Fundamentals of a Geothermal Warmth Pump System

Matthew Showers is an HVAC service technician, performing work in each the residential and business fields.  His specialty is in inverter and speaking techniques.  Comply with Matt on Instagram 

Lots of you within the trade have heard of geothermal warmth pumps: you might have additionally heard of the various potential advantages they provide, or maybe the excessive value of set up, or possibly nonetheless the rebates that go together with them.  You may additionally be confused as to how they function:  the place does water are available in? What do you imply there’s no outdoors fan?  The intent of this text, is to go over some fundamentals of geothermal warmth pumps:  how they operate, what functions they serve, and the variations in these functions.

To start out, geothermal techniques are similar to a typical air to air warmth pump you would possibly see in a house or business constructing.  The principle distinction between the 2 is that as an alternative of air, geothermal techniques use water because the medium for warmth absorption and rejection.  This enables for decrease excessive aspect pressures/saturated temperature situations, which results in higher compression ratios within the cooling mode and extra constant warmth within the heating mode.  That is attained by having comparatively constant water temperatures getting into the system, which is round 55 levels Fahrenheit.  Realizing that you’ve roughly 55 diploma water getting into the system, it ought to turn out to be extra clear why geothermal techniques are so environment friendly.

The place does this water come from?  There are two forms of water loops you’ll come throughout:  open and closed loops.  Each of those have their professionals and cons, which I’ll talk about.  Open loops pull water from a properly utilizing a properly pump, and after the water goes by means of the system, it’s deposited into one other location or properly.  Water stream is regulated through an exterior solenoid valve and a stream restrictor (older techniques) or an inside actuator valve (newer techniques). They are often referred to as “pump and dump” techniques for brief.  These techniques are nice for making certain constant water temperatures getting into the system.  The drawbacks, nevertheless, are that you’re losing water and in addition you have to some form of strainer to forestall minerals and different deposits from getting into the system, which additionally requires routine cleansing.

Instance of open loop strainers feeding two separate techniques

Closed loops are akin to a hydronic system: the water is moved through one or two circulators by means of the system after which by means of an intensive loop that’s buried underground outdoors, the place the water naturally cools or warms again up earlier than returning to the system, relying on what mode you’re working.  These techniques reuse the water, so there isn’t a waste and no strainer is required.  These techniques do require some form of antifreeze answer to be added (sometimes glycol) to decrease the freezing level of the water to 10 levels Fahrenheit ideally (relying on the realm and producer specs), as it may have a tendency to chill down extensively over long term instances within the winter, relying on the size of the loop.

Picture of a refractometer and checking glycol combination freeze level

It pays to really oversize these loops in residential functions to permit for higher warmth rejection and absorption, however many properly drilling contractors will go together with “guidelines of thumb.”  It was once mentioned that for each ton of cooling you want 100 toes of loop, which was discovered to be too small.  The usual then turned 150 toes of loop for each ton, and continues to be what many go by right this moment.  Personally, as I’ve a geothermal system in my very own home, I’d go together with 200 toes of loop per ton. 

Study extra about geothermal warmth pumps on this episode of the HVAC Know It All Podcast

Geothermal techniques are bought as each a package deal system and conventional cut up system.  In residential and business functions using a closed loop, you will discover package deal techniques extra usually.  These techniques are handy for servicing, as all of the parts are shut by, very similar to a business RTU.  They’re additionally critically charged, and are able to be commissioned as soon as put in.

Cut up techniques are much less frequent, and are usually present in houses with a number of techniques or business buildings using an open loop system.  These techniques do require the traditional finest practices when putting in another cut up system, akin to brazing with nitrogen, correct evacuation, and including refrigerant based mostly on lineset size.

On the service aspect, many geothermal producers make the most of a sequence of thermistors for sensing temperatures all through the system.  This makes troubleshooting simpler, as these techniques will lockout to forestall harm to the system itself or its environment and show an error code that may be retrieved by you, the technician. Total, when you totally grasp the fundamentals, geothermal techniques are usually not that completely different from their air warmth pump counterparts.

It is going to be attention-grabbing to see how the geothermal market adjustments within the coming years as rebates and tax applications stop for these techniques.  Nevertheless, current techniques will nonetheless want continued servicing for longevity, and understanding how these work may also help you broaden your horizons do you have to work in an space that makes use of them.

Matthew Showers

Subscribe to the HVAC Know It All app 

Comply with HVAC Know It All on Instagram, Fb, YouTube and LinkedIn and LISTEN to the HVAC Know It All Podcast

Save 8% on purchases at TruTech Instruments with code knowitall (excluding Fluke and Flir merchandise)