My Idea and Dumb Questions

[patty13]

What I want to do. I want to install 100% DC solar air conditioning. 2 mini split type units and I want to power my pool DC/solar as well. I don't want batteries. The idea is the system will run when the sun shines only. My plan is to use my central AC as well and of course at night. I plan to add batteries down the road most likely. I realize the solar system will have to be overpowered to allow for energy draw at start up. I would guess I can minimize the draw issues with staggered start up times for the 3 units. I live in Las Vegas so I have plenty of sun available.

The AC units are meant to be used to supplement my central AC and serve as a backup in case the big unit fails or we lose power. And of course for 'free' extra cooling when the sun shines and we need it most. You can't have too much cold air in Las Vegas in the summer. If your central AC is going to break down you can bet it will be on the hottest day of the year. And those units are now more expensive than a lot of cars. If you have to have a replacement immediately, the HVAC contractors can smell desperation a mile away. I am seeking to have choices and backup available.

How do I figure out start up draw to be able to design the system properly and price it out correctly? I do have an engineering background but I am a solar newbie. I think start up is the big issue. Am I missing something else? Thank you.

 

[newbostonconst]

Guessing you are on the grid? Are you trying not to back feed the grid? Is net metering available in your area and what is the rate?

If you have an approved solar connection but the net metering rate isn't good then you might be able to add a current monitor and turn on AC units as the back feed current gets higher, I do this with Smartthings right now.

If you are trying to hook up the AC to just the inverter then I don't think you will get this to work without a battery. But need more info to help.

 

[patty13]

Guessing you are on the grid? Are you trying not to back feed the grid? Is net metering available in your area and what is the rate?

If you have an approved solar connection but the net metering rate isn't good then you might be able to add a current monitor and turn on AC units as the back feed current gets higher, I do this with Smartthings right now.

If you are trying to hook up the AC to just the inverter then I don't think you will get this to work without a battery. But need more info to help.

Here is the pool pump. https://solarpool.com/#SolarPoolPumps They claim they have been selling this system for 15 years and it requires no batteries. I was planning on doing the AC units the same way. Too simple to be true?

Yes, I am on the grid. I am not wanting to connect my system to the grid at all.

 

[houseofancients]

What I want to do. I want to install 100% DC solar air conditioning. 2 mini split type units and I want to power my pool DC/solar as well. I don't want batteries. The idea is the system will run when the sun shines only. My plan is to use my central AC as well and of course at night. I plan to add batteries down the road most likely. I realize the solar system will have to be overpowered to allow for energy draw at start up. I would guess I can minimize the draw issues with staggered start up times for the 3 units. I live in Las Vegas so I have plenty of sun available.

The AC units are meant to be used to supplement my central AC and serve as a backup in case the big unit fails or we lose power. And of course for 'free' extra cooling when the sun shines and we need it most. You can't have too much cold air in Las Vegas in the summer. If your central AC is going to break down you can bet it will be on the hottest day of the year. And those units are now more expensive than a lot of cars. If you have to have a replacement immediately, the HVAC contractors can smell desperation a mile away. I am seeking to have choices and backup available.

How do I figure out start up draw to be able to design the system properly and price it out correctly? I do have an engineering background but I am a solar newbie. I think start up is the big issue. Am I missing something else? Thank you.

why not buy purpose made solar-powered only mini splits ?

Deye ( OEM for sol-ark) makes them

 

[patty13]

why not buy purpose made solar-powered only mini splits ?

Deye ( OEM for sol-ark) makes them

Thank you. I will look them up! Appreciate the information.

 

[Hedges]

Unless the motors are PV direct, your PV will have to deliver 5x nameplate watts to supply starting surge.

Grid-tie PV will give the same benefit, using grid for starting surge, but doesn't run when grid is down. You can get zero-export if net metering isn't available.

A hybrid inverter with small AGM battery to supply starting surge is another option. You need to design the system with controls to avoid draining batteries when PV production is insufficient.

Grundfos makes PV direct well pumps. I'm not sure what you can find for pool pumps. I have a VFD feeding 3-phase pump. Making a control system to turn it on and vary speed to match available power would be a project. With battery on inverter, it could seek to maintain battery at float voltage.

 

[patty13]

Unless the motors are PV direct, your PV will have to deliver 5x nameplate watts to supply starting surge.

Grid-tie PV will give the same benefit, using grid for starting surge, but doesn't run when grid is down. You can get zero-export if net metering isn't available.

A hybrid inverter with small AGM battery to supply starting surge is another option. You need to design the system with controls to avoid draining batteries when PV production is insufficient.

Grundfos makes PV direct well pumps. I'm not sure what you can find for pool pumps. I have a VFD feeding 3-phase pump. Making a control system to turn it on and vary speed to match available power would be a project. With battery on inverter, it could seek to maintain battery at float voltage.

Thank you. Now I know more about designing for surge. I have a lot of reading to do! This is the pool system I am considering. They have been installing it for 15 years with no batteries. https://solarpool.com/#SolarPoolPumps