Do “waterside economizers” with commercial water source heat pumps really save energy?
In a recent class on Commercial Water Source Heat Pumps (CWSHP), the subject of “WaterSide Economizers WSE” came up in a couple questions from the audience. I have to admit I did not have a lot of experience with these components so, as usual, after the class I began my research.
If you don’t have a lot of experience with CWSHP in general, I suggest going back to my first newsletter of 2014, (January / February), and read it as a prerequisite to this article. You can simply click on the “What’s New” tab in the upper menu bar on my website and scroll down to the January / February 2014 newsletter.
Structurally, the WSE adds a water coil and a 3-way valve to the CWSHP. The following is from a TraneEngineer’s Newsletter, Volume 63-2;
“During cold weather, the heat pumps serving perimeter zones often operate in heating mode and absorb heat from the water loop, which lowers the loop temperature. If the loop water temperature is allowed to drift down further than normal—to 45°F (7°C), for example—a waterside economizer coil can be used to provide ‘free cooling’ for interior zones. When the loop water is cool enough, a three-way valve diverts the water through the waterside economizer coil to cool the entering air, reducing (or avoiding) the need to operate the compressor. The three-way valve allows the economizer coil to be bypassed when not in use, saving pump energy. And, unlike other systems, no cooling tower energy is used to create the colder water; just the heat pumps serving the perimeter zones that are already operating in the heating mode.”
Well this all sounds like a “no-brainer”! Who wouldn’t want a WSE on their CWSHP? Well, I’ll tell you…
Two of the biggest players in the CWSHP market, ClimateMaster & WaterFurnace, in a presentation they co-authored back in 2006 expressed some real concerns about the true value of WSE.
As they put it, “there is no free lunch” and there are consequences for the addition of WSE…some of these consequences are as follows;
- On the water side, the 3-way valves increase pumping head.
Now, for those of us who are wetheads, we can get our heads, (excuse the pun), around this. In my class, I go through the procedure to size the pump for these systems and pressure drop through components, (like the heat exchanger of the CWSHP), must be taken into account. The increased pumping head will increase the size of the pump which will increase the cost of the pump and also increase the operating cost of the pump…it’s a slippery slope!
- On the air side, the addition of a coil can increases fan motor head.
Just like pumps move water, fans move air, and putting stuff in its way, (like another coil), will adversely affect the fan motor’s ability to move air at a design criteria / CFM.
- Reduced heat recovery from core to perimeter zones.
Ah…this is a good one! As I have discussed in my earlier newsletter, the magic of CWSHP systems is simultaneous heating and cooling. However, in the case where WSE are installed, the rejected BTU’s from the zones that are cooling will be reduced, thus reducing the BTU’s in the hydronic fluid loop servicing perimeter zones that are heating…reducing their efficiency.
In their research, three example cities were chosen, (Seattle, WA, Madison, WI and Boston, MA), to conduct simulation tests using two sample buildings…one with WSE and the other without. The Seattle, WA example, the building with WSE realized a 3% INCREASE in operating costs. The lion’s share of the additional cost came in the increase in natural gas consumed to fire the boiler used to add BTU’s to the hydronic loop when those CWSHP in the cooling mode were not rejecting enough BTU’s to satisfy the perimeter CWSHP that were in the heating mode….got it?
The Madison, WI example, the building with the WSE recognized a 2% INCREASE in operating cost.
The Boston, MA example, the building with the WSE recognized a 3% INCREASE in operating cost.
The conclusions of the research showed the following;
- There is little benefit gained from using waterside economizers.
- Small decreases in electrical use are offset by significant increases in natural gas consumption.
- There were some climates where small energy cost savings could be realized but nowhere close to the additional cost of the WSE.
- Economizers in perimeter zones are almost never energized.
So, when we look a little closer, all of a sudden it’s not a “no brainer” any more. The problem is there are states, cities and municipalities who had enacted codes requiring WSE on CWSHP installed within their jurisdictions.
Hmmm…what a surprise…government mandates causing the exact OPPOSITE of the intended result!
Don’t get me started…
Water to air vs. water to water geothermal systems…the later doesn’t feel the love!
Have you noticed that water to water geothermal systems just don’t seem to get the attention that water to air systems do…I have!
Ok…I have to take my wethead hat off and try to be objective here.
I understand that the majority of geothermal installations are water to air…doesn’t make me happy but this is the reality. It is the reality because the majority of the US outside of New England and the Mid-Atlantic region is a “warm air” market.
That said…I find it annoying that some geothermal manufacturers barely acknowledge the water to water market.
Let me give you an example…
In my geothermal class, I have been using my shop here in Orange County, NY as the sizing example for several years now. The software I use allows for me to design a water to water system, (my shop has an existing low temperature radiant floor system), and the software has a feature which allows you to compare the geo system you design to 5 other fuels / systems…none of which are hydronic…UGH!
This is a wonderful feature but fairly useless to those of us in the northeast.
Well, leave it to the fine people at Radiant Professionals Alliance RPA to come to the rescue of water to water geothermal.
The 10/27/14 issue of the ACHR The News had an article titled “RPA, IGSHPA Agree To Cross Promote Ground Source Heat Pumps”…here is an excerpt;
“The Radiant Professionals Alliance (RPA) and the International Ground Source Heat Pump Association (IGSHPA) have signed a memorandum of understanding to cross promote the application of ground source heat pump technology where it overlaps with radiant heating and cooling systems.
The two organizations will collaborate to develop education courses pertaining to ‘low temperature’ radiant heating and cooling applications and train IGSHPA instructors to effectively deliver education on these ultra-efficient systems. According to the organizations, ground source heat pumps represent a significant increase in energy efficiency when coupled with the comfort and efficiency associated with hydronic-based radiant heating and cooling systems.”
As a “certified IGSHPA installer and trainer” myself, I hope to be a part of this cooperative initiative to spread the good word of water to water geothermal systems..not only here in the northeast but well beyond!
Think about where radiant floor systems were here in the US just a short time ago…I can remember when there was just a handful of radiant zealots who designed and installed radiant floor heat. Fast forward, and now virtually every HVACR wethead has done at least one radiant job and most of us have made it a significant part of our day to day business.
The wide success of radiant systems came, in my opinion, from knocking down what I call the “walls of fear.” The average tech was scared…yes scared…to get underneath a floor and start installing tubing…and it was tubing, NOT pipe!
I like to think that I along with other technical trainers like John Barba, Wes Sisco and Dave Holdorf, helped to tear down the wall of fear in the radiant world, allowing that market to grow and prosper.
The “wall of fear” for most technicians when it comes to geothermal is the ground heat exchanger…we are not drillers…we don’t own drilling rigs…there is seemingly a lot to be afraid of there.
Come to my geothermal class…let me help you get beyond the mystery of geothermal and unlock its incredible potential for your business, for your customers and for the environment!
I had the honor of giving an award at the AHR EXPO in Chicago this past month!
I was beyond thrilled when I was asked to hand out an award for the most classes conducted within their territory as well as the most technicians trained for 2014 to my good friends, Greg Moore and John Forbes at Southland Marketing, Inc.
The most impressive aspect to this award in my opinion is the most technicians trained…it’s not necessarily hard to schedule a lot of training classes…it is VERY hard to get fannies in the seats and Greg and John did an incredible job at both!
If you are a manufacturer who needs a rep in Alabama, Georgia, Tennessee, Florida and the Carolinas, you should do yourself a favor and meet the crew from SMI. These guys are not your typical manufacturer’s reps…they are technical people who happen to sell…and sell they do!
You can see a picture of the award ceremony here.
Gerry is recognized as ACHR The News 2014 Best Trainer!
I am thrilled to be honored by the trade journal, ACHR The News, as the 2014 Best Trainer. I want to thank all those who nominated me as well as those who participated in the wonderful article that Jen Anesi, editor from The News,wrote about me, (November 24, 2014 issue). Jen actually took the time to visit with me and attend a class I conducted at the Keystone University in Gilbertsville, PA. Keystone U is the training entity of Keystone Sales & Associates, my good friend, Bob DellaSala’s agency who did a great job hosting the class.
If you missed the article, you can go to the ESPCO website and click on the red banner at the top of any page…it will link you to The News website and the article titled. “Best Trainer Lets His Personality Shine”. You can also click on the “MEDIA” tab on the upper tool bar of any page and then click on “VIDEOS” to view the video about the award.
ESPCO re-boot for 2015!
I am excited to announce that I will have all new “training partners” for 2015. Keep an eye on the ESPCO website for updates on new curriculum being offered in 2015 all around the US, Canada and Latin America.
See you soon!
The views and opinions expressed in this newsletter are those of the author and do not necessarily represent those of ESPCO’s sponsors and training partners.