checked and followed up on when installing and checking out a genset for the first time. When you tied in the transfer switch did you change any of the wiring in the main box? If so are the loads all balanced? Have you checked the balance on the leads coming in from the genset, L1 to neutral and L2 to neutral should both read 120 volts under load and 240 from L1 to L2. If that AC fan is running slow you had better cut it off or you are going to lose it.

I cut the AC fan immediately. My philosophy is anything I don't understand is dangerous until I do.

Transfer switch is preexisting with the house. Not my inexpert tampering. Electrician redid all of the wiring to include new breaker box in 2020. The house is all new wiring. The AC is new as of 2020.

Thanks for suggestions on what to measure and where. I'll be doing that.

 

[Scoobyshep]

Have you checked frequency?

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[WWRD99]

I cut the AC fan immediately. My philosophy is anything I don't understand is dangerous until I do.

Transfer switch is preexisting with the house. Not my inexpert tampering. Electrician redid all of the wiring to include new breaker box in 2020. The house is all new wiring. The AC is new as of 2020.

Thanks for suggestions on what to measure and where. I'll be doing that.

If you can have an ac guy or electrician check the in rush amps of the ac setup, you may find a soft start will work. They're about 300$ and easy to install.

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[98G]

Have you checked frequency?

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Only with the onboard gauge. I'll get a meter and get after it at the box in the basement and see what we're seeing in the house.

I'm still not really understanding why the 40 amp breaker didn't trip.

 

[Scoobyshep]

Only with the onboard gauge. I'll get a meter and get after it at the box in the basement and see what we're seeing in the house.

I'm still not really understanding why the 40 amp breaker didn't trip.

Breakers are typically thermomagnetic meaning that need a thermal event (overload) or magnetic event(sudden short) either way they react to current. The onboard breaker of the generator is a CT breaker it reads magnetic induction. Still current based. So unless you exceeded the current setting ot wouldn't. Me personally I do extra monitoring for voltage and frequency.

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[nextalcupfan]

Out of curiosity could you say how many tons your AC is? Or even better post a pic of the info sticker on it.
I know my 3 ton AC would make my 803a lurch on its trailer every time it started, It's much better with a hard start kit on it.
Still dims the lights though.

 

[98G]

Out of curiosity could you say how many tons your AC is? Or even better post a pic of the info sticker on it.
I know my 3 ton AC would make my 803a lurch on its trailer every time it started, It's much better with a hard start kit on it.
Still dims the lights though.

I'll have a look tomorrow and see if I can find a data plate on it.

 

[Coug]

typically it's frequency that affects timers and clocks running slow, not voltage.

On my MEP-802A the frequency gauge reads higher than it actually is, so I would definitely recommend using some type of a meter to check. Probably the easiest one I know of would be something like the kill a watt meters. You'd have to use a short extension cord or surge strip to plug it into the convenience outlet of the generator, sbut that's a bit easier and safer than using meter probes into various panels and whatnot.

There are a few versions, but Amazon has them as well as Harbor Freight

https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU?th=1