PTO Generator Question

[RalphVa]

I've a 12.5 kw "whole house" generator that runs pretty much the whole house excluding swimming pool and big heat pump through some magic load shedding on the circuit breaker box. From my electric bill, I figured out that my average usage is only about 2-3 kw (closer to 2). So, it sits there genning out only those average 2-3 kw but is good for up to near full capacity if needed. I've really never heard it laboring during a power failure, and the fuel consumption follows the fuel consumption curve for the 2-3 kw, e.g. very low (about 0.23-0.3 gph).

Commissioned it in early 2013.

Ralph

 

[Industrial Toys]

My Onan 15K unit did have some weird "Field Boost" clockwork timer switch. I never did know what it was for, but since I still have a copy of the manual, I am a little curious. MAYBE, in a chicken barn, you might need extra starting current for a whole bunch of ventilation fans, yet you don't want to allow the possibility of overloading your set continuously.

 

[CobyRupert]

I've a 12.5 kw "whole house" generator that runs pretty much the whole house excluding swimming pool and big heat pump through some magic load shedding on the circuit breaker box. From my electric bill, I figured out that my average usage is only about 2-3 kw (closer to 2). So, it sits there genning out only those average 2-3 kw but is good for up to near full capacity if needed. I've really never heard it laboring during a power failure, and the fuel consumption follows the fuel consumption curve for the 2-3 kw, e.g. very low (about 0.23-0.3 gph).

Commissioned it in early 2013.

Ralph

Don't be insulted, but I think average (total kW-hrs divided by total hrs) is poor way to size, or estimate the kW load the genny will see. Typically, if you're not retired, you might sleep 8 hours a day, and be at work another 10. Basically use a whole bunch of loads in a short timespan, then use very few loads other parts of day.
One really needs to size the genny on the peak load (and/or starting loads) it will see and the duration.
Depending on the time of year, and user, the load profile typically spikes in the morning, dips in day, then peaks in late afternoon or evening. Peak to valley might be 3:1, 5:1, 10:1, etc... Hard to say.

 

[TerryR]

Coby,
Your post sent me looking at the electric power usage feature our power company offers. I had hoped it offered hourly usage but it doesn't, just daily. So couldn't see directly the effect you describe, but do see some interesting data around the times we were gone on vacation. We are retired, so are in or around the house much of the day. Our heat is propane, and we have no air conditioning, so our usage isn't much effected by temperature, though you would expect the lighting load would increase during the darker days of winter. Here's what I found:


You can clearly see our long weekend away in mid-April, our 12-day vacation in mid-May, and a shorter trip in mid-Jul. The data in May is pretty dirty because of so many estimated days that week, but it's clear we have a base load of about half our normal usage. I'm surprised it is that high. We have two frigs and a freezer, so that's probably most of it. And we had someone in during our week plus trip to feed the cat, so she ran lights and water (pump) some. But that means our "variable" load isn't all that great, on average.

 

[CobyRupert]

Coby,
Your post sent me looking at the electric power usage feature our power company offers. I had hoped it offered hourly usage but it doesn't, just daily. So couldn't see directly the effect you describe, but do see some interesting data around the times we were gone on vacation. We are retired, so are in or around the house much of the day. Our heat is propane, and we have no air conditioning, so our usage isn't much effected by temperature, though you would expect the lighting load would increase during the darker days of winter. Here's what I found:

You can clearly see our long weekend away in mid-April, our 12-day vacation in mid-May, and a shorter trip in mid-Jul. The data in May is pretty dirty because of so many estimated days that week, but it's clear we have a base load of about half our normal usage. I'm surprised it is that high. We have two frigs and a freezer, so that's probably most of it. And we had someone in during our week plus trip to feed the cat, so she ran lights and water (pump) some. But that means our "variable" load isn't all that great, on average.

That shows your total energy use on a given day, but what the genny cares about (trips off on) is the power demanded any given second (milli-second actually).
For example, on the largest energy day, it may have been a 10 amp load that ran for 24 hours, whereas on the lowest energy use day you might have a 100 amp load that only ran for 1 hour.
You would need a 100 amp generator.

You really need to add up the loads that will run at any given time to size the genny.
How long they run for determines the fuel use ($) and generates the graph. :2cents:

 

[John_Mc]

And when you want PTO generator most... Sorry neighbor (or wife) the tractor is tied up keeping the house warm, and I cant help you get your big (DODGE/FORD/CHEVY- or little HONDA) pickup (car) out of ditch where it slid into on miserable slushy/icy road...

Dale

In my house, the conversation would be, "Sorry family. We're going to disconnect the power for an hour so I can [go plow the driveway / go pull the neighbor out]". We don't have a PTO generator. We run our house off a portable generator during power outages. My family already knows to expect that if a neighbor needs the generator for a bit to save the food in their freezer, fire up their heating systems for a bit, etc., then we'll be shutting down for a bit to help them out. We can easily go a few hours without in order to help someone with a real need in an extended outage.

 

[John_Mc]

yes and no on this one. You may not think you need to run a jacuzzi, but we lose power up here in north idaho in winter at 5F, I want my hot tub heater to cycle. If you have ever seen a hot tub after 4 days of no power..... the thing is ruined. Not a good idea on a $5,000 hot tub. The tub heater takes 5,000 watts at 240 v.

Nothing says you have to cycle the hot tub at the same time you are cooking dinner. I don't have a hot tub, but if I did, I'd either shut off other loads for a bit so I could cycle the heater, or if it were an extended outage, I'd just drain the thing.

But then I tend to be a minimalist during a power outage. We're comfortable. We protect the house from damage, but we don't plan on just carrying on with life as usual. In a weird way, our family enjoys the challenge. We sometimes don;t bother to start the generator, just to see how we can get by. We don't tend to do this when it's -20˚F out (but we could if we wanted to).

 

[crazyal]

Seams like for those who worry about running their tractor all night long or not having it to do other tasks a Tesla Powerwall would be a good option. From what (little) I understand it takes about 3 1/2 hours to charge up the smaller one from 2kw. Obviously if you have a high demand you probably would drain the battery down too fast to make it worthwhile.

 

[TerryR]

That shows your total energy use on a given day, but what the genny cares about (trips off on) is the power demanded any given second (milli-second actually).

Of course. Do you think I'm stupid?

I said it didn't display what you were describing, but I found it interesting that we apparently have a base load when no one is home equal to half our normal daily usage. That says we have some decent sized loads that run automatically all day. So if I were sizing a generator I'd want to identify those loads and consider the possibility they would all want to run at once. Maybe even start at the same time.

 

[grsthegreat]

Seams like for those who worry about running their tractor all night long or not having it to do other tasks a Tesla Powerwall would be a good option. From what (little) I understand it takes about 3 1/2 hours to charge up the smaller one from 2kw. Obviously if you have a high demand you probably would drain the battery down too fast to make it worthwhile.

Ask Walmart what they think about tesla solar systems....i see 7 of their stores have caught fire from them. Walmart sues Tesla over solar panel fires at seven stores