HAPPY BIRTHDAY ESPCO!
December 13, 2012 marks ESPCO’s second year and 2012 could not have been more exciting and busy…busy is good! Go to ‘About ESPCO’ to see a review of our 2012 activities…I have to admit it blows my mind!
Thanks to all who attended an ESPCO class in 2012 and to all our great class sponsors and training partners…you made it all possible!
If you’re not already a subscriber to Contractor then I strongly suggest you go to www.contractormag.com and sign up for a free subscription. Contractor calls themselves the ‘news magazine of mechanical contracting’ and you will find great articles on plumbing, piping, hydronics, radiant, tools, trucks and much more.
I have an article being published in Contractor early 2013 so sign up for your subscription now so you get your first issue…hopefully with my article!
Click on ‘Training Events’ to see our growing schedule for 2013. We have seventeen classes already scheduled starting in February and going through April and more will be posted as they are confirmed. ESPCO classes will be coming to a city near you in 2013 so please take a moment and register for a class today!
GEOTHERMAL…TO PRESSURIZE OR NOT TO PRESSURIZE…THAT IS THE QUESTION
A growing preference among geothermal installers is to create a non-pressurized system rather than the more typical pressurized.
Before we get too deep into this conversation lets define non-pressurized: to call a geothermal system non-pressurized is a bit of a misnomer…with the cover off the flow center canister, (I will explain what a ‘flow center’ is in just a minute), and no pumps running there is atmospheric pressure, 14.7 PSI, on the geothermal fluid.
Let’s go for a moment to my basic hydronics class where I talk about ‘head’ pressure as it applies to sizing circulators in a heating system. A column of water 2.31 feet high has a gauge pressure of 1 PSI thus 1 PSI = 2.31 feet of head
With this in mind, 14.7 PSI can support a column of water 34 feet high, (this is based on 100% water which has a specific gravity of 1):
14.7 X 2.31 = 33.957
We are going to come back to this equation at the end of our conversation because it is critical to remember when designing a non-pressurized geothermal system.
Pressurized is easy to understand for us ‘wetheads’…we have been creating and servicing pressurized hydronic heating systems for most of our lives. We can apply most of this knowledge to pressurized geothermal systems but the big difference is in the pressure itself…when we’re talking geothermal we ain’t talking 12 PSI.
Pressurized geothermal systems can have pressures such as the following:
winter = 50 – 75 PSI
summer = 35 – 40 PSI
idle = 40 PSI
The difference in the winter and the summer pressures is the expansion and contraction of ground heat exchanger GHEX tubing…in the summer time when we are rejecting heat into the ground the tubing expands and the pressure goes down.
Pressurized geothermal systems use ‘flow controllers’ which are prefabricated pumping stations of sorts that utilize fractional horsepower, wet-rotor type circulating pumps, (one pump for systems up to 3 tons and 2 pumps for systems greater than three tons). Flow controllers come with directional valves, (five positions), on both supply and return for ease of system purging.
Typically pressurized systems have the GHEX headers buried in the ground…this was done to limit the number and size of penetrations into the structure’s foundation bringing supply and return piping to and from the mechanical room.
This was a good thing but it posed disadvantages at the same time…mainly that you cannot segregate each loop independently with appropriate valving. The little fractional horsepower pumps on a flow controller cannot create enough flow to properly purge the entire ground heat exchanger, (2 feet / second), to remove all of the air from the system and as a result you need to use a flush cart which has either 1 ½ HP or a 2 HP pump. I plan on discussing flush carts in depth in a future newsletter but for now you can see a flush cart in use here, watch the video titled ‘Flush & Purge, Montgomery, NY’
Some other disadvantages of pressurized systems are: thermal expansion of the ground heat exchanger may cause a large enough reduction in system pressure to cause pump cavitation, (negative pump suction side pressure). This will result in the dreaded ‘callback’ to re-pressurize the system.
Another disadvantage to the pressurized system is that any air that was not removed from the system in the purge process will remain in the system.
So let’s talk non-pressurized; the best place to start is with the ‘flow center’ that I briefly mentioned earlier. A flow center looks a bit like a flush cart in that is has a cylinder where you can actually see the geothermal fluid…there is a removable cap so you can add fluid and introduce and maintain antifreeze levels very easily.
Here’s a killer advantage…you can use a tubular flowmeter to actually determine the system’s flow through the GHEX. The flowmeter slips onto a dip tube inside the cylinder of the flow center and you can direct the flow from the meter back into the cylinder or into a bucket or drain to remove system water to be replaced by antifreeze. You can see me using a flowmeter in an instructional video I posted on my website…click on the video titled,
‘How to Use a Geothermal Flowmeter’. The flowmeter is a great diagnostic tool that among other things, could identify a damaged loop.
Non-pressurized systems tend to have the loop connections inside the mechanical room, (manifold headers). Loops are valved so that each loop can be purged independent of the others allowing the small flow center pumps to do the job instead of a flush cart…another nice advantage!
You don’t think you got out all the air in the purge process…no problem! Non-pressurized systems will remove the air all by itself over time…nice!
Think about this one…let’s say you have a pressurized system that is leaking…what do you do? If you can identify which loop is leaking, (that may be tough and what if multiple loops are leaking), you may be able to abandon the damaged loop only if you have the loops valved inside the mechanical room, (not typical of pressurized systems). Maybe you dig up the GHEX but that is a needle in a haystack and if it is a vertical heat exchanger, well, as Tony Soprano would say…’forget about it’!
How about you simply convert that leaking pressurized system to non-pressurized? Think about it…a non-pressurized system is going to leak a lot less than a pressurized one…yes? Fluid levels can be easily ‘topped off’ periodically as needed by removing the cap of the cylinder of the flow center…brilliant!
A perceived disadvantage with having the header manifold inside the mechanical room has always been the concern over making multiple penetrations in the structure’s foundation to accommodate each loop’s supply and return. This concern can be addressed by simply making two larger penetrations or a ‘chase’ to allow all the pipes to come through one or two larger penetrations.
OK…let’s wrap this up.
Let’s go back to my comments about atmospheric pressure supporting a column of water 34 feet high. You need to consider this should you ever install a GHEX in land with a steep incline…think about it…if the GHEX was 34 feet above the mechanical room where the flow center is installed you will drain the ground loops into the mechanical room when you take the cap off the flow center…and this is NOT a good thing!
ADVICE I RECEIVED YEARS AGO FROM ONE OF MY HEROES / MENTORS
When I was in my twenties and still pretty new to this HVAC thing, (and even greener as a business person), I worked for and learned from one of the greats in the HVAC industry…Harry Eklof. I was one of a few young guys Harry had in his employ and he would tell us that “you have to make yourself recession proof”.
Now, on the surface that statement may seem overly simple because most of us in the service and install side of HVAC believe we chose a business, (either consciously or otherwise), that by its nature is recession proof…when times are good our customers have us install new equipment and when times are bad they have us repair their old equipment…either way we got a job!
Many of us have learned, the hard way, that when times are real bad like they are now, people do nothing and the next thing you know is you’re not recession proof and you’re taking it on the chin.
Harry and his contemporaries lived through the depression years so being recession proof to Harry meant diversification beyond your core business always trying to stay ahead of the curve and not being a market follower but rather a market leader.
As we look to a new year I share with you the wisdom of Harry Eklof…be recession proof…think outside the box and prepare yourself, your family and your company for better times because they are ahead for us…maybe not around the corner but there nonetheless. Keep learning and as a result you will keep growing…betting on yourself is the best odds you will find in this world.
I hope everyone has a happy and safe holiday season and a prosperous New Year!
See you all soon!