Radiant Floor Systems Coupled with Geothermal Heat Pumps

ByBrian Urlaub, Enertech Global

Why are you here?

Hopefully so you don’t end up with something like this!

Basic components of a water-water & combo geothermal heat pump system.

Tips on proper installation of a hydronic geothermal system

Limitations of a hydronic geothermal system

Some design considerations of the system Piping options for the load side Control options for the hydronic system

What are we going to cover?

Design water temp won’t heat space.◦ Insulation generally is the culprit

Heat pump is locking out on HP.◦ Waterflow, Waterflow, Waterflow!◦ To much load side antifreeze?◦ Controls, Controls, Controls!

High bill complaints.◦ Low loop temps, could be a multitude of reasons!◦ Running system at max 120F temps all season.

Design of the system must meet the expectations of the customer, and it is your job to install and verify your system will do the job!

What have the problems been?

What will be my design max water temp? What will be my design min water temp? Will I have a supplemental or backup

system?◦ If so, how will it be piped and controlled?

What is the heat distribution system?◦ High mass floors - concrete◦ Low mass floors – staple up◦ Radiation – high or low temp

Am I doing chilled water for cooling? Do I have areas that need antifreeze? Who is doing the insulation? What is it? What type of floor coverings do I have?

Questions to ask yourself?

Doing an accurate load calculation is priority number 1 including radiant design!

This will dictate your supply water temp and flow rates of the system.

Knowing the building materials, insulation values, floor coverings, etc. is critical.

Jobsite verification of building materials and insulation practices (pictures, pictures)

This all goes into a successful installation and a happy customer with low energy costs!

Proper design starts with Loads!

Insulation, Insulation, & Insulation

Floor Coverings & Design

Concrete slab with R-5 edge and horizontal.

Concrete slab with R-10 edge and horizontal.

Staple up tubing with no underneath insulation and carpet for floor covering.

Staple up tubing with R-10 underneath insulation and carpet for floor covering.

Staple up tubing w/ HE plates, with R-19 underneath insulation, and low R-value carpet & pad for floor covering.

Radiant floor tube spacing at 9” o.c. min. Do not mix more than 25% glycol antifreeze

on load side of heat pump (preferably 0%) Flow rate through each radiant floor loop to

be between .50gpm and .75gpm Pipe sizing is critical; flow = BTU’s Variable Speed pumps & zone valves! Insulation values, floor coverings, flow

rates, tube sizes, etc. all factor in to calculating system design!

Other Recommendations

Water-to-Water Heat Pumps

• Energy obtained from or rejected to a ground-coupled source (closed-loop)

• Utilized to make domestic hot water

• Utilized for hot water hydronic systems

• Utilized for chilled water hydronic systems

• Optional desuperheaters

Combination Heat Pump (Triple Function)

• Energy obtained from or rejected to a ground-coupled source (closed-loop)

• Utilized for hydronic heating applications (no chilled water )

• Utilized to heat or cool air in forced air applications

• Packaged system• Optional Desuperheater

Typical Water-Water System

Load Side

W2W Unit

Source Side

We are going to focus on the Load Side of the System!

ALL heat pump hydronic systems require a buffer tank (well almost ALL).◦ “Decouples” floor pumping and unit flow

requirements.◦ Usually 1 gallon per 1,000 Btuh

In most cases, controls are the most difficult part of the installation.◦ Know what you’re getting into!

Design systems for max. water temps of 120F or less for compressor life and efficiency!

Load-side “Guidelines”

V = T x (Qhp – Qload)/Delta T x 500

V = VolumeT = Desired minimum run time (minutes)Qhp = HP CapacityQload = Heat flow to load when HP is onDelta T = Differential set point (10F)

Example = 5 x (52,000 - 0)/10 x 500 = 52

Buffer Tank Sizing

The capacity of the heat pump and depending on the control strategy will determine the amount of storage needed.

Hot tank – single set point◦ Usually 10 gallons/ton or 1gal/1000btu’s

Demand controlled – single set point◦ Usually 6 gallons/ton or 1gal/1500btu’s

Combo units buffer should be smaller! Example = 5-ton (52MBH + hot tank)

◦ 5-tons x 10gal/ton = 50gal or 52,000btu/1000= 52gal

Buffer Tank Sizing

Both Source Side and Load Side Coaxial heat exchangers are typically identical◦ Pressure drop ratings are the same◦ Flow rates on the load side should be roughly

the same as the source side 2.5-3 gpm per ton

Connection size doesn’t always mean pipe size (unit or pump flange)

Load-side “Guidelines”

Hydronic radiant systems depend on supplemental heat source:◦ No supplemental heat – up size loop◦ Direct supplemental heat – same as W/A◦ Indirect supplemental heat – up size loop

Combo unit systems:◦ 100% radiant – size as you normally would depending

on supplemental heat source◦ Some radiant & some F/A – up size loop

Hydronic systems will need more loop based on the mass of the system vs. heating air!

Loop Field Sizing “Guidelines”

Ground Source Heat Pumps using R-410a refrigerant typically can only achieve a maximum load side temperature of 120F ELT. This prohibits the use of this technology with other forms or hydronic heating such as radiators and/or sometimes baseboard radiation.◦ There are new low temp baseboard radiators

available that will heat at lower than 120F!

GSHP Max Load Side Temp

Design the GSHP system to utilize the lowest water temps possible for proper space heating and highest system efficiency!Things to consider: - Tube spacing/sizing - Flow rates - Insulation - Floor coverings

With the COP of the HP going up as the load water design temp goes down, outdoor reset makes sense as a recommended control strategy.

Outdoor reset control will vary the design load temperature based on outdoor temperature. The colder the outside temp, the warmer the load temp.

This maximizes the COP of the system.

Outdoor reset controls

The Effect of Glycol on Microbial Activity

0%

20%

40%

60%

80%

100%

0% to 10% 10% to 20% 20% to 25% above 25%

Concentration of Glycol (vol%)

Pro

babi

lity

of

Con

tam

inat

ion

% of samples found with > 1000 CFU/mL

Glycol on Load Side

Water quality is also very important!!!

Affects of Antifreeze in System

Pipe sizing guidelines

Pipe sizeFlow (gpm)

Max P.D. (FT/100 FT)

Max. Vel (FPS)

1/2" 0-2 5.0 2.2

3/4" 2-4 4.4 2.4

1" 4-8 4.8 3.0

11/4" 8-15 4.0 3.3

11/2" 15-24 4.0 3.7

2" 24-45 4.0 4.4

2-1/2" 45-72 4.0 5.0

3" 72-130 4.0 5.7

• Notes:Use with hot water and chilled water closed piping systemsBased on schedule 40 BI or Copper pipe

• Water-Water Unit Applications• Pressurized piping systems• Controls

• Combo Unit Applications• Pressurized piping systems• Controls

Heating only Hydronic Systems

Water-Water Heat Pump◦Buffer Tank (Pressurized or HSS)

◦Load Side Pump◦Controls (Aquastat)◦Air Pad◦Flow Center Pressurized Non-Pressurized Hose kit

Components of a Water-Water System

Tubing◦ Fasteners◦ Manifolds◦ Fittings

Zone pumps/Zone Valves◦ Flanges (w/ pumps)

Hydronic Accessories◦ Air Eliminator◦ Expansion Tank

Controls◦ Zone Control◦ Pump Relay◦ Thermostats

Additional Components of System

Heat Only – W2W Unit & HSS

Load Side Pump

Buffer Tank

Aqua-stat

GW UnitZone Pumps

Manifolds

Tubing

PT Ports

Heat Only – W2W Unit

Load Side Pump

Buffer Tank

Aqua-stat

W2W Unit

Flow Center

Zone Pumps

Manifolds

Tubing

Heat Only – W2W Unit

115F

T1 T2

24V AQUASTAT WITH N/O DRY CONTACTSTHAT WILL CLOSE ON FALL IN TEMP!

HEATING ONLY CONTROLS!

Sensor in tank

Heat Only – W2W Unit w/ HSS

Heat Only – 2stg W2W Unit

Load Side PumpBuffer Tank

Aqua-stat

W2W Unit

Flow Center

Heat Only – 2stg W2W Unit

Heat Only – 2stg W2W Unit

Combo Heat Pump◦ Thermostat (Forced Air)◦ Electric auxiliary heater (Optional)◦ Air Pad◦ Buffer Tank (Pressurized or HSS)◦ Load Side Pump◦ Aquastat (hydronic control)◦ Flow Center

Pressurized Non-Pressurized Hose kit

Components of a Packaged Combo System

Tubing◦ Fasteners◦ Manifolds◦ Fittings

Zone pumps/Zone Valves◦ Flanges (w/ pumps)

Hydronic Accessories◦ Air Eliminator◦ Expansion Tank

Controls◦ Zone Control◦ Pump Relay◦ Thermostats

Additional Components of System

Heating Only - Combo Unit

Load Side Pump

Buffer Tank

Aqua-stat

GT Unit

PT Ports

Heating Only - Combo Unit

On Demand Control Strategy!

• Water-Water Unit Applications• Pressurized piping systems• HSS non-pressurized piping systems• Controls (heating & cooling)

• HSS System (on demand)• HBX Controls (either or, plus Outdoor Reset)• Geo-Tech (Don Schuster) (Set point)• Terra-Therm Hydronic Controller (Set point)• Do it yourself (who knows)

• Controls (Heating only)• HSS• HBX• Tekmar• Johnson Controls• Honeywell• Ranco

Hot/Chilled Water Hydronic Systems

W2W units have lower EER’s than Water-Air heat pumps

Be careful of sensible cooling capacities of the air handler or water coils – do not size strictly based on tonnage

All piping with chilled water needs to be insulated including pumps

Buffer tank must be insulated and have an air seal to prevent condensation

Advantage – one unit vs. two units

Chilled Water vs. DX Cooling

Sensible vs. Total Cooling

Heating & Cooling Hydronic Systems

Basic 2 Aqua-stat Wiring setup

Heating & Cooling Hydronic Systems

HBX ECO-1000 Wiring Diagram

HBX ECO-1000 Wiring Diagram (2stg)

Htg & Clg W2W unit w/ HSS

Htg & Clg W2W unit w/ HSS

Geo-Tech (Don Schuster)

Do It Yourself – Good Luck!

What is the boiler’s primary function:◦ Back up source only◦ Supplemental heat – same output temp◦ Increase supply temp to provide additional btu’s

to high load areas◦ What source of energy is the backup boiler

Gas Electric Wood

Back up Boilers

W2W unit w/ Boiler - Supplemental

W2W unit w/ Boiler - High Temp

Pool & spa heating Domestic water heating Snow melt Process water chilling Ice storage or Ice arena’s Waste heat recovery Simultaneously heating & cooling

Other Applications

Design the system properly, not using Btu’s per sqft, but rather good design practices.

Insulation is a huge factor along with thermal breaks, if you aren’t doing it, verify it is done right!

Select the proper control strategy for the application, buy off the shelf vs. build your own so anyone can service and troubleshoot!

Size your piping and pumps for proper flow. Select your piping strategy for the

application as well as the supplemental heat source.

So, the Keys to Success Are;

Questions or Comments???

Thank You!!!