What is the purpose of a cold room pressure valve?

What is the purpose of a cold room pressure valve?
Keskinso Refrigeration | Contact: 0537 917 16 95 |www.keskinso.com

1. Introduction: The Overlooked Hero in Cold Room Systems

When installing a cold storage room, everyone talks about the compressor, evaporator, and panel thickness. But there's one part that directly affects the system's lifespan and safety, and that nobody notices until it fails: the pressure equalization valve.

A cold room operating without a pressure valve creates a vacuum effect inside every time the door is opened. Doors not opening when pulled, torn seals, and panels bulging inwards are all due to the absence of this small part. In this article, we explain the function of cold room pressure valves, their types, installation, and malfunction symptoms, based on over 20 years of field experience.

2. Basic Physics: Why Does Pressure Change in a Cold Room?

The Ideal Gas Law is simple: $P \cdot V = n \cdot R \cdot T$ Volume in the cold roomConstant temperature.when the pressure dropsIt also has to fall. In practice, sudden pressure differences occur in the following situations:

Situation	Please	Pressure Difference
Initial Cooling	A room at +25°C will drop to -18°C in 4 hours.	The vacuum inside is approximately 1500 Pa compared to the outside.
After Defrosting	The evaporator heats up to +15°C, and the fans start working.	Instantaneous positive pressure inside.
Door Open-Close	Hot air enters, then quickly cools down.	200-400 Pa vacuum at each opening.
Product Entry	The palletized hot product enters the room.	Steam + rapid cooling = vacuum

1500 Pa may sound like a small amount. But that's the force it applies to a 10 m² door:

$F = P \times A = 1500 \, \text{Pa} \times 10 \, \text{m}^2 = 15000 \, \text{N}$

So you need to pull 1.5 tons to open the door. That's why when the staff can't open the door, they pry it open with a shovel, and the seal tears.

3. What exactly does a pressure valve do?

The pressure equalization valve is a bidirectional flap system designed to maintain the pressure difference between the cold room and the outside environment at ±10 Pa.

Its 3 main tasks:

Vacuum Release: When negative pressure builds up inside, it draws in controlled air from the outside. The door opens easily, and there is no panel pulling.
Positive Pressure Relief: If the pressure inside increases during defrosting or hot product inlet, it expels excess air. It prevents the panels from bulging outwards.
Energy Conservation: It doesn't stay on continuously. It only switches on when the pressure difference exceeds a threshold value. This minimizes heat loss.

In short: The pressure valve allows the cold room to "breathe".

4. What Happens If There Is No Pressure Valve? Field Results

Problem	Reason	Cost
The door won't open.	The internal vacuum seals the door to the frame.	Loss of workforce, hinge breakage.
panel bulging	A 100mm panel cannot withstand a 2-ton load.	Panel replacement: 1 panel 8000₺+
Gasket rupture	Removes the gasket from its housing using vacuum suction.	Heat leakage causes a 20% increase in electricity bills.
Lifting of the floor screed	Negative pressure pulls the ground upwards.	Breaking up and re-pouring the floor: 50,000 TL+
Evaporator fan malfunction	The fan works against the vacuum and burns out.	Service + parts: 6000₺+

At Keskin Soğutma, 34 out of the 120 repairs we serviced in 2024 were directly caused by the absence of a pressure valve. Failing to install a 1500 TL part results in a cost of 40,000 TL.

5. Types of Pressure Valves: Which One is Right for Your Room?

Not all valves are created equal. Choosing the right one is essential, considering room temperature and volume.

Valve Tipi	Working Range	Room Volume	Feature	Area of Use
Mechanical Clothing	+15°C / -5°C	0-50 m³	Spring-loaded, without heater.	Positive cold storage rooms, vegetable market
Heated Mechanical	-5°C / -25°C	20-150 m³	8W-16W resistor	Meat and dairy product warehouses
Electric Dump Truck	-25°C / -40°C	100-1000 m³	Motorized, with sensors	Shock freezing, frozen product storage
Mini with diaphragm	+15°C / 0°C	0-15 m³	Small, quiet	Rooms behind the supermarket aisles

Important Rule: If your room is -18°C, you must choose a model with a heater. Otherwise, ice will form around the damper, the valve will freeze, and it will not function. In a -40°C blast freezing room, a model with a double heater and thermostat is required.

6. How Many Valves Are Needed? Calculation Formula

The rule is simple: 1 standard valve for every 100 m³ of volume. But the details matter.

Account Steps:

Room volume: Length x Width x Height. Example: 5x4x3 m = 60 m³
Door traffic: Add 1 valve if more than 50 doors are opened per day.
Defrost type: If electric defrost is available, +1 valve. If hot gas is used, this is not required.
Product input: +1 valve if more than 1 ton of hot product enters daily.

Example: 200 m³, -18°C meat storage room, door opened 80 times a day, with electric defrost.
Requirement = 200/100 = 2 units + 1 traffic valve + 1 defrost valve = 4 units of valves.
It's best to distribute two of them against opposite walls and two against the ceiling.

7. Assembly: 5 Critical Points

Incorrect installation is worse than having no valve at all. It will freeze, leak, and not work.

Height: Install it at the top of the room, 20-30 cm below the ceiling. Warm air collects at the top, and the vacuum is most noticeable at the ceiling.
Orientation: The exterior side should face a window protected from rain and wind. Protect with a range hood if possible.
Opposite Installation: In rooms larger than 100 m³, place the vents on opposite walls. This ensures air circulation and prevents congestion at a single point.
Heater Cable: Be sure to connect the heating element below -5°C. Remove a separate 2A fuse from the panel. Set the thermostat to -5°C.
Slope: Give it a 2% outward slope. This will prevent condensation from leaking inside after defrosting.

8. Maintenance and Malfunction Symptoms

Pressure valves require no maintenance, but a check every 6 months is necessary.

Checklist:

Does the flap move freely by hand? If it gets stuck, there may be ice or powder involved.
Is the heater working? You should see 0.03-0.07A with a clamp meter.
Is there any frost buildup around the seal? If so, the heating element is weak or the door is being opened too frequently.
Is the outdoor mosquito net clogged? Dust can't get air when the bag is blocked.

3 Signs That Make You Say "My Valve Is Faulty":

If the staff says "the door sometimes doesn't open".
If the door seal keeps tearing/coming loose.
If there is a visible inward/outward bulge in the panels.

If you experience these symptoms, don't wait for service. Daily pressure differences will damage the panel.

9. Frequently Asked Questions

Q1: Does the pressure valve increase electricity consumption?
No. The heated model is 16W. If it runs 24 hours a day, that's 11 kWh per month = 35₺. Cold air escaping from a torn seal without a valve would cost 400-500₺ in electricity bills per month.

S2: I bought a prefabricated room, how can I tell if it has a ventilation system or not?
Look for 10x10 cm or 20x20 cm plastic-covered vents on the walls or ceiling of the room. From the outside, you should see a mosquito net. If not, your plumber hasn't installed them.

S3: Is a -86 ULT deep freezer also needed in the room?
Yes, and a pair. At -86°C, the pressure difference becomes very aggressive. You must use a dual-resistance, body-heated industrial type heater.

S4: Instead of a pressure valve, how about we drill a small hole in the door?
Absolutely not. A constantly open vent draws in heat and moisture 24/7. Moisture = frost buildup = longer defrosting time. The damage exceeds 1000 TL per month. The vent should only be opened when needed.

10. Conclusion: Small Pieces, Big Guarantee

A pressure valve, costing 0.5% of the cold room installation cost, prevents 30% of total failures. It extends the lifespan of doors, panels, floors, and evaporators. It ensures personnel safety.

Summary Review:

If your room is colder than -5°C, choose a model with a heater.
Plan one unit for every 100 m³. Increase the number if there is traffic.
Install it close to the ceiling, with an outward slope.
Check the damper and heating element every 6 months.

At Keskinso Cooling, we provide pressure valve selection, installation, and commissioning services suitable for your project. If your existing room does not have a valve, we can send our team for a site survey.

Keskinso Cooling – Industrial Cooling Systems
Web: www.keskinso.com
Get immediate information and a quote: 0537 917 16 95

Operating a cold storage room without a pressure valve is like driving a car without a seatbelt. It seems unnecessary until you need it. The day you don't have it, you'll wish you had.

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