1. Engineer Presentation

2. Efficiency - GAS

3. Clamshell Heat Exchanger 80% Efficient
Our current Engineered Product heat exchanger.

4. Typical two furnace unit
On a standard efficiency unit the leaving flue gas temperatures are around 400 degrees.
1700 °F

5. Typical two furnace unit
Unfortunately, for each furnace in series you lose 5-6% efficiency. That means for a dual and trip furnace, when the unit is firing at full fire, the overall unit efficiency is much lower. The ANSI 83.8 test standard requires each furnace to be tested separately so a units thermal efficiency per 83.8 is not the same as the unit’s overall efficiency.
80% Efficient
75% Efficient

6. Air Stratification - Typical Heat Exchanger
10-15 °F ΔT
Heat Exchanger
A typical unit has a burner at the bottom with flue gas entering the heat exchanger at approximately 1700 °F and leaving the unit at approximately 400 °F. Given the large delta T with the flue gas, there can be a large delta T between the supply air at the bottom of the unit and at the top of the unit. If the ductwork is run horizontally with the rooms in the space all being fed from the bottom of the ductwork, the first room served by the unit may come up to temperature very quickly. However, each successive room will take more of the “hot” air and leave behind the colder air. This can lead to the last room served by the unit being slow to come up to temperature and occupancy complaints.

7. Tubular Heat Exchanger 82-83% Efficient
A tubular heat exchanger is 2-3% more efficient than a clamshell heat exchanger. It also has improved reliability since each tube is made from one piece instead of two pieces welded together.
1700 °F

8. Primary Secondary 93% Efficient 91% Efficient 150 °F 1700 °F
In order to get efficiencies above 90%, the flue gas needs to stay in the air stream longer or the surface area needs to be increased (or both). The easiest way to do this is with a secondary heat exchanger attached to the primary heat exchanger. It should be noted that this causes the flue gas to change from a gas to a corrosive liquid.
1700 °F

9. Sizing - Series 20°F 70°F 120°F 91% Efficient 86% Efficient
Like the 80% efficient clamshell design, putting multiple heat exchangers in series each additional heat exchanger will be 5-6% less efficient. That means that if the first furnace is 91% efficient the second furnace will be 86% efficient. At 86% efficiency the second furnace is no longer fully condensing and your flue gas is above 130 degrees.
20°F
70°F
120°F
91% Efficient
86% Efficient

10. Sizing - Parallel 600 MBH input 300 MBH input 91% Efficient
The only way to maintain the 90+% unit efficiency is to split the air stream into multiple heat exchangers in parallel. This results in very tall or very wide (or both) units.
91% Efficient
91% Efficient

11. Air Stratification – High Efficiency
Heat Exchanger
??? °F ΔT
Heat Exchanger
With heat exchangers in parallel, the air will have to be mixed after leaving the furnace section. If the air is not properly mixed and the unit is operating around or below 40% load, you will have the above stratification issue with one side that has the burner on heating the air to setpoint and other side with the burner off supply unheated outside air.

12. Minimum Turn Down Limitation
Single Stage VS Modulation
The minimum turn down must be set to ensure condensing in the secondary heat exchanger or both heat exchangers must be made out of stainless steel.
The Power Venter/Draft Inducer’s airflow directly affects the gas to air ratio at the burner. The ratio must be set to keep Air Free CO below 400 PPM.
Single stage is limited that it can only fire at 100% fire. In order to maintain a temperature set point the unit has to rapidly cycle the burners. Each time a burner lights, it has what is called cycling lose which lowers it’s efficiency when it first fires. This is due to the amount of gas that is released prior to ignition to ensure that burner lights. With modulating gas control, since surface area is a constant, the efficiency of the unit will improve as the firing rate is reduced.
Below 130°F the flue gas condenses into a corrosive liquid. This means the minimum fire rate must be set so the flue gas will always be above 130 degrees before it enters the secondary heat exchanger. That way it ensures no corrosion and premature failure of the primary heat exchanger. The other option is to build the primary heat exchanger out of stainless steel which will increase the cost and weight of the unit.
Typically, the ideal air to gas ratio is 1:1. However, as you turn down gas, in a typical system, the air remains constant. This can lead to an increase in CO production above the legal 400 PPM. In order to eliminate this, the minimum turndown must be set above the point where this occurs or use a 2-speed/variable speed power venter to get the gas to air ratio closer to 1:1 at part load.
Combined these determine the minimum fire rate for the unit.

13. Instead of using a clamshell or tubular heat exchanger, Xcelon uses a high efficiency boiler and a hot water coil to transferring the heat to the supply air stream. The system uses a closed 35% Propylene Glycol Loop as an intermediary heat transfer medium. The loop is a closed loop which means no water connection is required to the unit. The only connections required are ductwork, gas and electricity.

14. Why Hydronic? Minimize footprint while maximizing efficiency.
Maximum efficiency at the widest range of ambient & design conditions.
Maximizing user comfort while minimizing operating cost.
VAV minimum CFM is now limited by the supply fan instead of heat exchanger.
No stratification issues.
“Green” unit/minimize emissions
Water holds more energy than air can so it is a better medium for transferring heat. You can transfer the same amount of heat in a much smaller surface area than an air-to-air heat exchanger.
User comfort is not just occupants, it can also be factory processes/etc that require a specific entering air temperature. Our unit can maintain a constant discharge air temperature to within ±0.5 °F.
Competition has trouble scaling to the larger sizes and maintaining efficiency (see previous slides).
At low CFM in a typical system, as you turn down the CFM the delta T of the supply air increases. With a modulating gas control you can turn down the gas valve but once you hit the minimum firing rate you risk cracking the heat exchanger or tripping the high limit if you continue to lower the CFM. Depending on the controller used for the unit, the minimum CFM is either defined by the maximum discharge temperature at full fire (for modulating gas control with room sensing) or on a more complex controller, the maximum discharge air temperature at minimum fire (for modulating gas control with duct sensing). The limiting factor on Xcelon is minimum speed of the fan and VFD.
Since agency classifies the unit as both a boiler and air handler, it may be eligible for boiler rebates.

15. Xcelon w/ Integral Condensing Boiler
90 °F
100 °F
The GPM is constant but the glycol loop temperature varies based on the discharge air setpoint and outside air temperature. While the flue gas still has a large delta T, the delta T of the propylene glycol loop is only 50 degrees. This control allows the unit to maintain a constant discharge air temperature within ±0.5 °F of setpoint.
This is an old diagram, the new design has a single boiler.
140 °F
1700 °F

16. Air Stratification - Heating
Hot Water Coil
With Xcelon, the glycol mix entering the hot water coil varies to maintain a constant discharge air temperature. In this case the entering glycol mix was 160 °F and the leaving glycol mix of 130 °F. This resulted in leaving air that was within 1 °F from top to bottom. In addition, the fan is AFTER the heating coil further mixing the air. This resulted in the air leaving the unit being with 0.5 °F from top to bottom (139.3 °F on the top and °F on the bottom). With a more even air temperature leaving the unit, you reduce the risk of inaccurate sensor reading with duct sensors. Also since you’ve eliminated the air stratification, you’ve eliminated the possible occupancy comfort complaints.

17. Constant Discharge Temperature
The discharge air temp is constant ±0.5°F of setpoint.
Note the top data is not the same time range as the bottom data. The top data was just a long straight line when I put it in so I shortened it so people could see how it worked at the start. The bottom data, it wouldn’t let me zoom in to just show Feb 23th.

18. Performance
93% thermal efficiency per BTS2000. With a discharge air temperature set at 70 degrees, that efficiency increases to 98% efficient.
Fully modulating gas valves.
10:1 turndown ratio
Closed Hydronic Loop requiring no water connections at the roof. Only connections are gas, electricity and ductwork.
35% Glycol Mix protects the unit to -30°F
Each burner has a 5:1 turndown ratio for a total of 10:1 turndown.

19. Performance
* CFM is varied to maintain air set point. Outdoor air temperature range reflects a 10:1 BTU input range.
The two graphs show the same data. It is just two different graph types to display the information.

20. The maximum allowed CO is 400 PPM CO (Air Free)
Variable speed power venter
High fire should be between % for CO2 and below the maximum 150 PPM for CO.
Low fire should be between % for CO2 and below the maximum 150 PPM for CO.
The variable speed power venter allows the unit to maintain a 1 to 1 gas to air ratio. This improves the efficiency at part load. With a constant speed power venter the to fuel ratio has a constant air input and a decrease in gas input at part load. This leads to an increase in CO2 and a decrease in efficiency.
Preliminary testing has shown the NOX to be as high as depending on conditions.

21. Efficiency - ELECTRICAL

22. Clamshell - Static Pressure
A typical Clamshell Heat Exchanger can have a static pressure drop of 1.12” per furnace.
This can result in a total static pressure of over 3” through the furnace sections.

23. Xcelon – Hot Water Coil
Regardless of the BTU input and CFM selected, the hot water coil was carefully selected to keep the air pressure drop below 0.5” of static.
This can result in a reduction in motor horse power by up to two sizes.
Further adding to the electrical savings, all units come with a VFD as standard.
It should be noted that all our fans come with spring isolators as standard to reduce sound and vibration.
It should also be noted that this electrical savings is not included in the 93% thermal efficiency.

24. Cooling Coil Bypass
Bypass Damper
In cooling mode the bypass damper is closed forcing the air through the cooling coil.
When not in cooling mode, the bypass damper opens to reduce the internal static pressure of the unit.
For units with a cooling coil (Dx or Chilled Water), by reducing the internal static pressure when the unit is not in cooling mode, the VFD can ramp down. This results in a reduced amp draw and lower electrical operating cost.
Cooling Coil

25. Integral Cooling with Dehumidification - Phase 2
A separate heat exchanger is used to transfer the heat from the Saturated Liquid Refrigerant into the Glycol Loop.
This results in the R-410A refrigerant being sub-cooled which improves the cooling efficiency.
This also allows the existing hot water coil to be re-used to reheat the air.
In order to dehumidify the supply air, for example 95/76°F outside air, it needs to first be cooled to around 49 °F to remove the moisture from it. The air is then heated up to around 58°F before leaving the unit. Normally this reheat would done with an additional 1 or 2 row hot-gas reheat coil. The draw back is the additional coil increases the unit’s internal static pressure drop and BHP. This will increase the unit’s amp draw. In order to maximize the electrical efficiency, we re-use the hot water coil to minimize the internal static pressure drops of the unit. As an added benefit, by using a heat exchanger to transfer the heat from the saturated liquid refrigerant to the glycol loop, we sub-cool the liquid refrigerant which increases the Cooling SEER (Cooling Efficiency).

26. Efficiency – Heat Recovery

27. Heat Recovery Layout
Motor
Boiler
Pumps
VFD & Transformer
-Highlight the main source of waste heat that is outside of the supply air stream.
-The air is transferred from the boiler compartment to the supply air stream using the pressure difference between the compartment and the hot water coil. The boiler compartment is at atmospheric pressure since there is an air inlet on the side by the pumps. The outlet against the hot water coil is at a negative pressure. Passive design using air pressure differential means no additional fans or motors.
-1” walls with R-value of 6.3 and optional 2” wall with an R-value of 11 to make sure no heat is lost.
This recovered waste heat increases the efficiency by 1+%

28. Additional Features

29. Cincinnati Fan
Notice the operating points are on the right side of the fan curve where there is only a single CFM for a given static pressure. All unit sizes when released will be able to handle a maximum of 3” of true external static pressure.

30. Spring Isolators
1” deflection spring isolator are provided underneath the fan as standard. This isolates the fan reducing noise and vibration transmission to the unit and the building.

31. Piping
It is a closed glycol loop so no water connection will be required to the unit or at the roof. You will need to maintain the glycol/water mix per the glycol manufacturer’s recommendations. In the case of the glycol supplied with the unit, the manufacturer recommends the glycol be changed when the PH is below 7. There is gallons of water/glycol in the system. When it comes time to charge the glycol loop, you will only need to supply (2) 5-gallon containers of water and (1) 5 gallon container of propylene glycol.
Discuss:
Air Separator
Expansion Tank
Drain, fill and purge valve
Flexible hose to allow for movement during shipping without breaking piping
Pumps
Pressure relief valve
Boiler Hy-vent and pressure gauge.

32. Condensate
Integral condensate trap designed to drain in the event of a power failure.
Condensate Neutralizer as a factory installed optional accessory.
Optional Dedicated heat trace power supply for long condensate runs.
The condensate trap has a condensate “weep” hole that allows the water to drain out of the trap in less than 60 seconds after a power failure. This is to prevent the condensate from freezing.
For the condensate neutralizer, the inlet is on the top of the neutralizer and the outlet is approximately ¼ up from the bottom coming out the end. In the event of a power failure the majority of the condensate will drain out. The remaining condensate has plenty of room to expand so freezing will not break the neutralizer. Once the unit regains power the 90+ degree condensate will quickly melt any frozen condensate in the neutralizer.
Also the condensate does have a bypass pipe that will bypass the neutralizer if it gets clogged (note agency required us to put the bypass in).
Condensate can either be piped out the side or bottom of the unit. If the condensate pipe will be exposed to temperatures below freezing it must have some form of protection. We offer an optional power supply for heat trace. The heat trace would be provided by others.

33. Controls - Overview Call for heat is received. Dampers open and prove.
Burners turn on.
After glycol mix reaches temperature, VFD slowly ramps up.
Glycol mix temperature is varied to maintain constant discharge temperature.
(Optional) if the unit is unable to maintain discharge temperature, it reduces the CFM until discharge temp is satisfied.
When the system first enables the burner(s) to fire, they bring the glycol mix up to the Air Temperature Setpoint. Once the glycol is up to temperature, the VFD is then slowly ramped up to speed as the control maintains the discharge air temperature. Once start-up is complete, the discharge air temperature and pressure are maintained.
Optional setting – If the unit is unable to maintain the discharge air temperature, the blower speed can be reduced to allow the discharge air temperature to be maintained.
Controller is capable of communicating with building automation system. Modbus standard, BACnet and LonWorks optional

34. Controls - Boiler
The PID loop looks at the Propylene Glycol mix temperature, the discharge air temperature and rate of change.
HRT Controls are configured to run the first burner to 50% fire then turn on the second burner.
True run time monitoring
PID = Proportional Integral Derivative. By looking at the rate of change, it keeps the boiler from making sudden, unnecessary changes. It also helps to prevent the system from overheating the discharge air temperature. When the P.G. mix is within the Heat Band, the boiler modulates to maintain a discharge air temperature. In the event the temperature rises above the heat band, the boiler will stage burners off until the discharge air temperature has fallen below the heat band minimum.
By limiting the max fire of each burner to 50% until all burners are on, it helps to maximize efficiency and ensure all boilers are condensing. At part load the boiler efficiency improves due to the larger surface air compared to the BTU input allowing for more heat transfer.
In order to ensure the maximize life expectancy of the unit, the run time of each burner is monitored and the “primary” burner is rotated so that burner “1” is always the one with the least run time.

35. Controls - Safeties
Boiler – High Limit, Low Water Cutoff, Ignition Control Fault and Software Operator Limit
Per code, unit complies with CSD-1.
Air Side – VFD Temperature Status and Damper Prove
High limit trips at 205°F +/-7. This means the high limit trips at 212°F and then automatically resets when the temperature falls below 198°F. Not finalized what the setpoint will be.
The low water cutoff uses a pressure switch to ensure there is sufficient charge in the glycol loop and the system is receiving adequate flow.
Ignition fault control ensure that burners have lit. Unit complies with CSD-1 and will lock out after failing to light on the first attempt.
Software Operator Limit reduces the fire rate of the boiler to minimize glycol loop temperature overshoot and to ensure that the boiler does not exceed the maximum glycol loop temperature. When the glycol loop temperature is in the Limit Band, the software operator limit limits the burner fire rate from % depending on where it is in the limit band and turns the boiler off if it exceeds the maximum limit. (Basically the software prevents nuisance trips that would result in the boiler tripping on high limit which would require a manual reset).
VFD temperature status prevents the VFD from running in temperatures below 25°F. When the temperature is below 20°F, the controller enables the electric heater within VFD enclosure to bring the box temperature up to an acceptable level. The electric heater is a small 150 watt heater. For larger HP motor and VFDs the heater may need to be increased to 300 watt.
Damper proving switch gives the damper 30 seconds from the time the dampers are told to open before shutting down the boiler and VFD. After the initial failure, the system will retry again in 10 minutes.
Optional Clogged filter switch will allow the unit to continue to run. It is used to indicate that filter maintenance is required.

36. Service Designed with ease of service in mind.
Isolation valves for ease of boiler service
Boiler is on a track for ease of repair.
Service lights standard on all units.
Optional Convenience Outlet available.
Optional Clogged Filter Switch.
External Control Terminal Strip on exterior of unit for ease of Thermostat wiring.

37. Roof Cap
The roof cap of the outdoor unit is sloped to prevent standing water on top of the unit.
It should be noted that underneath the roof cap is that actual roof of the unit which is a same panel construction as the walls (with the same R-value)
We are working on a new design for the unit that will only have a single combustion air inlet/flue gas terminal. The unit above shows concentric vent terminals. Those have been replaced with a single combustion air inlet on one side and a flue gas exhaust on the other side. The flue gas terminal will actually have a “T” coming off the end of the unit with a vent cap on top of the “T” and the bottom left open to allow any condensate to drain out. This keeps the combustion air intake and flue gas exhaust on different planes to minimize the chance of flue gas recirculation.
Internal Venting is Duravent Polypro which is ULC S636 vent pipe.

38. Performance Performance Initial offering 4,501 to 10,000 CFM
Max Discharge 140 ⁰F, Max temperature rise 100 ⁰F.
4, ,000 CFM
Able to handle 3” of external static pressure
800 – 1,600 MBH
Initial offering
4,501 to 10,000 CFM
800 & 1,200 MBH

39. Questions Also additional project ideas.
Stay tuned, coming soon integral cooling, evaporative cooling and Energy Recovery.