ASHRAE Standard 90.2

[CRG]

I am upgrading an all air heating system with the addition of air conditioning. It will be a 7 ton split system for a small convenience store. The summer design temp is 68 degF DB and 58 degF WB. The corporate facility engineer stated that an equipment installer in my area told him that the code required an economizer. For this location it would be awkward to install new ductwork for an economizer. I have always specified economizers for new air handlers in our Municipality; however, the issue requiring economizers for retrofits is new for me. I quickly glanced through ASHRAE Standard 90.2 and IMC (International Mechanical Code) and did not see the code requirement. I do not have a copy of the “International Energy Conservation Code” that is referenced in IMC. I have sufficient outside air to meet the ventilation code requirements. From a practical point of view, an economizer makes sense; however, first cost is very important. Can someone point me to the general area where the code requires an economizer on a retrofit?

Thanks in advance for any help or opinions regarding this type of retrofit.

 

[lilliput1]

ASHRAE 90.1-2001 Paragraphs 4.1.2 and 6.3.1 See also Exceptions to 6.3.1

 

[CRG]

Thank you lilliput1. I am not sure why I grabbed 90.2 (residential) instead of the appropriate 90.1 standard. One would think that the title which is printed in the largest font size is the first thing I should look at.

Regards,
CRG

 

[Promero44]

Try a software called ComCheck-EZ 3.0. This software is based on ASHRAE 90.2. It will help determine if econonmizers are required for your application.

The software is free. Google search it and download for free.

 

[ChasBean1]

1. 7 tons for a "small" convenience store with those summer design conditions??? Seems big.

2. Economizer typically operates when it's cold out; so you don't have to use mechanical heat when return air is available.