HVAC Equipment Start-Up

We are going to start a four part series on the procedures that need to be followed for effective equipment start-up after the installation is completed. The section will be as follows:

1 - Start-Up Procedures

2 - Test & Balance

3 - Commissioning

4 - Training & Documentation

Although the Start-up procedure is one of the most basic requirements of a new system, sometimes during the rush and excitement of installing a new system, small areas can be overlooked and can lead to early equipment failure.

Each piece of HVAC equipment has a checklist which has been provided by the equipment manufacturer. These must be not only followed, but in some cases initialed and date stamped, via fax or email, to start the warranty, no start-up, no warranty. With as tight as companies must be run in the current economic conditions, some companies are using this as a loop hole to get out of providing parts which for all intents and purposes should be covered. Some items covered in the checklist may seem obvious, but it is usually the "obvious" items which become overlooked.

Below is an example of just the requirements for the motor start-up, not even to mention the rest of the machine:

Compare the drive model number to what was ordered.

Be sure the following are for the same voltage: Drive, Power Line, Motor

Record the motor data: Voltage, Frequency, Full load current, Full load speed, Power

Check motor wiring

Verify appropriate short circuit protection is provided at the input of the drive.

Measure phase to phase line voltage and ensure measured voltage is within drive specification

Measure phase to ground voltage.

Drive mounting clearances observed.

Check all wiring connections are secure.

Each drive grounded individually, no daisy chain grounds.

Separated runs for input power, motor power, and control wiring.

Check the motor’s rotation from the drive.

Accelerate the motor to full speed and verify operation.

Ensure that the drive follows run/stop commands from the system.

As you can see from the above list for just one of the drive motors, there are a lot of check and balance to ensure the system is operating correctly. If a system is not operating correctly, then these problems can be caught early and correct before the lead to failure.

While some of this may look overwhelming, if you take your time and each item by itself, then there is no reason for this not to be done throughly and correctly. Make sure that if you are having a new system installed that you receive this paperwork from your contractor before signing off on a completed install.

Remember, a no mechanical system should ever be considered to be running unless it has gone through the start-up procedure. Thanks for reading, and we'll see ya on the roof!

How do items exchange temperatures

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I know we said that we would keep this information pretty basic, so don't get scared off just yet. The latter two (2) shown above used extensively throughout your HVAC equipment. Heat always wants to find and equal, either through warming other objects, and thereby cooling itself, or taking heat from another object in order to equalize itself with the surroundings. We are going to take each of these examples above and break them down to their basics. We will be using food to explain these examples because, well, I like to eat and now a fair amount about food :^).

The first example is Radiation. Radiating transfers heat the source to the first solid object the heat waves encounter without heating the air around it. This differs from transferring heat to objects through direct contact, like conducting or through air, like convecting. When you use a microwave oven to cook your food, this is an example of radiating. The "Micro Waves" go through the air without heating air and solely heat the object in the oven. Radiant floor board heaters are a good example of Radiant heat. As the coils in the heater gain temperature, and typically begin to glow, they heat the first object in which the heat waves contact.

The next example is Conduction. Conduction uses direct contact to transfer heat between sources. Think of Conduction as taking your hot food out of the microwave and holding the plate in your hand. You can feel the your hand holding the plate getting warmer and the food is now becoming cooler. Your plate is now starting to condition the food, much the same way and air conditioner conditions the air. The heat exchangers use this method to transfer heat. On some pieces of equipment, there are two water tanks, one is for cooling, one is for heating. These tanks are filled with water and metal plates. As the unit calls for warmth, the metal plate absorbs the heat from the water, and transfers it into the furnace.

The final example is Convection. The easiest way to describe convection is now that your hot plate of food is sitting on the counter since the plate became to hot for you to hold because of the previous method. You now begin to blow on or fan your food to cool it down. Your are passing cooler air over a hot object which is convecting into the air above it and therefore you are now conditioning your food. Your air conditioner uses convection throughout the system in the form of air, water, and refrigerant inside the ductwork and the equipments piping. As you feel the air come out of your ductwork, this is the most apparent example of convection in your HVAC system.

Next time you cook some food, take a moment and look at all the conditioning of the food you just did. Once you break it down into individual steps, it really is amazing and hopefully you have found this explanation to be informative and easy to understand. Next we will look at the specific components and selection. Thanks for reading, and we'll see ya on the roof!

Ventilation Design Basics

HVAC systems provide heating, ventilation, and Air Conditioning to buildings. Whether it is an office building with 300,000 square feet or a Japanese Steak House, the principals are all the same.

I have placed a diagram to the right which may help give you a better idea of the system layout. Air flows into ductwork from the building through ceiling registers and mixes with air pulled in from the outside at the air filter section. Next you have a blower which moves the air across two sets coils, one to cool, for the summer, and one to heat, for the winter. From there the air goes back into the building through ceiling diffusers.

The way you heat and cool the air is where a lot of people begin to get lost. But, this is typically because the person explaining is too scared to actually help and if they teach you, they are afraid you will not need them. What that does is create an cloak of magic that seems to engulf Ventilation system design. Whether trying to remove grease, smoke, heat, dust or airborne bacteria from an air stream the guiding principles are all similar. One of my goals here is to help remove the mystery and help educate, any feed back that can be given on these articles would be greatly appreciated.

One of the key elements you must remember when designing a well balanced air system is that you are designing for people in the real world and not in a laboratory. Engineers are great at coming up with ideas which work in theory, but then it leaves the customer scratching his head trying to understand why their restaurant is filled with smoke, the kitchen floor is greasy, and why his customers can not open the door to come in and eat. Same idea with office buildings, you can have trouble opening doors, residual moisture on windows, people constantly sick, and no one is comfortable. All because one person over looked the human element.

I do not want to overwhelm anyone so we will end this lesson here. Next we will look at how equipment conditions. Thanks for reading, and we'll see ya on the roof!

Environmental Systems Check List

To kick off our first Blog, we want to review the basics for HVAC Maintenance. When looking at your Environmental system, you should always be aware that like a car, it will require maintenance. The level of maintenance you choose to do will directly effect your investment in the system. The following is a good 20 point inspection which should be done quarterly for Roof Top or Split Systems:

1 Exposed Contacts

2 Check Motor Amps

3 Safety Devices

4 Lubricate as necessary

5 Blower Bearing Play

6 Condenser Fan Bearing Noise

7 Condenser Fan Blade Condition

8 Thermostat Operations

9 Condensate traps, lines, and pans

10 Outside Air Dampers

11 Fuse Holders

12 Capacity Controls

13 Exposed Piping within Sight of Equipment

14 Blower Wheel

15 Visual Signs of Leaks

16 Oil Color and Level

17 Equipment Panels

18 Belt Condition & Tension (replace yearly)

19 Visually Check Coils

20 Air Filters (replace quarterly as per agreement)

As we add more articles we will cover not only the general equipment design, but also what is required for larger more complicated and control schemes.

Thanks for reading, and we'll see ya on the roof!