DC Pool Heater

[Harj]

Hi All!

I'm looking to see if anyone knows if there is a pool heater out there that runs on DC so I can power it directly from solar panels without having to use an inverter. Any help is much appreciated

[russ]

The heat pump style water heaters make some great claims on efficiency.

[J.P.M.]

Hi All!

I'm looking to see if anyone knows if there is a pool heater out there that runs on DC so I can power it directly from solar panels without having to use an inverter. Any help is much appreciated

FWIW: It will be much more cost effective to:

1.) First get a pool cover.

2.) Get solar thermal pool heating panels.

The thermal panels will take up less space and cost a lot less. They are also about 2 -3 times as effective at providing thermal energy to a pool than PV.

Pay your money, take your choice.

[bcroe]

The heat pump style water heaters make some great claims on efficiency.

Do those heat pumps use MPPT DC inputs? I was thinking about Solar Queens comments
of also de humidifying the basement, which has been done here to no other benefit. And
that need coincides with maximum summer sun. Bruce Roe

[J.P.M.]

Do those heat pumps use MPPT DC inputs? I was thinking about Solar Queens comments
of also de humidifying the basement, which has been done here to no other benefit. And
that need coincides with maximum summer sun. Bruce Roe

Heating pool water with a heat pump in the basement is probably not a good idea: The heat pump uses air as the heat source. The basement air vol./turnover is probably too low --->>> the basement air temp. would drop, decreasing the COP of the pump. The basement would probably turn into a big walk in fridge, and the air would be dryer than a popcorn fart.

[bcroe]

Heating pool water with a heat pump in the basement is probably not a good idea: The heat pump uses air as the heat source. The basement air vol./turnover is probably too low --->>> the basement air temp. would drop, decreasing the COP of the pump. The basement would probably turn into a big walk in fridge, and the air would be dryer than a popcorn fart.

Guess I was trying to change the subject a little, to heat pump water heaters for the
sink, etc. The pump would only run enough to heat hot water being consumed. Most
likely the humidity here is a lot higher than much of the SW, and any cooling would
cancel some air conditioning, don't need a lot of that either. Since much happens in
this basement (same size as the main in a ranch), air is circulated to all, basement
deliberately is not isolated. Bruce Roe

[LucMan]

A heatpump pool heater will give you a COP of close to 4. That means you will get 4 btu's out for every 1 put in.
Much more efficient than resistance heaters. This is a great option if you have PV panels and are grid connected.
Unfortunately I have only seen them in a/c voltage.

[bcroe]

A heatpump pool heater will give you a COP of close to 4. That means you
will get 4 btu's out for every 1 put in. Much more efficient than resistance heaters. This is
a great option if you have PV panels and are grid connected.
Unfortunately I have only seen them in a/c voltage.

I thought since I am running a dehumidifier in summer anyway, it would be more efficient
to use a unit that preheats my house hot water at the same time. Could still do it with AC,
but DC might allow some more options not involving the current grid tie system.
Bruce Roe

[russ]

A heatpump pool heater will give you a COP of close to 4. That means you will get 4 btu's out for every 1 put in.
Much more efficient than resistance heaters. This is a great option if you have PV panels and are grid connected.
Unfortunately I have only seen them in a/c voltage.

I have seen them advertise significantly greater COPs - I suppose due to the low delta T - I have no personal experience with one but only what I have read

[bcroe]

I have seen them advertise significantly greater COPs - I suppose due to
the low delta T - I have no personal experience with one but only what I have read

My air to air claims a SEER of 14.5; my estimate is a COP in the range of 3 to 4. The actual
number is going to vary by conditions. When you are heating, the electric energy you put
into the unit helps supply heat, but when you cool it is blown away. So I would expect the
COP for heating to be 1 greater than for cooling if other factors could be the same. That
level of detail isn't forthcoming, and not trivial to actually measure. Bruce Roe

[LucMan]

With heat pumps the ratings are standardized at 47 and 17 degrees F by AHRI. These ratings are moving target. With a pool heater or a HP water heater operating at an ambient temperature above 70F the COP can be much higher than the AHRI ratings. The limitation in HP design is the refrigerant condensing temperature, usually between 110-120 F at system design pressures. As the ambient temps approach the condensing temperature the pressure in the system rises along with the amp draw of the compressor, this negatively affects the over all efficiency of the system.
So where is the sweet spot for a HP for max COP? I have no idea. But I will state that max outlet temperature whether it's air or water would be around 110 F.
As an HVAC pro my opinion is that the AHRI ratings have always been B.S because in the real world they don't mean Squat just like the mileage ratings on vehicles.

https://www.google.com/url?sa=t&source=web&rct=j&ei=Ihk4VebaHaiwsATyzICQAg&url=http://www.energy.ca.gov/2013_energypolicy/documents/2013-03-21_workshop/presentations/IEPR_Session_1_Part_2.pdf&ved=0CDEQFjAH&usg=AFQjCNEY_kW0E9MHhRs4SnKnaJRE4PX-0A&sig2=1wBvxGJTxbkPzFqaGBGw6A

[russ]

With heat pumps the ratings are standardized at 47 and 17 degrees F by AHRI. These ratings are moving target. With a pool heater or a HP water heater operating at an ambient temperature above 70F the COP can be much higher than the AHRI ratings. The limitation in HP design is the refrigerant condensing temperature, usually between 110-120 F at system design pressures. As the ambient temps approach the condensing temperature the pressure in the system rises along with the amp draw of the compressor, this negatively affects the over all efficiency of the system.
So where is the sweet spot for a HP for max COP? I have no idea. But I will state that max outlet temperature whether it's air or water would be around 110 F.
As an HVAC pro my opinion is that the AHRI ratings have always been B.S because in the real world they don't mean Squat just like the mileage ratings on vehicles.

https://www.google.com/url?sa=t&sour...xbkPzFqaGBGw6A

Thanks!

[bcroe]

With heat pumps the ratings are standardized at 47 and 17 degrees F by AHRI. These ratings are moving target. With a pool heater or a HP water heater operating at an ambient temperature above 70F the COP can be much higher than the AHRI ratings. The limitation in HP design is the refrigerant condensing temperature, usually between 110-120 F at system design pressures. As the ambient temps approach the condensing temperature the pressure in the system rises along with the amp draw of the compressor, this negatively affects the over all efficiency of the system.
So where is the sweet spot for a HP for max COP? I have no idea. But I will state that max outlet temperature whether it's air or water would be around 110 F.
As an HVAC pro my opinion is that the AHRI ratings have always been B.S because in the real world they don't mean Squat just like the mileage ratings on vehicles.

I have always assumed that the number is just one point on a multi dimensional curve. I consider the
SEER a standardized way to compare different units. Then I'm trying to estimate COP.

They aren't so anxious to talk about COP, which isn't such a great sounding number, or to show any
curves indicating actual performance vs temps. It would be nice to have a readout of the COP at
any time, guess that's comparing the input power (easily measured) against the temp differential
and flow of the air of the conditioned space; probably needs to be integrated over some time.
Bruce Roe

[LucMan]

The best number for comparing HP's is the HSPF #, but again it is a moving target. But you can enter your location in this calculator.

https://www.google.com/url?sa=t&source=web&rct=j&ei=N_U4Vf2LMsGkgwTQnIGoBw&url=http://www.eia.gov/tools/faqs/heatcalc.xls&ved=0CDMQFjAA&usg=AFQjCNHIZ1slQV864Q64IQ8tgHp74n439A&sig2=B5yFC8niy9STGI3FIFSOCg

[J.P.M.]

Given that a decent thermal flat plate pool heater will probably run ~ >= ~ 50% eff. or so if done right, and probably cost substantially less to purchase and maintain, I'd sure give that option a look before the heat pump/PV route, not only for cost but simplicity.