5 ton AC technology with Sol-Ark 15K

[robby]

Hi Bob, Thanks!, Just sent a reply as your post came in that talks about some points you mentioned. Before solar, my electric bill was only $140 with 10 tons of AC. Now it is $0 but still have to pay the $21 connection fee for the grid connection. What equipment are you using? Is it ducted? I love mini splits, but really need to stick with the ducted in my situation.

I am a bit confused.
Your Sol-Ark 15k is currently running 10 tons of AC units and you’re using zero utility power per month?
Is your reason for upgrading the AC units based on just a fear that both compressors will start at once and trip the Sol-Ark? It seems like a soft start system on both ACs gets rid of that problem with minimal expense.

 

[Daddy Tanuki]

It’s FL, swamp land is cheap, so is constructing large houses.

Pretty sure it’s humid there ?

Cue in Miami Vice theme and large white collar jackets.

 

[Daddy Tanuki]

I went with Mitsubishi equipment. They and a few other brands make ducted air handlers for situations like yours; I think theirs maxes out at 3 tons. I actually bought one but switched to ductless once I saw that my existing ducts were rusted through! ?

i do mitsubishi and diaken, and i can say they both do up to 30 tons for commercial. for ducted home here in japan they go up to about 5 tons. just a thought.

 

[TIHI]

I am a bit confused.
Your Sol-Ark 15k is currently running 10 tons of AC units and you’re using zero utility power per month?
Is your reason for upgrading the AC units based on just a fear that both compressors will start at once and trip the Sol-Ark? It seems like a soft start system on both ACs gets rid of that problem with minimal expense.

Hey Robby, sorry for the confusion. The SA has only been running since Feb and since the weather was nice then (during commissioning), the SA has never run either 5 ton unit. The newer AC has 5-stages and slowly ramps up so I think it would be okay running that one during a power outage. That one is downstairs and runs during the day. The other 5 ton is for upstairs where the bedrooms are and runs mostly at night, usually kicks on 5-12 times a night for about 10 minutes each time. From the looks of my Powerview app using the CTs to measure power use, it looks like it takes about 5,000watts to run it. Upstairs is set to 83F during the day and it only comes on a couple of times towards the end of the day, but no one is up there, then about 30 minutes before bedtime, it runs to cool down the upstairs to 78F. Not everyone likes that temp, but we prefer it. If a new homeowner ever came in and wanted 70F or so, you couldn't do it with less than 5 tons. Anyway, I'm ON grid with net-metering and I create enough PV to sell-back during the day and use some of my credit at night. So far, only 3 bills in, I have a net surplus with the power company. I'll probably use some of that during the hottest summer months with the hope that at the end of the year, I'll make as many Kwh as I use to break even. The SA is in the loop since the whole 200Amp panel runs through it, but the purpose of this thread is to try to figure out my NEXT upstairs AC solution BEFORE I need it. It is a Trane, but is getting older. I want to make the new one as efficient and SA friendly as possible with some type of inverter heat pump (looking for advice, brands and experiences about them) that works with existing ductwork. Does that help?

 

[ruralsolar]

It is a new ducted house, plan on water to air geothermal. Would like a DIY to save some coinage.

The pricey part of geothermal is the wells usually, it will perform better in the winter compared to air source. I have one winter with mine and the backup heating element only kicked on a handful of times during sub zero nights. The biggest thing is knowing your realistic heat load of the home and what is realistic with the heating degree days, basically don't design for the worst heating day/night, design for 95% and then have some form of basic backup, for me that's a 3kw resistive heating element in the water stream. John Siegenthaler has some excellent youtube videos going over air source heat pump systems.

 

[740GLE]

Once that second floor becomes heat soaked it takes a lot of cooling to take the heat down.

The idea of any modern HVAC system is staying ahead of heat soak. These inverter style will idle along when cooling demand is low, and ramp up as needed.

Set it and forget it. Don’t cycle off until it gets crazy hot and then crank the unit to max, way more efficient.

 

[Nobodybusiness]

The idea of any modern HVAC system is staying ahead of heat soak. These inverter style will idle along when cooling demand is low, and ramp up as needed.

Set it and forget it. Don’t cycle off until it gets crazy hot and then crank the unit to max, way more efficient.

I hear ya but not everyone has those.
Still remember turning off AC before work think 60 Degree day.

Surprise!!! Its 90 and AC been off all day!

I agree most people don’t let their house get that way.

My 2016 TRANE system on first floor off on off on off on. I think when I checked the Microair soft start it was 5000 starts in a year or something.

The newer Lennox is a DC compressor but it operates like a standard AC/Heat.

Thermostat calls for AC unit comes on and provides AC and turns off.

 

[Danke]

The pricey part of geothermal is the wells usually, it will perform better in the winter compared to air source. I have one winter with mine and the backup heating element only kicked on a handful of times during sub zero nights. The biggest thing is knowing your realistic heat load of the home and what is realistic with the heating degree days, basically don't design for the worst heating day/night, design for 95% and then have some form of basic backup, for me that's a 3kw resistive heating element in the water stream. John Siegenthaler has some excellent youtube videos going over air source heat pump systems.

My plan is horizontal placement of closed loop.

 

[AntronX]

If a new homeowner ever came in and wanted 70F or so, you couldn't do it with less than 5 tons

but the purpose of this thread is to try to figure out my NEXT upstairs AC solution BEFORE I need it.

Making 70F indoor temp in humid 95F Florida summer is a bit ridiculous but if that's the requirement then go with inverter drive variable speed central unit. Make sure it has active PFC (not passive or "reactor" type) on the compressor inverter in order to keep your SolArk happy. Look at condenser unit specs, it should say 0.99 PF in the electrical ratings section. Variable speed unit will allow you to run it at lower capacity for longer time period in order to better dehumidify the air. In addition running at low capacity will produce better COP due to heat exchanger coils effectively becoming way oversized. But you still have the capacity in case someone wants to igloo the house.

 

[stienman]

Pretty much everything useful has been said - go with inverter if possible, or use a soft start. A two or more stage might be ok, but only if the system starts every time on the lower stage and ramps up - cheaper systems start on the highest or higher stages to get spinning, then ramp down once the pressures have been established.

I'm biased actually against refrigerant based system after installing all hydronic in my new home.

Do I understand correctly that you don't have a heat pump, like most geothermal solutions?

What do you do when the ground loop saturates, or do you have such a large amount of ground loop that it never goes higher than your set point?

 

[ruralsolar]

Pretty much everything useful has been said - go with inverter if possible, or use a soft start. A two or more stage might be ok, but only if the system starts every time on the lower stage and ramps up - cheaper systems start on the highest or higher stages to get spinning, then ramp down once the pressures have been established.



Do I understand correctly that you don't have a heat pump, like most geothermal solutions?

What do you do when the ground loop saturates, or do you have such a large amount of ground loop that it never goes higher than your set point?

I have a monbloc air to water heat pump. All refrigerant is "outside" the home and I did not require an HVAC pro or any special tools to complete the install, just "regular" plumbing tools.