How exactly is your house heated? Geothermal Liquid-to-Water, Liquid-to-Liquid, Liquid-to-Air? Is the expansion tank you mentioned in the ground loop circuit, hydronic heating and or cooling distribution system or one expansion tank for each? Are your ground loops pressurized or not (sounds like they’re pressurized and not open loop or from the well)? Is your flow centre pressurized or non-pressurized?

Or is you geothermal system DX (I’m guessing not)?

IMPO

SR

Geothermal Anti-freeze to air (18 years old... replaced the system once) . A pressurized closed loop runs through three wells. I assume it will not be affected by being frozen. I guess I need to check! [Addendum... I checked with the installer and the system won't be hurt by 'freezing'} One expansion tank is with the water heater. We also have a pressure tank from the well. I've never heard of DX before. I looked it up... interesting.

Will not freeze above freeze protection of actual antifreeze solution mixture within the ground heat exchanger. The rest of the house is as any other house.

DX (Direct Exchange) system is with copper ground loops and refrigerant circuit extends throughout the copper ground-loop piping. No special freeze precaution necessary for DX systems.

IMPO

SR

Agreed. The rest of the house it what I'm worried about!

We have a camp in northern PA. Ours is heated by propane. A 500 gal tank. The most we are away from camp is 2 weeks during the Christmas holiday. We just keep our fingers crossed that the electricity isn't off at camp or our home long. Lol. In both places we haven't been off for more that a few hours. I can check on my phone if the electricity is off. Do you have a friend that could fire up a gasoline generator incase of a prolonged outage. We have relatives in both places that could help.

Or maybe you can look into a propane back up generator that would switch on automatically in case of a power failure. Of course you would have to get a larger propane tank than something you would use on a grill. The propane company would know the size you would need for it to last 2 weeks. Don't rent the tank, but buy it so you are able to shop for propane fuel prices.

Re Modeling

If you can afford it, the First World way of addressing your issue is to install a whole house generator that runs on propane from your tank. You can turn your thermostat down to a temperature your HVAC contractor recommends will keep internal plumbing well above freezing. I have a friend with exactly that setup at a vacation home in a location with winter snow and cold. I think he said he adjusts his thermostats to the mid-50s when the house is vacated and, in the modern way, he can check on what's happening and change thermostat settings over the internet. I think having web connected thermostats are the rule rather than the exception these days

With that, you can have confidence that your house will stay warm and the system will continue to work should the grid electricity go out.

I appreciate the feedback!! I've looked into a backup generator but can't stomach spending ten thousand dollar for something that may never provide significant benefit (yet I religiously pay my insurance bills).

We have a 4400W gas generator that I roll outside when we have longer outages. It powers our water pump, septic pump (not at the same time) and a few outlets. That and our vermont castings stove are my means of addressing power outages when at home.

I'm hoping for thoughts on a smaller scale. Has anyone used a non-electric/propane heater or other means for backup heat in your basement?

If you can group the pressure tank and hot water expansion tank into an insulated mechanical room maintained at the same temperature as your home, you can likely tolerate a 24-hr outage without the need for supplemental heat.

In our last house we had natural gas ventless moore heaters in the garage and basement. We had to control the temp manually though. Loved them. Maybe now they make some that the temp is controlled by battery. I know they also make them for propane. The only difference is the orifice. It is something that you might want to research.

I would also be nervous if home was set at 50 if it could survive 24 hour without freezing on a single digit day. As I said before we set ours at 55, shut off the water and turn down the hot water tank and pray.

OK. I started looking into a whole house generator. For budgeting purposes (to help decide if we want to look into this further), how do I determine approximately what size generator I'd need for a whole house system... 5-ton geothermal unit (Bosch SM060, 18.9 EER, 3.9 COP, 5 ton, 2-stage with smart-start), an optional 24k BTU Fujitsu mini-split (13.3 EER), 1hp septic and 1hp well pumps, washer/dryer, refrigerator and freezer, lights, TV? I know there's be other benefits besides vacation protection that may be appreciated as we age.

The Kohler company has a generator sizing tool that can assist you in selecting the right generator for your needs. https://kohlerpower.com/en/residential/generators/generator-selector#your-home

I'm hoping a 24kW Generac will work (and I can avoid the expense of liquid cooling). Any reason I should not go with a Generac or is there a 'better' option? Thanks to all!!

When you get bids for the installation, the contractors will work with you to determine the proper size needed.

You need to know the maximum current draw of your HP during start up otherwise the generator might not have the power to start it. Speak to a knowledgeable electrician and the HP manufacturer. Look at your HP specs for LRA (Locked Rotor Amps) for the compressor as a guide. At 24kW, at least you’re looking at a capable generator. A liquid cooled generator will likely be quieter than air cooled, something you might appreciate during a long outage.

You can also look at a NG, propane or diesel generator, CAT or Onan.

IMPO

SR

152.9 LRA... x240 = 36,696. We did purchase a soft start module. I need to find out it's affect. Thanks again!!

Here’s a very brief explanation in an understandable way as to why the ‘LRA’ spec is important when choosing a generator (really an alternator).

When an AC induction motor starts up its in the ‘Big Bang’ current phase of drawing the maximum current that can be drawn based (basically) on the total length of the varnished (insulated) motor wire (usually the stator) and its gauge or size thickness. This is its total DC resistance (pure resistance). After the 1st few cycles (60-cycles or Hz) have past, the motor is then in its ‘inductive’ phase of AC resistance (called ‘reactance’ for AC resistance, called just ‘resistance’ for pure DC current - no capacitive or inductive reactance). This (inductive reactance) comes after the magnetic field has been created and established and things settle down from LRA to RLA (Running Load Amps), which is the ‘normal’ or nominal AC current draw when properly running, its ‘steady state’ so to speak that is always much lower than LRA phase.

The LRA should be thought of as if you have an electric motor of any size (think BIG) running with a spoked pulley or fly wheel mounted on the motor rotor shaft and then you throw a crowbar in between the spokes to seize or ‘Lock the Rotor’ - while running. The spike in current drawn at that moment or point in time is the ‘Locked Rotor Amps’ of maximum current draw, if sustained, this will pop a breaker or blow a fuse or fuses. If connected to an under powered generator (really an AC Alternator, generators generate DC even though both are referred to as ‘Generators’) will cause the ‘Generator’ to stall out, pop a breaker, blow a fuse or burn out.

That’s why a properly sized ‘Generator’ is a ‘must’ requirement. When starting in generator mode, either you have connected a generator that can handle the entire load of everything connected or every appliance that can be, is turned ‘OFF’ and started sequentially, starting with the AC or HP, the biggest loads 1st. Once all loads are running it’s less likely to have 2 or more loads starting simultaneously in LRA mode so the generator should be able to handle the spiked loads - momentarily.

Variable speed or 2-speed HPs or AC condensers are more desirable as they will have longer run times with less generator peak load stressing. Some HVAC units, particularly inverter units might be able to spool up slowly drawing even less in-rush current. That means less stress on the HP or AC and generator.

Always consult with the right professional. Don’t assume that the ‘professional’ that shows up at your door will have all the right answers. I like it when they’re willing to admit and say that they don’t know when they don’t but will find out and get back to you. That’s someone I can often still work with.

BTW: My expertise is in Geothermal Heat Pumps, Ground Heat Exchangers (Ground Loops), Amateur Radio, emergency and disaster radio communications but I should be considered as just, ‘some guy on the Internet’.

IMPO

SR

I really appreciate your description and it all makes sense!

When I spoke with the Geothermal Installer he indicated (from his experience at a very large local installer) our unit could be started/run (alone) on a 14kW generator. The numbers don't make sense (to me) 36.7kW based on locked rotor amperage and a 14kW generator?!?! I know the LRA only impacts for an instant, but it still need to be overcome. While our unit has variable speed compressor/blower fans, that should already be figured in the 152.9 LRA.

I saw another (2 year old) discussion where it was indicated that you'd want a 25kW generator to run a 3.5 ton system and I assume the rest of the house.

Am I unrealistic to think a 24kW generator will run our whole house? I see there's also a 26kW Generac...

If you size your generator based on LRA you'll oversize it. Voltage dips when starting a heat pump or air conditioner and the current drops proportionately. Instead of LRA you'll want to consider instead the surge current capacity at 30% voltage dip. A generator dealer would be a good person to consult for sizing help.

I have contacted a couple generator dealers and sent them load information. I always try to learn as much as I can (in advance) about projects I'm working on and assume the person I'm dealing with does not know what he/she is doing. That way I can usually tell whether they do know what they're talking about AND I'll understand the decisions that will need to be made during design/implementation. I don't like surprises. What I'm learning here is priceless. Thank you!

When I spoke with the Geothermal Installer he indicated (from his experience at a very large local installer) our unit could be started/run (alone) on a 14kW generator.

Go to YouTube and search for "AC soft start kit" or "Micro-air Easystart" You will find videos of live demonstrations showing portable generators starting up 4 and 5 ton AC condensers. A 24 KW generator to protect you house when you are not home seems to be overkill. That's equivalent to having a 200 amp service.

IF we go this route I figure we might as well be able to run the whole house. However, it would also be good to know how little we can get away with...

I haven’t read the entire thread, but in our mountain cabin you have to blow out all the lines in order to keep them from bursting. That even includes the shower heads and hoses. We do use antifreeze for toilets, but be sure to flow directions. It doesn’t work if you just add it to the tank and bowl.

I have heard anecdotal stories even from Master electricians about being able to start and run 3 to 4-ton HPs with 5 to 7-kW generators. It might be possible - but it’s not for me. Undersizing might result in trying to start a compressor in essentially a prolonged brownout condition that might stress the HP. That’s not something I would want to do. I would sooner invest in an oversize unit to be on the safe side. The last thing I would want to hear is my wife telling me, “The generator is out again, would you mind please going out and start it again?” - especially in the winter and especially at night or if we’re not even there!

If there would be an electric car or house extension in the foreseeable future I would want to plan for that now.

A few more thoughts on generators as applies to me and what I would and would not do.

Just as air-source HPs are out for me so are ‘Generac’ type ‘Standby’ home generators and their like.

What I would install would be a liquid cooled CAT, Caterpillar or Kubota type diesel engine with an Onan type Generator (alternator). The reason being that these are usually tractor diesels mated to an alternator.

Why does this matter? These types of diesels are typically in-line long bore, long stroke, low RPM engines (think - ‘Harley’) like those used in tractors with tons of low-end torque that can almost tow a house away at near idle speed. That means your HP more likely is going to start - that diesel motor will not be your weak link! They can run almost forever (think bulldozer or tugboat).

A liquid cooled engine is usually quieter, better for sleeping. A diesel engine can be run on diesel fuel, Bio-diesel (French-Fry oil) or heating oil - so that you’re not paying all the built-in ‘road’ taxes as it’s a stationary engine and the only ‘road’ it ever sees it the trip to your place. You can also store the diesel oil in a standard size furnace heating oil tank or a ‘½-tank’ size tank without having to refill the generator for perhaps days or even longer. No messing with gasoline that is even more combustible.

This is my own opinion based on my own knowledge and life experience. To be sure, there are many ways to skin a cat - But there is only ONE ‘CAT’©!

IMPO

SR

A diesel engined whole house generator may not be a good choice for this person. There are many disadvantages compared to engines that run on natural gas or propane:

1) Diesel engines are noisier than gas or propane burning ones

2) The OP is concerned with protecting his house in winter during his absence should a power failure hit when temperatures are cold/below freezing. Diesel fuel gets waxy at below freezing temperatures and doesn't flow well. A stone-cold diesel engine may fail to start as a result. Additives can be used in the fuel but this ties into the next problem

3) Diesel fuel has a limited storage life. Anyone who has had a boat with a diesel engine (as I have) knows that. It starts to break down, engines with stale fuel may have trouble starting or can run rough. "Winterized" diesel fuel with additives is sold during the season in cold winter areas but to have that at the beginning of the next winter, it would have to be held over from the preceding wintertime. Or, the tank needs to be empty over the summer to be filled the next fall when winterized fuel is again available.

How does one use up a tank with enough storage capacity for a reasonable period of use?.

3) Algae and other contaminants grow in diesel fuel that isn't used when fresh and can grow in untreated tanks. There are additives for that too but the general rule is:

Diesel fuel shouldn't be stored for long periods of time if it can be avoided.

These problems are not present with natural gas or propane fueled generators.

Note, you mentioned

"The last thing I would want to hear is my wife telling me, “The generator is out again, would you mind please going out and start it again?”

His inquiry has to do with when his house is unoccupied. He mentions he uses a cast iron stove when he's there so using a generator at such times isn't a need.

It's always best to understand requirements before proposing solutions.

About a third of our clients request installation of an emergency generator. We've installed some monster units, but the Kohler 20 kW (air-cooled) model with an automatic transfer switch is our go-to unit. It's advertised as being capable of starting a 5-ton air conditioner--but that doesn't mean it will do it with everything else in the home running. If you're content to just keep the beer cool in the fridge, some lights and the TV on, and sit under a ceiling fan like me, you can be comfortable with a much smaller unit (I use a 6 kW portable generator.)

When figuring the cost of a generator, keep in mind that emergency generators are typically programmed to exercise themselves weekly and annual dealer service is recommended so consider availability of service in your area when deciding on which brand to install.

"keep in mind that emergency generators are typically programmed to exercise themselves weekly"

I can attest to that! Our neighbor has a big ol' natural gas, air cooled, Generac that tests itself every Saturday morning at 11:30am. That sucker is noisy - I wouldn't want it running all night when I'm trying to sleep.

Now that we're looking into a generator, I think it only makes sense to have it capable of powering the home while we're there in case of outage... if we do it. It's not that much to increase the generator size once you are already installing everything else that's needed. We're planning on propane for it's longevity (as noted above) and since we already use propane. I'm thinking 24kW(?) Generac vs Kohler and would appreciate any thoughts you may have between the two. We'll see what the electricians say about size, I'm just guessing. I assume whatever generator is chosen, the heater can be given priority when starting or in use? Fortunately our bedrooms on the other end of the house so hopefully noise is not an issue if we're home. Note: We currently use a roll-out gasoline-powered 4400w generator when the power's out in the winter (for more than a couple hours), along with our propane stove... when we're home.

My local generator dealer sells both Kohler and Generac. He feels that Kohler excels in residential-scale applications and Generac for commercial-scale applications. We used to install Generacs and got customer feedback that they tended to consume a lot of oil and would shut down due to low oil level. It's not fun, I'm told, adding oil to your standby generator in the middle of a hurricane.

A less expensive way to go is to get a temperature controlled light- it turns on (battery operated) when the temp gets below a set temp. Have someone drive by every day or so while you’re away to check on the house. This worked for my grandparents home in VT and saved their plumbing and extensive repairs several times!

"Have someone drive by every day or so"

Not a practical solution, in my opinion. So they pass by, see the indication the power is off (which they may know if it's a neighbor), and then what?

Every situation is different and plenty of people have helpful neighbors that would be happy to check in on a home while someone is away. I’m glad to have had those kind of neighbors in my life (and to be that kind neighbor too). When you own a home, you have back up plans in case of emergency. Such as- neighbors have a key and can start up the propane heater to run for a few hours.

Not everyone can afford a generator as backup power supply.

Of course, I agree. There are surely alternatives that wouldn't involve sticking such an obligation and responsibility on a neighbor, not even a willing one. In a power outage, neighbors have their own issues to deal with.

Maybe this would be a good service to ask of a local landscape/yard maintenance business, people who don't have much work but for clearing driveways and such during the winter.

Since I've gotten varied opinions about generator sizing I've continued this discussion with a question about geothermal sizing here... https://www.houzz.com/discussions/6302833/sizing-a-backup-generator-for-a-5-ton-geothermal

I checked with my insurance agent yesterday. My (State Farm) policy states that we need to make a reasonable attempt to maintain temperatures at or above 55 degrees in the home to retain coverage for frozen/burst pipes. If the electricity is on, the heater is running/working, we set the thermostat at 55 degrees and we leave for vacation we will be covered (even if there's an extended power outage causing the pipes to freeze). Now, if we turned the heat off, that would be another matter.