Looking to power HVAC

[gisean04]

I'm looking for information on how to grid tie solar my HVAC, I have two 5 ton units the outside condensers are each on 20 Amp breakers. I would like to take them and the inside air handlers full solar during the day, and only draw from the grid outside from 5pm to 8am. No batteries yet. We have had 75 days over 100 this summer so electric bill are $500 a month.

 

[sunshine_eggo]

Same but in Phoenix. All options I have seen are either really expensive or runs the risk of backfeeding to grid that would get my pee pee smacked...

I'm considering this:

EG4 Hybrid Solar Mini-Split Air Conditioner Heat Pump AC/DC| 24000 BTU | SEER2 21| Plug-n-Cool Do-It-Yourself Installation (PRE-ORDER)

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

Only 2 ton, but runs on PV when available and falls back to grid, plus it's crazy efficient. IMHO, this could take a lot of the load off the 5 ton unit and realize substantial savings.

 

[gisean04]

I brought that up, but my mom does not. Wanna add any additional AC units. We're looking at getting several bottles of closed cell Foam spray and spring the attic to help increase insulation. What I wanna do is put a EG4 18k Have both AC's fed off of that prioritize using solar and use the grid as backup for when the solar is not enough or tapers off. That shouldn't back feed onto the grid when not in use, correct?

 

[SilverbackMP]

I brought that up, but my mom does not. Wanna add any additional AC units. We're looking at getting several bottles of closed cell Foam spray and spring the attic to help increase insulation. What I wanna do is put a EG4 18k Have both AC's fed off of that prioritize using solar and use the grid as backup for when the solar is not enough or tapers off. That shouldn't back feed onto the grid when not in use, correct?

If you have a vented attic, that probably isn’t the best idea.

 

[gisean04]

It's not well vented, I want to add solar power vents to vent the hot air. It's hitting 120+ In there and we're a high humidity area. I've had humidity in the 80% range in the middle of the day. Still no rain. The big problem is the existing insulation is a fiber glass insulation from the nineteen eighties. And it's just not enough to keep apart to the house. Cool in these extremely hot days. Play an august in the winner keep the house warm. I looked at all the different types of insulation that we could get for retrofitting. And it seemed like the closed cell sprays were the most Bang for your buck, so to speak. They seem to offer the highest r rating per inch.

 

[SilverbackMP]

It's not well vented, I want to add solar power vents to vent the hot air. It's hitting 120+ In there and we're a high humidity area. I've had humidity in the 80% range in the middle of the day. Still no rain. The big problem is the existing insulation is a fiber glass insulation from the nineteen eighties. And it's just not enough to keep apart to the house. Cool in these extremely hot days. Play an august in the winner keep the house warm. I looked at all the different types of insulation that we could get for retrofitting. And it seemed like the closed cell sprays were the most Bang for your buck, so to speak. They seem to offer the highest r rating per inch.

But they aren’t suitable for an attic space designed to carry moisture up and out. Just pile on more of the pink stuff, mineral wool (my pick) or cellulose (my secondary pick).

 

[gisean04]

I'll need to do more research on my atic

 

[RV10flyer]

I'm looking for information on how to grid tie solar my HVAC, I have two 5 ton units the outside condensers are each on 20 Amp breakers. I would like to take them and the inside air handlers full solar during the day, and only draw from the grid outside from 5pm to 8am. No batteries yet. We have had 75 days over 100 this summer so electric bill are $500 a month.

Do you seriously have 10 tons of cooling typically for a 5,000-6000 sq ft home? Are you sure you don’t have two 2 ton units because a 5 ton unit takes a 50 or 60 amp circuit breaker not a 20A. If you live in a 5-6000 sqft house, I would choose to downsize into a very efficient home before switching to solar.

 

[Supervstech]

I'm looking for information on how to grid tie solar my HVAC, I have two 5 ton units the outside condensers are each on 20 Amp breakers. I would like to take them and the inside air handlers full solar during the day, and only draw from the grid outside from 5pm to 8am. No batteries yet. We have had 75 days over 100 this summer so electric bill are $500 a month.

What 5 ton units do you have on 20A breakers?

 

[RV10flyer]

What 5 ton units do you have on 20A breakers?

Yeah, they must be 50 SEER.

 

[Solar Guppy]

Go back to the drawing board and start with the lowest hanging fruit, which is proper insulation and ventilation in the attic. In Texas, you should have at minimum R40 or about 12" with blown in fiberglass. I have 14" in mine here in Florida and was done before adding Solar.

If one is looking to power the AC's, well your looking at very very large sums of money, permit packages to get things installed to code, so spend some time looking into all that.

Most important is don't just start doing random projects without the researched plan.

 

[gisean04]

What 5 ton units do you have on 20A breakers?

It's a train, 220v so its 2 20amp breakers. One for each phase.

 

[gisean04]

What 5 ton units do you have on 20A breakers?

It's a train, 220v so its 2 20amp breakers. One for each phase

Do you seriously have 10 tons of cooling typically for a 5,000-6000 sq ft home? Are you sure you don’t have two 2 ton units because a 5 ton unit takes a 50 or 60 amp circuit breaker not a 20A. If you live in a 5-6000 sqft house, I would choose to downsize into a very efficient home before switching to solar.

Yup its two 5 ton units, I know this because we are good friends with our HVAC guy. He helps us out when we have questions or problems. We have had to replace the Capacitor on the Condents are unit twice. That was something we could do ourselves. But we contacted him for troubleshooting and everything. And he told us what part to get and where it was and how to replace it. So I know for sure that each one is a 5 ton. The house is a L shape. So each unit handles separate zones. It's a total of 6 breakers between the 2 units. A twenty breaker for each of the air handlers. And 2 breakers for each of the outside condensers And they're 20 amps on each side. Mind you. These units are R22 refrigerant. And we checked the pressures whenever it gets too hot in case it's leaking. And we found that they're not leaking the pressures. Or within the correct range. It's just so hot here that they can't keep up. We've had it up to a 109 And that's not the heat index.

 

[gisean04]

Go back to the drawing board and start with the lowest hanging fruit, which is proper insulation and ventilation in the attic. In Texas, you should have at minimum R40 or about 12" with blown in fiberglass. I have 14" in mine here in Florida and was done before adding Solar.

If one is looking to power the AC's, well your looking at very very large sums of money, permit packages to get things installed to code, so spend some time looking into all that.

Most important is don't just start doing random projects without the researched plan.

I know it's not blown in, It's the pink fiber glass you can get in rolls and roll it out between the 2x4's. From the 1980s.

 

[Quattrohead]

I don't understand how your AC compresses are wired, care to give us a model number or a wiring diagram for them.
But others have said and your last post confirms, you really should be looking at insulation first. It's not sexy but it's way less expensive and far greater gain.

 

[Solar Guppy]

I know it's not blown in, It's the pink fiber glass you can get in rolls and roll it out between the 2x4's. From the 1980s.

Get a quote from a local contractor to blow in 12" over the 3.5" roll in you likely have, this by far will be the best payback for investment. Typically its $1000-2000 depending on square footage of the home. Doing it yourself won't be lower cost as the contractor gets bulk pricing on the materials, at least around here.

Having 10 tons of cooling is beyond absurd, I designed and built a 3400sf energy efficient home and heat cooled with a 2.5 ton unit, had radiant barrier, ventilation and R60 blown in the attic ( Florida , similar temps that Texas gets ). The whole electric bill was covered by a 5kw solar system.

It is ALWAYS lower cost to reduce the energy demand than increase the heating/cooling to meet building needs.

Finally a 5 ton R22 ( which has long been phased out ) AC is likely only a SEER 8 to 10 best case.

 

[sunshine_eggo]

I can't be judging. I have a 5 ton on 2300sq-ft in Phoenix.

 

[Solar Guppy]

I can't be judging. I have a 5 ton on 2300sq-ft in Phoenix.

Pay now ( more usage ) or pay later ( new system cost that uses less energy for the same BTU's ) is a common dilemma

 

[sunshine_eggo]

Pay now ( more usage ) or pay later ( new system cost that uses less energy for the same BTU's ) is a common dilemma

It's a 14 SEER unit replaced in 2015 for $3200 installed. My average monthly bill is $185 (utility allows me to pay the average adjusted twice a year), and it can keep up with Phoenix heat. I'm very comfortable with my choices and my situation.

 

[Vigo]

While it's definitely good to get your facts straight before you go asking anyone else to remotely reengineer your system, it also seems like the tone of the thread got kinda persnickety over being helpful..

I think it's true that something like the 18k inverter with some kind of interlock to prevent simultaneous compressor starts, should be able to power the two ACs with as much solar is available and use grid power for whatever cannot be met with solar. So that basic concept i think is sound.

I also agree that insulation upgrades should be done first and will be cheaper.

Depending on how much of the house is actually 'in use' you might also be able to improve your comfort level for free by just prioritizing airflow to the areas which are most often occupied. That may be as simple as partially or fully closing some vent registers which might be doing silly things like cooling closets or storage areas.

Also, cold air sinks, hot air rises. Look for air leaks near the floor and address those. Even without good air sealing to the attic, hot air in the attic will not willingly sink into the conditioned space unless cooler air is leaking out somewhere near the bottom. The fiberglass is still there to address conduction and radiant heat transfer, but as far as hot air getting in, there would have to be cold air leaving.