Author Topic: Experience with Heat Pump Water Heating  (Read 7733 times)

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OperaHouse

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Experience with Heat Pump Water Heating
« on: April 17, 2014, 09:46:13 AM »
Experience with Heat Pump Water Heating


The beginning of the year I bought an add on heat pump water heater.   It probably seems insane to those in other
countries, but in the US we heat up 50 gallons of water in a tank and let it sit around until it is used. 
Heat pumps installed on a hot water tanks are now starting to take hold in the market. I just got a special deal
on a new discontinued NYLE Nyletherm HPWH.  Including buying a PEX tool I paid about $400 for the total install.
Many are paying more than a thousand dollars for this add on or twice that for a combined system just to cut their
electrical usage in half.   I thought efficiency would be higher but all the studies I've seen give a COP of close
to two regardless of brand.  The NYLE is built in Bangor, ME.  Their core business is industrial products for the
wood industry and this was the first home product. The NYLE are slightly more efficient in colder climates than other
heat pumps.  I had heated water with natural gas.  When the tank failed, I hooked up an 30 gallon electric as a
temporary fix while looking for a deal on a gas model. It was plugged into 120V for an effective heater rating of
700W. That required us to schedule usage because of a long recovery time.  That temporary system lasted never two
years. We only spend about seven months at our winter home and a HPWH only became practical when one became available
at less than half price.  Another advantage is these units dehumidify the basement.

I've instrumented mine just to see what the real savings are. One fact stuck out.  Even with an additional thermal
blanket on the water heater, the standby heat loss per day with no water usage is 3-4 KWH a day for purely resistive
heating.  The HPWH consistently uses 800WH for a 12 hour period at night when no water is used.  We are low useage
and for a 25 day period we used 85.32KWH or 3.41KWH a day for April.  During the very cold January daily useage was
typically 4.7KWH per day.   Power consumption running is 600-750W which could easily be handled by RE systems.  The
HPWH runs about 5.92 hours a day.  If you are sensitive to fan noise this will drive you crazy.  The unit goes into
defrost mode and runs the 31W fan for an additional ten minutes after each cycle wether it needs it or not.  Noise
level is that of a quiet window AC unit.

I mounted the fan on the outside for better internal airflow.  The fan needs to have a thermal break from the case
to the fan which easily reaches 37F.  Thermal breaks were also added to inlet and outlet pipe mounting. For power
monitoring I used this $14 ebay special power/time meter that uses a handy 100A current transformer to just slip
over a wire.  Accurate enough for what I was doing. Pictures show internal construction which  is made from off
the shelf components.  Condenser is four core, Compressor is Carrier (Korea), brass water pump is Grundfos, and
water heat exchanger is Turbotec made in CT. Refrigerant has threaded fill cap and copper is used for for all water
plumbing.

MaryAlana

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Re: Experience with Heat Pump Water Heating
« Reply #1 on: April 17, 2014, 02:19:02 PM »
On demand gas water heater would have been more effective... when my electric tank goes that is what I am switching to with a solar preheat tank on the input to take my ice cold ground water to a little higher temp.

OperaHouse

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Re: Experience with Heat Pump Water Heating
« Reply #2 on: April 18, 2014, 06:36:57 AM »
Honestly, all this stuff is just buying someone elses dream.  You spend a lot of money with the hope you make
it back before it breaks. How do you pay for anything saving 20 cents a day? At least I didn't buy a GE for $1800
like a neighbor did. It is almost guaranteed that you will be spending $400 to fix one of those after three years. 
This unit will pay itself off in 5 years even with just 6 months use a year, Wish my PV panels had that kind of
payoff.  I searched for an instant gas one for a couple of years without luck.  The cheap ones have big problems. 
Anyway, I won't be here in 5 years and this is easy to move.  The dehumidifier is a big bonus for my basement. 
It might be a viable option for someone who wants to get off propane.

phil b

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Re: Experience with Heat Pump Water Heating
« Reply #3 on: April 21, 2014, 10:14:32 AM »
With propane going through the roof and grid electricity prices going higher because the newest power plants are using natural gas for power, solar and wind is becoming much more viable as a primary energy source.

I had a choice of spending $1000 to buy propane or adding to my existing solar setup. I paid $5000 for new solar panels and $3800 for new forklift batteries. The energy it replaces in one year is $4010. That was not a hard decision. Here is the start of the system: http://ecorenovator.org/forum/solar-power/3516-temporary-pv-solar-hookup.html   Since then, it's grown to 5700 watts and will get a bit bigger.

The new on demand water heating systems still seem beyond reach on a solar application for me. Heat pumps that can provide cooling as well as heat and hot water looks like a viable option.

A mini split might be the best answer if they can be adapted for hot water too.

I hope you update this thread as time goes on Operahouse. It will be interesting to see how much energy you use and save over time. I've heard nothing but good about the NYLE systems.
Phil

OperaHouse

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Re: Experience with Heat Pump Water Heating
« Reply #4 on: April 22, 2014, 07:58:24 AM »
A house has to be thought of as a system.  My parents have an ideal application for a HPWH.  Thier house is only 15
years old but it has a very inefficient oil heating system.  It is ironic that this was once a solar heated home.  The
rock storage tanks took up almost the entire basement. The high efficiency gas backup furnace the had now heats my home.
Thier oil furnace remains at 170 degrees all summer heating an exchange tank.  The furnace/laundry room is like a sauna. 
They use a tank of fuel oil in the summer just to heat water.A HPWH would pay for itself (at my price) in a year when air
conditioner costs are also factored in.  Without a sourceof "free heat", a HPWH is not practical.


tomtank

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Re: Experience with Heat Pump Water Heating
« Reply #5 on: July 10, 2014, 08:01:57 PM »

OperaHouse

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Re: Experience with Heat Pump Water Heating
« Reply #6 on: July 11, 2014, 07:36:05 AM »
That is where I got mine.  These are all units left over from the Hot Shot program a utility was running years ago in the northeast.  I'm toying with the ides of buying six dead ones if he will break them up from the pallet of sixteen.

At camp I am heating with excess PV.   Just hooked up the second 19 gal tank to the existing 10 gal tank.  The heaters are 120V but the work well with 36V array operated at the power point with PWM driven by a UNO.  When   first tank reaches temp it switches over th heating the second.  Works well, haven't had to turn on the propane heater last year or this.  This is one of the most practical uses of PV for the home.
« Last Edit: July 11, 2014, 07:43:45 AM by OperaHouse »

MattM

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Re: Experience with Heat Pump Water Heating
« Reply #7 on: July 21, 2014, 08:58:25 AM »
Is the load low enough and predictable enough where you could run it in the attic year around?  The drip line coming out the soffit would be about the only handicap I could imagine.  Even up north the attics act as heat sinks.  As long as the heat load was always there in the winter day-time it should be a net gain.  I can't imagine it's never enough any time of day during the summer.

MattM

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Re: Experience with Heat Pump Water Heating
« Reply #8 on: July 26, 2014, 10:59:46 AM »
Wasted Attic Heat Being Put to Good Use

http://www.fortis.edu/blog/business-and-professional/wasted-attic-heat/

1. Heat during winter
2. Per-heat DHW supply during summer months

http://www.fortis.edu/blog/business-and-professional/wasted-attic-heat/

So in the southern states it does make considerable sense.

earloflondon

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Re: Experience with Heat Pump Water Heating
« Reply #9 on: January 11, 2015, 04:16:11 PM »
Hi OPERAHOUSE.......I replied to this thread a few weeks ago, but it appears to not have made it through, so I'll try again. I recently picked up one of these units as well, as of yet not yet installed. A couple of things from your initial post confuse me a bit.

1."the standby heat loss per day with no water usage is 3-4 KWH a day" "The HPWH consistently uses 800WH for a 12 hour period at night when no water is used"  Would not the heat loss then be .8 KWH per day not 3-4 if it uses 800WH? This seems more reasonable, as my solar outdoor tank will only drop from 42C to 37C from 5PM to 8AM - and that's when it's -20C outside.

2. The gizmo you hooked up to track KWH usage......I take from the photo that it is not connected to the HPWH.....since mine doesn't have a clock inside of it? Since there is only one current transformer, does the unit double all the readings itself? Would like to get the same unit, but unsure of how it does its magic.

3. Agree with the "free heat" statement. Our outdoor solar evacuated tube water heater does all our water from May-September, even here in Canada. Since we heat with wood, the heat in the winter is essentially "free" other than my sweat, so the HPWH "should" cut our water heating cost by at least 1/3 if not more. This equates to savings of about $30/mo in hot water costs ( I currently have 240 Hobbs meters connected to the elements in my water heater so I know how many KWH I use per month). Payback then for us is after 2 years ( 7months/year x 2) The added benefit as well is that its load is bearable for an off-grid RE system which is also in the works. The standard 3kw draw of a standard water heater would be hard on the batteries after a while!

Would love to hear a report back as to how yours is working, and if you have any tips for me before I install mine - moving the fan to the outside is already a great idea!

OperaHouse

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Re: Experience with Heat Pump Water Heating
« Reply #10 on: January 16, 2015, 04:01:51 PM »
In response to your PM.

1. Measurements were made after the HPWH was installed.  I tried to make all comparisons to a standard electrical resistance water heater.  All these heat pumps have a COP of about 2.  Therefore, 800W used for a 12 hour period at night would equate to 1.6KWH at night if resistance heating were used.  For a 24hour period that heat loss would double 3.2KWH of heat loss. This water heater was more than 15 years old before it was ever installed for the first time and had fiberglass insulation instead of the foamed ones now.  It did have an extra thick external thermal blanket. Your results may be better.  At an average useage of under 40 cents a day, buying a better tank before I needed it would never give a payback.  Resistance heating values are so other members can convert this to BTU loss.A friend of mine has the same unit with a foamed heater tank and he borrowed this meter.  The numbers looked somewhat similar but he never wrote down when he actually started.  No good numbers are expected.

2.  Now you will really get confused.  Only one current transformer needs to be used because it is a 220V device.Current in is the same as current out if there is no connection diverting current to neutral.  This meter would read the wattage directly. Since that picture I have put the meter in a box and I power it off a 120V outlet.  That gives me power readings half of what they should be, so I just double them. for a 240V circuit.  This is not a permanent attachment.  It allows me to easily monitor a circuit by just removing a single wire and passing it through s doughnut.I would not buy any of these that do not use a doughnut for sensing.  This one is rated at 100A and was less than $15on ebay.  The timer section is very handy.  Not a true wattmeter.  I have several costing over a thousand but itg will give numbers that can be useful.

3.  I used thick faucet washers to suspend the fan off the steel frame as a thermal break and then foam between the supports.The fan housing will get ice cold and you don't want to transfer that back to the body that also holds the outlet pipe.I removed the screws that hold that pipe section to break that thermal conduction also. The fan frame has to be spaced out in order to get the lid to close.  I have been using these $3.65 digital temperature controllers and am quite impressed with them. Think they are pictured on my PV water heater thread.  Being able to set temp, delay and differential could be very
useful.  I use a 220 ohm .47uF RC network to simulate the heater load and prevent possible damage to the little relay.

earloflondon

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Re: Experience with Heat Pump Water Heating
« Reply #11 on: January 16, 2015, 04:39:26 PM »
In response to your PM.

1. Measurements were made after the HPWH was installed.  I tried to make all comparisons to a standard electrical resistance water heater.  All these heat pumps have a COP of about 2.  Therefore, 800W used for a 12 hour period at night would equate to 1.6KWH at night if resistance heating were used.  For a 24hour period that heat loss would double 3.2KWH of heat loss. This water heater was more than 15 years old before it was ever installed for the first time and had fiberglass insulation instead of the foamed ones now.  It did have an extra thick external thermal blanket. Your results may be better.  At an average useage of under 40 cents a day, buying a better tank before I needed it would never give a payback.  Resistance heating values are so other members can convert this to BTU loss.A friend of mine has the same unit with a foamed heater tank and he borrowed this meter.  The numbers looked somewhat similar but he never wrote down when he actually started.  No good numbers are expected.

2.  Now you will really get confused.  Only one current transformer needs to be used because it is a 220V device.Current in is the same as current out if there is no connection diverting current to neutral.  This meter would read the wattage directly. Since that picture I have put the meter in a box and I power it off a 120V outlet.  That gives me power readings half of what they should be, so I just double them. for a 240V circuit.  This is not a permanent attachment.  It allows me to easily monitor a circuit by just removing a single wire and passing it through s doughnut.I would not buy any of these that do not use a doughnut for sensing.  This one is rated at 100A and was less than $15on ebay.  The timer section is very handy.  Not a true wattmeter.  I have several costing over a thousand but itg will give numbers that can be useful.

3.  I used thick faucet washers to suspend the fan off the steel frame as a thermal break and then foam between the supports.The fan housing will get ice cold and you don't want to transfer that back to the body that also holds the outlet pipe.I removed the screws that hold that pipe section to break that thermal conduction also. The fan frame has to be spaced out in order to get the lid to close.  I have been using these $3.65 digital temperature controllers and am quite impressed with them. Think they are pictured on my PV water heater thread.  Being able to set temp, delay and differential could be very
useful.  I use a 220 ohm .47uF RC network to simulate the heater load and prevent possible damage to the little relay.

Hey thanks for the reply!

1> OK - that makes sense that the measurements were taken AFTER. I thought some were pre and some were post HPWH install. Makes more sense now.
2> So you do have to double the kw/h readings on the unit then since it is only reading one "half" of the 240V circuit. I like the idea of putting it in a box with a 120V plug on the end of it - have any pics of that? It would be like a portable TED5000!
3> What are you using the temperature controllers for? Will look up the PV water heater to see if i can find them, though I admit I'm not at all sure what you're doing with them.......maybe I'm just a bit dopey today!

Thanks again for the reply, So the HPWH is working OK then? How did you end up mounting it? That right now is my biggest conundrum right now......Think my wife will shoot me when she sees something ELSE connected to the water heater.... :)

Tim

OperaHouse

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Re: Experience with Heat Pump Water Heating
« Reply #12 on: January 19, 2015, 11:53:58 AM »
Search using 100A power meter    http://www.ebay.com/itm/100A-AC-Digital-LED-Power-Meter-Monitor-Voltage-KWh-Watt-Voltmeter-Ammeter-SU-/381109766988?pt=LH_DefaultDomain_0&hash=item58bb  You'll hve to go through twenty or more before there is a listing that tells you how to connect it, they don't send instructions.  If you connect to the cold water inlet, remove the check valve in the nipple.