Glycol Power Pack Sizing: Sizing the Chiller for Long Draw
An undersized glycol pack is the single most expensive mistake on a long draw spec sheet — warm beer, foaming pours, return service calls, lost margin. This guide gives you the BTU math, the HP reference table, and a working calculator that gets the size right the first time.
To size a glycol power pack, calculate the heat gain through the trunk line (lines × length × per-foot factor × ambient correction), add pour load (500–3,000 BTU/hr), then add a 25% safety margin. Divide the total BTU/hr by 10,000 to get rough HP requirement. Always size up at the next standard pack — never down.
The glycol power pack sizing calculator
Set the number of lines, total trunk length, ambient temperature where the trunk runs, and expected pour activity. The calculator returns the BTU/hr load, the recommended horsepower, and the right Foxx glycol chiller category for the spec.
Glycol Power Pack Sizing Calculator
Foxx Free ToolHow we got there
BTU factors are industry-standard averages. Manufacturer ratings vary — always verify the specific chiller's capacity at your operating glycol setpoint (typically 28–30°F) before final purchase. The calculator output is a sizing guide, not a substitute for the equipment data sheet.
How glycol cooling works on long draw
A small refrigeration unit chills a food-safe glycol bath and pumps it through the trunk to hold the beer cold the whole way.
A glycol power pack is a small refrigeration unit with an integrated bath of propylene glycol — a non-toxic antifreeze rated for food contact. The chiller cools the glycol bath to around 28–30°F, and a circulating pump pushes that chilled glycol through a supply line in the trunk bundle, around a return line, and back to the bath.
Inside the trunk, the glycol lines run alongside the beer lines. Heat from the surrounding air (and from any heat conducted by beer movement) is absorbed by the cold glycol, keeping beer lines at 36–40°F across the entire run. The trunk is wrapped in insulation to slow that heat gain — every BTU the insulation prevents is a BTU the chiller doesn't have to pump out.
The BTU load equation
The total load is heat conducted through the trunk insulation plus heat brought in by pouring.
Where Insulation Factor is BTU/hr per foot per line for the trunk's insulation quality, Ambient Multiplier corrects for the temperature where the trunk runs, Pour Load adds heat brought in during pours, and the 1.25 factor is a 25% safety margin. Divide total BTU/hr by 10,000 for a rough HP requirement, then round up to the next standard pack size.
The four BTU sources
1. Trunk heat gain. The dominant load. Each foot of beer line in the trunk gains heat from ambient through the insulation. Multiply lines × length × per-foot factor. A standard insulated trunk gains roughly 5 BTU/hr per foot per line. A 16-line × 40 ft trunk = 16 × 40 × 5 = 3,200 BTU/hr before any other corrections.
2. Ambient correction. Trunks running through hot ceiling space pull more heat than trunks in a cool basement. Cool basement: 0.8×. Typical interior: 1.0×. Warm ceiling or kitchen: 1.2×. Hot mechanical room: 1.5×. This factor multiplies the trunk heat gain.
3. Pour load. Each pour pulls cold beer out and lets ambient-temperature beer take its place upstream. The chiller has to cool that new beer back to serving temp. A bar serving 100 pours/hr adds ~500 BTU. A busy restaurant at 300 pours/hr adds ~1,500 BTU. A stadium concourse at 500+ pours/hr can add 5,000+ BTU.
4. Safety margin. 25% on top of the calculated load. This accounts for hot summer days, dirty condenser coils that reduce capacity, slight insulation degradation over time, and the inevitable spec creep where the customer adds a tap two years in. Never skip the margin to save money on a smaller pack.
HP & BTU reference table
Industry-standard mapping from BTU/hr load to glycol power pack HP. When the load lands between two pack sizes, always step up — never down.
| HP Rating | BTU/hr Capacity (approx.) | Typical Application |
|---|---|---|
| 1/4 HP | 2,500 BTU/hr | Compact 2–4 tap installs, short runs (under 15 ft) |
| 1/3 HP | 3,500 BTU/hr | Small bar, 4–6 lines, 20 ft runs |
| 1/2 HP | 5,000 BTU/hr | Mid-size bar, 6–12 lines, 25–35 ft runs |
| 3/4 HP | 7,500 BTU/hr | Busy restaurant, 10–16 lines, 35–50 ft runs |
| 1 HP | 10,000 BTU/hr | High-volume brewpub, 16–24 lines, 40–60 ft runs |
| 1.5 HP | 15,000 BTU/hr | Large multi-bar property, 20–30 lines, longer runs |
| 2 HP | 20,000 BTU/hr | Stadium / event venue, 30–50 lines, complex layouts |
| 3+ HP | 30,000+ BTU/hr | Major venues, multi-zone systems with redundancy |
Capacities are nominal at 28–30°F glycol setpoint and standard 90°F condenser ambient. Manufacturer ratings vary by 10–15% — always confirm against the unit's data sheet.
Worked example: a 16-tap brewpub
A realistic install. Walk-in in the basement, 45 ft from the bar with a 6-ft rise, standard insulated trunk through a typical-interior ceiling, 300+ pours/hr at peak.
Trunk heat gain. 16 lines × 45 ft × 5.0 BTU/hr/ft/line = 3,600 BTU/hr base trunk load.
3,600 BTU/hrAmbient correction. Typical interior (75°F) multiplier of 1.0× — no adjustment needed for this location.
3,600 BTU/hrPour load. 300 pours per hour during peak service adds approximately 1,500 BTU/hr to the chiller load.
1,500 BTU/hrSubtotal. 3,600 (trunk) + 1,500 (pour) = 5,100 BTU/hr before safety margin.
5,100 BTU/hrSafety margin. Add 25% for summer, dirty coils, future growth: 5,100 × 1.25 = 6,375 BTU/hr.
6,375 BTU/hrThe calculated load of 6,375 BTU/hr falls between the 1/2 HP and 3/4 HP categories. Always step up — spec the 3/4 HP unit. The 1/2 HP would run at 100%+ duty cycle on hot days, shorten compressor life, and lose temperature control under peak pour load. The 3/4 HP runs at a healthier 85% duty cycle with headroom for the customer to add taps later.
Common sizing mistakes
These show up on service calls month after month — most are spec-stage errors that lock in problems for the life of the system.
Sizing to the price target, not the BTU load
1/3 HP packs are cheaper than 3/4 HP packs, and an undersized unit looks fine on a hot August commissioning day for the first hour. Then beer warms up, foam complaints start, and the customer calls you back. Run the math first, then size the pack.
Ignoring ambient where the trunk runs
A 16-line trunk running through a hot kitchen ceiling pulls roughly 50% more BTU than the same trunk in a cool basement. Skip the ambient correction and you spec the same pack for both jobs — and one of them fails.
Forgetting pump head capacity
BTU capacity is one rating. Pump head is another. A pack with enough BTU for the cooling load may still have a pump that can't circulate glycol over a 60-foot trunk with vertical lift. Verify both capacities against the manufacturer spec.
Using the wrong glycol concentration
Glycol packs ship empty. The installer mixes propylene glycol with water on commissioning. Too much water freezes the bath; too much glycol reduces heat transfer. Industry standard is 30–35% propylene glycol by volume.
Oversizing "just to be safe"
A 1 HP pack on a 3,000 BTU load short-cycles the compressor — running for short bursts, shutting off, restarting. Compressors fail early under short-cycling. Right-size to load plus 25% margin, not load plus 100%.
Frequently asked questions
How do you calculate BTU load for a glycol power pack?
Total BTU/hr equals heat gain through the trunk line plus the pour load. Heat gain is lines × length × a per-foot factor (typically 4 to 6 BTU/hr/ft/line) adjusted for ambient temperature. Pour load adds 500 to 3,000 BTU based on activity. Always add a 25% safety margin.
What size glycol pack do I need for a 16-line trunk?
A typical 16-line trunk at 50 ft in 75°F ambient produces around 5,000 BTU/hr of heat gain plus pour load, which calls for a 3/4 to 1 HP glycol power pack with proper pump head for the run length.
How many BTU does one horsepower of glycol cooling produce?
Industry rule of thumb is approximately 10,000 BTU/hr per HP for glycol chillers operating at typical beer system conditions. Exact capacity varies by manufacturer and refrigerant temperature setpoint — always check the data sheet.
Can a glycol pack be oversized?
Yes. A grossly oversized pack short-cycles the compressor, wastes energy, and fails earlier. Right-size to BTU load plus 25–30% margin. Don't double-size as a safety move.
What glycol concentration should I use?
Industry standard is 30–35% propylene glycol by volume, mixed with deionized or distilled water. Too little glycol risks freezing the bath; too much reduces heat transfer efficiency. Use only food-grade propylene glycol — never automotive antifreeze.
How often should glycol be replaced?
Test glycol concentration and pH annually. Replace when concentration drops, pH drifts acidic, or visible discoloration appears (typically every 3–5 years for a well-maintained system). Top off the bath periodically as glycol evaporates and trunk lines absorb minor amounts.
Does a glycol pack need its own dedicated circuit?
Yes for any unit 1/2 HP or larger — dedicated 115V or 230V circuit per the data sheet. Smaller packs can sometimes share a circuit but check local code and the unit nameplate. Always GFCI-protect units in wet locations.
Recommended components for a long draw cooling system
The glycol pack is one piece. A complete long draw cooling system also needs the trunkline bundle, propylene glycol, and the accessories that tie it together.
Glycol Chillers
1/4 HP through 2+ HP glycol power packs from leading manufacturers, sized for direct draw and long draw applications.
Shop Glycol Chillers →Food-Grade Propylene Glycol
USP-grade propylene glycol concentrate. Mix to 30–35% by volume with distilled water for the chiller bath.
Shop Glycol →Chiller Accessories
Replacement pumps, reservoir lids, glycol filters, test strips, and the fittings you need to commission a pack on site.
Shop Accessories →1/4" ID Trunkline Bundles
Pre-insulated multi-product trunkline with 1/4" ID barrier beer lines plus integrated glycol supply/return.
Shop 1/4" Trunk →5/16" ID Trunkline Bundles
Higher-flow trunkline for longer runs or higher-volume beers. Common for stadium and high-throughput installs.
Shop 5/16" Trunk →3/8" ID Trunkline Bundles
Maximum-flow trunk for very high-volume venues. Used where line resistance must be minimized over long distances.
Shop 3/8" Trunk →Forced Air Cooling Systems
Blowers and air ducting that push chilled cooler air into the tower base, eliminating first-pour foam from warm tower bodies.
Shop Forced Air →Trunkline Accessories
End-caps, insulation, conduit, tie-wraps, and the parts that finish out a trunk run cleanly through walls and ceilings.
Shop Accessories →Beer Testing Equipment
Thermometers, pressure gauges, and refractometers for verifying glycol concentration and beer-line temperature on commissioning.
Shop Test Gear →Size it right. Cool it cold.
Foxx Equipment has supplied beverage installers for over 40 years — trade pricing, same-day shipping on stock items, and a technical team that knows the difference between a 1/2 HP pack that'll do the job and one that won't.
Foxx Equipment Company — commercial beverage dispensing equipment and expertise. BTU factors and HP capacities above are industry-standard averages, not guarantees; confirm against the chiller's data sheet at your operating setpoint before purchase. Contact a specialist to verify your glycol sizing.