HVACR318 – Refrigeration II

1. HVACR318 – Refrigeration II Ice Machines, General Information

2. Ice Machine Overview • All Ice Machines are Rated in pounds per hour. • Over 30 Manufacturers of Ice Machines • Each has their own unique design features.

3. Ice Appearance

4. Main selling points • There are two main selling points when it comes to ice machines; they are: • Purity • Clarity • These qualities are achieved by continuous pumping of water over the face of evaporator, which • Keeps air from being trapped; and • Keeps suspended solids from adhering to the ice.

5. Purity and Clarity • This differs from home refrigeration cubes, where water does not move and air bubbles cause cloudy cubes, along with unpleasant smell and taste.

6. Ice Machine System • Each manufacturer produces one of two types of ice: • Cubed • Flaked

7. Ice Cube Machines • Cuber water circuit - All cubers circulate water over the face of an evaporator using a water pump. • The temperature of this evaporator is below freezing. • Some of the water turns into ice and remains on the evaporator surface. • The rest falls back into the sump where it is re-circulated back to the evaporator. • The water pump is in constant operation while the ice is being formed.

8. Ice Cube Machines • Cuber water circuit, cont’d: • Plastic or tygon tubing carries water over the entire face of the evaporator • A means of distributing the water over the entire face of the evaporator is required. • Stationary spread bar • Oscillating bar • Rotating or agitating bar • Small diameter holes

9. Ice Cube Machines

10. Ice Cube Machines • Types of harvest • Hot gas (most common) • Hot water bath • Electric (very rare)

11. Ice Cube Machines • Harvest initiation types • Pressure • Temperature • Switching Arrangement • Probe switch • Timer Cams • A fixed number of cubes is made during each cycle (e.g., 60 or 120 cubes, etc.)

12. Ice Cube Machines • Most cubers drain remaining water via the sump at the end of each cube batch. • Remaining water consists of suspended solids and impurities. • Water is drained and new water replaces it. • If this is not done, mineral content will build up and clog water passages.

13. Ice Cube Machines • Most machines will have a mechanism for draining impurities at the end of each cube batch. For example, Crystal Tip dumps and flushes the entire system. • Most cubers will also cycle off the circulating pump during harvest cycle (e.g., Crystal Tip).

14. Ice Flake Machines • Flakers are more limited in design • Drum is submerged in water. • Inside of drum acts as an evaporator. • A film of ice forms on its surface. • The film is continuously scraped by an auger. • Ice is pushed or compressed out of the drum by the auger. • Ice then falls into the bin. • This machine runs continuously (no harvest cycle) until the thermostat opens.

15. Ice Flake Machine

16. Ice Flake Machines • Flaker water circuit • Water is held in a reservoir above the drum. • Float valve mechanism maintains the water level in the reservoir. • Water flows by gravity to the lower portion of the drum.

17. Ice Flake Machines • Flaker water circuit, Cont’d: • Auger turns approximately 25 rpm inside the drum (this is done with a motor and a reduction gear coupled to the end of the shaft). • Auger picks up water while turning. • Water is dispersed over the inside face of the drum and turns to ice.

18. Ice Flake Machines • Flaker water circuit, Cont’d: • As the auger turns, it scrapes the ice off the inside of the drum. • The shape of the auger lobes carries the ice to the upper portion of the drum. • Ice is compressed through a small opening where it is directed down a chute and into a bin. • As the float in the reservoir drops, the water level is made up with fresh water.

19. Ice Flake Machines • Flaker Ice, Purity and Clarity • Ice is cloudy, not clear. • Can have traces of discoloration • Can have odors • Can sometimes have bad taste

20. Ice Flaker Machines • Flaker Ice Purity and Clarity, Cont’d: • These traits are associated with the condition of the supply water, and the rate of water movement through the evaporator. Solids remain suspended and air is trapped. • For these reasons, filters and softeners are often used in the water supply lines of flaked ice that is used in drinks.

21. Ice Machine Circuits • All ice machines have three circuits: • Refrigeration Circuit • Water Circuit • Electrical Circuit

22. Refrigeration Circuit • The refrigeration circuit • Same as most other circuits. • Major differences are: • The shape of the evaporator determines the shape of the cubes. Evaporator Types include: • Flat Plates (Inclined or tilted) • Upside down cubes (shot glasses) • Cylinder shaped • Embossed spots

23. Refrigeration Circuit • Ice machines use a standard condensing unit that you would find on other low temperature systems. • Flow controls can be: • TXV • Capillary Tubes • AXV (Flakers only)

24. Refrigerant Pressures • Low side pressures generally correspond to a 15 to 20 degree evaporator temperature. • When the water is warm, the pressures are high. • As ice builds up, the pressures gradually drop into design range. • Example: R12 = about 5 degrees.

25. Refrigerant Pressures • Setting of the superheat should only be done when ice has begun to form on the evaporator. • Harvest cycles are short: 5 to 10 minutes. • Freeze cycles can be as long as an hour for large capacity, or 20 to 30 minutes for small capacity.

26. Newer Refrigerants • Refrigerants are slowly changing: • R12 (most older machines – need to use drop in replacement) • R502 (high capacity) • R22 (Some split and newer machines)