When purchasing a cooling unit for your Le Cache wine cabinet, there will be questions along the way, especially from the Cooling Unit Buying Guide for Wine Cabinets. Here’s a great one we received recently, along with our response.
How were thermal loads calculated in the diagram?
Question from customer:
For the 5200 Le Cache wine cabinet, the 55°F table shows the thermal load increasing by 161 BTUH for each 5°F increase in ambient temp. If I work backwards and calculate the thermal load at ambient temps of 65, 60, and 55°F I get 897, 736, and 575 BTUH respectively. There should be zero thermal load at 55°F ambient temp, so where does the 575 BTUH come from? This is more than half of the cooling capacity of the 1800QTL.
If I do the same calculation for the 1400 cabinet, the 55°F ambient number works out to be 424 BTUH, so it does not seem to be consistent.
Perhaps you could explain the calculation methodology so I can make a more informed choice of cooling unit?
Thermal load calculation methodology
Answer from Le Cache wine cabinets:
- The graph is non-linear; ie at the lower ambient temps, the graph is steeper, and as ambient temps get warmer, the slope becomes more linear.
- The thermal load consists of 5 main components: Transmission, Internal, Infiltration, Product and Safety. For the 5200 wine cabinet, the components lay out as follows.
- Transmission load is the temp load from the outside environment. At 55 ambient, the transmission load is 0.
- Internal load is the heat generated from the cooling unit itself and a light, both assumed to be on 24/7. Therefore, this load number doesn’t change as ambient temps increase. The internal load of the cooling unit is 170 BTUH, and the internal load from the light is 69 BTUH.
- Infiltration load is the latent load from moisture infiltration. At 55 ambient, the infiltration load is 24 BTUH.
- Product load is the load from the wine bottles. We assume 8 bottles at 80 degrees are added every 12 hours. (Obviously this would never happen, but we wanted to be conservative.) At 55 ambient, the product load is 46 BTUH.
- Safety load is our cushion. At 55F, the safety factor is 31 BTUH.
When you add the components, they should sum to 340 BTUH at 55 ambient. In 5 degree increments, the sum increases to 617 BTUH at 60 ambient; 811 BTUH at 65 ambient and 1058 at 70 ambient.
Want to know more? Read the buying guide to find your own wine cellar cooling unit online at IWAwine.com.