ERV And RTU On Rooftop At MicroMetl

Abbie Stancato At MicrometlMicroMetl is celebrating 50 years of serving the HVAC industry. Over those years we have guided countless customers through an ever-changing maze of options to consider when installing or replacing equipment.

Energy Recovery Technology (ERV) has become the norm. I compare it to the internet… fifteen to twenty years ago, a web page was an edge over the competition. Today, it’s not only mandatory to your business plan, but a prerequisite to opening the doors of any virtual or mortar business.

Changes In The ERV marketplace…

We are approaching an interesting time in the ERV marketplace; the replacement of the first generation of ERV’s. Most were designed and installed in accordance to detailed engineering specifications. However, replacement often comes with less guidance and consideration.

A recent conversation with a MicroMetl Technical Service Rep is the motivation behind this article. He is receiving a greater volume of calls from customers seeking to replace their customer’s first ERV. However, he’s not receiving engineering spec sheets to quote the job, but more often only the part numbers of the existing equipment for identical replacement.

The replacement of an HVAC rooftop is often done with much consideration… more than the replacement of an ERV. The skill set of most HVAC and mechanical companies often does not focus on ERV units. Furthermore, large brand rooftop manufacturers educate and inform us of the most current innovations, options &  SEER values of rooftop units, not EER values which is the result of integrating an ERV into an HVAC system.

ERV Replacement Considerations…

Energy Recovery has come a long way over the years. Before replacing an ERV, ask the client; what has changed? What is the purpose for the room(s) currently in place? As an example, an ERV may have been installed for a smoking room. Smoking rooms have become taboo, and have gone the way of the rotary home telephone. Smoking rooms required a significantly high air change rate. The chances of reducing the size (and replacement cost) of an ERV supplying this type of room is good.

Perhaps a room which was previously an office space and is now a meeting room. Meeting rooms require fresh air during usage. Perhaps you can change the ERV design from a need to provide constant fresh air, to a CO2 driven, on demand system.

The bottom line: Matching the identical specs could be a complete waste of the building owner’s money.

What is the CFM and Goal of the Existing ERV?

ERV’s are designed and sold with a CFM range. As an example, 1000 to 3000 CFM based upon 0.5 inches of static pressure. So what is the CFM specifically set to on the existing ERV? Unless proper airflow testing is conducted, you can’t set the proper airflow for the replacement.

If an ERV is coupled to an RTU, testing the CFM may not be so simple should your new style ERV require you to adjust pulleys, or manually set fan speed. Why… the RTU fan causes negative pressure upon the ERV supply fan. This effect will often cause the ERV supply fan to produce a higher than expected CFM. Furthermore, the higher CFM could cause the ERV supply motor to thermally trip.

To complicate the situation further, opening the ERV door to use a “Amp Clamp” removes much of the system static pressure on the fan, returning a different motor amp draw than when the door is closed.

Each ERV is designed to capture a specific percentage of heat or cooling, and return it to the building with fresh air, and/or to remove humidity. Each ERV is designed to return different percentages of efficiency, each according to its specific design. Therefore, do you know the current ERV efficiency, and does the existing percentage meet your new goals and your budget?

Just A Few ERV Options…

So much has changed over the years… Including the profile, or the size. Be prepared to not only consider a better, wider range of options, but time to consider curb adapters!

The actual Energy Recovery section of an ERV comes in two primary forms: A rotating wheel, and a fixed core. Each has its pros and cons, and is too in depth to discuss at this time. Be certain you know if your ERV contains a wheel or core. Knowing the difference will allow you to receive better guidance from an engineer or service rep.

Economizer – An ERV can replace an RTU economizer, while offering much more control and flexibility.

Power Exhaust – An ERV can integrate all the functionality of Power Exhaust at a lower cost.

MicroMetl’s “EZ-ERV” delivers airflow monitoring which takes the guesswork out of achieving proper airflow. It allows you to specify the exact supply and exhaust CFM, regardless of system static, HVAC Rooftop supply fan effect, or dynamic system static changes created by dirty filters or changing dampers.

Seek Skilled Guidance!

Before you can design an ERV to meet new goals and expectations, you must define them. Question any perceived normal. ERV’s at first glance appear to be simplistic in operation and design. However, like much in life, the more you learn about them, the less you realize you know about them. Contact an engineer or MicroMetl before replacing that existing ERV with an identical unit.

MicroMetl has been in the ERV market for many years and has the expertise to assist you with any training or questions you have. Feel free to contact our Technical Support, Customer Support, or Sales Department for assistance and guidance!

 

Sorry... No Questions Found.

Ask A Question

Attach YouTube/Vimeo clip putting the URL in brackets: [https://youtu.be/Zkdf3kaso]