The plant engineer has received a number of complaints that the factory area is just too hot. She called the HVAC contractor the company normally uses, and they are booked solid for the next three days. She called another contractor and they said four days. Then she called you.

You’ve been at this plant only two months, but so far, you’ve done a good job as the Electrical Maintenance Manager. Thus, while she was waiting for you to arrive, she decided to help you by tapping the system to get information on the plant’s HVAC and how it’s laid out.

Most of the chillers are 20-ton roof units, ranging from six years old to eight years old. There’s a row of condensers along the south side of the main building. The records show the HVAC contractor has been performing spring and fall maintenance. There have been no service calls or maintenance calls other than those, going back at least three years.

You don’t have training or experience in HVAC, but she really wants your help with this. What are some things you should look at?

Answer to Quiz

You can probably rule out things like a mismatch between the chillers and the roof curbings, as that sort of thing would already have been discovered by the HVAC contractor. Don’t go down a rabbit hole of chasing structural issues, as they are unlikely at best.

First, check things that are not part of the HVAC system itself. Check the building envelope for major air leaks. Walk around the entire perimeter inside and look for gaps in the wall, a wall vent stuck open, or a door that is ajar. An appliance plant had “hot shop” complaints all summer long, and it turned out to be a small section of the exterior wall just wasn’t there; a narrow length of siding and insulation had been removed as part of some project and simply not put back.

Look at vents. Are any automated vents stuck open and leaking heat into the building? Are any hot process vents closed and preventing heat from escaping? Are vent fans working? Is insulation missing from barrel heaters, dipping pots, or similar equipment? Is there any non-essential or off-season process heating equipment running? Finally, ask operations if any hot process operations can be scheduled outside the hottest times of the day.

Now you can move on to doing non-expert checks of the HVAC system. Start by checking the airflow and circulation. Check all interior return vents. If there is not a list of these, go through the building drawings and make one. Look for anything that is interfering with airflow to these — stacks of boxes, a production machine that was moved in the past few months, work in progress, raw materials, etc. The do the same with any outside intake vents (aka, “make-up air”), but in this case also look for things like vegetation, trailers, and pallets.

Cold air vents can also be blocked, diffusing the air instead of circulating it. This will cause hot and cold spots in the plant. It could be that all of the problems are in the hot spots created by this issue. As you walk these down, record the ambient temperature at each “compass point” plus roughly the center in each area or room being surveyed.

Then check each HVAC unit. The goal here is to find all simple problems with each one. You want to ensure each unit is online and contributing to the cooling effort. If one unit is down, the remaining units probably cannot keep up. As you go, record what you check so the HVAC contractor doesn’t waste time duplicating your work.

 The first thing to check is that its disconnect is closed. Check these also:

• Is it running? If it is running, you have confirmed that it runs. If it is not running, it might simply be off for the moment; check the output line to see if it’s cold (unit has been running).
• Check the evaporator coils, if you can. If the evaporator is iced up, you have found your problem. To fix this, you can wait for the ice to melt, or you can speed that process up using a leaf blower (always wear hearing protection when using one). Make sure the unit stays off until the ice is nearly gone, and make sure the thermostat is at a reasonable setting and tamper-proof. The number one cause of icing is someone turned the thermostat down during the afternoon heat, and the unit froze up overnight.
• If there’s an air filter, check it. If it’s dirty, at least blow it out if there’s not a ready replacement.

Then check each condenser. Again, keep a record. Condensers need airflow to work properly. If they are outdoors and vegetation has grown around them since the HVAC company was last there, get a reciprocating saw and cut back (or cut down) rogue shrubs.

A common problem with condensers located outdoors is the coils are full of debris such as cottonwood fiber or grass clippings. If you see debris, shut the associated HVAC unit off so there’s no air pressure holding the debris in place. Make a note whether this is significantly clogged or only slightly dirty. Then use one of the following methods to remove debris:

• Rinse from top down using a water hose. This would require a faucet reasonably close by, and one should have been installed for this purpose.
• If you have a faucet, you might want to check whether a local home center or HVAC supply center has one of those specialized coil cleaner hose attachments that will allow you to rinse from the inside out for a more thorough, faster job.
• If you don’t have a faucet, use a leaf blower. It will do an adequate job. Blow across first, not into the coils; this will remove most of the debris without having to force it completely through the coils. Follow that effort by blowing into the coils to remove material that was already stuck there.
• Once the coils are reasonably clear of debris, look at the fins. You might think they should all be perpendicular to the coil tube, but most modern configurations are not that way. It can look damaged to the untrained eye but be perfectly fine. Look for non-uniformity in the general pattern, take a few photos, and provide those photos to the HVAC contractor. Don’t try to straighten this with a screwdriver. The proper tool is called a fin comb and using it delicate work; let the HVAC contractor address the issue.

These efforts will likely solve the problem. If not, wait for the cavalry to arrive. If the heat is intolerable, rent some large low-speed fans or other portable cooling equipment to help cool people in the worst areas.