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Old 06-28-12, 07:05 AM   #41
charlesfl
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I was thinking that the reason heat pump water heaters are not more popular is that the heat pump is too small compared to an electric water heater and takes too long to heat the water.

Am I missing something?

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Old 06-28-12, 07:56 AM   #42
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The big difference is the power (KWh) used to heat the water.
The resistive heating element uses a lot of power. (1 KWh for each 3412.142 BTU).

Whereas the HP is just moving heat, out of the air, into your water tank. (Using less power per BTU).

Yes, the HP is slow. So, if you are in a big hurry to take a shower, right after doing a wash, the standard hotwater heater is for you.

But, if you know how to plan when you are going to shower, the HP will save you some money on power.

Today, we will spent about $2 for oil, to heat our water.
I think this A7 ASHP will cut that down to about $1. (If it uses 6 kw hours per day).

I think the HW ASHP is not very popular because of it's initial cost.
And because people know that regular HW heaters will fail, many times, within 5 or 6 years.

~~~
Today, I'm considering the size of my tank.. The A7 is good for up to 70 gal.
But, if demand is low..(Ours is quite low) Maybe a smaller tank would be cheaper to run.?.
Instead of a 50 gal, maybe a 40 gal tank would be more efficient?
Less water, less leakage (smaller surface area of tank)=less KW hours?
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Old 06-28-12, 10:34 AM   #43
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I don't think I've ever seen an ASHP without a resistive backup element though... It should work just as fast or very close to as fast as a normal electric heater while being more efficient.
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Old 06-28-12, 11:11 AM   #44
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"And because people know that HT heaters will fail, many times, within 5 or 6 years."

This is because people don't maintain the unit by replacing the anode rod or they take it out when the water gets a sulfur smell and then the tank quickly rusts out without the anode material.
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Old 06-28-12, 11:54 AM   #45
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Quote:
Originally Posted by MN Renovator View Post
"And because people know that HT heaters will fail, many times, within 5 or 6 years."

This is because people don't maintain the unit by replacing the anode rod or they take it out when the water gets a sulfur smell and then the tank quickly rusts out without the anode material.

Will HW storage tanks without any 230 power to the heater elements have problems with their anode rod?


Our old 74 gallon tank started leaking because of rusted hardware, after only a few years.
I was able to repair the tank, but lost interest in repairing the leaking HX, due to corroded clean-out hardware.
At the time, my wife wanted the roof cleaned off for new asphalt shingles, and oil was dirt cheap..
So, we scrapped the system, as more trouble than it was worth.
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Old 06-28-12, 12:10 PM   #46
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Quote:
Originally Posted by Daox View Post
I don't think I've ever seen an ASHP without a resistive backup element though... It should work just as fast or very close to as fast as an ASHP while being more efficient.
If you read the reviews, you will find there are people using Geyser Hot water ASHP
Geyser-R | Nyle Systems – Energy Saving Heat Pump Solutions
(and some of the new 1 piece hybrid units) that have turned off their heating elements.

One local guy who has a basement the size of mine is having great success with his Geyser, without using any 230v power..

When I want a hot shower, it's normally not an emergency. So, I can deal with the recovery time.
If it was really a problem, I'll still be able to quickly burn a few bucks in oil to heat up some water quickly..
I'll just need to turn on the ASHP system's by-pass valve, and fire up the oil burner (one switch).

I'm leaning towards the 40 gallon tank, since it will recover a bit faster.
But, more a little more planning ahead will be required.
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Old 06-28-12, 12:47 PM   #47
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Xringer Wrote:
Today, we will spent about $2 for oil, to heat our water.
I think this A7 ASHP will cut that down to about $1. (If it uses 6 kw hours per day


Just thought I would throw a wrench in. The solar hot water we have been collecting Via flat plate panel since about April is costing us about $2.16 per month for the little circ. pump operation. Anyone could build a panel with just basic skills and plumb it into an exsisting tank. Old patio door glass some 3/8 copper tube 3/4 copper tube aluminum flashing material a little sweat presto,, no more oil.

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Old 06-28-12, 01:45 PM   #48
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Quote:
Originally Posted by Xringer View Post
Will HW storage tanks without any 230 power to the heater elements have problems with their anode rod?


Our old 74 gallon tank started leaking because of rusted hardware, after only a few years.
I was able to repair the tank, but lost interest in repairing the leaking HX, due to corroded clean-out hardware.
At the time, my wife wanted the roof cleaned off for new asphalt shingles, and oil was dirt cheap..
So, we scrapped the system, as more trouble than it was worth.
I only have experience with gas tanks, the anode rod has nothing to do with electric or gas heating. It is a sacrificial rod that gets eroded easier than the tank and as long as you have a rod that hasn't eroded all of the material off of it, the tank stays protected as long as you don't have weird water properties that passivate the rod and prevent it from eroding first, which makes it useless. The water in my area usually makes water heaters leak a year before their warranty is up. I'm planning to check my anode rod every 5 years and I expect that I'll be replacing it about that often too.
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Old 06-28-12, 03:05 PM   #49
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Quote:
Originally Posted by randen View Post
Xringer Wrote:
Today, we will spent about $2 for oil, to heat our water.
I think this A7 ASHP will cut that down to about $1. (If it uses 6 kw hours per day


Just thought I would throw a wrench in. The solar hot water we have been collecting Via flat plate panel since about April is costing us about $2.16 per month for the little circ. pump operation. Anyone could build a panel with just basic skills and plumb it into an exsisting tank. Old patio door glass some 3/8 copper tube 3/4 copper tube aluminum flashing material a little sweat presto,, no more oil.

Randen
Sounds pretty good, but I've had solar hot water before and know about the hardware problems that are possible.

Plus, I do recall periods of over-cast and rainy days when our hotwater tank dropped down under 75F.
Sometimes, solar isn't so great around here.. We are a bit below average.

Not so bad during the coldest part of the winter..


But, the main problem we have with solar, is the location of the panels.
They would have to be located about 100 feet down hill from the point-of-use.
(Wife will not allow any more panels on the roof)..
The panels would be located where my PV arrays are currently installed.
(I would have to get rid of the PV). The area has so much shade,
it's a horrible location for PV, but shouldn't be very bad for HW solar.
The area gets good sunlight 4 to 5 hours per day on average.

But, I do have an idea about using the warm air in my attic (which now at 117F).
I could pump hot air down from the attic during the winter to keep my basement warm (around the ASHP)..
I really like the whole idea of keeping the basement warmer..

Secondly, I am currently using 800w of PV connected to a HW heating element. (Extra low efficiency).
So, if I were use that 800w to power my ASHP for 4 or 5 daylight hours, that might save some money..
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Last edited by Xringer; 06-28-12 at 03:18 PM..
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Old 08-05-12, 03:07 PM   #50
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This project looked like it would be fun, but it was abandoned.
I went ahead and took the easy way out with the A7 AirTap.
http://ecorenovator.org/forum/geothe...er-heater.html

At 7,000 BTUh, it's a bit more powerful than either one of my small window ACs..
It's likely the best way for me at this particular time.

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