Need some help picking a generator for single-phase and 3-phase use

[cdhendrix]

@Light in the Dark @MatthewWBailey I've got attached pictures of the data tags for my well pump, hot water heater, and ac unit. I also forgot to mention I have 2 upright freezers, 2 fridges, and a large chest freezer that I'd like to keep running. The ac unit would be nice to keep running in the summer but not a necessity. Ideally I'd like to be able to run the whole house off of the MEP until grid power is restored. I've got a 250 gallon fuel tank I can place next to the MEP. It's just a matter of getting one that can handle the power demand

 

[2Pbfeet]

@MatthewWBailey On your earlier post with the solar array going in, that's a heck of a hole. I was looking at the hole picture, thinking that looks like a big chunk of granite, thinking "how the heck", and then I saw your second photo. That's one of the largest diamond core bits I have seen on an electric portable unit. I like the idea of welding a platform to your FEL. Nice job! I had only seen rock coring done with hydraulic augers or coring rigs.

Yes very nice indeed. The 3% freq is pushing the limit for some appliances. That's 1.8hz plus or minus which is greater than the utility tolerance. Some swamp coolers like BreezeAire for example, require a 0.5 hz tolerance bc they're using a speed control, and shut down if there's a higher frequency.
But, again, some Enginerring accounting, if there are no sensitive appliances in the house, then there's no problem with the MEP. It just needs attention and detail.

if the n-g strap can be removed, so the neutral is only connected to the house systems bond, then yes, that's the goal. But a dedicated ground EGC is then also needed back to the house panel so the gen frame doesn't become a shock point. Most gens are relying on that strap to ground the metal parts of the frame. It's so simple yet is so overlooked.

While I think that individual usage, and tolerance for power quality variation are definitely "YMMV", can I pass on a bit of real world experience?

I have intermittently used portable backup generators to run a pretty modern (electronically, at least) house for close to 20 years. All of my generators get checked for voltage and frequency before the initial use, adjusted if necessary/possible, and regularly checked thereafter while in use. I have never seen more than a +/- 1% variation of frequency (59.5-61.5Hz). While running the whole house, I have seen an old diode/capacitor regulated 4kW model drop 5% in voltage when a 3/4HP booster pump kicked on. My 5kW and up have held up better, in part, I think due to more modern regulator systems.

I agree that many folks install generators with a high capacity to be able to not make any adjustment of their daily living during an outage. I understand that. For example, have an elderly neighbor with a handful of AC mini splits that are needed for health reasons, so the plan is that all the AC units might be running, resulting in a big generator. I would say that if the owner is able to make some adjustments in daily living, I think that it is easily possible to run a home on backup power with a much smaller generator, with savings in fuel, and improvements in generator lifetime.

One thing I would flag for propane generators, in particular, is double checking how much propane might be needed for an expected outage, and in particular how much might be needed in cold weather when the tank size and residual volume/fill will greatly reduce the amount of propane available for a generator. Generac and others have propane tables in their installation instructions, with the limits on drawdown at various temperature and loads. Natural gas is also not without its supply limitations as many Texans have found out over the years. In the end, I think it comes down to what any one persons particular needs are.

All the best,

2Pbfeet

 

[2Pbfeet]

@Light in the Dark @MatthewWBailey I've got attached pictures of the data tags for my well pump, hot water heater, and ac unit. I also forgot to mention I have 2 upright freezers, 2 fridges, and a large chest freezer that I'd like to keep running. The ac unit would be nice to keep running in the summer but not a necessity. Ideally I'd like to be able to run the whole house off of the MEP until grid power is restored. I've got a 250 gallon fuel tank I can place next to the MEP. It's just a matter of getting one that can handle the power demand

A half HP well pump should be generally pretty easy to handle. However, the LRA on your AC may set your minimum generator size; 69A is a chunk, and might put you up into a 20kW unit, if you can't install a soft start to lower that number. Can I also suggest considering moving to a heat pump water heater that will draw much less power? Currently, there are a number of rebates/credits available. Sometimes, slightly shifting the particular appliance types can make a big difference in the back up power needs. FWIW: Inverter style AC units tend to have much lower LRA values.

All the best,

2Pbfeet

 

[cdhendrix]

A half HP well pump should be generally pretty easy to handle. However, the LRA on your AC may set your minimum generator size; 69A is a chunk, and might put you up into a 20kW unit, if you can't install a soft start to lower that number. Can I also suggest considering moving to a heat pump water heater that will draw much less power? Currently, there are a number of rebates/credits available. Sometimes, slightly shifting the particular appliance types can make a big difference in the back up power needs. FWIW: Inverter style AC units tend to have much lower LRA values.

All the best,

2Pbfeet

The ac isn't a have to have it'd be nice though but power loss in my area is more likely in the winter. The water heater I'd hate to have to replace but I've been kicking around running some copper lines near my wood furnace in the basement and plumb it in before the water heater

 

[2Pbfeet]

The ac isn't a have to have it'd be nice though but power loss in my area is more likely in the winter. The water heater I'd hate to have to replace but I've been kicking around running some copper lines near my wood furnace in the basement and plumb it in before the water heater

There are lots of ways to skin a cat... We lived in a house plumbed like that for awhile, and it was basically "free" hot water, though I might check the stove temperatures before you get too far into it; most of the versions that I have seen use steel, usually stainless. If the water heater is above the wood stove, you might be able to run it on just thermal gradients, though you might want to add a thermostatic mixing valve to the water heater outlet, as the wood stove might make the water quite hot. (Scalding risk). I would still check your local heat pump rebates; some can be quite generous.

All the best,

2Pbfeet

 

[cdhendrix]

There are lots of ways to skin a cat... We lived in a house plumbed like that for awhile, and it was basically "free" hot water, though I might check the stove temperatures before you get too far into it; most of the versions that I have seen use steel, usually stainless. If the water heater is above the wood stove, you might be able to run it on just thermal gradients, though you might want to add a thermostatic mixing valve to the water heater outlet, as the wood stove might make the water quite hot. (Scalding risk). I would still check your local heat pump rebates; some can be quite generous.

All the best,

2Pbfeet

Copper was just the first thing to come to mind since a lot of the old water service lines I'm finding are getting replaced with Copper. I'm not opposed to replacing the water heater down the road but currently I'm in the process of replacing the roof of the house and remodeling the master suite. Also I'm trying to learn more in this realm of expertise for when I start building a new house.

 

[MatthewWBailey]

@Light in the Dark @MatthewWBailey I've got attached pictures of the data tags for my well pump, hot water heater, and ac unit. I also forgot to mention I have 2 upright freezers, 2 fridges, and a large chest freezer that I'd like to keep running. The ac unit would be nice to keep running in the summer but not a necessity. Ideally I'd like to be able to run the whole house off of the MEP until grid power is restored. I've got a 250 gallon fuel tank I can place next to the MEP. It's just a matter of getting one that can handle the power demand

I would add those 3 units this way:
1/2hp well - 3kw starting 1kw run (depends on depth)
HWH - 4.5kw start and run
AC - 63*208=13kw start (LRA on a motor is given at the lower voltage when calculating wattage fyi). 15.2A total running = 3kw
Total start: 20.5kw. Total run: 8.5kw (non continuous).

As @2Pbfeet said, the AC start is a chunk, however those AC units don't advertise "start amps" bc it depends on the pressure setup. That affects the loading the motor sees as it starts to turn. So they list locked rotor amps LRA. I'd expect a lower start amps than LRA typically. But 20kw seems right for this, without any load coordination/management.

a rock solid solution for an MEP to house connection is to install a 2pole transfer switch at the main, open the N-G bond at the gen, install 4 wires between the gen and transfer switch: L1 L2, N, G. full size N. Do not connect N and G together at gen or transfer switch as they're already connected in the house main. Install
A ground rod at the gen and connect it to the G wire.
Put UPS' on sensitive electronics in the house. Set and maintain the gen Governor frequency.

 

[MatthewWBailey]

All of my generators get checked for voltage and frequency before the initial use, adjusted if necessary/possible, and regularly checked thereafter while in use.

I agree with your post. What you said above is what no one else does, MAINTAIN. You're doing the functions of the warranty on those turnkey house gensets. So that's the key element.

Lesson learned: My friend in Yardley PA shit his pants during Sandy. Called me daily complaining about the utility outage. He ran out first thing and bought a portable genset. Hooked it up and then burned it up bc he's a sales manager. A person either has to own the whole job or hire an expert to do it. With the SteelSoldiers crowd, I trust everyone is a serious person willing to own the whole job.

 

[MatthewWBailey]

@MatthewWBailey On your earlier post with the solar array going in, that's a heck of a hole. I was looking at the hole picture, thinking that looks like a big chunk of granite, thinking "how the heck", and then I saw your second photo. That's one of the largest diamond core bits I have seen on an electric portable unit. I like the idea of welding a platform to your FEL. Nice job! I had only seen rock coring done with hydraulic augers or coring rigs.


While I think that individual usage, and tolerance for power quality variation are definitely "YMMV", can I pass on a bit of real world experience?

I have intermittently used portable backup generators to run a pretty modern (electronically, at least) house for close to 20 years. All of my generators get checked for voltage and frequency before the initial use, adjusted if necessary/possible, and regularly checked thereafter while in use. I have never seen more than a +/- 1% variation of frequency (59.5-61.5Hz). While running the whole house, I have seen an old diode/capacitor regulated 4kW model drop 5% in voltage when a 3/4HP booster pump kicked on. My 5kW and up have held up better, in part, I think due to more modern regulator systems.

I agree that many folks install generators with a high capacity to be able to not make any adjustment of their daily living during an outage. I understand that. For example, have an elderly neighbor with a handful of AC mini splits that are needed for health reasons, so the plan is that all the AC units might be running, resulting in a big generator. I would say that if the owner is able to make some adjustments in daily living, I think that it is easily possible to run a home on backup power with a much smaller generator, with savings in fuel, and improvements in generator lifetime.

One thing I would flag for propane generators, in particular, is double checking how much propane might be needed for an expected outage, and in particular how much might be needed in cold weather when the tank size and residual volume/fill will greatly reduce the amount of propane available for a generator. Generac and others have propane tables in their installation instructions, with the limits on drawdown at various temperature and loads. Natural gas is also not without its supply limitations as many Texans have found out over the years. In the end, I think it comes down to what any one persons particular needs are.

All the best,

2Pbfeet

If you like that, you'll love these...

Hole7. Drilling for gold!? Or solar? If I find Jimmy Hoffa I'll let ya know

youtube.com

Hole9: still going strong. The Drill mud is perfect😉

youtube.com

Luckily, there's no granite here, but it's virgin mountain ground, so lots of basalt. Impossible to dig a hole that isn't the size of a car due to massive boulders. So I thought I'd just drill thru them and pour bag mix into them, no forms. Those slugs are a PITA to get out. I'm still perfecting my rig. I did 12 holes and ruined my shoulders digging those chunks out. For the next 30 holes, I'm adding a vacuum system to the bit (16") and a small crane lift so I can just lift out the whole bit when it's full of Earth bits. The 430D is nice for leveling the drill.

I'm getting good at perfecting the art of drilling mud. Once I get that perfect solution, that Husquarvrna goes like crazy. It's a 2800W motor driven concrete core drill. Used of course.

as an electrical engineer, I'm very good at earthwork

 

[2Pbfeet]

That Husquavarna is impressive. I really like the load LEDs that seem to make it a lot easier to stay within the loading of the drill.

I am in the process of planning on adding a ground mount array, and I know that I will hit rock somewhere. Some of the rock is barely aggregated limestone, some of it is a high quartz shale, and some is jasper, which I really hope that I don't have to drill through. I can auger through the first two, but the jasper might require upping my game. I need to do a couple of test holes to see how bad it is, before I commit to a design (monopole vs an array like yours).

All the best,

2Pbfeet

 

[cdhendrix]

I would add those 3 units this way:
1/2hp well - 3kw starting 1kw run (depends on depth)
HWH - 4.5kw start and run
AC - 63*208=13kw start (LRA on a motor is given at the lower voltage when calculating wattage fyi). 15.2A total running = 3kw
Total start: 20.5kw. Total run: 8.5kw (non continuous).

As @2Pbfeet said, the AC start is a chunk, however those AC units don't advertise "start amps" bc it depends on the pressure setup. That affects the loading the motor sees as it starts to turn. So they list locked rotor amps LRA. I'd expect a lower start amps than LRA typically. But 20kw seems right for this, without any load coordination/management.

a rock solid solution for an MEP to house connection is to install a 2pole transfer switch at the main, open the N-G bond at the gen, install 4 wires between the gen and transfer switch: L1 L2, N, G. full size N. Do not connect N and G together at gen or transfer switch as they're already connected in the house main. Install
A ground rod at the gen and connect it to the G wire.
Put UPS' on sensitive electronics in the house. Set and maintain the gen Governor frequency.

So what MEP would work for my situation? Also how about I leave the electrical to you and you leave the dirt work to me?

 

[dav5]

Probably just 2 burners and the oven plus the well. Depending on the time of year maybe the ac. Usually once a year 1 to 5 days. Worst case a week to 10 days. I'd like to be able to at least be able to use the oven, well, hot water heater and the ac in the summer. I've thought about the pto generators in the past but I have never had a tractor around when I've had power outage. I have multiple farms and rarely have equipment at my house but have diesel at my house

I have a tractor readilly available but I have never understood the reasoning of running a $60,000 tractor to produce the same power output as my $2000 MEP803A. I know prices have come up since I bought it but not enough for it to make sense.

 

[cdhendrix]

I have a tractor readilly available but I have never understood the reasoning of running a $60,000 tractor to produce the same power output as my $2000 MEP803A. I know prices have come up since I bought it but not enough for it to make sense.

I've got a few different farms spread out and rarely ever is there a tractor at the house so the pto generator is pretty much useless. Plus the old tractors I have are probably going to be louder than a MEP

 

[MatthewWBailey]

That Husquavarna is impressive. I really like the load LEDs that seem to make it a lot easier to stay within the loading of the drill.

I am in the process of planning on adding a ground mount array, and I know that I will hit rock somewhere. Some of the rock is barely aggregated limestone, some of it is a high quartz shale, and some is jasper, which I really hope that I don't have to drill through. I can auger through the first two, but the jasper might require upping my game. I need to do a couple of test holes to see how bad it is, before I commit to a design (monopole vs an array like yours).

All the best,

2Pbfeet

That'd be great if you can just auger. Drilling still makes for lots of hand digging. I can't auger at all. Had a big one on the backhoe, tried it and it's useless in this Rocky stuff.
I really use those LEDs religiously as they tell you when you're about to jam. It's odd, the harder the soil, the easier the process. If I hit loose stuff, the bit starts jamming and wobbling. The hole is like a sleeve bearing when it's solid stuff.
I still have to augment with a jackhammer as those slugs can be thick and impossible to lift out. Im hoping to strike oil but everyone says I'm delusional.

 

[MatthewWBailey]

So what MEP would work for my situation? Also how about I leave the electrical to you and you leave the dirt work to me?

Yes that's a plan lol. But I love my track loader! No one drives that but me. And I have 3000 hours of backhoe operating time. Digging electrical trenches requires exacting skill. See my fleet attached..

Im no expert on military gens. I had a small 3kw MEP unit awhile back. Worked fine, just small.

The thing I see in the list of available units for MEPs is that they quickly go from single phase to 208 three phase at around 10kw. My assumption from conversations with Army Sargents I knew at Los Alamos is that these trailer MEPs are for powering remote bases. 208/120Y 3 phase is a great voltage for barracks and living quarters. Whereas the smaller units are for field tent power etc. I know the army likes to shock their troops in the shower, that was a theme of many stories I've heard.

You need a 240/120 single phase 20kw generator end bell attached to a nice diesel engine. The 20kw and up MEPs all seem to be 3 phase. The home genset market is oriented towards single phase gens obviously.

now you could use a 10kw MEP-803a like the gentleman above and just not run AC or switch to a soft starter on the AC compressor. The running load is only 8.5kw based on your numbers. So That's more practical but you've got to do some electrical work. I like this approach bc you can run a smaller unit. Plus the mil gens have a higher standby rating to continuous rating ratio than civilian commercial alternators so you can tolerate some short term overload more than with civilian equip.

in the end, IMPO, the goal is to run the smallest unit possible by using load and demand management. That way your fuel lasts the longest and your cost is the smallest. I run a 11kW diesel 3cyl gen which is actually a Miller bobcat 250 welder/genset. It's fuel efficient and gets double duty as a welder, so is regularly exercised and maintained. I use a manual transfer switch. Freq stability is on the edge of 1-1/2% so its not the best but I've only had to use it in spring & fall for a handful of outages, which are moderate temperature seasons, so no ac running.

 

[Light in the Dark]

MEP-803A with the AC soft start sounds like good middle ground to me.

 

[cdhendrix]

Yes that's a plan lol. But I love my track loader! No one drives that but me. And I have 3000 hours of backhoe operating time. Digging electrical trenches requires exacting skill. See my fleet attached..

Im no expert on military gens. I had a small 3kw MEP unit awhile back. Worked fine, just small.

The thing I see in the list of available units for MEPs is that they quickly go from single phase to 208 three phase at around 10kw. My assumption from conversations with Army Sargents I knew at Los Alamos is that these trailer MEPs are for powering remote bases. 208/120Y 3 phase is a great voltage for barracks and living quarters. Whereas the smaller units are for field tent power etc. I know the army likes to shock their troops in the shower, that was a theme of many stories I've heard.

You need a 240/120 single phase 20kw generator end bell attached to a nice diesel engine. The 20kw and up MEPs all seem to be 3 phase. The home genset market is oriented towards single phase gens obviously.

now you could use a 10kw MEP-803a like the gentleman above and just not run AC or switch to a soft starter on the AC compressor. The running load is only 8.5kw based on your numbers. So That's more practical but you've got to do some electrical work. I like this approach bc you can run a smaller unit. Plus the mil gens have a higher standby rating to continuous rating ratio than civilian commercial alternators so you can tolerate some short term overload more than with civilian equip.

in the end, IMPO, the goal is to run the smallest unit possible by using load and demand management. That way your fuel lasts the longest and your cost is the smallest. I run a 11kW diesel 3cyl gen which is actually a Miller bobcat 250 welder/genset. It's fuel efficient and gets double duty as a welder, so is regularly exercised and maintained. I use a manual transfer switch. Freq stability is on the edge of 1-1/2% so its not the best but I've only had to use it in spring & fall for a handful of outages, which are moderate temperature seasons, so no ac running.

Is that a 953? I'm not opposed to doing some electrical work and if I have to dig a ditch I can handle it. I've thought about the engine driven welder but like the tractor the likelihood of it being home when an outage happens isn't great. The fuel isn't much of an issue because I can have about 250 gallons of diesel on hand. Plus I'm looking at getting a 350 gallon to 500 gallon fuel trailer

 

[MatthewWBailey]

Is that a 953? I'm not opposed to doing some electrical work and if I have to dig a ditch I can handle it. I've thought about the engine driven welder but like the tractor the likelihood of it being home when an outage happens isn't great. The fuel isn't much of an issue because I can have about 250 gallons of diesel on hand. Plus I'm looking at getting a 350 gallon to 500 gallon fuel trailer

Yes I hear that. Tools get used and betrothed to projects. Despite the trash talk I've given them on here, the MEPs are plentiful and lots of knowledge-base on here to support them. Cheap too. Those are major plus'. Gov Planet seems to have them in droves.

That's a 963 from '86. I was lucky to find that with only 2700 hours. Like the LMTV, it needed TLC but is a workhorse and reliable. I was tempted into getting the 973 bc of its 5yd bucket but I had a brief moment of sanity and thankfully passed on that monster. 963 is better all around anyway at 21tons. 3304 engine.

 

[cdhendrix]

Yes I hear that. Tools get used and betrothed to projects. Despite the trash talk I've given them on here, the MEPs are plentiful and lots of knowledge-base on here to support them. Cheap too. Those are major plus'. Gov Planet seems to have them in droves.

That's a 963 from '86. I was lucky to find that with only 2700 hours. Like the LMTV, it needed TLC but is a workhorse and reliable. I was tempted into getting the 973 bc of its 5yd bucket but I had a brief moment of sanity and thankfully passed on that monster. 963 is better all around anyway at 21tons. 3304 engine.View attachment 918247

963s are good rigs. You don't need a 973 they're too heavy for anything other than quarry work. I ran one clearing and it gets stuck easily. My big thing is I've got a few different farms so stuff tends to live there. Plus I have jobsites that stuff tends to live there. I'm also kicking around getting into making biodiesel and getting a waste oil furnace.

 

[MatthewWBailey]

963s are good rigs. You don't need a 973 they're too heavy for anything other than quarry work. I ran one clearing and it gets stuck easily. My big thing is I've got a few different farms so stuff tends to live there. Plus I have jobsites that stuff tends to live there. I'm also kicking around getting into making biodiesel and getting a waste oil furnace.

I've learned to appreciate the middle ground from this 963 lol. Never stuck, even driving thru a pond, and has the power to move rocks bigger than it.

I'd like a waste oil furnace as well. No one is taking the used motor oil anymore. When run at temp, those are great heating sources with minimal emissions. My Father's friend had one back in PA when I grew up. Just a modified boiler really.