You don’t want your equipment cycling on and off. Not only is it not efficient, but it’s hard on the equipment and uncomfortable for the building inhabitants.
https://www.load-calculations.com/what-is-acca-manual-s-.html
Some takeaways from the load-calcualations.com website include the following:
- A Manual J load calculation is useless without the Manual S to accompany it. The Manual S provides the equipment specs and sizing to compare against the Manual J.
- The Manual S lays out parameters including the fact that air conditioning cannot be more than 115% of the (total) calculated cooling load (heat pump cooling is set at 125%) and heating equipment cannot be more than 140% of the calculated heating load OR the next nominal size that’s available to cover the heating / cooling loads.
- Do not use the AHRI Certificate for equipment sizing. The sizing needs to come from the OEM data. AHRI sets their test conditions to 80F indoor temperature and 95F outdoor. For example, in Basalt, Colorado, the (summer) indoor design temperature is 75F and the (summer) outdoor design temperature is 85F. AHRI will yield performance results from what’s actually needed.
- The CFM that is calculated in the Manual J is the blower capacity needed.
Manual J calculations have been required by the I-codes since 2006, yet contractors still are using rule of thumb data that will most likely result in equipment that is not sized correctly.
Full Circle will perform your Manual J load calculation and will work with your mechanical subcontractor to dial in the Manual S and get equipment that will operate efficiently, saving you money and increasing indoor comfort!
Full Circle Construction Services 