Home Backup Gen in Heatwave

[UncleDave]

We're on about day 5 of a heat wave an last night at around 10:30 we heard the power go out.

10 seconds later genny kicked in.

PGE have a turbine bird flying throughout the county following lines.
No reason given by PGE but site shows, ETA 2 PM today. Well see.

It's 11:30 and we just hit 100 air temp.
It powered a variable speed 5 ton AC all night and is currently powering it and the whole house.

Gens under a reflective canopy.
Gens got a fresh sump of 0W-40 in her and Ive got a mister cooling down the area in front of the inlet.

I'm running a 1/4 GPM 3 head mister choked back down to the point where it will atomize and Im guessing it's about 1/8 GPM a minute.
Water is double filtered and softened.

Front of unit is dry but the area is "about" 20 degrees cooler than surrounding air.

 

[bdcardinal]

We have been pondering getting a backup generator. There is a gas line fairly close to where I would put it and I don't care about the neighbors on that side.

 

[earlyre]

several years back, Dad had a 20KW Generac installed. had it wired up to run every thing BUT the A/C.
it's nice, but it does use a LOT of Gas.

luckily we've not had any extensive outages during the Hottest parts of the year.
We get spoiled on this Rural Electric Co-op... most of the outages we have are more like a "Blip" the power will be out just long enough for the Genny to kick in. you'll hear it's little v- twin fire up, idle for a minute, and shut down.
the only "long Term" outages (2 hrs-a few days) we've had, have been from winter storms.

My Brother and uncle both live just a couple miles away, but they're on AEP, ( the "big" power corp), they'll be out of power for hours at a time, where we never even dipped out

 

[4WD]

We have been pondering getting a backup generator. There is a gas line fairly close to where I would put it and I don't care about the neighbors on that side.

Those B&S or Generac in the original case are not that noisy - for the portables there are many examples (internet) of DIY enclosures both for sound and cooling …
I keep a 55 watt box fan plugged into mine to sweep heat/exhaust

 

[UncleDave]

several years back, Dad had a 20KW Generac installed. had it wired up to run every thing BUT the A/C.
it's nice, but it does use a LOT of Gas.

luckily we've not had any extensive outages during the Hottest parts of the year.
We get spoiled on this Rural Electric Co-op... most of the outages we have are more like a "Blip" the power will be out just long enough for the Genny to kick in. you'll hear it's little v- twin fire up, idle for a minute, and shut down.
the only "long Term" outages (2 hrs-a few days) we've had, have been from winter storms.

Im at something like 200 hours of run time in 24 months - we get em all the time here in this area.

It consumes a fair amount but is overall less dollars than a gasoline genset and you dont have fuel problems.

After the solar gave me comprehensive load monitoring I realized Im nowhere near its 18K (max on nat gas)

For that matter have never seen the house use more than 6-7KW even with at the 5 ton AC and 2 water pumps, electric washer, dishwasher with heater .... so I'm way under loaded from that perspective, but I do have gas water heating, stove and dryer, and heat.

I could have gotten by with a 10 or 12.

That said - Ive got plenty of overhead should I need to charge an electric car in here.

 

[brianl703]

Might be better to mist your AC condenser with that hose.

 

[UncleDave]

Might be better to mist your AC condenser with that hose.

I dont think so.

Its barely running - consumes about 2KW

I do think under certain conditions a mister on your AC coils can help, maybe not save much, but cool quicker and save by reducing run time a bit.

 

[jhellwig]

Don't mist it. It isn't going to over heat and if the oil temp gets to high it will shut down.

 

[brianl703]

I dont think so.

Its barely running - consumes about 2KW

I do think under certain conditions a mister on your AC coils can help, maybe not save much, but cool quicker and save by reducing run time a bit.

I used to work for a place that had an AC system with a "low ambient kit". This cuts off the outdoor fan when the outdoor coil gets too cold, to allow it to run in freezing temps, like you'd need for cooling a computer room.

One day I was hosing the units down because they were clogged with pollen, and I noticed that if I kept the water on the coil long enough, the outdoor fan would cut off.

Cooling the coils with water can make a big difference in energy use. Just the difference between operating at 90F outdoor vs 65F outdoor is about 1kW on my 4-ton unit. I'd expect that misting the coils with water at 90F outdoor would make a bigger difference than that.

 

[4WD]

I dont think so.

Its barely running - consumes about 2KW

I do think under certain conditions a mister on your AC coils can help, maybe not save much, but cool quicker and save by reducing run time a bit.

you really wanted water mist in coils - or swamp cooler effect for the gen set ?

 

[UncleDave]

Don't mist it. It isn't going to over heat and if the oil temp gets to high it will shut down.

Im not misting " it".

Im misting the air in front of it - there is no visible moisture on the unit.

Avoiding a shutdown due to overtemp is the goal.

Im in the country on a well and transfer pump - no power no water/ toilets/ shower/ drinking water. much less the two fridges and freezers full of stuff.

 

[UncleDave]

you really wanted water mist in coils - or swamp cooler effect for the gen set ?

Swamp cool the intake air.

 

[UncleDave]

I used to work for a place that had an AC system with a "low ambient kit". This cuts off the outdoor fan when the outdoor coil gets too cold, to allow it to run in freezing temps, like you'd need for cooling a computer room.

One day I was hosing the units down because they were clogged with pollen, and I noticed that if I kept the water on the coil long enough, the outdoor fan would cut off.

Cooling the coils with water can make a big difference in energy use. Just the difference between operating at 90F outdoor vs 65F outdoor is about 1kW on my 4-ton unit. I'd expect that misting the coils with water at 90F outdoor would make a bigger difference than that.

I recall watching a guy test this on some channel and he didnt see anything in terms of draw.

Im intrigued though, what is the mechanism by which the load is reduced?
I have several theories, but Im not an HVAC guy.

 

[UncleDave]

Investigation continuing on outage -

2Pm just became 5pm.

Im glad I invested in this backup power.

 

[brianl703]

I recall watching a guy test this on some channel and he didnt see anything in terms of draw.

Im intrigued though, what is the mechanism by which the load is reduced?
I have several theories, but Im not an HVAC guy.

Higher temps on the condenser coil mean higher pressure, which means more load on the compressor which means more power consumption. Reducing the temp reduces the pressure which reduces the load on the compressor which reduces the power consumption.

When the evaporator coil is running at lower temps, heat transfer is also increased, that is, more BTU (heat) is moved per kwh consumed, but this isn't nearly as easy to measure as power consumption. There's also an increase in the capacity, or rate of heat transfer--a 4 ton 48,000BTU AC is specified as such at some standardized outdoor temperature, and temperatures above that reduce the capacity to something below 4 tons/48,000BTU. Temperatures below that increase the capacity above 4 ton/48,000BTU.

Misting the coil has the same effect as reducing the outdoor temperature, in terms of heat transfer, efficiency, and power consumption.

 

[UncleDave]

Higher temps on the condenser coil mean higher pressure, which means more load on the compressor which means more power consumption. Reducing the temp reduces the pressure which reduces the load on the compressor which reduces the power consumption.

When the evaporator coil is running at lower temps, heat transfer is also increased, that is, more BTU (heat) is moved per kwh consumed, but this isn't nearly as easy to measure as power consumption. There's also an increase in the rate of heat transfer--a 4 ton 48,000BTU AC is specified as such at some standardized outdoor temperature, and temperatures above that reduce the capacity to something below 4 tons/48,000BTU. Temperatures below that increase the capacity above 4 ton/48,000BTU.

Misting the coil has the same effect as reducing the outdoor temperature, in terms of heat transfer, efficiency, and power consumption.

so you get a twofer on both ends of the deal.

Im only pulling like 3 amps on low now, but it seems like a low cost experiment to try.

Ive got 3 kinds of water -

well -direct after the sediment filter, its really hard and a little acidic.
well-run through the sediment filter then to a calcite/ softener then a carbon polishing block - its soft as butter and PH neutral but expensive from a processing standpoint.
Irigation (no pump) - half a miners inch off a stream you get whats in the stream.

My unit is very high end and Im pretty sure I'd want to keep it build up and corrosion free.

 

[PimTac]

Investigation continuing on outage -

2Pm just became 5pm.

Im glad I invested in this backup power.

I’m guessing the reason the power was cut was because it’s too hot and a fire might occur from one of their power lines?

 

[UncleDave]

I’m guessing the reason the power was cut was because it’s too hot and a fire might occur from one of their power lines?

No that would be a PSPS and they would have to announce that - there is something else afoot here.

a PSPS would be be much wider than this. Im the blue dot.

 

[UncleDave]

Our local outlet that keeps up the best is Yubanet. They supply better data than PGE somehow.

Happening Now - July 2023

Happening Now brings you community news, updates and announcements throughout the day. New fire starts are also posted here fist.

yubanet.com

 

[390pcode]

I could have gotten by with a 10 or 12.

Our 12kW will not start our newer 5 ton unit without a soft start kit.