1 Heat Pump for Space Conditioning+Hot Water

what do you think of this cool multi-use split system heat pump.
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1) heat pump (1kW) http://www.smallplanetsupply.us/sanden-sanco2-heat-pump-water-heater-3rd-gen-83-gal-system/
2) hot side
3) cold side
4) electricity source  
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Hot Side  = Hot Water Tank + Winter Space Heating + Pool Heating + Sous-Vide cooking and baking
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Cold Side = Cold Fridge + Refridgration + Summer Space Cooling)
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Electricity Source
The unit uses 1kWHr/day in the summer and about 4kWHr/day in the winter.
This could be powered by about $2,000 worth of solar panels ($1000 inverter and $250/250W(summer) to $1000/1000W(winter) solar panels)

Cold Side-Split System Condenser
This will chill the air down to 5F with COP=4.5, it will operater at a lower COP down to -25F
This can be placed into a insulated walking room/box/fridge.
With some type of air flow to prevent the air from going under 5F and maybe ice for thermal storage = Freezer
Some of the cold air can also be send to a seperate box with a temp of 35F = Refridgerator.
Some of the cold air can also be sent directly to the living space in the summer or mushroom grow room.

Hot Side
The unit comes with a 83gal stratified hot water tank.
The unit has an optional $1,500 add-on to used it for space heating.
An additional add-on could also be used to power a always on sous-vide insulated cooktop.
A similar add-on could also be used to heat a pool the unit would use alot more electricity

What it's 'capable' of doing and what it actually does are two different things.

I doubt you'd be able to use it for both a water heater and a fridge at the same time, at least I doubt it would do both well most of the time.

Besides, for that price it would be cheaper to buy all the parts separately, and a whole lot less work.

I bought a heat pump add on to a water heater off ebay for $365 (delivered) and a mini-split heatpump for $800.  I built a duct system that allows me to pipe the cold air from the water heater into the living room during the summer and out the old chimney (from the previous propane water heater)  during the winter.

Simply heating water for a day barely provides any cooling, enough to measure with a digital thermometer, but not enough to really notice.

Desert air needs alot more cooling than mines
Desert tap water is naturally warmer than mines and so it needs less heating than mines
it is also very possible that due to water restriction water usage is less.
So with your hot water system producing less waste cooling and you overall cooling needs way higher than mines, I can see how the observation would differ and it really does depend on the location/situation.

You do bring up a good point
In the summer if I need more cooling, what do I do with the extra heat/hot water that I am not using for shower.
In the winter when I need more heat, what do I do with the extra waste coolth that I don't need.

The extra coolth in the winter I will just send outside like you.
The extra heat/hot water that will be produced in the summer, right now with your $800 mini split you just dump it outside, I will heat some water and possible grow some algae in a bio-reactor, cook sous vid style, etc

In terms of forcing the heat pump to go below freezing temp and reducing it's efficiency a multi-stage setup might be better. So I think I will keep with the cut the freezer idea but keep the heating plus space conditioning combo.

To get the most out of this system I will have to make sure that i only heat the water when the house is hot (afternoon) because that is when the waste coolth is needed the most. And I will have to limit my summer time indoor cooking, and make the house super insulated to keep the coolth inside.

If I was living in Arizona with low humidity, I would do radiant calling panel vs AC run some 70F tap water into a radiator fin have the hot air in the ceiling come it contact cool and sink at 70F ish and then have some "new" air and new water replace it.  Sadly this is not a good fit for me due to dew point condensation/mold (water vapor condensing on the surface of a cold glass of water)    

With the close to 100gallon hot water tank, only afternoon heating works fine and the heater does come with a timer.

I will also have to try my best and replicate the optimal lab condition to get the wonderful COP of 5.5 that they claim to achieve, (no bends, super insulated plumbing, etc)

You have a point, although your shoulder seasons (begining and end of winter) will be closer to my winter.  
I admit I was enamored with the idea of using a heat pump to heat water and cool the house at the same time (I was looking into desuperheaters), but again it came down to costs.  It was significantly cheaper to buy the individual components, and another solar panel, that a one unit does everything, and they were easier to install.
There is also the single point of failure vs multiple units considerations.  Multiple units are (typically) more likely to experience a failure, but it's less catastrophic when they do fail.

FWIW I used an E-Tech heat pump water heater, they are still available brand new on eBay for $365
https://www.ebay.com/itm/NEW-Heat-Pump-Water-Heater-SAVE-50-or-more-on-your-Hot-Water/273016394493?hash=item3f910b92fd:g:RMQAAOSwj0NUa3~6

I was actually thinking about using one of these combined with a night sky radiant cooling setup, and solar water heater.  The heat pump could enhance both of those systems during those days when they weren't running optimally (due to weather, etc.)

However, so far the Pioneer heat pump combined with evaporative cooling and solar space heating have been working great so I haven't pursued it yet.  My solar space heater is just my attic crawl space.  I noticed that even when outside temps are down near 40 degrees, the attic was over 70 deg, so I rigged up a blower motor from a worn out furnace to blow the air from the attic, through a filer and into the house.
Note: the water heater above is setup to pull air from the attic during the winter and exhaust it outside, this improves it's efficiency significantly.
During the summer it pulls air from the living room near the roof, and returns the cold air back to the living room.  This means it's effectively working like your idea (to a smaller extent)

Again, as you've pointed out, climate in my area is more favorable to using these ideas, but I figured they might be useful to you, or others, at least part of the time.

If you decide to pursue your idea, please keep up posted.  I'm curious as to how well it will work in the real world.

Peter, could one run that mini-split or water heater directly(after inversion) off a panel or panels?

No, there is hardly anything that you can run directly from panels.  Sunshine isn't constant, clouds get in the way occasionally as well as a small planet and occasionally a moon.

You need something (batteries) to buffer the energy for when the sunshine isn't available and just as importantly you need something to match the 'impedance' of the panel to the load (charge controller).

To run this heat pump you need either a grid-tied inverter or batteries, a charge controller, and an off-grid inverter.

Some things can be run on DC instead of AC so you can avoid the inverter, although you still usually want a battery and charge controller.  
They even make compressors suitable for a heat pump that run on DC, but they tend to be expensive.

You can plug the heat pump into a smart "power strip" that only turns on during the day after the batteries have started to charge, you would need a stratified hot water tank and a 100gallon ish water tank, if you want to time shift your input.

the heat pump that I listed gives out a max of 19,00BTU of heat and 15,000BTU of cooling at the same time, it uses about 700W-1500W per hour.

I thought I'd show why you need batteries with Solar.  Below is a graph of power usage by my water heater, solar space heater and the mini-split heat pump.  Everything is running on one circuit and measured using one channel on my energy monitor and then I wrote a program to try to guess what was running when, based on instantaneous power levels.  While it occasionally guesses wrong, over all it does pretty well.



At any rate, you can see how the mini-split is typically drawing about 250 watts (it's lowest setting) when it runs, but occasionally has spikes up as far as 550 watts.  Even on a clear sunny day, those 500+ watt spikes means that it could not run directly off one panel, and if it had two panels, most of the energy would be wasted.  Not only that, but if a cloud happened to pass just as the heat pump was starting up, that could damage the compressor.  It's not shown, because it happens too quickly, but there is also a brief surge when the compressor starts up, possibly 600 watts or more.
According to the spec sheet, it's rated to produce up to 17,250 btus of heating or cooling, but I've never seen it run anyway near that power.  Also, the lowest input power listed is about twice what I'm seeing, so I'm not sure how accurate the specs are.

The mini-split mostly runs at night and keeps the temperature in the 'living area' from dropping below 65 degrees, on this day the outdoor temps got into the low 30s over night.
The 'living area' is the living room, dining room and kitchen, basically one large room that takes up almost 1/2 the house.

The green line is the temperature in the small bedroom where my computers are, it gets a couple degrees colder at night since it's not getting any direct heat from the mini-split.  

Recently the temps have been dropping down to 29-30 degrees and the mini-split runs almost constantly through the night and early morning.  I expect if the temps drop below 27-28 the mini-split will kick up to the next power level.

When conditions are right, the solar space heater provides much more heat for the same energy, since it's just moving hot air down from under the roof, plus it heats the whole house, not just the living area.

Peter and S Bengi,

Nice graph. Wow, I want to try the water heater attachment. I have powerful inverter, controller, and panels, but not a big battery because of the weight. It's all in a 12 ft cargo trailer with a lot of other energy projects.  My battery is about 180 ah at 24 volts. So maybe the timer Benji mentions would be a good idea. Is that a Kill A WAtt power strip? Someday I'd like to graph my consumption also. And invest in Lithium batteries.

I may have found where the eTech HPWH on eBay came from. I found a report on a utility program in Conneticut:
https://aceee.org/files/pdf/conferences/hwf/2008/2a_johnson.pdf

Jeremy Baker wrote:Peter and S Bengi,

Nice graph....Is that a Kill A WAtt power strip? Someday I'd like to graph my consumption also.

No it's a Brultech ECM-1240 energy monitor.  It uses current transformers that are typically mounted around the wires in you circuit breaker panel.  It can monitor 7 different channels at the same time.  They have a larger model called the "Green Eyed Monster" that can measure 32 channels.  They can also count pulses from water/gas meters (1 channel on the 1240, 4 channels on the GEM) and the GEM can also measure temperture.

They both measure "true power" and both have at least a couple channels that can tell which way the power is flowing.  This is good for me since I have a grid-tied solar array, knowing which way the power is flowing tells me if I am pulling power from the grid, or pushing it back.  

I originally used one channel for monitoring the water heater.  Back before I installed the heat pump it was a 5500 watt water heater so it have a 30 amp circuit.  Then I installed the heat pump and now it maxes out at 650 watts (less than 3 amps), which left me with a lot of spare power available on that circuit.  So I moved the wires over to a new sub panel in the garage and added the mini-split, the blower for the space heater, my freezer, etc.  Long term goal is to add a generator back up to just that panel and have my critical loads all re-terminated to garage panel.

Anyway, that's why I have one channel measuring multiple appliances right now.  Using software to guess which was which worked pretty good until last night when the temps dropped down to 22 degrees.  Now the mini-split is pulling almost 1000 watts.  Fortunately I ordered another ECM-1240 for the garage panel, hopefully that will be in this week.

This my what my whole house looks like:

Jeremy Baker wrote:I may have found where the eTech HPWH on eBay came from. I found a report on a utility program in Conneticut:
https://aceee.org/files/pdf/conferences/hwf/2008/2a_johnson.pdf

Interesting, I'd heard they had some problems with the early models.  I think they eventually sold the whole product line to a different company.

I haven't had any problems with mine, although I have been thinking about buying a second one just to have spare parts or to use in another project I've been toying with.

S Bengi,

I see you are in Massachusetts. I’ve been considering the SanCO2 and live in Eastern MA. Just curious if you worked with any particular installer and if so, if you were satisfied? There aren’t many reviews in the US, so I’ve been reading reviews from AU and it sounds like the install can really make or break the performance of the system.

My other big concern is power outages and frozen pipes. Any experience and/or recommendations in these regards? Are you still feeling satisfied with this system?

Many thanks!