Stand by generator upgrade

[dave*99]

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

Agreed, soft-start eliminates the spike due to compressor start-up.

It may not matter. He asked how much he should upsize his generator to run his existing equipment. It’s a simple question. He is willing to write the check. And clear about his intentions. Many of the posts in this thread likely chased him away as they suggested good alternatives but not in line with his desires YMMV.

 

[mm08822]

It may not matter. He asked how much he should upsize his generator to run his existing equipment. It’s a simple question. He is willing to write the check. And clear about his intentions. Many of the posts in this thread likely chased him away as they suggested good alternatives but not in line with his desires YMMV.

I beg your pardon.......no one here has ever done such a thing

 

[mm08822]

It may not matter. He asked how much he should upsize his generator to run his existing equipment. It’s a simple question. He is willing to write the check. And clear about his intentions. Many of the posts in this thread likely chased him away as they suggested good alternatives but not in line with his desires YMMV.

There is one simple question asked that OP didn't answer......gas pressure.

If it is too low to start with or drops off as a heavy load gets added, then that is at least part of the problem. Maybe all of it.

A bigger gen will most likely need something replaced in the existing fuel line.

OP could also look at putting a switch in the heater element circuit. Manually cut out 1/2 of the elements when running on gen. OK, so you have to remember to turn it back on.....may be easy to be reminded, if the house does get cold without all 10kw glowing.

 

[dave*99]

There is one simple question asked that OP didn't answer......gas pressure.

If it is too low to start with or drops off as a heavy load gets added, then that is at least part of the problem. Maybe all of it.

A bigger gen will most likely need something replaced in the existing fuel line.

OP could also look at putting a switch in the heater element circuit. Manually cut out 1/2 of the elements when running on gen. OK, so you have to remember to turn it back on.....may be easy to be reminded, if the house does get cold without all 10kw glowing.

OP answered in post 21. Pressure was measured and line upsized.

 

[AA/FC]

It seems like you have plenty of back-up (generator) electricity when you're not trying to run the 10KW built-in heater...... Buy some 120 volt space heaters and put them in the rooms that you spend the most time in. If the power goes out during the really cold months, run your HP like normal and turn on the space heaters as needed. I couldn't imagine owning a 20KW backup generator AND talking about possibly buying a bigger one. lol

Hey, to each his own. I bought a big enough generator to run my central A/C, so who am I to talk? lolol

 

[mm08822]

OP answered in post 21. Pressure was measured and line upsized.

I missed that. But answer only has about 5% of the info needed.

After the modification, have pressures been measured at the gen during stated conditions?
What else consumes LP?
Were those items running during the test?
Did anyone check the regulator capacities for combined demand?

 

[My Old Tools]

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?

With a highly efficient heat pump, yes it can be more efficient. My system has a COP of 4.4, meaning it produces 4.4 units of heat for every one unit input with electricity.

 

[mike93lx]

With a highly efficient heat pump, yes it can be more efficient. My system has a COP of 4.4, meaning it produces 4.4 units of heat for every one unit input with electricity.

But to get that power, you have to run it through an incredibly inefficient ICE

 

[wyliesdiesels]

With a highly efficient heat pump, yes it can be more efficient. My system has a COP of 4.4, meaning it produces 4.4 units of heat for every one unit input with electricity.

the inefficiency is the source of the electricity not the HP itself

 

[ericm]

But to get that power, you have to run it through an incredibly inefficient ICE

The generator is only for backup power.

How often does the OP's power go out? A week each year would be a lot for most places in the US. Even if he's running the generator for a week per year, there's 51 other weeks where the grid is up and he's heating with electricity. Unless his electric rates are insanely high like here in CA, running an electric heat pump likely costs less even with the propane used by the generator during outages.

However, instead of getting a bigger generator I'd look into a newer heat pump that doesn't need the supplemental resistance heaters in cold weather. Air based heat pumps have come a long ways in low temperature efficiency in the last few years. It'll be more efficient the rest of the time as well.

 

[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.

Using current specs for a 26kw generac on LP is 23.6% eff@ 1/2 load, 26.9% eff@ full load.

 

[mike93lx]

The generator is only for backup power.

How often does the OP's power go out? A week each year would be a lot for most places in the US. Even if he's running the generator for a week per year, there's 51 other weeks where the grid is up and he's heating with electricity. Unless his electric rates are insanely high like here in CA, running an electric heat pump likely costs less even with the propane used by the generator during outages.

However, instead of getting a bigger generator I'd look into a newer heat pump that doesn't need the supplemental resistance heaters in cold weather. Air based heat pumps have come a long ways in low temperature efficiency in the last few years. It'll be more efficient the rest of the time as well.

I know.

The OP isn't looking for the most economic option, so no need to shove it down his throat.

He wants a bigger generator to run his existing hvac

 

[ericm]

I know.

The OP isn't looking for the most economic option, so no need to show it down his throat.

He wants a bigger generator to run his existing hvac

Then why were you (and a bunch of other people) commenting on the inefficiencies of powering the HVAC with a generator and saying he should get a gas furnace? That's shoving a solution down his throat, and it's going to cost more as well.

 

[wyliesdiesels]

The generator is only for backup power.

How often does the OP's power go out? A week each year would be a lot for most places in the US. Even if he's running the generator for a week per year, there's 51 other weeks where the grid is up and he's heating with electricity. Unless his electric rates are insanely high like here in CA, running an electric heat pump likely costs less even with the propane used by the generator during outages.

However, instead of getting a bigger generator I'd look into a newer heat pump that doesn't need the supplemental resistance heaters in cold weather. Air based heat pumps have come a long ways in low temperature efficiency in the last few years. It'll be more efficient the rest of the time as well.

read the OP. he used the word FREQUENT and is on day 3 of an outage as of thursday. then stated there will be more outages when it snows. so im guessing its more than just 1 week per year

 

[mike93lx]

Then why were you (and a bunch of other people) commenting on the inefficiencies of powering the HVAC with a generator and saying he should get a gas furnace? That's shoving a solution down his throat, and it's going to cost more as well.

I am not arguing against what he wants at all.

You and I are on the same page. My argument was against the post insinuating that a heat pump is so efficient that it is the better way to go

 

[theoldwizard1]

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.

You guys are barking up the wrong tree !

... if Aux heat strip kicks in, it (the generator) bogs, almost stalls.

 

[mm08822]

If the time delay before heat strips kick in is 2 minutes or so (t-stat standard I believe), then it shouldn't matter. If it is a variable time and his is way below that, then this could be a problem - adding a high current load onto a gen that is still recovering from a motor start-up. How long is the gen bogged down for?

Not sure if time is fixed.....I don't see any heat pumps in my area.

 

[Bert_]

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.

We don't often think the same but this is a great option.

 

[dave*99]

You guys are barking up the wrong tree !

You might try reading the entire thread. Much better than using quotes out of context.

 

[green jeans]

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

Hey all,
the electric code says you must power manage the entire load on generator for unit to operate safely and not shut down. there's only two way to do thing. 1- install generator large enough to handle load( need to add up all wattages and surges used at 100%) 2- load management, dropping loads not needed to support larger loads coming on line (surge power adds more power to this calculation) only rate generator to 80% for power( needing bigger gen). so generator only has 16Kw full time power with 4Kw of surge power( there is calculation for this) so small gen can be used. the last thing u need is gen dying do to over overspeed( now in the dark in middle of weather event)
once over 20Wk range gens get very $$$ and needing a very large propane supply on hand as well. Management is the better choice IMO

 

[dave*99]

Hey all,
the electric code says you must power manage the entire load on generator for unit to operate safely and not shut down. there's only two way to do thing. 1- install generator large enough to handle load( need to add up all wattages and surges used at 100%) 2- load management, dropping loads not needed to support larger loads coming on line (surge power adds more power to this calculation) only rate generator to 80% for power( needing bigger gen). so generator only has 16Kw full time power with 4Kw of surge power( there is calculation for this) so small gen can be used. the last thing u need is gen dying do to over overspeed( now in the dark in middle of weather event)
once over 20Wk range gens get very $$$ and needing a very large propane supply on hand as well. Management is the better choice IMO

Yes.... But, the OP has a big house with big loads and is willing to write a big check. All for the convenience of avoiding load management.

 

[Firebrick43]

It may not matter. He asked how much he should upsize his generator to run his existing equipment. It’s a simple question. He is willing to write the check. And clear about his intentions. Many of the posts in this thread likely chased him away as they suggested good alternatives but not in line with his desires YMMV.

Yes.... But, the OP has a big house with big loads and is willing to write a big check. All for the convenience of avoiding load management.

While your sentiment may be prudent and wise if you have a tyrant boss to keep your job, “willing to write a big check” is illogical reason to not to challenge patently incorrect statements made here on the forum?

If false facts are presented why wouldn’t one point it out and explain why? Others might well do a search down the road not realizing they are false.

That is the very purpose and definition of a forum, it’s not a place to be “yes men” to those whom are well to do.

 

[dave*99]

While your sentiment may be prudent and wise if you have a tyrant boss to keep your job, “willing to write a big check” is illogical reason to not to challenge patently incorrect made statements here.

If false facts are presented why wouldn’t one point it out and explain why? Others might well do a search down the road not realizing they are false.

That is the very purpose and definition of a forum, it’s not a place to be “yes men” to those whom are well to do.

I don't disagree. And most of the posters made comments along the same lines. Essentially telling the OP not to follow his plan to upsize the generator. Many good alternatives were suggested. He didn't get much advice on his ask: "How big should my generator be to support my loads?" I don't have that answer - and the OP left the chat....
BTW - there is nothing incorrect about upsizing the generator, even if it is the most expensive or least efficient option.