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Snow and Ice Melting with Infrared Heaters

Fostoria Electric Infrared Heating Manual in .pdf format (32 Pages, 6.5 mb) (You must have the free Adobe Acrobat Reader plug-in.)

The Fostoria Multi-Mount (UL listed for completely exposed/unprotected outdoor applications) is frequently used for snow and ice melting.  They have quartz lamp heaters which are less susceptible to heat loss from wind and they reach high temperatures. The quartz lamps have less mass to hold heat which can be lost to a rise in temperature of the air crossing it. The following is a case study prepared by Fostoria, showing a general comparison of using infrared or other types of systems.

Comparative Study of Snowmelt Systems
Application to Owings Mills Metro Station
By N. Thompson

Mechanical/Electrical Section Facilities Engineering, MTA
March, 1999

CONTENTS

EXECUTIVE SUMMARY

In view of MTA’s strong commitment to provide a safe and reliable transit system, elimination of hazards along pedestrian pathways within its precincts is mandated.  Ice and snow covered walkways constitute one such hazard.  This report evaluates several snowmelt strategies for keeping these walkways safe and seeks to settle the ongoing debate on the efficacy of manual versus automatic snow removal systems Reisterstown Plaza, West cold Spring Lane, Rogers Avenue, Penn North, and Upton area currently, the metro stations with automatic snowmelt systems.  Photographic and other evidences taken during and after a snow showers demonstrate that these systems do function effectively.  However, minor problems, and the installation and operating costs of the systems have precipitated cries for, what appears to be the less costly Shoveling with chemical treatment method.

This study demonstrates that:  (a) the Shoveling with chemical treatment snowmelt approach is more costly to operate and less effective than the automatic approaches, and (b) that the automatic snowmelt systems facilitate drier and slip-free pavement more consistently.  The objective of a snowmelt system is to keep the pavement dry and safe for commuters.  It is widely recognized that corrosive chemicals used to slowdown pavement refreeze have caused serious and rapid deterioration of metro station infrastructure and capital equipment.  Engineering studies have shown that the life of concrete is reduced by 50% when exposed to the chemicals over a short time.  A recent survey of entrance escalators revealed numerous corrosion and deformity of crucial components attributable to exposure to these chemicals.  The study indicates that the estimated annual cost of using the shoveling with chemical treatment approach is 88,000.  This cost is 22,400 more than the most expensive automated system.

Equal to the task of building and presenting an argument for automatic snowmelt systems, this report also compares and presents the strengths and weaknesses of four snowmelt techniques.  Effectiveness and costs rank these techniques. The platform at Owings Mills metro station was the test site.  In terms of estimated annual cost and maintenance requirements, the infrared technique appears to come out on top.  However, the need to find suitable mounting locations for infrared fixtures limits the effect and the infrared methods for platform applications has strong potential efficiency and cost savings benefits.
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SNOWMELT SYSTEMS

1.0  Comparative study of Snowmelt Systems.
The platform at Owings Mills train station is used as the test area.  Platform area is 12150 sq. ft. and is partially covered by a canopy, area: 13,200 sq. ft.  The study looks at three approaches to removing and keeping the area free of slippery and frozen precipitation.  The approaches are Shoveling with Chemical treatment, Embedded Cable system, and Overhead Infrared Heating System.  The attributes of the approaches were theoretically applied to the physical features of the platform, using the winter precipitation trends in the Baltimore area as the boundary conditions.  Data gathered from local and national weather-watch authorities show that snowfalls greater than one inch occur, on average of 7 days per year.  Ice or freezing rain occurs on average of 2 to 3 times per year.

In addition to these snowmelt approaches, consideration was given to modifying the existing canopy.  This strategy involves extending the canopy over the entire platform to provide protection against vertical and angular precipitation.  However, extending the canopy at Owings Mills is not feasible.  The substructure of the existing platform was not engineered to accommodate the additional loads that extending the canopy would create.  Hence to pursue the canopy extension strategy for this station is deemed too costly and disruptive to be viable.  The selection of an alternate approach to do the job is highly favorable. 

Each snowmelt system is briefly described in a section below.  The strengths and weaknesses of the systems were gleaned from studies of technical manuals, engineering handbooks, and interviews with systems manufacturers, and MTA Facilities Maintenance personnel.  The findings are summarized in a table for quick reference.  The Appendix section of the report presents details on the derivation of the estimated annual cost for operating each system.  The choice of system is based on the comparative analyses of strengths and weaknesses and estimated annual operating costs.
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2.0  Shoveling with Chemical treatment
This approach employs manual labor, snow blowers, and other mechanical devices to remove the precipitation.  Attractive features of this approach include: little or no capital cost, no added system to maintain, no appreciable increase in electric power demand, and no need for extra maintenance staff because available  contract   services provide a ready pool of laborers.  This approach, however, has several strong negative effects on the short term and long term structural health of the facility and on the life of capital equipment.

Use of corrosive chemicals to delay re-freezing of pavement has damaged vital escalator components, accelerating the deterioration of the platform, and threatens the substructure of the stations.  See Table 1 for summary of the system’s strengths and weaknesses and comparison with other systems.  The costs and effects of the chemicals on the station structure and capital equipment are often over looked.  This is because the deterioration process is not immediately evident.  The American Concrete Institute classifies an environment where deicing agents are present as a severe environment.  Typically calcium or sodium chloride is used as the chemical agent.  The chloride ions react with and break down the binding agent, cement paste, of the concrete.  Due to the relatively small size of the chloride ions, the deterioration moves through the concrete with each wet and dry cycle.  Eventually the chloride ions reach the reinforcing steel and rapidly consume it.  Once the adhesion is lost between the sand, gravel, and the reinforced steel, the concrete fails structurally.  The only solution left is to replace the concrete. 

The impact of corrosive chemical on concrete structures is demonstrated by the rate of deterioration of parking garages.  Parking garages are not treated with snowmelt chemicals.  However, these chemicals are tracked on to the premises by incoming vehicles.  The garages are generally constructed using a low water-cement ratio (f>45000psi), fly ash, and epoxy coated reinforcement to reduce the effects of salt.  Even with these precautions, the time to major repairs ranges from 7 to 15 years.  The major repairs include replacement of floors, beams, and columns.  Without this chemical exposure the life expectancy of the concrete is approximately 40 years.  MTA’s platforms are subjected to far more salt than parking garages and are less resistant to chloride ion penetration.  As a consequence, our platforms have to be repaired more frequently and suffer more rapid decline in structural integrity.  There are other chemicals sold as deicing agents that have even more destructive effects on concrete than salt.  MTA once used such chemicals, which resulted in structural failure in concrete members.

Capital equipment such as elevators and escalators are similarly affected by deicing agents.  Elevators and escalators at station entrances deteriorate from the bottom up.  A recent survey of these escalators exposed damaged base supports, and rust build-ups, resulting in deformation of crucial support members, and, in a few cases, actual shifting of the entire escalator assemblies were observed.  Thus, the total annual cost of using this method to clear snow and ice must include the hidden costs of major repairs or replacement of the infrastructure, inconvenience patrons suffer, and accidents.  Using our

10 freezing event for Baltimore, we estimate the annual cost to clear ice and snow at Owings Mills to be 88,000.  Details of this estimate are outlined Appendix, A.10.
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3.0  Overhead Infrared Approach
Infrared radiation is an electromagnetic emission generated in a heat source by rapid vibration and rotation of molecules.  The most attractive feature of Quartz lamp Infrared heaters is that it instantaneously provides radiant heat to melt snow without raising the temperature of the intervening air space.  The infrared fixture requires no more maintenance than would a fluorescent fixture, and the quartz lamps are rated for 5000hours.  The average duration of freezing precipitation is less than 150 hours per year.  Hence, the lamps will render many years of useful service.  With the infrared approach there is no refreeze of pavement.  Hence, there is no need for the use of corrosive chemical.  The system is equipped with temperature and relative humidity sensors.  Thus, it is automatically turned on some time before there is freezing precipitation.

Infrared fixtures are typically installed overhead.  Without a completely covered platform, a large number of fixtures would have to be mounted on poles.  The number of poles required could compromise space and the aesthetics of platform.  This is one of the drawbacks to the infrared approach.  See Table 1 for a summary of the system’s strengths and weaknesses and a comparison with other systems.  Another weakness of this approach is its high electric power demand.  For the Baltimore area, the system is required to output 90W/sq.ft to provide the desired result.  The total annual cost of using this method to clear snow and ice is estimated at 47,108.  See Appendix A.20 for cost derivation.
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4.0 Embedded System Approach
This approach requires implanting ferromagnetic tubes and or high resistance power cable in concrete, 2-4” below the finished surface of the platform.  The Direct Buried Cable and the Skin-effect methods are currently the most effective embedded systems in use.  Like the infrared approach, there is no refreeze of pavement.  Hence, there is no need for the use of corrosive chemical.  The system is equipped with temperature and relative humidity sensors.  Hence, it is automatically turned on some time before there is freezing precipitation.

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4.1 Direct Buried Cable
The Direct Buried Cable System is designed to deliver an average of 30w/ft.  A system designed to output 40W/sq.ft is generally required to yield the best result.  The fact that the cable is directly buried in concrete constitutes the system’s biggest weakness.  See Table 1 for a summary of the system’s strengths and weaknesses and a comparison with other systems.

      Correcting any fault in the buried cable would require jackhammering the concrete.  One weakness of this system, relative to the infrared system, is that much energy is expended to raise the pavement temperature before snow melting begins.  Other weaknesses include high installation cost and the potential for high repair cost.  Additional attractive features of this system include; low annual operating cost, very little maintenance requirements, and lower electric power demand than the infrared system.  The total annual cost of using this method to clear snow and ice is estimated at 44,340.  See Appendix A.30 for cost derivation.
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4.2  Skin-Effect Heating System
Skin-Effect heating system is designed to deliver 50W/sq.ft to the pavement.  It is best suited to large area applications.  The system is founded on the principles of electromagnetic induction and the skin-effect phenomenon that occurs in current carrying conductors.  Insulated conductors are used to heat the ferromagnetic tubes, embedded in the concrete.  The distinct advantage of this system over the direct buried system is that the cable can be pulled in and out of the tube in the event of a cable fault.

One weakness of this system, relative to the infrared system, is that much energy is expended to raise the pavement temperature before snow melting begins.  The biggest drawback to this system is its initial cost.  At 50/sq.ft this system is the most expensive on the market.  This cost does not include pavement demolition and reconstruction.  Another weakness is the potential for high repair cost.  Additional attractive features of this system include; low annual operating cost, very little maintenance requirements, and lower electric power demand than the infrared system.  See Table 1 for a summary of the system’s strengths and weaknesses and a comparison with other systems.  The total annual cost of using this method to clear snow and ice is estimated at 65,640.  See Appendix A.40 for cost derivation.
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5.0  Conclusion
The shoveling with Chemical treatment has been shown to be the most costly and inefficient of the approaches to control the accumulation of frozen precipitation on pavements.  It has been demonstrated that this method generates indirect costs that, in the final analysis, make it more costly than the most expensive automated system.  The inherent weaknesses of this method far outweigh its strengths.

The analyses also showed that the infrared system could be the method of choice based on its instantaneous heat production, lower annual cost than the skin-effect system, and low maintenance cost and requirement.  The advantages of the infrared systems outweigh its relatively high power demand.  The primary   drawback to the total use of infrared in platform application is the requirement for additional poles to mount the heat fixtures.  This problem would be eliminated if the platform were totally covered.

Of the two embedded systems discussed, the Skin-effect system would be the better choice for platform application.  The higher initial cost for the Skin-effect is compensated for by the fact that probable cable faults are much less costly to repair with the Skin-effect system.  The Direct Buried system falls short as an option because exception is taken to the prospect of jackhammering the platform to fix a cable fault.

Although our analysis suggests that automatic systems would be ideal for snow and ice control, they are not widely used in the Transit industry.  The current systems installed in the MTA are yet to receive unanimous acclaim within the MTA.  WMATA is still in the process of evaluating its needs.  Personal Rapid Transit, PRT, in Western Virginia, employs a hydronic system installed in 1971.  Reports indicate that the system is working well.  However, annual operating costs for the hydronic system range from 75,000 to 250,000.  Chicago Transit Authority, CTA employs infrared and other systems for snow and ice control.  The extent of the application of these systems could not be confirmed at this time.
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6.0  Recommendations:
The MTA should use an automated snowmelt system to control the build-up of frozen precipitation at its metro stations.  The infrared system is suitable for applications where the areas are totally covered with a canopy or the use of mounting poles would not be an exception.  A combination of the Infrared and Skin-effect systems for semi-covered platform applications, such as Owings Mills station could prove cost effective and efficient.
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7.0  Summary of Cost Analysis Table 1  

SNOWMELT
COST BENEFIT ANALYSIS

SYSTEMS

ANNUAL
COSTS

ADVANTAGE

WEAKNESSES

SHOVELING WITH CHEMICAL 
TREATMENT
88,000.00 No capital
equipment cost

Shoveling crew dispatched after snowfall-high probability of accidents, such as slipping from platform onto rails and delays during snowfall

Slick residue must be treated with chemicals to prevent refreeze

Chemicals attack concrete, exposing rebars to corrosion; Life is significantly reduced

Chemicals also attack station sub-structure; Life of station shortened

Chemicals corrode entrance escalators, stairs and elevators resulting in costly repairs or replacement

BURIED CABLE 44,340.00 Low annual operating cost

Little or no maintenance required

Auto snow detect and system control

No refreezing, pavement remains warm and dry

No need for corrosive chemicals

High initial capital cost

System embedded in 2-4” of concrete

Costly system repair-may require jackhammering platform

Expend energy to preheat pavement before melting precipitation

 
SKIN-EFFECT 65,640.00

Low annual operating cost

Low maintenance required

Auto snow detect and system control

No refreezing, pavement remains warm and dry

No need for corrosive chemicals

High initial capital cost (50/sq.ft)

System embedded in 2/4” of concrete

Costly system repair, may require jackhammering platform, but cable can be pulled from tube and replaced

Expend energy to preheat pavement before melting precipitation

Added utility demand

INFRARED HEATER 47,100.00

Low annual operating cost

No refreezing, pavement remains warm and dry

No more maintenance than on a fluorescent fixture required

Auto snow detect and system control

Instantaneous direct heat on ice/snow

No need for corrosive chemicals

Lower capital cost than embedded snowmelt system

High kilowatt demand

High capital cost relative to manual system

Requires overhead mounting support canopy or poles

Must be installed at least 5 feet above combustible material

Some possibility for injury to patrons who stand directly under a fixture for an extended period

 
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APPENDIX
A.10 Derivation of annual costs for Shoveling with Chemical Treatment

A.11 Direct Cost
Assumptions:  Combined snow and ice showers occur approximately 10 times per annum over a 2 months period.  Ice storms take 5 times more man-hours to clean up than comparable snowstorms
Man-hours:  average 40 hours (assumed typical for 4” snowfall and or icing with a 5-man crew)
Contractor hour-rate: weighted avg.: 60 per hour.
Average duration: 12 hours
Equip. & material per snowfall: 400
Estimated operating cost per snowfall: 40 x 60 + 350 = 2,800
Estimated annual operating cost: 10 x 2800 = 28,000

A.12 Indirect Costs:
Assumptions:
(1)   Entrance escalators need to be cleaned after each snow/ice event.
(2)   More frequent escalator repair/refurbishment.
(3)   Approximate normal escalator life of 35 yrs.; reduced life, 20 yrs.
(4)   50% reduction in the platform life (assume 20 yr. Life)
(5)   Cost of escalator replacement approximates 700,000
(6)   Cost of platform replacement approximates 600,000

Estimated added annual cost per escalator for service and refurbish
= 700,000(35-20/700) = 15,000
Total cost (Owings Mills has 2 escalators)  = 30,000
Estimated added annual cost for platform replacement 
= 600,000(20-10/200) = 30,000

Estimated total annual cost   = 88,000

A.20 Derivation of annual cost for Overhead Infrared
To heat the entire platform, infrared lamps have to be installed on the canopy and on poles, planted in the platform, for areas not under canopy.  Fixtures will be mounted at 14 ft above the platform.  The layout of the fixtures provides the light pattern coverage and a power density of 90W/sq.ft, recommended to handle frozen precipitation in Baltimore.

Estimated # of fixtures required = 12150sqft/79sqft/fixture = 154
Recommended fixture:

Fostoria: Multimount 343-30-THSS-480V.
Dimensions: 46”x21.5”x7.9”
Weight: 49.5lb
Electrical: 480V, 3 Ø, 10,950W, Quartz lamps-3 elements, with 30º sync. Beam pattern

A.21 Direct Costs: Installation and Operation
Estimated system installation cost:
154 fixtures @ 652.5 = 100,485
1 lot mtg. Hardware @ 12000 = 12,000
1 snow switch @ 819 = 819
1 snow sensor @ 315 = 315
6 60-120A contactor @ 107 = 642
Electrical connection @ 5/sq.ft = 60,750
Total = 175,000

Estimated Annual Operations Cost:
Assumptions: Combined snow and ice showers occur approximately 10 times per annum over a 2 months period.
Electric power demand: 154 fixture @ 10950W/fixture = 1700KW
Utility demand rate/KWh: 0.03/KWh = 8.32/KW/month
Average snowfall duration: 12 hr.
Estimated system runtime: 14 hr. (12 hr. + 2 hr. hold-on time after precip.)
Estimated operating cost per snowfall: 1700 x 0.03 x 14 = 714
Estimated annual operating cost: (10 x 714) = 2(1700 x 8.32)       
= 35,428
Estimated life of system, approximately 30 yr.
Annual depreciation = 175,000/30 = 5,840
Estimated life of heater (lamp) = 5,000
Estimated annual operating time = 140 hrs.
Annual maintenance cost (clean/re-lamp) = 30 hrs @ 40/hr + 4400       6,600
Estimated total annual operating cost:
= 47,108  

A.30 Direct Buried Cable:
The costs for demolishing and reconstructing the platform pavement are not included in these cost estimates since the “platform rehabilitation project” assumes these tasks independent of the snowmelt system used.

A.31 Direct Costs: Installation and Operation
RayChem, EM2-XR cable 5.25/ft
Expansion joint kit 14/unit
Tie-wraps (100/box) 12/unit
Cable splice kit 18/unit
Power end kit 19/unit
Nema 4x nonmetal J.B. 92/unit
Control panel & snow sensor 770/unit

Assume 8” loop spacing
Required cable length = 12150 x 12 /8 + terminations = 20000ft
Maximum length of cable 50A circuit = 358ft
No. of circuits = 20000/358 = 56 

Estimated system installation cost:
20000ft cable = 105,000 
Installation accessories = 15,000
Control panel & snow sensor = 770
Electrical connection @ 5/sq.ft 60,750
Subtotal = 181,520

Annual Operations Cost:
Snowfall per annum: greater than one inch occur on an average of 7 days per year.  Ice or freezing rain occurs on average of 2 to 3 times per year.
Electric power demand: 20000ft @ 30W/ft = 600KW
Utility demand rate/KWh: 0.03 + 8.32/KW/month
Average snowfall duration: 12 hr.
Estimated system runtime: = 17 hr (12 hr. + 5 hr. hold-on time after precip)
Estimated operating cost per snowfall: (600 x 0.03 x 17) = 306
Estimated annual operating cost: (10 x 306) + 2(600 x 8.32) = 13,044
Estimated life of system, approximately 20 yr.
Assumed annual cost of demo. Platform due to cable fault = 15,000
Annual depreciation = 181,520/20 = 9,100
Annual maintenance cost = 200 hrs @ 36/hr = 7,200
Estimated total annual cost = 13,044 + 9,100 + 7,200 + 15,00
= 44,340

A.40 Skin-effect:
The costs for demolishing and reconstructing the platform pavement are not included in these cost estimates since the “platform rehabilitation project” assumes these tasks independent of the snowmelt system used.

A.41 Direct Costs:  Installation and Operation:
Platform area is 12150sqft
Estimated system installation cost @ 50 per sq.ft = 608,000

Annual Operations Cost:
Snowfall per annum: greater than one inch occur on an average of 7 days per year.  Ice or freezing rain occurs on average of 2 to 3 times per year.
Electric power demand: 20000ft @ 30W/ft = 600KW
Utility demand rate/KWh: 0.03 + 8.32/KW/month
Average snowfall duration: 12 hr.
Estimated system runtime: = 17hr (12 hr. + 5 hr. hold-on time after precip)
Estimated operating cost per snowfall: (600 x 0.03 x 17) = 306

Estimated annual operating cost: (10 x 306) + 2(600 x 8.32) 
= 13,044
Estimated life of system, approximately 20 yr.
Assumed annual cost of demo. Platform due to cable fault = 15,000
Annual depreciation = 608,000/20 = 30,400
Annual maintenance cost = 200/hrs @ 36/hr = 7,200
Estimated total annual operating cost: = 65,640
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