New from Az

Im a new guy from Arizona. I primarily got interested in diy powerwall after buying a Tesla. Main use, being in Az is to run my air conditioning. I am self employed as a welder and fab shop, my shop is at my house. I am curious about powering my 230 volt welding equipment and possibly my 3 phase machines currently running on an RPC.

Welcome and "...is to run my air conditionin...." is a interesting comment for me as AC is more of an 'advance power' topic compared to lights, microwave, TV, fans.

I have a working off-grid system (7kw array, 40kwh battery, 12,000w inverter) and am powering my home comfortably except for heat/AC. My next step is to try to power heat/AC!

I've been looking at a whole house heat pump - my home needs 6-7ton size. Here is an interesting web site to estimate power requirements.... https://www.energy.gov/eere/femp/energy-cost-calculator-commercial-heat-pumps-54-20-tons#output

I put in 6 ton (2700sq ft home)and got this:





Notice that under "Best Available" ANNUAL ENERGY USE = 17,305kwh. YIKES!

My current 24panel 6.885 PV array produces 9,000kwh/year - so by extension I would need 48panels 'just' for whole househeat/AC. Of course, if I go with heat only - e.g. set annual hours of operation for cooling = 1 (instead of 1500) then it goes down to 7,920. So some heat might be possible.

Take these numbers as you will - but maybe this web site will help you think about the scale of what you need

The cost of running a welder off grid would be madness - the grid is really cheap when you factor in lifespan. & welcome to the community

I run a 12000btu ac mini-split off my 2.4kw inverter. It cools and heats my room all year. It's not a whole house, but it packs a punch with it's high efficiency and reduces my overall bills. The mini-split is a dc inverter style, so no startup loads at all on the compressor, unlike those nasty central units or window units. Right now it's running at a low 600W heating my room and will ramp up slowly to 1kw if needed.

not2bme said:

I run a 12000btu ac mini-split off my 2.4kw inverter. It cools and heats my room all year. It's not a whole house, but it packs a punch with it's high efficiency and reduces my overall bills. The mini-split is a dc inverter style, so no startup loads at all on the compressor, unlike those nasty central units or window units. Right now it's running at a low 600W heating my room and will ramp up slowly to 1kw if needed.

Click to expand...

Cool to get these stats. I recently purchased a Honeywell Model: MM14CHCSCS portable AC and *Heat Pump* to test the power use of heat pumps without actualy having to install stuff. This unit claims 12,000BTU Heating Capacity (i.e. 400 sq ft). Itdraws 1,050watts (as advertised) when 'on' (which is pretty reasonable compared to resistance element heat) and goes off when temp is reached so overall power is less that 1050watts / hour.

Sounds like its in the same ballpark as your experience with mini-split. By extension then - my house is 2700sqft, so 2700 / 400 = 7 of these. 7 * 12,000BTH = 84,000BTU. 7 * 1050watts = 7,350watts. 7,350watts / 240a = 31amps. I'm running AIMS 12,000watt inverter - which can definately handle 31a @ 240v.

Sounds like heat-pump technology really can heat a house in milder temperature ranges and that my solar could actually fire it to some degree. Of course power requirements are sovariable depending on temps but we do live in a 'mild temp' area where regular low is only 40-45deg in winter.

OffGridInTheCity said:

Cool to get these stats. I recently purchased a Honeywell Model: MM14CHCSCS portable AC and *Heat Pump* to test the power use of heat pumps without actualy having to install stuff. This unit claims 12,000BTU Heating Capacity (i.e. 400 sq ft). Itdraws 1,050watts (as advertised) when 'on' (which is pretty reasonable compared to resistance element heat) and goes off when temp is reached so overall power is less that 1050watts / hour.

Click to expand...

Those portable units are worse than a window unit. They still have the hard start full-on compressors as a window unit (unlike the vfd that is on the mini-split), and on top of that they're usually a single hose set up. Typically with a single hose, it is only exhausting, so in order to replace the exhausted air, air is drawn from the cellar/cracks in doors/etc. which is essentially drawing in cold air from outside, so it dramatically reduces the efficiency.

The mini split I have is fairly to install, some kits sold on amazon even comes with the lines precharged, so completely diy if you're more inclined. All you need is roughly a 1 1/2" hole drilled to the outside and electrical wiring. The air handler inside is light, about maybe 20lbs. The unit outside just sits on the ground, not bolted or anything.

not2bme said:

OffGridInTheCity said:

Cool to get these stats. I recently purchased a Honeywell Model: MM14CHCSCS portable AC and *Heat Pump* to test the power use of heat pumps without actualy having to install stuff. This unit claims 12,000BTU Heating Capacity (i.e. 400 sq ft). Itdraws 1,050watts (as advertised) when 'on' (which is pretty reasonable compared to resistance element heat) and goes off when temp is reached so overall power is less that 1050watts / hour.

Click to expand...

They still have the hard start full-on compressors as a window unit (unlike the vfd that is on the mini-split), and on top of that they're usually a single hose set up.

Click to expand...

Thanks for this detail, and yes its a single hose. Your comment helps explain why the mini-split numbers that I see on youtubes are even better than this portable unit - appreciated. Its so hard to get actual 'facts' a lot of times.