Bohn DFT-005 Service Manual
DIRECT DRIVE FLUID COOLERS
Technical Guide
Models DFT and BFH
BNFCTB
April 2007
(Replaces 10108.1, 06/02)
Table of Contents
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Direct-Drive Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Selection Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Selection Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Given Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Correction Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Model DFT Capacity Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Model DFT Specications and Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Model BFH Capacity Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13
Model BFH Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Model BFH Specications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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© 2007 Heatcraft Refrigeration Products LLC
Overview
Our engineers have carefully selected and matched components to provide excellent performance, long service life
and a wide range of performance selections. Specically engineered for outdoor installations, the DFT and BFH uid
coolers are constructed of aluminum and heavy gauge galvanized steel to resist corrosion in all climates.
Fluid coolers are available in a wide range of sizes. Each model is available with several circuit options to ensure
the exact uid cooler for your requirements. Our uid coolers are designed to reduce the cost of time required for
installation. Each unit is completely assembled and tested at the factory. All motor leads are wired to a junction box
providing a single point for eld wiring.
Direct-Drive Design Features
• Cabinets are heavy-duty construction and designed for outdoor
applications; tube sheets and all structural members are fabricated from
galvanized steel
• Cabinet panels are fabricated from heavy-gauge aluminum for an
attractive appearance and corrosion protection
• Coils are fabricated with corrugated aluminum ns with staggered
copper tubes for optimum heat transfer; all units are pressure-tested,
dehydrated and pressurized prior to shipment
• Alternate coil constructions are available — copper ns, BohnGuard™
ns and coated coils
• BFH models incorporate the Floating Tube™ coil design that reduces the
possibility of tube sheet leaks
• DFT models available in either horizontal or vertical air ow; BFH models
available in vertical air ow only
• Fully baed fan sections provide structural strength and prevent fan wind-milling in the o cycle
• Energy ecient fan motors with direct-drive fans available at 1140 RPM; fan motors have thermal overload
protection and permanently lubricated ball bearings
• DFT models are available in 208-230 V single-phase, 208-230/460 dual-voltage, three-phase or 575 V three-phase
motors; BFH models are available in 208-230/460 dual voltage, three-phase or 575 V three-phase motors
• Statically and dynamically balanced fan blades are aluminum and riveted to painted steel spider and hubs
• Fan guards are PVC coated steel for optimum corrosion protection
• All fan motor leads are wired to a weatherproof electrical enclosure for single-point eld wiring
• Fan cycling controls are available that cycle all fans in response to BFH only; DFT fan cycling is ambient air
• All controls are factory mounted and wired; control circuit voltage is 230 V standard, 24 and 115 V controls are
also available
Dramatically Reduces Tube Sheet Leaks
The Floating Tube™ Coil Design
• A wide selection of circuit options maximizes performance at minimal cost
• Sizes available from 10 GPM through 500 GPM
• Units are UL listed for US and Canada
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Selection Procedure
Selection Formulas
Design Capacity = GPM x (Entering Fluid Temperature - Leaving Fluid Temperature) x Fluid Constant, Table 1
Average Fluid Temperature = (Entering Fluid Temperature + Leaving Fluid Temperature)/2
Initial Temperature Dierence, I TD = Entering Fluid Temperature - Entering Air Temperature
Base Capacity = Design Capacity/(1,000 x ITD x Capacity Correction, Table 2 x Altitude Correction Factor, Table 3)
Pressure Drop, Fluid = Pressure Drop, Catalog x Correction Factor, Table 4
Given Conditions
Direct Drive 120˚F Leaving Fluid Temperature
50 GPM 100˚F Entering Air Temperature
20% Ethylene glycol solution 20 feet maximum uid pressure drop
130˚F Entering Fluid Temperature 1,000 feet altitude
Solution
1. Calculate design capacity. From Table 1, select the uid constant for 20% of 484.
Design Capacity = 50 x (130-120) x 484
Design Capacity = 242,000 BTUH
2. Calculate average uid temperature
= (130 +120)/2
= 125˚F
3. Calculate the initial temperature dierence, ITD
ITD = 130 - 100
ITD = 30˚F
4. Calculate Base capacity. From Table 2, for a 20% solution and an average uid temperature of 125˚ F, interpolate
to obtain a correction factor of 1.035. From Table 3, obtain an attitude correction factor at 1000 feet of 0.98.
Base Capacity = 242,000/(1,000 x 30 x 1.035 x 0.98)
Base Capacity = 7.95 MBH / ˚TD
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Correction Factors
5. Select the model and circuiting required. From the capacity tables, locate the GPM you desire and read down
until you nd a base capacity equal to or greater than your calculated base capacity. Read horizontally to the
left to obtain the model and circuiting (Feeds) for your application.
The selection is a DFT 16, with 32 feeds, with a base capacity of 8.34 MBH/1˚ TD and a uid loss of 15.1 feet
of water.
6. Calculate the pressure drop of the uid. From Table 4, using 20% glycol solution and a 125˚F average uid
temperature, interpolate to get a correction factor of 0.86.
Actual Fluid Loss = 15.1 x 0.86
Actual Fluid Loss = 13.0 feet of water
Table 1. Fluid Constraints
Percent
Glycol
Fluid
Constant
0 500
10 493
20 484
30 470
40 453
50 435
Table 3. Altitude Correction Factor
Altitude
(Feet)
Correction
Factor
0 1.00
1,000 0.98
2,000 0.95
3,000 0.93
4,000 0.90
5,000 0.88
6,000 0.85
7,000 0.83
Table 2. Capacity Correction Factor
Percent
Glycol
0 0.97 1.01 1.03 1.05 1.07
10 0.96 1.00 1.02 1.04 1.06
20 0.94 0.98 1.00 1.02 1.04
30 0.92 0.96 0.98 1.00 1.02
40 0.90 0.94 0.96 0.98 1.00
50 0.87 0.91 0.94 0.96 0.98
Note: For average uid temperature less than 50˚F or greater than 130˚F, consult
the factory
Average Fluid Temperature ˚F
50 70 90 110 130
Table 4. Correction Factor for Fluid Loss
Percent
Average Fluid Temperature ˚F
Ethylene
Glycol
50 70 90 110 130
0 0.88 0.82 0.78 0.75 0.71
10 0.97 0.90 0.86 0.82 0.78
20 1.05 0.98 0.94 0.89 0.85
30 1.15 1.07 1.02 0.98 0.93
40 1.24 1.15 1.10 1.05 1.00
50 1.33 1.23 1.18 1.12 1.07
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