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Old 05-01-16, 04:40 PM   #1
Geo NR Gee
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Default Heat pump water heater intake from hot attic

A couple of years ago, I picked up a barely used Airgenerate ATI66 (out of business now) heat pump water heater. It was placed next to my gas water heater with the thought of hooking it up inline with the gas water heater to bring the temperature of the water up to a higher level.

I ended up pulling the gas water heater out and installing the hpwh this last week. It was the only hpwh that had ducting for the intake and exhaust air. The intake air is being drawn from the hot attic and the exhaust is dumped into the garage at the moment.


Today at 1pm, 86 degrees attic temp, 66 outside temperatures and 58 exhaust air at the heat pump water heater. This is just with a hand held temp. sensor.

The cost of the hpwh new was in the $3000 range without the tax incentives and installation. I paid $400 and installation was about $200 for power wire, breakers and plumbing. We have ran the dishwasher, clothes washer, and taken showers without running out of hot water.

While shopping at a local hardware store last year, the clerk rolled out a Boush whole house instant hot water heater for $40. marked down from $595. I was the closest to get my hands on it and had 4 other men asking me if I didn't want it. There was a few parts missing. They cost $145. for all the missing parts including shipping, so I now have $185 into it.

Would putting this Bosch unit inline with the heat pump water heat make sense for those days where using the hpwh doesn't make sense?

Electricity per kWh is $ .0955 tier one (first 600 kWh used) $ 0.11 tier two (above 600 kWh)

Gas is $0.443910
Gas Cost $0.405120
Other Natural Gas Charges & Credits $ 0.011270

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Old 05-02-16, 06:35 AM   #2
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Your rates appear to be PSE rather than Seattle city light.

I saw the line, A couple of years ago, and thought - too bad he cannot get the $800 rebate from PSE.
You might check the PSE website for rebates, it may be that the rebate is good up to a month after INSTALLATION vs. purchase. (too lazy myself to lookup for you)


For others in the PSE service area (parts of WA), there is a $600 or $800 rebate on hybrid WH. Bought a GE Hybrid last Sept. and PSE sent me a check for all but the sales tax (DIY install) and get $300 back from IRS for tax credit!

I have the GE set on HP only, 50 gal WH. Running the DW and two consecutive showers one does run shy of HW. The non-100% HP setting does kick in the 4 kW regular heaters, but that defeats the energy saving purpose, so better to shower together <G>

Last edited by mejunkhound; 05-02-16 at 06:38 AM.. Reason: add data
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Old 05-02-16, 09:55 AM   #3
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Your'e right, I do have PSE for power and gas. I live south of Seattle. Sounds like I should check with PSE for a rebate, but since it is a used unit, the first owner might have claimed it already. The previous owner ordered this when it first came out. He is a buyer for a large plumbing supply or distribution warehouse. Used it for a short amount of time and his wife decided there wasn't enough hot water for their family size and they switched to a whole house instant unit.
Thanks for the rebate tip, Mejunkhound.

I still wonder if I should have a back up with the gas fired Bosch unit that I have sitting here collecting dust?
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Old 05-02-16, 10:42 AM   #4
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By all means install the Bosch for backup.

PSE does require the ORIGINAL receipt for the hybrid WH, if you don't have that, no reason to even look into it.

BTW, if your fridge is older than 1992, PSE will GIVE you a new frigidare and deliver it and haul the old one away. Zero cost to you (absorbed in future rate increase on everyone).

Same with washing machine older than 1998. New one free - although since we are on a well (east of Renton) and water is no problem, we passed on the free wash machine as the review on the one they give you were pretty pathetic. Long time to sash, harsh on clothes, etc.
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Old 05-11-16, 02:43 PM   #5
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Wow that's pretty cheap electricity but it's odd that the rate goes up as you use more. Most places it goes down as you use more. We can switch providers here but we don't use enough electricity to get the lower rates. Need to use 1k minimum and at 2k you get the much lower rate. .13 is average here. If we used over 2k that would go down to .06 per kwh.

Our gas is measured by mcf here for some reason so hard to compare without doing the math. And our water is cubic feet instead of per 1k gallons. The only standard measurement they use here is for electricity. Water also goes down as you use more.


Your plan to use the attic air is a good idea. Here when I was doing the ac duct work it was 85* and the attic temp was 106*. So lots of heat up there to use. Cooling the garage is a great idea. Garage ventilation is totally ignored in all construction including the energy efficient side. The garage will get hotter than outside and will hold that heat overnight as it has very few methods to loose that heat.

I don't like the idea of daisy chaining the two waterheaters together. Those tankless waterheaters don't save any energy. In fact in most cases they end up costing you more in gas and water because they provide endless hot water. Also the heat pump will work year round in most climates unless it's sitting on the back porch of a house in canada..


I don't like the idea of the Elec company there giving free fridges and washers away. Wreaks of robin hood. Take from one and give to another. Also a form of taxation without representation in a way. Bad idea really but good for the manufacturers. That said the cost to the Elec companies is a tiny bit of their profits and really shouldn't be passed on to the customer but we all know it is.
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Old 05-12-16, 12:34 PM   #6
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What about using hot attic air as the intake? Did you do anything with that?
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Old 05-17-16, 01:53 PM   #7
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Just a comment on utility companies giving away free equipment. Utility companies normally face growing population bases and growing demand for their product. That means that they must make plans, years in advance, to finance and construct additional capacity. (The exception is natural gas companies). There are times where it is cheaper to reduce demand by replacing homeowners' badly inefficient equipment like old refrigerators than to build another coal or far more expensive, natural gas, power plant in your area. So the idea that the cost gets passed on to you the taxpayer or you the utility customer is actually quite unlikely.
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Old 05-22-16, 07:54 AM   #8
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There are 29.3KWH in a therm of gas. 29.3 x.11 cents per KWH (do you stay under 600KWH most months?, most people don’t) = $3.22 Gas is 44 cents, you need a COP of 3.22/.44 = 7.3 for the HPWH to make sense. Most tank water heaters get about 78% THERMAL efficiency, which means you need a net COP of 5.85 to make sense.

Odds are the bosch tankless is NOT modulating, which makes temp control difficult. Fine for a cabin or a single person, but it ain’t gonna fly if you have a family.

Sad to say, but the plain boring NG tank is probably your best option. Natural gas is cheap, it doesn't cost THAT much to heat water to begin with...
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Old 05-22-16, 07:59 AM   #9
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Quote:
Originally Posted by kabutomushi View Post
Just a comment on utility companies giving away free equipment. Utility companies normally face growing population bases and growing demand for their product. That means that they must make plans, years in advance, to finance and construct additional capacity. (The exception is natural gas companies). There are times where it is cheaper to reduce demand by replacing homeowners' badly inefficient equipment like old refrigerators than to build another coal or far more expensive, natural gas, power plant in your area. So the idea that the cost gets passed on to you the taxpayer or you the utility customer is actually quite unlikely.
Wait until utilities start implementing time of use electric rates. They only need the grids full capacity for a few hours per week, and they will charge more during peak demand times. For a utility, getting people to SHIFT use is more important than getting them to REDUCE use...
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Old 05-22-16, 10:48 AM   #10
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They already do time of use in some parts of the country. Some are optional like up north you can have your AC on a seperate meter and they charge you a lower rate but they have the capability to turn off the meter when demand is high. I have friends and relatives that have done theirs and they have never shut the power off to them at peak load.

Some do have a true peak hours electricity fee rate.

Then there are places like here where we were deregulated and prices skyrocketed. Now we have lots of so called providers but there are only about 3 real producers with txu being the main one. (They split txu into two companies one delivery one production at the time of deregulation)
Some of the providers are offering plans with free night and weekends electricity. The catch is you are still paying all the taxes and delivery fees on that electricity so it isn't really free.
It's their way to start edging into peak rate fees.


As for the free appliances. Yeah it isn't a big amount of $ for the Elec companies and it's probably a write off anyway but it still wreaks. Not to mention those frigginair refrigerators are not the best on the market and usually have a short service life. Lots of compressor failures and their electronic defrost boards are a high failure item that run around $80 for the board and new wiring harness.
You may save $ on electricity with that new fridge but you will end up shelling out the savings in repairs (common for stuff these days)

And as for reducing the need for generation plants that is needed in many places however in tx it isn't an issue. A few years ago they started shutting down electric plants due to having way too much generation capacity. These were mainly natural gas plants, only a couple coal plants in south tx) Some were totally decommissioned but many of them are pickled so they can fire them up when the demand is there.
Even with the vast population explosion there isn't a need for more generation, yet anyway...

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