Carlin Combustion Technology, Inc., East Longmeadow, Mass., introduced its new EZ-H2L Burner at the AREE Show last month in Atlantic City. This new residential oil burner is capable of two positions, 50 percent turndown, step modulation (lo-hi-lo) mode of operation, and was warmly received. Beyond the burner development success, Carlin and Econox Technologies, LLC (the inventor of the underlying patent pending technology) managed to assemble one of the largest teams of players ever to collaborate on a single oil heating project. The project was sought by and funded by NORA. In addition to Carlin, Econox and NORA, other players included: Brookhaven National Labs, Bock Water Heaters, ECR International’s Olsen Furnace, Buderus Boilers, Thermo-Dynamics, Field Controls and Delavan Nozzles.
Installed equipment today tends to be grossly oversized. Testing performed by Brookhaven has quantified the efficiency penalties attributable to this oversizing. When considered along with the fact that all equipment regularly operates at part load conditions and very infrequently at design conditions, the need for reduced input at part load conditions becomes obvious. By being able to operate at half its rated capacity, the Carlin EZ-H2L with Econox technology greatly increased the fuel reduction opportunities for appliances using this new burner.
In order to optimize the efficiency gains possible from the turndown capabilities of this technology, new control strategies had to be developed to direct the burner to low or high fire, based upon variable load conditions. And this required a closer look at the demand load each of the four types of heat exchangers is required to respond to. For example, oil fired storage water heaters typically see two periods of high demand a day followed by long periods of low or no demand. Warm air furnaces and cold start boilers on the other hand typically see a more steady demand that varies directly as outdoor temperature changes. Boilers with tankless coils, of course, share a little bit of each of these two demand types. The one common element was that all applications could benefit in some way from a control strategy that was based upon ‘rate of temperature change” rather than a fixed temperature set-point with a differential.
Oil Fired Storage Water Heaters
To meet the demands of oil fired storage water heaters, Carlin upgraded its EZ-Temp Model 90000 temperature controller, currently supplied with its water heater burners, to monitor ‘rate of temperature change.” This ‘rate of temperature change” capability, dubbed ‘slope control,” allows for the addition of two new and very important operating features never before available on a water heater control. Remembering that residential storage water heaters typically experience two high demand periods a day followed by long periods of low or no demand, by monitoring the ‘rate of temperature change,” the microprocessor knows which of the two periods the tank is seeing.
If the rate of change is low and consistent (commonly, a half of a degree an hour), the control knows there is no demand. So, when the set-point less differential is reached, the control will instruct the burner to start in low fire and slowly replenish the stand-by losses. Brookhaven has measured a twenty percent reduction in stand-by losses using this control strategy with the Carlin EZ-H2L.
On the other hand, if the control senses a rapid change in the ‘rate of temperature change,” it will immediately instruct the burner to come on in high fire. Then the control will continue to measure the ‘rate of temperature change” in the tank. If the tank is losing temperature, it will keep the burner in high fire. But if the tank temperature is rising, it will drive the burner back down to low fire, allowing it to operate longer at a higher efficiency. The burner will continue to modulate back and forth between low and high fire in an attempt to match the burner input to the load.
Cold Start Boilers
Cold start boilers pose a very different challenge. To meet these challenges, Carlin upgraded its soon to be released EZ-Temp Model 90524 temperature controller for use with the new EZ-H2L Burner. The 90524 is a boiler-burner-circulator control, commonly referred to as a triple aquastat. The program changes allowed for the addition of the ‘slope control” feature that was built into the water heater control noted above and a low circulator limit feature.
By definition, cold start boilers will from time to time return to room temperature during times of no demand. When there is a call for heat, it is not unusual for condensation to form as the boiler begins to heat up from a cold start. To minimize the formation of condensation from a cold start, the control has the burner start in high fire and prevents the system circulator from coming on until the boiler water temperature exceeds 110 degrees. This accelerates the warm up time and gets the boiler past the condensation point quickly, before energizing the circulator.
Above 110, the ‘slope control” feature takes over. If the boiler water temperature is rising beyond a predetermined ‘slope,” the control sends the burner to low fire. Conversely, if the boiler water temperature is falling, the processor brings the burner up to high fire. If a call for heat comes at a time when the boiler water temperature is above 110 degrees, the burner can be asked to start in either high or low fire as boiler water temperature conditions might require at any given time.
Boilers With Tankless Coils
Boilers with tankless coils require that some minimum boiler water temperature be maintained at all times to ensure domestic hot water is always available on demand. This requires a new level of control functionality to be added to the mix and a new challenge to achieve the highest level of overall efficiency. To obtain the desired mix of functionality, lo-hi-lo fire control and maximum efficiency, another variation on the EZ-Temp Model 90524 needed to be created. The end result combines all the features of both the water heater and cold start boiler controls and also addresses the unique tankless needs.
The control has a low limit that maintains a minimum water temperature to satisfy the tankless coils domestic water needs. During stand-by periods with no DHW demand, the microprocessor monitors the ‘rate of temperature change” in the boiler water temperature. If the boiler water temperature decays to the low limit set-point less the differential, the control signals the burner to start on low fire. And just like the water heater control, it slowly replaces the stand-by temperature loss. Also, similar to the water heater control, the control responds to a rapid ‘rate of temperature change” by signaling the control to move to high fire.
When a call for heat is received, the control starts the system circulator and by-passes the low limit setting enabling the boiler water to potentially rise to the high limit setting. But the ‘slop control” also kicks in and watches the rate of change in boiler water temperature. Like the cold start boiler control, if the boiler water temperature is rising, the burner is instructed to move to low fire and if the temperature is falling, it instructs the burner to go to high fire.
Warm Air Furnaces
Warm air furnaces, like cold start boilers, experience a relatively steady demand that varies directly with outdoor temperatures. So the decision to be in low fire or high fire is relatively simple and straight forward. Ironically, it probably will prove to offer the greatest fuel savings exceeding the cold start boiler. By utilizing a two stage thermostat, the first call for heat would be to ask the burner to start and continue to run in low fire at 50 percent of the nameplate rating. The low firing rate is likely to satisfy the heating demand for most of the season. The EZ-H2L Burner will only go to high fire if the heating demand cannot be met by the low firing rate and the room temperature drops and trips the second stage of the thermostat.
The control challenge here is with regard to the furnace system fan. ECR International is in the process of optimizing the Olsen Furnace fan speed for low fire operation to achieve the ideal air flow across the heat exchanger to extract heat as efficiently as possible while at the same time controlling the exiting flue gas temperatures to guard against the formation of condensation in the flue.
A preliminary AFUE calculation showed an initial improvement from 83 percent AFUE to nearly 88 percent AFUE. ECR will be concluding production model AFUE levels that balance the need for high efficiency gain while ensuring reliable and safe venting.
From the commercial side of our business, we all know the efficiency gains available by modulating commercial burners between high and low fire. But very little data is available to document these potential savings. So, part of the scope of this project is to employ Brookhaven National Labs as a partner in the project to measure these savings. That testing is ongoing at Brookhaven, and these appliances with their fuel savings results will be incorporated into the new FSC (Fuel Savings Calculator) being developed jointly by NORA, Brookhaven and PriMedia.
Led by NORA, without whose funding a project of this size would not have been possible, Carlin, Econox and all the project partners have achieved all its objectives in a very short period of time. The new EZ-H2L Burner with the new temperature controls and all four appliances will be featured at NAOHSM in Hartford May 20th and 21. An outside exhibit will feature live fire demonstrations on all four appliances.
Thomas J. Tubman is executive vice president and general manger at Carlin Combustion Technology, Inc., and has been with the company for almost ten years. A thirty-six year veteran of the home heating oil industry, Tom began his career in the residential retail home heating oil sector after graduating from Roger Williams College in Rhode Island with a degree in Mechanical Engineering. Prior to joining Carlin, he spent fifteen years with Power Flame, Inc., a leading manufacturer of commercial/industrial oil and gas burners located in Parsons, Kan.