Master thread for disasters and generators.

[KITROBASKIN]

Consider getting LiFePoh battery chemistry as well, for safety, longevity.

 

[MyUsernameTX]

Got my latest gas bill today, surprised to see its actually reduced quite a lot. New 24 hour running cost is $20 with a very high estimate of 6.25kw load

Actual usage

Peak is 5.26kw and average 2.77kw

Funnily enough, that means its cheaper to run the generator than power for most power plans around here. Tell me how that makes sense?

 

[TPA]

What are you using for power monitoring? That looks pretty nice.

I haven't done the math in awhile, but it used to be cheaper for me to run off my Honda EU2000i than Tampa Electric per kWh.

At some point I need to run the calcs again, but do it like aviation costs are calculated, with maintenance and replacement costs built into the hourly costs. I am curious.

 

[MyUsernameTX]

What are you using for power monitoring? That looks pretty nice.

I haven't done the math in awhile, but it used to be cheaper for me to run off my Honda EU2000i than Tampa Electric per kWh.

At some point I need to run the calcs again, but do it like aviation costs are calculated, with maintenance and replacement costs built into the hourly costs. I am curious.

IoTaWatt Into Grafana, I detailed it here on my website

Power Monitoring Setup (IoTaWatt + Grafana)

After getting solar panels I got used to checking the Enphase app for power details, but it's not very reliable as sometimes the data is delayed, it requires internet access and it can't get me any information other than solar and grid consumption. So if I want to see how

blog.networkprofile.org

 

[MyUsernameTX]

Do you have an NG Kit on that EU2000i? That would be even better!

 

[MyUsernameTX]

This is my calculation on a much lower 3kw load with my gasoline generator, a Champion 8750w Inverter

Crazy how much cheaper it is to run the much, much larger engine in the Generac (2.4L I4) on NG at 1800RPM

 

[TPA]

No natural gas in this area, so it'd be propane or gasoline, with the latter being far easier to manage, especially in an extended power outage situation. Trying to get propane after a natural disaster is a nightmare. Most of the larger gas stations in the area have generators. Pro tip: If you need gas during a natural emergency, go out AFTER curfew! The gas stations are usually open, if not the pumps are usually still turned on.

I'm still using an ancient The Energy Detective, but the original TED1001 model.

What are you running that gives you a steady 3kW load? My 18 year old central AC only draws 700-850 watts most of the time. It can spike up to 1600 watts in extreme cases. Fridge is inverter-based, so it also sips electric. Water heater draws 4800W, *but* I've been able to have enough hot water to last for 3+ days without power to it, provided we take quick, but hot showers.

When I'm in "hurricane mode", I drop down to a single window AC (~400-500 watts) and/or small dehumidifier. I usually use about 2-3 gallons/day of gas.

 

[MyUsernameTX]

Could go Diesel. If I had no Natural Gas, I think I would go for a standby Diesel unit

The steady 2kw load during the night is a combination of mini splits, one cooling the bedroom down to 68 (And its been quite warm outside), lots of exterior lights, and my server rack full of networking equipment, my desktop PC's, fridge, freezer. etc

During the day, its all that but probably more AC usage, lights, monitors, etc

What window AC unit do you have thats pulling just 400w?

 

[TPA]

We used to be diesel at the beach condo until the environmental regs became too oppressive and we switched to a large buried propane tank. Then a few years later the enviroweenies made us UNbury the tank and keep it above ground. During the hurricane, storm surge ripped it from its supports and it floated away, spewing propane into the environment the whole time as it floated away. We still haven't located the tank, almost 600 days later.

On the window AC, I don't remember the model, but it's a Frigidaire, probably 18 years old. It was one of their higher efficiency models with a high EER, around 12 IIRC. If I were to buy one today, it'd probably be the Midea inverter models as those have an EER around 15.

I'm not sure where you are in TX, but be careful with lower indoor temperatures like that. Remember that moisture will condense on any surface which is less than the dewpoint. I've run into problems in Florida with this. They'll cool a building down to 72F or so, but our dewpoints here can reach 80F. Most homes are under negative pressure, so warm, moist air from outside infiltrates into the walls and condenses on the back side of the drywall and studs. Mold grows. Bad things happen. When possible, I go with a positive pressure system, so the moist air can't get inside and do damage.

I also focus on humidity rather than temperature in my HVAC designs. Humidity matters more to comfort than temperature. In my office it's currently 74F / 39% RH and it actually feels cold. Similarly, at my home I keep the thermostat at 78F with the humidity between 40-44% and it feels quite pleasant. Lowering the humidity in the office fixed almost all of the "too warm" and "too cold" and "too stuffy" complaints, without having to make adjustments to each office.

 

[MyUsernameTX]

Wow, I figured those window units would be more efficient, my mini splits are 33 SEER. Sometimes I feel like the ratings are pretty useless though, if you're only really drawing 500w and getting the cooling you need, it sounds like a decent deal

No problem so far with moisture, its usually about 9000% humidity outside, so no chance I could ever not have it lower than the dew point

Humidity does take some adjustments when using mini splits, they cool so fast it can often not dehumidify well. I've learned to get around that though, and know when to turn it off vs turning it up, etc

 

[TPA]

Commercial equipment is still rated in EER, so that's what I stick to. BTUS / watts = EER. Simple; no way for manufacturers to game the system for better numbers. Letting the blower run for an additional 90 seconds after the compressor shuts down will get a manufacturer at least 1 extra point in the SEER rating, *BUT* at the expense of pumping humid, damp air back into the conditioned space -- moisture I paid money to condense and remove, and moisture that will make it more uncomfortable.

I was going to ask about the mini-splits. I like the concept of mini-splits, but every place I've been which had them had high interior humidity. All of my condos' ACs have some variant of my special sauce on them. For some, it's a whole custom PLC-driven multi-stage, multi-compressor setup. For others it's just a modified (reduced) evaporator coil and a crude blower speed switch based on humidity. I have dehumidifiers in most of them.

 

[MyUsernameTX]

Good info! Thanks

Its probably all due to poor sizing honestly, if I were to buy everything again, I could do better

I have a Dual head system with 2 x 9K BTU indoor units, one in my office and one in my bedroom. The outdoor unit is 18K BTU. I got this installed by a company, and what I didn't know at the time is that while a double head unit does save exterior space, and save a circuit run, it means the compressor can't ramp down nearly as much as the lower units. My 9K BTU units can only ramp down to say 5K BTU (Made up number) before turning the compressor off, but a standalone 9K BTU unit can ramp down much further, which helps with humidity

In my living room which is attached to the kitchen, I have a single standalone 9K BTU unit, which is quite undersized for the area, and it does fantastic with no high humidity. I got this one for free, and installed myself (Which is why the sizing is off, it was free)

If I were to do it again, I would get a 7K BTU standalone if I could find it, for the office, and a 9K for the bedroom. Or even just 2 x 9K BTU standalones

But, its not a huge problem now as I use some Mysa thermostats with them, and have automations setup to control humidity. If it gets high enough, I actually have them turn their fans way down and then just blast the main AC for a little to get the level down.

The mini splits probably halved my power usage, all while keeping the house significantly cooler

 

[TPA]

That's some good info too!

Which brand mini-splits did you go with and what types? Cassette, hidden ducted, floor, wall? Standard or inverter? 120v? 208v? 240v?

I didn't know alternate control systems for mini-splits existed. That was one of my hang-ups -- I'm focused on humidity whereas most manufacturers don't have any provision for controlling it individually.

Dumb question: Can you 'fool' the system into thinking the inside unit and outside units are different sizes than they actually are? I've done this at a few locations, usually setting the dip switches for the system to think it has a smaller condensing unit than it really does, so it runs the blowers slower... Slower airflow = more latent heat (humidity) removal. I still prefer to undersize the evaporator coil by 1/2-1 ton depending on the size of the system.

Re: capacities, I ran into a similar issue when spec'ing out the Carrier Infinity system for one of my condos. At the time, the lower-EER heat pump used a 2-stage Bristol reciprocating compressor, while the higher efficiency one used a scroll compressor. BUT, the scroll only unloaded down to 65% capacity, whereas the recip could unload down to 40%. I went with the reciprocating. I did the maths and even in Florida, the price difference between the 16 SEER and 19 SEER systems wouldn't make sense over the entire lifetime of the system....in Florida, which told me higher-SEER systems weren't worth the price.

When setting up homes for generators, I usually spec out a 110v inverter mini-split in the master bedroom, so if need be, it can run off a single EU2200i generator. It also acts as a spare in case the main central AC croaks.

 

[MyUsernameTX]

The dual head unit is a Daikin and the single unit is Fujitsu, both Cassette, both Inverter and both 240v. I went for 240v so that the load was more evenly balanced when running on generator power. While I do have the 27kw Generac, I also want the ability to power the house via my portable generator. When I got my power monitoring setup I realized that the legs were so unbalanced that I wasn't even near 6kw at times, but one leg was over 30a so would probably trip the circuit breaker. I figured the more 240v loads, the better
I don't know if you can fool the units, but you can just set the fan lower, they all usually have 3 or 4 fan levels

If someone had 120v mini splits, it would be neat to add one of these EZ Generator switches to each of the disconnects, then in an emergency you could power the mini split directly from a generator. You could even install it inside, and then power it with a battery, etc

EZ Generator Switch - EZ Generator Switch

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