Stand by generator upgrade

[ukrkoz]

Hi all
Here's the situation
Live in PacNW. Area I'm in has frequent power outages. We just had cyclon and are on day 3 no power and more to come.
House is 4100sf, multiple refrigerators, regular utilities, inverted heat pump (I bought this one 2 yrs ago on purpose, as it has low power draw). HP has 10KW Aux heat strip.
I have 20KW standby generator installed and connected via 2 automatic switches. Entire house, everything.
I have 25KW transformer from utility company in my property.
Here's my question.
My generator powers everything just fine, AC included. Problem is, if Aux heat strip kicks in, it bogs, almost stalls. Basically, I dicontinued heat strip yesterday via T-stat white wire and HP keeps house at 69D without issue.
But, winter is coming and I'd rather have that heat strip functional as HP struggles with heat, when it gets real cold outside.
And we WILL have more outages when it will snow.
System has no issues, with Aux heat strip On, when running on external power via that 25KW transformer.
I do not mind upgrading generator but, what do I upgrade it for, to safely run heat strip? I'm on propane tank, that limits options, I'm not going diesel or gas one.
That said, will 26KW propane generator suffice? 30? 30s start looking quite spendy too.
Thank you

 

[dcg9381]

To figure this out, I'd clamp the main, manually kick in the aux heat and report back amps.
Alternately, you can install a power monitor lie an emporia vue and you get a pretty good picture of how your house draws power. My high draws in the summer can reach 17kW.

Do you have any propane drops in the house? My solution to this has been to "T" off a couple drops and I use 20k and 30k BTU ventless propane units as non-electrical heating.. Just throwing the 30k one downstairs in the hall pretty much heats our entire home without any electrical power. It does incur some moisture, but for the <5 days that we're typically below 20 degrees, it works fine.

 

[ukrkoz]

Thank you.
I'm rather dumb electrically, so " clamp and report" is a bit above my paygrade. Assuming, it is referred to a crab claw looking meter, clamped over a power line? And how do I get to it? Standard wall panel, 200 amp.
What you saying is, it's not as much wattage consumed that matters, as amperage?

 

[dcg9381]

Thank you.
I'm rather dumb electrically, so " clamp and report" is a bit above my paygrade.

It's a tool with a "claw" that goes around a wire (one of your mains). If you're not familiar, you probably don't want to go fiddling around with it, hire an electrician.

Assuming, it is referred to a crab claw looking meter, clamped over a power line? And how do I get to it? Standard wall panel, 200 amp.

See above, but here's a video. I wouldn't do it if you've never worked with a "live" panel before. It's dangerous.

What you saying is, it's not as much wattage consumed that matters, as amperage?

Power (watts) = current (amps) * voltage. With amps we can make a good guess at total watts. Clamp meters measure amps.

Either way, if you know how many watts the main is pulling, that's good enough.

If your POC has a modern interface, some of them can show you total watts by hour or smaller resolution, so you don't have to measure anything...

 

[ukrkoz]

Thank you.
I have buddy who might have that meter and know how.
No, house built 2005, no fancy panels.
Basically, measure the draw before jumping to conclusions. Have everything turned on, trip the heat strip, measure.

 

[ukrkoz]

Ok, so say, I measure draw at 19kw. Just a number.
How much surplus of generator power should I have above that? 1K? 2K?5?

 

[FJ 432]

I sell Cummins products. The three large manufacturers (Generac, Cummins and Kohler) all make air cooled generators which yours probably falls into this category. Only Generac makes a 26kw I believe. Going larger would require possibly going to a liquid cooled generator that can be over double an air cooled unit. So I would invest in an quality electrician to determine your load with everything running and work on load management (shutting off certain items) if you're over the limit.

 

[FJ 432]

Ok, so say, I measure draw at 19kw. Just a number.
How much surplus of generator power should I have above that? 1K? 2K?5?

What's hard to determine is when appliance turn on they draw more amps. It also depends on your elevation to see if your generator is de-rated due to elevation.

 

[bobg03]

An electrician should be able to calculate your exact needs.

I have a 22KW and here it's a licensed install to get a permit. The generator (here in the county I live in SC) has to be able to provide 90% of a full load on a house. I had a 50 AMP sauna and a 50 AMP hot tub and figured 18KW would be more than enough as I wouldn't be using either of those appliances during a storm related outage, I was forced to get the 22KW, the hot tub is gone now and the sauna power is secured.

I had an independent licensed electrician do the calculations before I got a quote as I didn't want to get upsold by the company selling the unit. It was nice to know that my HVAC contractor who offered generators and installs gave me the same calculations.

 

[My Old Tools]

I have a 37kw Generac water cooled that runs my 3850sf home, my 1200sf shop, 5 ton geothermal system, double electric ovens, 2 refrigerators, freezer, etc, etc. I love the water cooled genny. It is quite economical to run (propane). It's barely loaded at all running everything, and it will do it for weeks if need be. That generator came with the house. It's a good 15 years old at least. It's powered by a Mitsubishi 4 cylinder engine the same as they put in their small trucks, so parts are easy if needed.

 

[ukrkoz]

Thank you all for your input.
I agree, it's guesswork without proper load testing.

 

[Badgerstate]

Id look at a 30kW unit. That way, you know that you have enough capacity. Take it from someone who is a former Generac generator tech.

 

[mm08822]

Hi all
Here's the situation
Live in PacNW. Area I'm in has frequent power outages. We just had cyclon and are on day 3 no power and more to come.
House is 4100sf, multiple refrigerators, regular utilities, inverted heat pump (I bought this one 2 yrs ago on purpose, as it has low power draw). HP has 10KW Aux heat strip.
I have 20KW standby generator installed and connected via 2 automatic switches. Entire house, everything.
I have 25KW transformer from utility company in my property.
Here's my question.
My generator powers everything just fine, AC included. Problem is, if Aux heat strip kicks in, it bogs, almost stalls. Basically, I dicontinued heat strip yesterday via T-stat white wire and HP keeps house at 69D without issue.
But, winter is coming and I'd rather have that heat strip functional as HP struggles with heat, when it gets real cold outside.
And we WILL have more outages when it will snow.
System has no issues, with Aux heat strip On, when running on external power via that 25KW transformer.
I do not mind upgrading generator but, what do I upgrade it for, to safely run heat strip? I'm on propane tank, that limits options, I'm not going diesel or gas one.
That said, will 26KW propane generator suffice? 30? 30s start looking quite spendy too.
Thank you

What do you mean - 2 automatic switches? 2 transfer switches, 1 slaved off of the other?
25KW pad mount transformers can deliver more than rated for short term w/o issue. With a comparatively limitless supply of grid power behind it, it handles start-up spikes and overloads better than a dinky gen with minimal inertia.

Could you change the single 10KW heat strip to two 5KWs? (Yes, you would need additional control hardware for one element. It could be as simple as a load management relay with a higher priority than other misc loads you wouldn't care if dropped off.)

Yes, Generac has a 26KW air-cooled LP hsb gen. Same footprint as the 20KW Guardian. Running on LP gives you the full rating of the gen. (NG is usually 1-2KW lower.)
What is mfr name on the "automatic switches"?

Liquid cooled is about twice the footprint and cost (even for the same KW size as air-cooled.) Not sure of fuel consumption between the 2, but easily found in specs.

You would be best informed with an energy monitoring system added on to your main panel and various circuits. Trend it for a year (at least through a winter.)

Anything that is low priority could easily be load shed to limit the overall gen size needed. Of course you can also manage what you run during a grid outage too.

Capacity to run everything at the same time is easily achieved, just need $$ and ear muffs. Running everything at once is unlikely but some people can't fathom an ounce of inconvenience.

 

[wyliesdiesels]

Any reason why youre not running propane heaters? it will be more efficient than electric heaters especially running on a generator powered by... wait for it... propane...

 

[mm08822]

An electrician should be able to calculate your exact needs.

I have a 22KW and here it's a licensed install to get a permit. The generator (here in the county I live in SC) has to be able to provide 90% of a full load on a house. I had a 50 AMP sauna and a 50 AMP hot tub and figured 18KW would be more than enough as I wouldn't be using either of those appliances during a storm related outage, I was forced to get the 22KW, the hot tub is gone now and the sauna power is secured.

I had an independent licensed electrician do the calculations before I got a quote as I didn't want to get upsold by the company selling the unit. It was nice to know that my HVAC contractor who offered generators and installs gave me the same calculations.

That 90% requirement is BS from the county. As long as load shed capability is provided, you meet NEC requirement. Same for the licensed install requirement. Are these legally adopted requirements or just somebody's opinion in the building dept?

 

[Sumboodie]

Good lord. What do you all even do with ~4000 sq feet in a home?
Have like 15 kids?

I'd go broke just trying to keep that much house going!

Plus have a ton of empty rooms

 

[Bert_]

Transformer size doesn't really correlate to generator size. You can overload a oil filled transformer 200% for a couple hours and it's fine.

Can you stage the elements? Normally it's going to be (2) 5kw elements inside already.

You should put an amp clamp on the main. It's very easy and you can buy your own meter for less than the price of a service call from an electrician.

 

[Firebrick43]

Any reason why youre not running propane heaters? it will be more efficient than electric

Only 14 post to state the most obvious answer. Something like a rinnai wall furnace is fairly easy to install for back up or supplemental heat and MUCH cheaper than a new generator and new switch gear.

It’s also probably 75% more efficient to heat directly with propane in comparison to converting heat to mechanical energy to electricity and back into heat.

 

[Chuckster in NJ]

Is the gas piping sized properly?…….. Have you checked the gas pressure at the machine while running and under the load that bogs it down?

 

[ukrkoz]

Any reason why youre not running propane heaters? it will be more efficient than electric heaters especially running on a generator powered by... wait for it... propane...

Because I'm on tank. And heat pump heats entire house, instead of areas. And it's more cost efficient than to keep buying propane.
I have no problem with HP, the only concern is heat strip.

 

[ukrkoz]

Is the gas piping sized properly?…….. Have you checked the gas pressure at the machine while running and under the load that bogs it down?

Yep. Propane people even upsized the line from tank to house.

 

[ukrkoz]

Good lord. What do you all even do with ~4000 sq feet in a home?
Have like 15 kids?

I'd go broke just trying to keep that much house going!

Plus have a ton of empty rooms

Yep. Just the 2 of us. And 6 acre. We like it that way. Plus, we bought it for half price.

 

[wyliesdiesels]

Because I'm on tank. And heat pump heats entire house, instead of areas. And it's more cost efficient than to keep buying propane.
I have no problem with HP, the only concern is heat strip.

but it isnt efficient to use propane to spin a generator to make electricity to in turn heat the house. youre actually losing a lot in inefficiencies.... if its just the 2 of you why do you need to heat an entire 4000 sq ft house during a power outage much less during non-power outages?

 

[ukrkoz]

What do you mean - 2 automatic switches? 2 transfer switches, 1 slaved off of the other?
25KW pad mount transformers can deliver more than rated for short term w/o issue. With a comparatively limitless supply of grid power behind it, it handles start-up spikes and overloads better than a dinky gen with minimal inertia.

Could you change the single 10KW heat strip to two 5KWs? (Yes, you would need additional control hardware for one element. It could be as simple as a load management relay with a higher priority than other misc loads you wouldn't care if dropped off.)

Yes, Generac has a 26KW air-cooled LP hsb gen. Same footprint as the 20KW Guardian. Running on LP gives you the full rating of the gen. (NG is usually 1-2KW lower.)
What is mfr name on the "automatic switches"?

Liquid cooled is about twice the footprint and cost (even for the same KW size as air-cooled.) Not sure of fuel consumption between the 2, but easily found in specs.

You would be best informed with an energy monitoring system added on to your main panel and various circuits. Trend it for a year (at least through a winter.)

Anything that is low priority could easily be load shed to limit the overall gen size needed. Of course you can also manage what you run during a grid outage too.

Capacity to run everything at the same time is easily achieved, just need $$ and ear muffs. Running everything at once is unlikely but some people can't fathom an ounce of inconvenience.

Yes, automatic transfer switches. 2 of them, in parallel, because I have 2 panels. One per panel. Don't remember the name, one came with generator. Kohler.

 

[ukrkoz]

but it isnt efficient to use propane to spin a generator to make electricity to in turn heat the house. youre actually losing a lot in inefficiencies.... if its just the 2 of you why do you need to heat an entire 4000 sq ft house during a power outage much less during non-power outages?

Well, because we like it that way? Comfortable. My office is on the second floor.
And no, it's not more efficient to "spin" generator. But like heck is more convenient. Even my wife finally accepted that.
And running propane truck to fill is heck of expensive. Ongoing 2.30 a gallon plus service fee. And my tank normally lasts me over a year, so why would I ask for more refills using propane more?

 

[Firebrick43]

Well, because we like it that way? Comfortable. My office is on the second floor.
And no, it's not more efficient to "spin" generator. But like heck is more convenient. Even my wife finally accepted that.
And running propane truck to fill is heck of expensive. Ongoing 2.30 a gallon plus service fee. And my tank normally lasts me over a year, so why would I ask for more refills using propane more?

You will use MORE gallons of propane running a larger generator fully loaded to produce electricity to run resistance heat strips

A gallon of propane has 91,500 btu per gallon. You will only get ~30% of the btus of that gallon into the house via heat strips/generator or 27,450 btus

You will use less propane to run your current smaller generator at partial load and use propane directly in a wall furnace or similar heater. 95% efficiency on the wall heater means that 86,877 btus will be put into the house per gallon of propane vs heat strips.

You can still run the heat pump at the same time to help distribute the heat around the house. It’s the heat strips and all the phase changes in energy that is the problem

 

[mm08822]

Last time I looked at the energy input to a gen vs its output, it was around 30%. I don't remember if at 1/2 load or full load.

Perfect reason to manage gen run time during an outage.

 

[wyliesdiesels]

Well, because we like it that way? Comfortable. My office is on the second floor.
And no, it's not more efficient to "spin" generator. But like heck is more convenient. Even my wife finally accepted that.
And running propane truck to fill is heck of expensive. Ongoing 2.30 a gallon plus service fee. And my tank normally lasts me over a year, so why would I ask for more refills using propane more?

welp its your money..... makes no sense.... have to upgrade the genny to power heat strips which will consume more propane than just running a propane heater or 2

 

[bobg03]

That 90% requirement is BS from the county. As long as load shed capability is provided, you meet NEC requirement. Same for the licensed install requirement. Are these legally adopted requirements or just somebody's opinion in the building dept?

I don't know but after losing power for 13 days in Hurricane Matthew in 2015, I was happy that i'd never go thru that again.

 

[Two Sheds]

Have you considered replacing the air handler on your heat pump with a high-efficiency propane furnace? It would probably cost way less than upgrading the generator. The high efficiency furnaces can be vented with PVC pipe, so you won't need to add a flue. We have a heat pump with gas auxiliary that can be run from a small generator. (I am considering replacing the generator, not because of capacity, but because of reliability issues, but that's a different story).

 

[pbon]

Is there any sort of soft start devices that could reduce the bog when the heat goes on? The description in the original post suggests the big is an initial bog and not continuous. Or could a load shedding box temporary drop a couple of nonessential draws as the heat starts? If not, my guess with zero input from clamp measurements is that another 30% capacity from a 26KW over a 20 would be provide the overhead.

 

[dave*99]

Have you considered replacing the air handler on your heat pump with a high-efficiency propane furnace? It would probably cost way less than upgrading the generator. The high efficiency furnaces can be vented with PVC pipe, so you won't need to add a flue. We have a heat pump with gas auxiliary that can be run from a small generator. (I am considering replacing the generator, not because of capacity, but because of reliability issues, but that's a different story).

This solution is worth investigation for the OP. It is an efficient way to make heat when he is on generator power. But I suspect under normal grid power, he prefers the heat strips. They will run indefinitely without incurring additional propane refills - he commented on the expense of that.

The hybrid approach might be to keep the air handler (with heat strips) and add the furnace provided there is room for all that equipment. But I'd love to see look on the face of the future HVAC technician seeing that setup for the first time.

The OP volunteered his checkbook to provide the most convenient option - not the most efficient. A larger generator fits the bill. But keep in mind propane usage will be high when feeding the heat strips from the generator. A large propane tank would be a good idea.

 

[wyliesdiesels]

This solution is worth investigation for the OP. It is an efficient way to make heat when he is on generator power. But I suspect under normal grid power, he prefers the heat strips. They will run indefinitely without incurring additional propane refills - he commented on the expense of that.

The hybrid approach might be to keep the air handler (with heat strips) and add the furnace provided there is room for all that equipment. But I'd love to see look on the face of the future HVAC technician seeing that setup for the first time.

The OP volunteered his checkbook to provide the most convenient option - not the most efficient. A larger generator fits the bill. But keep in mind propane usage will be high when feeding the heat strips from the generator. A large propane tank would be a good idea.

he's gonna have increased propane usage either way. a larger generator will do that. so what makes more sense is to not be inefficient by spinning a load to generate electricity to in turn make heat...

 

[dave*99]

he's gonna have increased propane usage either way. a larger generator will do that. so what makes more sense is to not be inefficient by spinning a load to generate electricity to in turn make heat...

Maybe I wasn't clear.

Two Sheds offered up the possibility of replacing the air handler (that has backup heat strips) with a propane furnace. When on generator power and the HP can't make enough heat, the propane furnace kicks in to supplement. That is an efficient solution. Sounds good, but:

When on grid power, cold weather, HP not keeping up, auxiliary heat needed...... Now he is burning propane in the furnace because the heat strips are gone. With the HP and heat strips he burns no propane if the grid is powering his home.

 

[mike93lx]

he's gonna have increased propane usage either way. a larger generator will do that. so what makes more sense is to not be inefficient by spinning a load to generate electricity to in turn make heat...

I bet the OP uses the heat strips a hell of a lot more when utility power is active than not. You are focusing on just the impact while power is out

 

[theoldwizard1]

Hi all
Here's the situation
Live in PacNW. Area I'm in has frequent power outages.

Installed a vented propane heater in the basement. By far the cheapest option (after sweaters and blankets).

Next cheapest, zone the house. Being able to shut off ducts and close off rooms that are not generally used will make a difference !

Last, check into heat pumps that do not require an auxiliary heat strip. There are many mini-splits that will make heat down below zero F !

 

[theoldwizard1]

Any reason why youre not running propane heaters? it will be more efficient than electric heaters especially running on a generator powered by... wait for it... propane...

Because I'm on tank. And heat pump heats entire house, instead of areas. And it's more cost efficient than to keep buying propane.
I have no problem with HP, the only concern is heat strip.

Like I said, put propane heater (not a furnace) in the basement an leave it turned off until you need it ! It will heat the basement and therefore will het the house above.

It might actually be CHEAPER to run that heater as a BASE instead of the heat strip even when the generator is not running !

If you like to look, propane fireplaces are great back up for heat pump.

 

[mm08822]

I wouldn't touch the gen until you install a soft-start on the HP and install an energy monitoring system.

The emon system's data will show you how much those heat straps cost to operate. A 10 kw spike is easy to track.

 

[dave*99]

I wouldn't touch the gen until you install a soft-start on the HP and install an energy monitoring system.

The emon system's data will show you how much those heat straps cost to operate. A 10 kw spike is easy to track.

The OP has an inverter heat pump. I thought those were inherently soft start.

 

[mm08822]

The OP has an inverter heat pump. I thought those were inherently soft start.

He said it was inverted, so I assumed he meant that he hung it upside down.

Agreed, a soft-start/vfd (ramped up to speed) eliminates the spike due to compressor start-up.