I need to design the roof structure for a sports facility. I have no information with regard to HVAC design at this stage. Also, the HVAC may change in future. Thus I don't know what load to apply to the structure. I intend to give the HVAC and electrical engineers a weight envelope in which they can operate. Is there a standardised list available which would give an indication of what loads I can assume for this? I don't think what you are looking for really exists, in terms of a standardized list of HVAC/services loadings. Building codes don't usually specify dead loads, probably because they are, in principal, known. Typically only imposed (live) loads are specified. From the buildings I have worked on the services loadings were essentially copied from similar buildings/agreed with the HVAC contractor. There are some generic guidelines available. The Structural Engineers Pocketbook uses 0.15 kPa for ceiling and services The Arup Structural Scheme Design Guide has 0.25 kPa nominal and 0.4 kPa for HVAC (I only have an old version so don't know if that has changed...)

The Steel Construction.info site (which is a pretty good resource) has 0.25 kPa as being a typical services loading. ASCE 7-10 in Table C3-1 lists a dead load of 4 psf as a minimum 'mechanical duct allowance'. air conditioning unit indiaWhich is likely where the 4 psf (0.19 kPa) mentioned in the comments originally came from and is consistent with the above references.wiring for air conditioner units The Designing Buildings Wiki has 0.85 kPa for Raised floors, ceiling and building services equipment combined.my outside ac unit fan not working Hard to say if these would be applicable to your situation. you would need to deal with heavy equipment (condensers, fans, heaters, etc) which are not considered in these loadings.

The HVAC contractors tend to want to put holes all over your structure as well, so it would probably save time and money to consult with them early in the design and sort out what they need. In my experience, appealing to codes that may or may not have been intended for your specific application is a costly business practice. There is no guarantee a load rating will be sufficient for the variables involved. If I were in your situation, I would contact the intended HVAC company or another prominent HVAC company in you area. Take one or two of the engineers out to lunch and ask them to review your design as a colleague. They will immediately be able to see the red flags, be able to give you a model number for the largest possible air handler for that size building, know the capability of cranes in your area, and will be 100% familiar with the codes in your area. They will be glad to help because in a couple months they will need to ask you a roof structure question for one of their unrelated projects.

Even if you do find the exact code specification you are looking for I would encourage you to reach out for those kind of connections to experts in your community.Browse other questions tagged structural-engineering hvac or ask your own question. Sex crimes are soaring in NYC Never Miss a Story Get The Post delivered directly to your inbox By clicking above you agree to our Terms of Use and Privacy Policy. A few years ago, a student of mine told a funny story in a home energy rater class. He was an HVAC contractor and said he was installing a new air conditioner for an elderly woman. As he was explaining things to her, he mentioned that they would be installing a 4 ton unit. "Oh, my," she said. "How are you going to get something so big into my backyard?" The confusion here is completely natural. HVAC and home energy pros find this story funny because when you say an air conditioner is 4 tons, we know it's not weight. It's a number that tells how much heat the air conditioner can remove from the house in an hour.

(Let's ignore the issues of nominal vs. actual capacity and AHRI de-rating.) A 4 ton air conditioner is one that can remove 48,000 BTUs of heat per hour from the house. For most people, though, 4 tons means 8000 pounds. (A BTU is a British Thermal Unit, approximately the amount of heat you get from burning one kitchen match all the way down.) Most pros also know how such a common term as 'ton' turned into a bit of HVAC jargon. Before Willis Carrier invented the modern air conditioner, people used to cool buildings in the summertime with ice harvested from rivers and lakes in the wintertime. A Green Homes America article quotes ice production figures from the 19th century Ice and Refrigeration journal, indicating that the 1890 crop from the Hudson River was about 4 million tons. OK, so people used to cool and refrigerate with ice. How does that equate to air conditioning capacity in BTUs per hour, you ask? Well, let's get quantitative and find out. When ice is below freezing and it absorbs heat, the temperature increases.

When ice is at its melting point, 32° F, and it absorbs heat, its temperature doesn't change. If you've had a physics or chemistry class, you may recall that the amount of heat needed to melt ice is called the latent heat of fusion. In Imperial units, that number is 143 BTUs per pound. That's actually a lot of heat to pump into a pound frozen water. Once the ice is melted into liquid water, it takes only 1 BTU per pound to raise the temperature 1 degree. So if you've got a pound of ice at 32° F, you put 143 BTUs into it to melt it completely. Then it takes only 180 more BTUs to raise the temperature of that pound of water from 32° F to 212° F, the boiling point. Anyway, getting back to our main discussion, if you have a ton of ice, it takes (143 BTU/lb) x (2000 lbs) = 286,000 BTUs to melt it completely. You could do that in one hour or 10 hours or a year, depending on how quickly you pump heat into it. Somewhere along the line, though, someone decided to use 1 day—24 hours—as the standard time reference here.

If the ice melts uniformly over the 24 hours, it absorbs heat at the rate of 286,000 / 24 hrs = 11,917 BTU/hr. Rounding that number up makes it a nice, round 12,000 BTU/hr. In air conditioning jargon, then, a ton of AC capacity is equal to 12,000 BTU/hr. If you're wondering how this term got institutionalized, it was probably the usual way. People in the industry start using it, and then the professional organizations make it official. An architecture website has a quote from 1912 that claims the American Society of Mechanical Engineers standardized it. It sounds likely, but their numbers don't work out, so I'm gonna go with Honest Abe on this one and remain skeptical. For the fearless: If you want to read some funny HVAC banter on this topic, check out this thread in the HVAC-Talk forum. And if you figure out what 'heat of zaporization' is, let me know! The Magic of Cold, Part 1 - How Your Air Conditioner Works It's Called an Air Conditioner — Not an Air Cooler!