Operational checks on WSHP's & Geothermal Units

Originally Posted By: sdurazo
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The difference between a WSHP & a geothermal unit is the Way it dissipates


Or Collects heat to permit its Heating & or Cooling function.


Normally WSHPS are used mainly on multi office buildings

In homes you will normally find more than 1 WSHP
1 for upstairs & one for downstairs or more than 1 wshp
In every level of home depending the size of home

Other times for purposes of Zoning 1 wshp in ea home area
Living, Dinning, Bedrooms permitting this arrangement
To have a better Utilities control.

A WSHP is connected to a closed loop for circulating water to go thru
A Cooling Tower to cool the water in summer & a Hot water Boiler in Bypass in Loop to reheat water in winter

A Geothermal Unit is connected to a closed Loop Also
but Instead of closed loop Going to a Cooling Tower

the copper or other type of tubing of loop is buried
Into the Ground several feet below the surface where it rejects or absorbs heat
From the ground depending if on cooling or heating

Some times the Geothermal unit Might be piped to a well, river , lake or other source of water

During Summer Time operation

The WSHP is Rejecting heat thru the water going thru its Condenser
Entering water at about 85 degs & leaving water 10degs higher at 95 degs

(Normal TD thru Water Condenser coil is "10 degs?. 95-85=10 deg TD +- 3 degs)

Which is connected "piped? Normally to a Cooling Tower, well, lake or other source of clean clear water
Which dissipates execs heat to outdoors, where water supplied to
Wshp is supplied between 75 & 85 degs constantly during summer time.

When connected to cooling tower water is cooled down by water falling
Between baffles of tower & air stream going across water droplets & cooling
Tower fan to max leaving water temp of 75degs

Cooling tower fan/Blower will normally cycle between 75degs & 85Degs
On at 85 & Off 75degs

On some cooling towers in winter time when water temp drops below
65 degs water will be bypassed from supply condensing water side
To return Condensing water to avoid going thru cooling tower & avoid
Over cooling of condensing water


During Winter operation of WSHP

The Reversing Valve reverses the refrigerant Flow Thus the Water Cooled
Condenser Coil Becomes a Water Cooled Evaporator coil & the water going
Thru the Evaporator is cooled down 10 degrees entering at about
60 degs & leaving at 50 degs
(Normal ?TD is 10 degs ? ) 60deg EWT -50 deg LWT =10degs TD)

EWT = Entering water temperature
LWT = Leaving water temperature

The WSHP is Collecting Heat from the Water loop thus cooling the water in the Loop

The cooling tower fan is normally turned off by thermostat at about 75 deg water
Temp when temp of circulated water drops to about 55 degs the reheat Source
Or HW Boiler goes On to maintain a minimum temp of 55 degs & max of 60 degs
Supply water temp to loop
Boiler Cycles On at 55 deg & Cycles Off at 60 deg

*** Cooling Tower Check out. Report any or all following!!

If all these item Visible & Readily accessible
Check for Worn, loose, or noisy Belt (s), Noisy bearings, Rust Build up in & out of
Cabinet, Any sediment in basin, Green Algae inside tower, uneven
Water distribution thru tower baffles , blocked water spray nozzles.

A Geothermal unit can be just as Regular WSHP Water Source Heat Pump.

Where it extracts Heat from the Soil during winter or Dissipates Heat to the
Soil during the summer. Via a Buried several feet deep in Ground loop of
Copper or other type tubing.

Or it could just be a water source cooling unit only.

Where it Dissipates Heat to the soil in the summer & Provides

Heating in winter thru a Separate Heating Source.


During Summer Time operation

The Geothermal unit is Rejecting heat to the water going thru its Water Cooled Condenser
Normal entering water at about 85 degs & leaving water 10degs higher at 95 degs

(Normal TD thru Water Condenser coil is "10 deg?. 95-85=10 deg TD) +- 3 deg

Which is connected "piped? to a Buried in Ground copper or other type tubing loop which dissipates
heat to ground .Water supplied to geothermal unit is
Supplied between 75 & 85 deg constantly during summer time.

On some Geothermal units condensing water flow going thru condenser the water flow volume may be
Controlled by a water flow valve in response to condenser pressure to maintain proper condensing
Pressure in condenser coil which will permit proper TD of water going thru Condenser which is 10Degs
(Normal " TD 10 deg) 95degs LWT -85degs EWT =10degs TD

In winter time this valve may be bypassed to permit full flow of loop water


During Winter operation of the Geothermal Unit

The Reversing Valve reverses the refrigerant Flow Thus the Water Cooled Condenser Coil Becomes
A Water Cooled Evaporator & the water going thru the Evaporator is cooled down
10 deg Entering at about 60 deg & leaving at 50 deg
(Normal ?TD is 10 degs) 60degs EWT -50degs LWT =10degs TD

The Geothermal Unit is Collecting Heat from the Water loop buried underground

Normal Water Temps in winter
Entering Water to Unit at about 60deg Leaving at about 50 deg =10deg TD


1. - To check geothermal unit like any AC Unit
First Unit must have been powered for least 12 hrs

That is Voltage leaving disconnect sw & powering compressor unit
Full Voltage as per unit Nameplate

To allow compressor crankcase heater or other means of off cycle
Compressor heat device to maintain compressor oil diluted & no liquid
Refrigerant contained in compressor shell which can cause valves
Or crankrods rupture on compressor start up

(If Disconnect or breaker turned off or blown fuses or no power at unit)

** Report unit need be checked by qualified Licensed HVAC

Contractor & (Pull Off & Proceed with Other Parts of Home Inspection)

?Remember we are not Trouble shooters"

If Disconnect or Breaker Turned off there can be a short on unit or wiring or other defect
On unit or you can cause a short when switching on if something wrong with unit


If unit powered ? & proper voltage leaving disconnect & power at unit "

2. - Check for clean filter, Clean Coil, Clean Squirrel cage ?Blower?
tight belt & not Cracked or Loose

If Filter Dirty remove before start up.
(Make Sure You Replace All Blower Compartment Covers
before starting unit)

** (Report Dirty Filter, Dirty Evaporator, Dirty Squirrel Cage blower.
Worn or cracked belt Report as Defective need attention)

Check Disconnect sw or breaker to be located next to unit
Fuses Size or Breaker type should be as per unit name plate Recommended

Disconnect Checks: Look for overheated & Discolored Fuses, Fuse Holders, Disconnects Blades & or Wiring & connections
** (Report as Defective & need attention)

Switch off Power to Unit & Check control panel on unit. (Caution Hot wiring if disconnect on)
Look for frayed or burned wiring, Charred contactors contacts & relays
If Excessive defect on controls
** (Report any Defects)

If Any Disconnected wires with wire ends exposed
STOP & Report do not turn on unit Disconnect Tag as Unsafe to Run!
** ( Report Need check by Licensed HVAC Contractor )

Check for Manual Water Valves at unit (Note POSITION if not fully open) Do not Move

AIR SIDE

Check for no blockage on Supply & Return air Grilles & all Dampers on grilles open
If some Dampers on Grilles are closed (Take Note ?Do Not Move ? )

Some Dampers on Grilles Close to unit are likely to be closed or partly closed

** If Excessive noise off grilles Report as Need Attention

NOTE Most Dampers on grilles should normally be open
Specially ones further away from AC Unit

Proceed to start up unit on Heating
If outdoor temperature is below 75 degs

If higher than 75 degs Unit (might trip )
Be Reluctant to test unit on heating at this higher outdoor temps
Maybe reschedule testing heating on cooler temps

Some Units will reset after you turning Stat on & off after 15 minutes it tripped
Other units you will need locate Manual Reset Switch &
Reset after 15 Min it went off
(Caution Turn power off to unit before sticking hands in panel or unit cabinet)


(Some times a red Button other times a small metal button)

After reset of safety switch

Reset Disconnect ON
Switch thermostat on heating set at least 10 deg higher than ambient

Verify condensing water circulator pump came on & water Flowing
Once pump on if any continuous gurgling or noise in water piping

Locate any auto & manual vents in unit & loosen caps for air to escape
If Visible & accessible check & open manual vents till all air escapes
Loosen auto water vents caps to let air out.


The cap is normally the type found on tire inflating stem
Check for No Noise in Water Flow Gurgling or noise or air pockets
If Water pockets or gurgling in water flow (Unit Might Trip)



** Verify if Fill valve for water loop open & no water leaks in
Water Fittings valves & other

Before leaving site verify if no water being supplied by fill valve

** If water being supplied after a while turn off valve

& Report NEED ATTENTION

** If You Found Fill valve closed before unit start up
** Report Unit need Attention by Licensed HVAC Contractor
Always write in report Findings (cover you?re Tracks)




Once circulator pump On compressor should come On some units have
Time Delay & will start after 3 to 5 Minutes after circulator pump goes on

Run compressor unit for 15 to 20 Minutes

Check Supply Air Temp in supply air duct at about 3 ft from coil unit
& Return Air Temp should have a 20 to 30 deg TD
(Normal TD on Heat 20deg Min 30 deg Max)


SAT = 90 deg ? 60 RAT = 30 deg TD if much higher Blockage on air supply or return dirty Coil Loose or Worn Belt ducting blockage
SAT = 90 deg ? 70 RAT = 20 deg TD if much lower Possible low charge

SAT = Supply air Temperature
RAT= Return air temperature

** If Higher than 32 deg TD Report Need Attention by Licensed HVAC contractor
** If Lower than 20 deg TD Report Need Attention by Licensed HVAC contractor

Cooling Operation Check out

Wait at least 5 minutes before switching from heat to cool
If out door Temps above 65 Deg
If Lower than 65 deg (Unit Might Trip)
Reschedule Unit Cooling test run

At Stat SW on Fan To ON & leave fan blower running while
Waiting the 5 minutes for unit cool off.
Heat from coil need be dissipated to avoid unit overload & Trip

Switch on Stat set 10 deg lower than ambient temp
After running unit for 15 to 20 minutes in cooling

You want to have a 16 to 20 Deg TD between Supply & Return Air Temps

RAT 80 deg - SAT 60deg = 20 deg TD

RAT =Return air Temp
SAT = Supply air temperature

** If Higher than 20 degs TD Report Need Attention by Licensed HVAC Contractor
** If Lower than 16 degs TD Report Need Attention by Licensed HVAC Contractor


Sergio Durazo
Residential,Commercial,Industrial
35yr+ HVACR Service Technician
sdurazo1@sbcglobal.net


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35 yr HVACR Residential,Commercial ,Industrial Service technician