small, inexpensive solar heat pump idea

gordonstarr3

My first shot at a solar installation is in the design phase now and I could use some advice. The house is 800 square feet and has gas forced air heat, currently. I plan to install an hotspot energy acdc12b - an incredibly efficient heat pump/air conditioner minisplit which draws 720 watts but generates 12,000 btu/ hr of heating and cooling. It is a dc heat pump, runs on hybrid power , calls for two or three panels connected (up to 900 w) of solar dc power plug n play directly into the heat pump. It also runs off 220 house current which must be wired in.

My plan is to mount four 300w semi-flex solar sells with silicon and screws directly to the roof. These will be overhanging the edge of the roof in such a way as to allow easy wiring of the cells under the eaves. The overhang will also protect the outside portion of the heat pump. Two of the 300w panels will connect to the acdc12b directly, and the other two panels will go through a 600 w grid tie inverter wired back to the main pane. So, two dedicated lines to the breaker box are the grid tie inverter output and the 220w power supply of the heat pump. None of the components carry high power (15 amp max at 220v for the heat pump) 4.5 amp and 120 v for the grid tie inverter. I have found waterproof toggle switched which I propose, possibly incorrectly for exterior shutoffs for the two AC lines. I have not designed in any dc shutoffs because of the plug n play nature of both the inverter and the heat pump.  No DC power enters the house and there are no batteries involved.

So that is it, basically two systems that are electrically separate but in the same place - a 600w grid tie inverter and a 720 w mini-split hybrid heat pump. According to my calculations the numbers are incredibly low with regard to cost and payback time. but, I may be missing something. If you've read through this so far and found some flaws in my thinking, let me know. I really want to see this thing knock out ALL of my HVAC power costs.

Thanks in advance,

Gordon Starr

Johann

Heatpumps do not like overhangs or roofs over them, usually it will block or reduce airflow and this will increase power usage and lower the efficiency of the unit .
Mounting solar panels directly on the roof is not good either. Panels need a airspace between the panel and roof  to keep them  cooler . The cooler the panels the more power they produce.
Why use semi-flex panels?

gordonstarr3

Thanks for your thoughts on this. From what you say, doing a more conventional rooftop installation could improve efficiency. The reason for semi-flex panels was they were very inexpensive (four panels at total of 625$ for 1220 watts including delivery). At that price for power, losing some efficiency in trade-off for gaining some labor and material savings could be well worth it. Screwing them/silicon directly to the roof (which is brand new) would save on materials and labor (all those braces, racking, grounding would be unnecessary). It has a south face with around 30 degrees of pitch.

The overhang from the edge of the roof would be just enough to keep the heat pump out of the runoff from the roof (there are no gutters). The acdc12b is a very attractive and impressive unit with a stainless steel rack that mounts to the wall. It is also qualifies as solar equipment, so gets the 30% us government tax credit. I was mainly looking to the solar panel roof overhang to keep rain off it. That position could turn out to be a bit cooler for the panels than mounting them way up in the middle of a hot roof.

Photowhit

I would be very leery of claiming the air conditioner for the solar tax credit/1 I would want a statement from the company, so when the IRS came for their money I would have someone to sue.

Flex panels have a shorter life span than glass panels, please don't mount directly to the roof, too many bad things can happen on top of the lower efficiency.

I asked the people over at HotSpot energy some questions about their unit, (over paneling, if the 208/230V needed to be split phase) they never got back to me. I'll call it vaporware until I hear someone with an installed unit.


Haha, I now get a flag for Malware on their site! perhaps they are just collecting pennies.

gordonstarr3

I see your points. I only have the salesman's word that it is eligible for the tax credit. I would also like to hear from someone who has the heat pump installed.

Here are the major hardware items, manufacturer, and costs including delivery:

ACDC12B heat pump $1875 direct from Hotspot Energy (no reviews) http://www.hotspotenergy.com/

Four 305w panels $625 from Santan Solar (five star product reviews)

600w waterproof grid-tie inverter $150 (no reviews) http://www.ebay.com/itm/351851524081

Two heavy duty waterproof AC toggle switches rated 15 amps at 220 volts $15 (five star product reviews)http://www.ebay.com/itm/111529145661

I've attached pics of the heat pump and the solar panels.  The panels are huge and weigh 50 lbs or so. They are stiff enough for rack mounting if I decide to go that route. However, in defense of my design, it is versatile, compact, and inexpensive. Also, I have ordered 1220w while the heat pump only requires 720. I live in Ohio where you seasonally need both heating and cooling and there are times when you need neither. So the versatility to heat, cool, and generate AC grid tie power means VERY BIG savings.

gordonstarr3

"Haha, I now get a flag for Malware on their site!" If that's true, and I seriously doubt it, why do you think it is funny?

gordonstarr3

Estragon

Had a quick look at the specs for proposed inverter. One thing that stands out is the higher voltage version appears not to be N.American (ie it's 230v-50hz, NA is 60hz). Heat pump looks to be NA-60hz.

Photowhit

gordonstarr3 said:

"Haha, I now get a flag for Malware on their site!" If that's true, and I seriously doubt it, why do you think it is funny?

Because now, I've gotten something from them, Nothing good....

Guess you called them, I would get the tax info in writing and then you can sue them if they still exist. You might read what the government says about solar tax credits.  ...and there may be a smaller tax credit available for high efficiency appliances, I thin you could take it on the panels, if installed to code, and if they are code complaint panels.

The grid tie inverter does NOT appear to be a UL listed inverter and I would NOT be able to install it up to code. Understand if the power company isn't contacted and they discover the inverter back feeding the grid they can shut off your electric. Also some of the new electronic meters measure only current flow and may charge you for back feeding the grid! 

gordonstarr3

Just got off the phone with the folks at hotspot energy and directed them to this blog. Hopefully they will weigh in on some of the questions/issues that have been raised here. They confirm a 30% federal tax credit on the solar heat pump, plus anything your state has in the way of solar incentives. Ohio has nothing, unfortunately.

HotSpotEnergy

Hello, Official HotSpot Energy Inc. rep here - we would like to address some comments and provide additional information.

In regards to a malware flag – we always appreciate anyone letting us know about such a problem. Today after being informed of this thread we looked into this and we don’t see a problem. We are not IT pros, we design and build energy products, but according to https://app.webinspector.com/public/reports/65706241 it appears to be clean. If someone can let us know a specific page that appears to be a problem, or some other way to see such a problem on our web site, please do so. As you may know, hackers are a persistent problem for all webs sites and we do our best to secure our site. Please also know that we do not collect any personal information on our website, we have no online ordering, no site-based credit card processing, etc. Please always be careful with any website.

In regards to the federal tax credit, we are not professional tax advisors and do not give tax advice. With that said, please see the actual code:

> 26 CFR 1.48-9 - Definition of energy property.
d) Solar energy property— (1) In general. Energy property includes solar energy property. The term “solar energy property” includes equipment and materials (and parts related to the functioning of such equipment) that use solar energy directly to (i) generate electricity, (ii) heat or cool a building or structure, or (iii) provide hot water for use within a building or structure. Generally, those functions are accomplished through the use of equipment such as collectors (to absorb sunlight and create hot liquids or air), storage tanks (to store hot liquids), rockbeds (to store hot air), thermostats (to activate pumps or fans which circulate the hot liquids or air), and heat exchangers (to utilize hot liquids or air to create hot air or water). Property that uses, as an energy source, fuel or energy derived indirectly from solar energy, such as ocean thermal energy, fossil fuel, or wood, is not considered solar energy property.

Please note, the ACDC12b is solar powered equipment (a “solar energy property”) that uses directly derived solar energy and is used to heat or cool a building. We always suggest that a user contact their tax professional to confirm any specific tax related questions.

In regards to the original post and the comments regarding power, please allow us to clarify. The ACDC12b uses both solar (DC) input and AC input, blending the two, generally as follows: The first approximately 70w used comes from the AC grid. Above that, the unit can use up to 740W of solar/DC power, based on availability and need. If power above this total amount of AC+DC is needed, it is pulled from the AC connection. If a cloud passes over and DC power drops temporarily it is seamlessly replaced with grid AC power as needed. And as the sun goes down, power usage is gradually transferred over to 100% AC. The use of inverters or batteries is not part of our system although users may do so in various ways, in one example, as mentioned by the OP.

We have been producing this product, now in its 4th generation, since 2010. It is fully certified under UL 1995 and carries an EnergyStar label as well as an official AHRI rating, it is further approved by US Department of Energy and the California Energy Commission. It’s a real product.

About AC input power – it is designed for global use and can accept 50hz or 60hz power at voltages from 208 to 240. DC power should be (VMP) at least 29v up to a max of 39v. This includes a safety buffer for 72 cells panels over-producing in cold weather. Note the DC voltage ratings we refer to are not the “open circuit” rating but refer to the Vmpp rating.

About any inverter/microinverter mentioned above – not a HotSpot product and is not a part of an ACDC12b system. We do offer inverters/microinverters for use with other systems that we produce, all of the inverters we offer are UL Listed.

We hope this helps clarify things.

Thanks,

Official HotSpot Representative

Dave Angelini

I remember looking at them years ago, I think that they used the Panasonic mini-split but I could be wrong.
So, without looking at their website and getting possibly infected, what is the price/ warranty/ SEER/ shipping location please?

Photowhit

HotSpotEnergy said:
Official HotSpot Representative

I wish you had a name, but perhaps you could answer some questions.

Is there any problem with over paneling? I would think that having more than the 900watts of array would present no problem as the energy doesn't need to be used and could draw what is needed. I have 8 - 185 watt panels, that have a vmp of 36, They would provide an extra cushion for overcast days.

You say "...this is not an "off-grid" unit, 220v utility power is required" in reference to the ACDC12B, I think this is just a misnomer and that what is meant is that it is not a "stand alone unit" and requires AC input? There should be no reason that this unit wouldn't work with an off grid home that creates 208-240v with a pure sine inverter or even an auto transformer. Many/most off grid inverters provide a cleaner sine wave than the power company.

I currently only have 120v but would consider a 230v / 50hz international inverter this would have a fairly low tolerance for peak energy draw, is this purely inverter based A/C? what would the peak startup current be? Would it run off a 230v 1000 watt inverter with only a 1500 watt peak?

Happy to report no flags today, I'll record any and pass them on if I have issues again.

HotSpotEnergy

Hello, Official HotSpot Energy Inc. rep here - we would like to address some comments and provide additional information.

In regards to a malware flag – we always appreciate anyone letting us know about such a problem. Today after being informed of this thread we looked into this and we don’t see a problem. We are not IT pros, we design and build energy products, but according to https://app.webinspector.com/public/reports/65706241 it appears to be clean. If someone can let us know a specific page that appears to be a problem, or some other way to see such a problem on our web site, please do so. As you may know, hackers are a persistent problem for all webs sites and we do our best to secure our site. Please also know that we do not collect any personal information on our website, we have no online ordering, no site-based credit card processing, etc. Please always be careful with any website.

In regards to the tax credit, we are not professional tax advisors and do not make any claims in this regard. With that said, please see the actual code:

> 26 CFR 1.48-9 - Definition of energy property.
d) Solar energy property— (1) In general. Energy property includes solar energy property. The term “solar energy property” includes equipment and materials (and parts related to the functioning of such equipment) that use solar energy directly to (i) generate electricity, (ii) heat or cool a building or structure, or (iii) provide hot water for use within a building or structure. Generally, those functions are accomplished through the use of equipment such as collectors (to absorb sunlight and create hot liquids or air), storage tanks (to store hot liquids), rockbeds (to store hot air), thermostats (to activate pumps or fans which circulate the hot liquids or air), and heat exchangers (to utilize hot liquids or air to create hot air or water). Property that uses, as an energy source, fuel or energy derived indirectly from solar energy, such as ocean thermal energy, fossil fuel, or wood, is not considered solar energy property.

Please note, the ACDC12b is solar powered equipment (a “solar energy property”) that uses directly derived solar energy and is used to heat or cool a building. We always suggest that a user contact their tax professional to confirm any specific tax related questions.

In regards to the original post and the comments regarding power, please allow us to clarify. The ACDC12b uses both solar (DC) input and AC input, blending the two, generally as follows: The first approximately 70w amp used comes from the AC grid. Above that, the unit can use up to 740W of solar/DC power, based on availability and need. If power above this total amount of AC+DC is needed, it is pulled from the AC connection. If a cloud passes over and DC power drops temporarily it is seamlessly replaced with grid AC power as needed. And as the sun goes down, power usage is gradually transferred over to 100% AC. The use of inverters or batteries is not part of our system although users may do so in various ways, in one example, as mentioned by the OP.

We have been producing this product, now in its 4th generation, since 2010. It is fully certified under UL 1995 and carries an EnergyStar label as well as an official AHRI rating, it is further approved by US Department of Energy and the California Energy Commission. It’s a real product.

About AC input power – it is designed for global use and can accept 50hz or 60hz power at voltages from 208 to 240. DC power should be (VMP) at least 29v up to a max of 39v. This includes a safety buffer for 72 cells panels over-producing in cold weather. Note the DC voltage ratings we refer to are not the “open circuit” rating but refer to the Vmpp rating.

About any inverter/microinverter mentioned above – not a HotSpot product and is not a part of an ACDC12b system. We do offer inverters/microinverters for use with other systems that we produce, all of the inverters we offer are UL Listed.

We hope this helps clarify things.

Thanks,

Official HotSpot Representative

HotSpotEnergy

Hello:

@Dave Angelini
One of our earliest systems (DC 48v, not hybrid, 17000 BTU, used a Panasonic compressor, this was back in 2007. You have a good memory ;-)  I don’t know how to get out from under the “malware” cloud – actually our site is clean. Fake news ;-) Anyhow, list price is $1695, SEER 21 (at night with no solar), warranty 3 years. For any further info please give us a call, we don’t want to use this forum as a sales vehicle.

@Photowhit
We do have names ;-) But we are not always the same person ;-)

Over-paneling – really there is no worry with this, panels don’t “push” power, they can only provide power that is “pulled”. Note, our unit uses max 20a DC. So for example on a 3x300w system, we would use max 740w. But having 900w total PV footprint is not a bad idea considering the performance benefits on an overcast day, or at poor incident angle (early/late sun angles). A 300w panel rarely produces 300w.

>There should be no reason that this unit wouldn't work with an off grid home that creates 208-240v with a pure sine inverter

Yes. Exactly right. But we make an all-DC system that may be a better fit for off-grid.

>inverter this would have a fairly low tolerance for peak energy draw

No problem with this, the ACDC12b has a very soft start with slow ramp up. No surge.

Thanks,

Official HotSpot Representative

Dave Angelini

Thank-you!  I am sure Bill "the moderator" would say something so please pass on a phone number. The store here does not sell heatpumps and I think they should. Many of my clients want a one source place to buy an offgrid system that has a heat-pump.
Even nicer if it can avoid the conversion loss, but, that might make it harder to install in an existing 240vac inverter based system.

My source does not sell them either so I get it. How do you deal with the line set and vacuuming it down for an install?

BB.

I believe this is their website:

www.hotspotenergy.com

-Bill

HotSpotEnergy

> that might make it harder to install in an existing 240vac inverter based system.

Actually, if you are running 48vdc batteries in an off-grid application, the suggestion for connecting the all-DC 48v version of the solar AC would be to connect it directly to the load terminals of the charge controller (same terminals the inverter connects to).

> How do you deal with the line set and vacuuming

They system should be evacuated to <400 microns before releasing the pre-charge. No EPA permit is needed for r410a but a vacuum pump and gauge manifold set would be needed therefore we suggest a professional to perform, at a minimum, the final commissioning.

##

I do worry that we are pushing the limits of what we can/should be doing on this forum in regards to offering sales information. We are new here and don’t want to cause trouble. Please contact us directly for sales related questions.

Thanks,

Official HotSpot Representative

BB.

You are doing OK... Answering direct questions is fine. As is providing technical information. And you can put your website/short description in your signature for your company.

http://forum.solar-electric.com/profile/signature

Take care,
-Bill "moderator" B.

Raj174

Just how is the DC input from the PV used to augment the refrigeration cycle of this unit? Electrical and/or thermodynamic details please.

Photowhit

HotSpotEnergy said:

Over-paneling – really there is no worry with this, panels don’t “push” power, they can only provide power that is “pulled”. Note, our unit uses max 20a DC. So for example on a 3x300w system, we would use max 740w. But having 900w total PV footprint is not a bad idea considering the performance benefits on an overcast day, or at poor incident angle (early/late sun angles). A 300w panel rarely produces 300w.

>There should be no reason that this unit wouldn't work with an off grid home that creates 208-240v with a pure sine inverter

Yes. Exactly right. But we make an all-DC system that may be a better fit for off-grid.

>inverter this would have a fairly low tolerance for peak energy draw

Thank you for your prompt reply, If I had received these answers a couple years ago you would have made a sale.

It might be good to make changes and take out wording that you have just refuted.

"Up To 3 Panels 900W  Max"
and
" is not designed for off-grid operation" (I think this statement on it's own creates the idea of ignorance of off grid systems and may create a hostile reaction by people living off grid. There are a whole lot of people out there thinking we're living in a cave.)

I suspect may people, like me, have a designed off grid system and would be interested in adding this unit to their existing system, for use when there is plenty of extra energy in the summer. Your "off grid" Air conditioner, appears to only be sold as a system/kit?

Dave Angelini

Raj174 said:

Just how is the DC input from the PV used to augment the refrigeration cycle of this unit? Electrical and/or thermodynamic details please.

I looked at their web page again after a few years. They have modified a Panasonic Heat pump to run on nominal 48v DC voltages.  They have a few other choices also which involve direct to 72 cell solar and their voltages and something I did not understand.

The decision to use this really gets down to a few things. Can you locate the heatpump close enough to your battery to avoid long distance DC voltage loss or low gage wiring. If so you would save some conversion loss that all mini-splits have and for offgrid, the loss at night makes sense unless your system is robust enough to support it already, or plan that down the road.

The prices I saw are much more than a 240vac heat pump of similar SEER. Pretty much what I saw last time a few years back.
There are also better SEER units out there. They have a 3 year warranty and most splits have 5 which is another subject of ?

Johann

Photowhit said:

HotSpotEnergy said:

Over-paneling – really there is no worry with this, panels don’t “push” power, they can only provide power that is “pulled”. Note, our unit uses max 20a DC. So for example on a 3x300w system, we would use max 740w. But having 900w total PV footprint is not a bad idea considering the performance benefits on an overcast day, or at poor incident angle (early/late sun angles). A 300w panel rarely produces 300w.

>There should be no reason that this unit wouldn't work with an off grid home that creates 208-240v with a pure sine inverter

Yes. Exactly right. But we make an all-DC system that may be a better fit for off-grid.

>inverter this would have a fairly low tolerance for peak energy draw

Thank you for your prompt reply, If I had received these answers a couple years ago you would have made a sale.

It might be good to make changes and take out wording that you have just refuted.

"Up To 3 Panels 900W  Max"
and
" is not designed for off-grid operation" (I think this statement on it's own creates the idea of ignorance of off grid systems and may create a hostile reaction by people living off grid. There are a whole lot of people out there thinking we're living in a cave.)

I suspect may people, like me, have a designed off grid system and would be interested in adding this unit to their existing system, for use when there is plenty of extra energy in the summer. Your "off grid" Air conditioner, appears to only be sold as a system/kit?

I came across this unit about 3 years ago and I would had bought it also, but like Photowhit said.....it was deemed  NOT to be an '' off grid unit''  and  that it can use only ''up to 900 watts'' of solar panels. Both those things turned me away from it back then. Those statements back then gave me the info/feeling/impression that I could not operate this if I have more than 900 watts of panels and that it does not work in an off grid situation and I wanted it to use it in an off grid situation and with more panel power without having to run 2 seperate systems.


 

gordonstarr3

It certainly helps to know that I could take this system off grid and all I would need is a low power 220 v inverter. Hey, I might like to do that someday! Or, wait, am I missing something? again..

HotSpotEnergy

@Raj174

All  “Inverter” high efficiency units use DC power – actually the 220vac that enters this type of unit is immediately converted to DC before powering the compressor. Our unit also uses some AC (converted to DC) blended with solar DC, to the extent solar DC available, as mentioned previously.

@Photowit
We use a 3x300w as a recommendation, of course you can use more or less panels or no panels at all as is the case at night. We also offer an all-DC similar unit which for most people is better for off-grid use. I guess the short story is that we design and build products and you can’t be an expert at everything - we admit we are not experts at marketing. We will consider your comments in our next web site revision. Both systems are available ala carte or as a system kit (although we generally don’t provide batteries as they can usually be better sourced locally).

@Dave Angelini
The ACDC12 series hybrid has never been built based on a Panasonic compressor, it has always exclusively used a Toshiba/GMCC compressor. The all- DC units have been built with both Toshiba/GMCC and Panasonic compressors.

For the 48vdc unit, the panels can be a long distance from the batteries without much difficulty, however we suggest that the batteries be within 25 ft. of the DC48 outdoor unit to avoid voltage drop/cabling issues.

About cost – when you consider the installed cost of ACDC12b compared to the installed cost of a standard unit, they end up being about the same net after-tax-credit cost.  Any cost difference can be paid back quickly via savings.

@Johann
There is no maximum number of panels allowed on the ACDC12b but there are some practical considerations. The unit will only pull 20a DC from the solar side, about 740w max. Using 3 panels or 30 or 300 won’t hurt the system.  Based on our 7+ years of experience in designing, testing, manufacturing, and supporting the ACDC12 systems we think that 3x 300w/315w is an appropriate configuration.

Don’t hesitate to call us to discuss. We offer friendly and knowledgeable support and will be happy to try to help you come up with the best system for your application.

Thanks,

Official HotSpot Representative

Photowhit

HotSpotEnergy said
There is no maximum number of panels allowed on the ACDC12b but there are some practical considerations. The unit will only pull 20a DC from the solar side, about 740w max. Using 3 panels or 30 or 300 won’t hurt the system.  Based on our 7+ years of experience in designing, testing, manufacturing, and supporting the ACDC12 systems we think that 3x 300w/315w is an appropriate configuration.

You might consider reassessing this, today's solar panel costs are a small fraction of those 7 years ago, it might well be very cost effective to have 1500 watts of panel with 1/2 facing south east and 1/2 south west....

Thank you for being so responsive, it shows a great deal of responsibility and integrity, wish I had gotten answers earlier.

HotSpotEnergy

>today's solar panel costs are a small fraction of those 7 years ago, it might well be very cost effective to have 1500 watts of panel with 1/2 facing south east and 1/2 south west....

That's a great point - If you can't point the panels south then more footprint could be used, also facing some east and some west should work out fine.

Estragon

In summer, when you really want AC it could work out better than a straight south array. AC could run longer and keep space cool vs shorter and have to make space cool.

Dave Angelini

Estragon said:

In summer, when you really want AC it could work out better than a straight south array. AC could run longer and keep space cool vs shorter and have to make space cool.

Of course! This just shows you how few people actually live offgrid and would know this

gordonstarr3

Ok, suppose my unit is over-paneled. I have 1200 w south facing and I want have the heat pump draw all it needs of dc power, then route everything else to my grid tie inverter, or alternatively, to a battery bank if you are off grid. How hard would that be?