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Thursday, May 7, 2015

What the heck is a heat pump water heater and why should I care?



What the heck is a heat pump water heater and why should I care?

If you read my previous blog article regarding the new Federal Energy Mandate (effective April 2015 ) regarding electric water heaters, you would be well on your way to understanding why you should care.  The new 2015 DOE energy efficiency mandates require higher EF ratings on most residential gas, electric and oil fired water heaters. This will have impact how water heaters are designed, manufactured, tested, distributed, and installed. It is my understanding that the new energy mandate no longer allows for standard / conventional  electric water heaters over approximately 55 gallons in size to be installed (simply because there are no units available that meet the new energy requirements, but perhaps will be in the future).  This likely affects many homeowners in my area, (Hilton Head Island, Bluffton, Beaufort, SC) since there are so many 80 gallon tanks in service. 

So, you wonder what you will have to do to replace your electric water heater that is a 55 gallon capacity or larger?  Well, the most common options are going to be “on-demand (tankless)” water heaters, and heat pump water heaters, and possibly gas if you have provisions for gas. Let’s tackle one thing at a time and look at heat pump water heaters and find out how they work and the pros and cons.  A future blog will discuss “on – demand (tankless)” water heaters.
I know you probably like glossy pictures, but how about just a basic diagram of a heat pump hot water heater?  
Home Inspection, Hilton Head, Sun City, Bluffton, Beaufort, SC



Heat pumps basically move heat from one location to another. There, how simple an explanation can you get?  Yes, there is a lot of wizardry going on in these units, but it is always good to have a mystery in life.  OK, so what else is special about how they work, you ask.  A heat pump water heater moves heat from your basement or mechanical room into the hot water tank. This will likely reduce humidity and lower the temperature in the area where the unit is installed. This can be good in warm climates, but not so much in cold weather climates.  Heat pump water heaters have electric heating elements installed (just like the conventional heaters they are replacing) to compensate for large hot water demands. Most HPWH can normally heat 8 gallons of water per hour. In comparison, a conventional electric unit can heat 20 gallons per hour. Not to worry though, since most are going to function in 3 to 4 different modes of operation:
“Hybrid Mode” – uses both electric heating elements and the heat pump. This is the recommended setting  and should be the default setting on units. 
“Heat Pump Mode” – uses only heat pump. Not a recommended setting as the hot water recovery time is considerably diminished
“Full Electric Mode” – works just like the dinosaurs they are replacing,  (a conventional electric hot water tank)
“Vacation Mode”- when on vacation, puts unit into sleep mode, (not all units will have this feature)
If you are expecting a Co- mode, that is a totally separate plumbing device. Quit interrupting me. On a more serious note, please pay attention to the types of operating modes if you are purchasing a heat pump water heater.

OK, you are wondering just how this beast is controlled, aren’t you?  Well, lucky for you I have pretty picture of a typical controller. Study it well.  

Home Inspector, Home Inspection, Heat Pump Water Heater, Hilton Head, SC

By now, I am hoping some of the mystery is gone for you.  But there are other mysteries here to look at. 

The Cons:
Heat pump water heaters have actually been around for some time, but they were an add on to a conventional electric water heater (imagine a large box next to a water heater).  As you can see from the illustration above, they are now neatly organized into one BIG container. Notice the emphasis on big. That was intentional. These critters are much bigger than the dinosaurs they are replacing (just one trade off).  They typically will require a large area to function properly (approximately 1000 square feet or more).  They are also heavier and larger (occupy more space) than a comparable electric water heater.  Can you guess that it will take more people and expertise to install one? You would be correct. Oh, and let’s not forget about maintenance, it will be more technical and expensive (remember the days of changing your own elements or thermostats?). And finally, the cost. Yes they will be more expensive. Enough, enough I say. No more negatives. Moving on to the positives. 

The Pros:
Testing by the “Electric Power Research Institute”  indicated that heat pump water heaters are 2.5 times more efficient than conventional electric water heaters, and in addition draw less than 25% of the electrical power compared to a conventional electric water heater. Water heating accounts for 15 to 20% percent of electric energy use in homes with electric water heating. Some new heat pump water heaters (HPWH) have demonstrated savings of up to 50% or more of a home's water heating energy use (perhaps under ideal conditions).
Units will typically have user-friendly digital temperature controls with vacation settings and options for operating modes.
Dehumidification of the installation area and some cooling effect is possible. This may be a benefit in warm climates but not cold climates. The amount of dehumidification and cooling may also be minimal.  
If you need help comparing the costs of operating water heaters, you may want to visit the Federal Governments’ web site that provides an energy calculator to do just that: http://energy.gov/eere/femp/energy-cost-calculator-electric-and-gas-water-heaters-0

Considerations when installing a heat pump water heater:

Adequate physical space: heat pump water heaters are generally larger in all dimensions) compared to standard water heaters. Having limited physical space may prevent the water heater from being installed in a desired location within a residence or where the conventional water heater was installed.
Adequate air volume and circulation: heat pump water heaters have specific air volume and circulation requirements that can lower their performance if installed in a confined sealed space, such as a closet or a small room.
Condensate removal:  access to a drain or to the outdoors is required for removing the heat pump water heater’s condensate (liquid). Typically, existing water heaters will have a drain pan, but additional piping may be required for handling condensate removal. Also they will need an exhaust line (piping) for the TPR (temperature pressure relief valve), just like the conventional water heaters.
Noise: heat pump water heaters generate a humming or whirring noise when operating. Depending on the heat pump water heater model and location , this may be offensive.
Exhaust air:  as stated above, heat pump water heaters exhaust cool, dehumidified air into their surroundings, which may or may not be beneficial.

Conclusion:
Hopefully you are now better informed if you need to choose a water heater, however I would urge you to do your homework and find out more about your choices.   Fortunately in our location, numerous 80 gallon tanks were installed not because the homes or villas needed that capacity heater, but simply because the Electric Company had a program that made it inexpensive to install one. I suspect a lot of folks can do well just by reducing the size of their water heater when it is time to replace it, and opting for a smaller capacity water heater (conventional).
One more interesting piece of information to digest: the water heaters are not hot water heaters. If the water is hot you do not need a heater, right? OK then, that is settled. Note that the grammar police will not arrest you if you still use the term “hot water heater”.  
As a Home Inspector in Hilton Head, SC and surrounding areas, I welcome your opinions, ramblings, musings, and fleeting thoughts.  

Thanks for reading

John M. Wickline, President
JW Home Inspections, Inc.   

Home Inspection, Hilton Head, Beaufort, Bluffton, Okatie, Sun City, SC
JW Home Inspections Inc., Hilton Head, Bluffton, Sun City, Okatie, Beaufort, SC, Home Inspector


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