Planning the Rockspan HVAC system

Brother Mike Chiles is responsible for the planning and design of the HVAC system.  We’ve also had help from Mike Jones and his team from Hydro-Temp in Arkansas, Tony Wellnitz and from Art Boyt with SolSource Greenbuild.  Ken Hurley is helping with the ERV and humidity management.


Below is Build 4 of the system logic for heating and cooling.  You can download a full size of the document here.


HeatProduction4.png

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HomeHome.html

Below is Mike’s original whiteboard sketch for the mechanical panel.

Below is the CAD version as drawn by Jon Schrader at Watts Radiant. 

Below are some current images for the mechanical room in the basement

ERV

Pipe entry

Watts Mechanical board

Hydro-Temp

heat pump

InDirect tank

ERV

Dan and Margy Chiles Residence / Hydro-Temp Water to Water variable Heat Pump


4 inputs will be provided to be field connected:

  1. 1.Input to start / stop system. [Dry contact to ground = start]

  2. 2.Input to set mode. (heating or cooling) [Dry contact to ground = Cooling]

  3. 3.Input 0-10 vdc (speed select) 0 vdc = off, 10 vdc = compressor at 100%.

  4. 4.Temperature sensor for DHW tank.

Priority / On Demand DHW water heating: If no heating or cooling is calling and the temperature of the hot water tank drops below the priority start set point the system will come on at 50% compressor to begin heating hot water.  The compressor will run at 50% until the tank temperature rises to the priority stop set point.
If however the temperature of the tank continues to drop another 5 degree the compressor will ramp up to 100% output and run at 100% output until it reaches the priority stop set point. 

Cooling mode: When start is enabled and cooling is enabled the system will look at the speed select 0-10 vdc input to modulate the compressor accordingly. 

Cooling and Hot water: If at any time while running in cooling mode the temperature of the DHW tank drops below the Priority max temp set point and the DHW tank temp is less than the hot gas temp the system will start the DHW pump.
If the DHW tank Temp drops below the
priority stop set point while running in cooling the ground loop pump will be turned off to dump 100% of the extracted heat from the space into the hot water tank.  If the system is running in cooling mode and trying to heat hot water a minimum compressor speed of 20% is maintained to provide plenty of cooling and hot water.

Heating Mode: when start is enabled and heating is enable the system will look at the speed select 0-10 vdc input to modulate the compressor accordingly. 

Heating and Hot water: If at any time while running in heating mode the temperature of the DHW tank drops below the Priority max temp set point and the DHW tank temp is less than the hot gas temp the system will start the DHW pump.
If the DHW tank Temp drops below the
priority start temp set point while running in heating the compressor will ramp up to 100% output regardless of speed select input, this is to heat the space and heat the hot water both at once. 



Setpoints adjustable via bacnet or Bacview controller:

Priority Max Temp: 130
Priority Start: 112
Priority Stop: 116



I/O list for IO flex 6126 controller:

Input1: BAS start / stop                DO1: Reversing Valve
Input2: BAS Mode select            D02: Ground Loop Pump
Input3: Speed select input            D03: Heater / Chiller Pump
Input4: Master Switch                D04: DHW Pump
Input5: Ground loop Freeze             D05:
Input6: Chiller Freeze                D06:
Input7: Limits (High and low)            A01: Vstar compressor (0-10volt)
Input8: DHW Tank Temp            A02:
Input9: Hot gas Temp                A03:
Input10: Medium limit                A04:
Input11: un used                A05:
Input12: un used                A06:

Control comments on the new HydroTemp heat pump from James Ross at HydroTemp:

Spreadsheet from Mike Chiles for the I/O planning concerning heat pump, control and house:  Download the Excel spreadsheet ENV Point List Chiles 1.0.xlsx:

David and Will’s Schedule of Zones, sensor and zone valve locations.  Version 2, May 23, 2012.

Below is Mike’s notes on the Watts schematic. 

Tony Wellnitz control planning 6.1.12

Tony Wellnitz is working on the control logic for the system based on Brother Mike’s original notes.  Below is Tony’s current thinking:

Mike Chiles schematic: Geo Loop, Solar /Radiant Panel
6.2.12

Chiles System Logic Barn and Hybrid

Introduction: This system logic is designed to work with the updated schematic dated 6/2/2012, titled Chiles Geo Loop/Solar/Radiant Schematic. List of suggested sensors follows at end along with optional ENV controlled solar DHW system if desired.

Heat the Barn (winter daytime)

When slab sensor (3) is below the user desired, or programmed temperature, and when the temperature of sensor (1) is above the temperature of sensor (3) by a programmable difference, let us assume 5F; Pump 8 circulates antifreeze through the circuit shown in orange. The ENV system integrates the temp difference between sensor 2 and the temp sensor in VFS 5-100 with the flow rate to calculate and store the cumulative heating energy delivered into the barn slab for the heating season.

Because the temp of sensor 1 may vary depending on placement in the solar array, the ENV system monitors the temp of the sensor in the VFS 5-100 as a backup. If the VFS temp does not maintain at least a 3F difference above the slab sensor S 3, the Pump 8 is shut down for a adjustable time (perhaps 20 minutes)

Optional Control feature (The speed of pump 8 may be varied according to the temperature difference between S#2 (solar supply) and S#5 (solar return), ie the greater the temperature difference the faster the pump operates.

Cool the Barn (summer nighttime)

When slab sensor (3) is above the desired programmed temperature, and when sensor (1) is below sensor (3) by a programmable difference, let us assume 5F; Pump 8 circulates antifreeze through
the circuit shown in orange. The ENV system integrates the temp difference between sensor 2 and the temp sensor in VFS 5-100 with the flow rate to calculate and store the cumulative cooling energy delivered into the barn slab for the cooling season.

Because the temp of sensor 1 may vary depending on placement in the solar array, the ENV system monitors the temp of the sensor in the VFS 5-100 as a backup. If the VFS temp does not maintain at least a 3F difference below the slab sensor S 3, the Pump 8 is shut down for a adjustable time (perhaps 20 minutes)

Optional Control feature (The speed of pump 8 may be varied according to the temperature difference between S#2 (solar supply) and S#5 (solar return), ie the greater the temperature difference the faster the pump operates.

Normal Geo Loop Operation for the House

Heating

When the ENV system determines that the ground temperature (will need to add at least one other sensor [shown as sensor #4] in the soil near the geo pipe) is warmer than any of the external wythes (and there is a need for home heating or DHW) then Tekmar V #1 (on the home panel) is rotated to position A-sending fluid to the Geo Loop. Similarly Tekmar V #2 (to be located in the barn) is rotated to position B – sending fluid to the return side of the Geo Loop and back to the home panel.



Cooling

When the ENV system determines that the ground temperature (S#4) is cooler than any of the external wythes (and there is a need for home heating or DHW) then Tekmar V #1 (on the home panel) is rotated to position A-sending fluid to the Geo Loop. Similarly Tekmar V #2 (located in the barn) is rotated to position B – sending fluid to the return side of the Geo Loop and back to the home panel.

Hybrid Solar Home Heating

Note: Normally the hybrid solar is prioritized to heat the barn, however the system logic should be set up so that (by user preference) the solar hybrid panels can be prioritized to heat the home.

When the ENV system determines that the hybrid solar panel array is warmer than any of the external wythes, and warmer than the ground sensor [#4]; then heat is extracted from the hybrid panels in the following manner.

Tekmar Valve #1 and Tekmar Valve #2 both rotate to the A position, and the fluid path follows the piping marked in green, traveling through the hybrid solar heat exchangers, and then returning to the mech panel in the home. P #8 is always disabled while the system is in this mode.

Measuring Heating Production

When the system is in the Home hybrid panel heat production mode the ENV system should integrate the temperature difference between sensors S#2 and S#5 (embedded in the Grundfos VFD5-100) with the measured flow rate from the flow sensor in the VFD to measure and record the cumulative amount of heating produced by the hybrid panels, when operated in conjunction with the Heat Pump.

Because of the cooling effect of running the fluid through the Geo Loop we don't project that the hybrid panels will used to directly heat the house. (without the use of the Heat Pump)

Note: The cumulative hybrid home heating production record is separate from the barn heating production record.

Because of the cooling effect of running the fluid through the Geo Loop we don't project the hybrid panels being used to directly heat the house. (without the use of the Heat Pump)

Hybrid Solar Home Cooling

At night, especially on clear evenings, the hybrid panels may be cooler than the external wythes or the ground, and as much as 6F cooler than the ambient air temperature. Due to their very low mass the hybrid panels may cool off much more quickly than the high mass external wythes. Because of this it will sometimes be advantageous to reject heat from the solar panels at night and store cool in the thermal mass of the internal wythes and the ground floor slab.

When the ENV system determines that the hybrid solar panel array (S#1) is cooler than any of the external wythes, and is also cooler than the ground sensor [#4] then cool is extracted from the hybrid panels in the following manner.


Tekmar Valve #1 and Tekmar Valve #2 both rotate to the A position, and the fluid path follows the piping marked in green, traveling through the hybrid panel heat exchangers and then returning to the mech panel in the home. P #8 is always disabled while the system is in this mode.

Measuring Cooling Production

When the system is in the hybrid panel heat rejection (cooling) mode the ENV system should integrate the temperature difference between sensors S#2 and S#5 (embedded in the Grundfos VFD5-100) with the measured flow rate from the flow sensor in the VFD to measure and record the cumulative amount of cooling produced by the hybrid panels.

Note: This cumulative home hybrid solar cooling production record is distinct from the barn cooling production record.

Solar DHW System (optional ENV controlled system, alternative to standard Watts control)

The earlier thought was to use a prepackaged Watts Radiant solar pumping system coupled to the solar thermal panels and the Caleffi solar tank. However, the ENV system could run this as well.

This option requires a solar panel sensor, a solar storage tank sensor and modest programming so that when a 10F or so temperature differential existed between the tank and the panel that the system would operate, along with a high limit that would deactivate the system once the tank reached a programmed high temperature limit (such as 180 or 190) See Caleffi literature for their specified high limit. The solar system will also need a mixing valve installed so that the water exiting from the tank is at a safe temperature (110 or so) The Watts solar pumping panel can be ordered with a Grundfos VFS so that cumulative solar energy production can be collected.

Sensor Input to optional ENV controlled Solar DHW system in barn (not shown on diagram) 1 AI from solar thermal panel
1AI on solar supply line
1 AI from solar storage tank

1 Pulse AI from VFS on solar thermal pump package 1 AI from VFS (solar return line)

Sensor Input to ENV controlled system for Geo Loop, Solar Hybrid and Barn Heating/Cooling

1 AI from Sensor #1 (mounted on piping connected to the solar hybrid heat exchanger outlet (well insulated from ambient air) at discharge end of array.
1 AI from Sensor #2 (mounted on supply line to solar hybrid array-also well insulated, but can be inside the barn)

1 AI from Sensor #3 (slab sensor-ideally between the hydronic radiant circuits and near the end of the circuits)
1 AI from Sensor #4 (measures temp of ground very close to the Geo Loop-I'd place it near the return side of the Geo Loop, a couple of inches away from the piping, embedded in the ground, and sealed in a sensor well w silicone.

1AI from the Grundfos VFS 5-100 on return side of the solar hybrid piping.
1 Pulse AI (flow rate) from the same Grundfos VFS 5-100
Plus will need: two outputs to control position of the second Tekmar valve (in barn)




one output to control pump #8