Selection of HVAC Capacity for a New Plant

I would like to request you that kindly guide me deeply please.

How can i calculate the heat load?

I have no idea

GA! Several years ago my boss did a big expansion of his house. I am a refrig guy, not an AC guy, so I had a former associate, who is a wiz at manual J and manual D do the load for me. He said just under 3 tons. Boss: "I don't want to be hot when we have company. Put in 4 tons." Me: "That may be too big to control the humidity. (Location is in deep south USA) Lets see if we can get a 2 stage so we can get adequet run time." Boss: "Too expensive. Freddie says his unit will do it."

I could not walk into that house for the humidity. (He sold it. so not my problem anymore)

In other words, let the machinests machine, the electricians electrify and get someone who knows what they are doing to calculate the A/C load properly. -- JF

Try this.

Guide you deeply? You need professional help, if you've never done this before.

If you do this yourself, I predict that you will grossly under-size the system because you won't want to spend the money necessary to properly size and install an adequate system.

Good luck.

Here is a good source: http://www.gobookee.net/krack-refrigeration-load-estimating-manual/

Did you google this?

I have a hard copy, but I Googled to find a possible online source.

I like that website.

It depends on what type of manufacturing and how large the building is....In some environments 100% fresh air is required, in some others a portion of the air can be recycled....In some manufacturing processes the humidity must be closely controlled, in some dust is an issue...some areas may need to be exhausted.....It's never as simple as it seems...It's not just cooling the air, it's controlling the environment....

Dear SolarEagle

Yes u r absolutely right, i am in latching relay manufacturing company and here we have a limit of max 65% of RH.

Not more then 65% of RH

But is there any substitute of dehumidifier to controlling RH without dehumidifier.

One can reduce the RH by raising the temperature and raise the RH by reducing the temperature. Is that what is needed?

yes but if i will increase the temp then sweating will start and it will not good for our product that's why i can't increase so much amount of temp but can you please tell me upto what level of limit i can increase the temp for maintaining the 65% specially in rainy season.

2 floor building (GF + FF), Area - (1415x1060)sq-ft for one floor, approx 20 manpower work on the G Floor & approx 80-100 manpower work on F Floor, wall thickness is approx 9", roof thickness is approx 9",

is any others factor to calculate the capacity for the HVAC then plz ask and guide

and we also have to maintain the RH under the limit of 65%.

Kindly guide

a 200 ton built up system should keep that pretty cool, I'd go with two twin 150 HP open drives, 480 V of course powering twin 200 ton Tranes with unloaders

HVAC designing needs to be done carefully and with professional help.

The HVAC operating costs will depend on how system is designed. Occupants comfort and exposure to pollutants also need to be taken care of.

Follow standards like ASHRAE 55, ASHRAE 62 and ASHRAE 90.1 for proper design.

For any new building project, HVAC designing is the most important criteria when you consider operating cost, people working in the area and productivity.

Never try to save on the proper design procedure.

i am in the field of hvac since 1 year,

Plant heating load calculation comprises of many points but approximately following points can approximately calculate the heating load:-

1) Plant Size:- l*b*h ; 125 sqft with height 10 ft = 1 TR

2) Machine Load:- installed machine KW* no machines: with conversion factor -1TR=3.5KW

3) No of occupants :- No of persons*200W(each person)

4) HEAT losses:- No of windows, doors, curtains.

Hope this will help you to calculate HVAC capacity:-

Form More information :-

Vipul Sharma

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I've managed several HVAC, refrigeration and steam projects and this was my typical thought process.

1. I'll find the HVAC&R firm I would like to have do the work and then contract them to design the project (not free) and put together a detailed "Scope of Work" with preliminary P&ID's and process flow diagrams - that I now own and can freely distribute.

2. Have this preferred contractor and at least two other companies bid the job based on the detailed project package - so you are comparing apples to apples - and the bids are like kind - otherwise purchasing will reject them.

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Basic info from the web ..................

Most HVAC contractors, home energy raters, and others in this field know about Manual J. Many people even know about Manual D, which describes how to design the duct system. Not so many, however, know about the missing links - Manual S and Manual T. If you want a properly designed HVAC system, you have to go through the whole process in all four protocols: J, S, T, and D. (It's easy to remember the order. As a friend of mine says, first J, then STD.)

Here then is a brief description of each manual.

Manual J

This one is for determining how much heat the house loses in winter and gains in summer. You do this room-by-room for the whole house, which allows you to determine how much conditioned air each room needs for both heating and cooling. It factors in all the surfaces of the building envelope, with their areas and insulation levels. Each wall is given its proper orientation, because windows and doors are attached to them. Other important data include the location and tightness of the duct system, the infiltration rate of the house, the internal loads (appliances and people), and where the house is located.

The results specify the BTUs of heat lost by each room in the winter and gained in the summer. The heat gain is split into two parts: Sensible (related to temperature) and latent (related to humidity). The heat gained or lost in a room then determines how much conditioned air that room needs, in cubic feet per minute (cfm).

Manual S

Once you know the amount of conditioned air necessary in each room, you have to select the equipment. What air conditioner, heat pump, furnace, or boiler are you going to install? With forced air systems, this part is critical because every piece of equipment has different characteristics - sensible and latent capacities, the amount of air moved, and the static pressures being the key ones for the next stages.

Manual T

From the room-by-room loads and cfm requirements, you can determine how to distribute the air in the room so that you get enough to meet the needs (the higher of the heating and cooling cfm requirements from Manual J). The questions you answer here are: Where will the supply registers, diffusers, or grills be located? Where will the return grills be located? What type of register, diffuser, or grill will you use? How big does it need to be?

Good choices here will eliminate problems of feeling drafts from the moving air or having inadequate mixing of the air. It's possible to get enough conditioned air into a room but still have it uncomfortable because all the air just sits at the register.

Manual D

Finally, once you know how many cubic feet per minute of conditioned air you need for each room, what equipment you're using, and how you're distributing the air in the room, you can design the duct system. Here you look at the location of the air handler, the distance to the ducts, how many turns the ducts have to make, and how much air needs to be delivered. The type of duct has a big impact on the results, as sheet metal ducts have a lower friction rate than flex duct or rigid fiberglass duct board.

Basically, with Manual D, you're trying to balance the delivery of the correct amount of air against the friction rate of the ducts and the static pressures in the system.

Pulling It All Together

When you get all four manuals done and have a well designed HVAC system, the result can be a high performance system that's more efficient and comfortable than what's typically installed. Of course, you can have the best HVAC design in the world, but if it's not installed as designed, your performance goes out the window. That's why it's a good idea to have every new system fully commissioned - and that's the topic for a future article!

Sir,

I can't and won't design a system for you, nor can I size it. However, I can tell you the factors to consider in a design:

• The amount of insulation (if any) in each of the walls and the roof.
• The orientation of the building.
• The surface area of each wall, window, door, roof, etc.
• The number of workers and where they are in the structure.
• The electrical loads being consumed--this adds to the total heat load.
• The amount of thermal mass--is this a mass-construction building with thick concrete walls or a light-construction building with steel frame and siding, or something in-between.
• The amount of ventilation required to maintain a healthy workplace and replace air that is removed by processes.
• The relative humidity and temperature you must maintain at any location.
• The maximum temperature your design must be able to handle.
• The maximum amount of humidity/moisture you must remove from the air--not only from outside air as it enters, but from processes/sources within the building.
• Required/desired number of air changes per hour.
• Available budget.
• Competence of the installer.
• Competence of the management.

There are other factors also, but this list should tell you how big this question is and how easy it is to make assumptions that send you wrong.-JMM

First of all thanks to all of you to share your experience here with us

I know that it has not a short answer or discussion but nothing is impossible to understand with ours right efforts and with the help/guide of superiors.

May we discuss more on this topic? Its a request to all of you that kindly guide me more on it.

Can u share any online calculator for this or any free software for it.

Thanks & Regards

J Mueller has guided you correctly. However, Heat load calculation is a detailed process for each room/condition & an intricate process involving several factors with data available with professionals. I have designed HVAC system for various factories & can give you general guidance(watches, pharmaceuticals, automobiles, printing, food products, beverage etc). Only proper method is to ENGAGE A LOCAL AC CONSULTANT with experience in related industry, to ensure a proper techno commercial design. Several clients in India go directly to contractors (to save consultant's fees) end up getting fleeced with installation not working

I have designed air conditioning systems for various type of industries. To achieve an economically & technically viable design of any capacity, you definetly need to hire a consultant along with an architect & provide building drawings, equipment & operational details for each area, preferably some one closeby. Do not waste your time in doing yourself