Category Archives: ventilation

Hunting for replacement ERVs

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It was time to research replacement ERVs (Energy Recovery Ventilator) after two of our units broke down in 2020. A couple of key aspects re-emerged in that process.

  1. The heat recovery efficiency of our Recoupaerator 200 DX was unmatched based on HVI (Home Ventilation Institute) data, which was confirmed with my own testing.
  2. It looked like the Recoupaerator 200 DX was the only residential ERV on the U.S. market that used an enthalpy wheel for the heat and moisture transfer.

Other residential ERVs use a static core heat exchanger, or core in short. Unlike an enthalpy wheel, the core functions on the principle of cross flow.  The exhaust and fresh stream flow across each other in the core without mixing. In the process thermal energy is transferred through the core’s membranes. And if we want to get all technical, we are talking about sensible energy (heat) and latent energy (moisture).

The cores come in two shapes: square and hexagonal. And this apparently small difference has a big impact when it comes to energy recovery. A hexagonal core has more surface area and thus provides more opportunity for sensible and latent energy transfer.

A quick review of product specifications led me to conclude that an ERV with a square core would be out of the question for us, because of the rather poor energy recovery rates.

Looking at products with a hexagonal core, I was left with three available options:

  • Zehnder CAQ350 ERV
  • Panasonic FV-20VEC1, and
  • Broan ERV200 ECM (also sold under the Venmar brand name).

To help in the decision making process, I pulled the HVI performance data for each product so that I got a good comparison.

The three hexagonal core options appeared to be all in close range of each other. Zehnder seems to be a little bit of an outlier on the net air flow side for the test data, while the Panasonic and Broan are in close range.

Looking at the power consumed in watts, it was a close race, where Broan emerged with the least power consumption.

As for the energy recovery rate – or if you prefer the technical term, the Adjusted Sensible Recovery Efficiency (ASRE), we have another close race with Zehnder squeezing into first place, closely followed by Panasonic and Broan.

These were useful data to have, but I still was left without a clear preference between the three options. So I began to look at cost. And remember, these were pre-inflation prices. Zehnder came in just above $3,000, Broan landed just under $3,000, and Panasonic just under $2,000.

It looked like I was left with two favorites in this horse race: Panasonic and Broan.

Between the two, the Broan ERV seemed to be the most compatible. It has similar dimensions to the old Recoupaerator 200 DX and as such would fit nicely into the ventilation closet. It also had very similar controls and low voltage auxiliaries, just like the Recoupaerator 200 DX.

The Panasonic also had very similar dimensions to the old Recoupaerator 200 DX and as such would fit nicely into the existing ventilation closet. But its controls seemed rather primitive, and the auxiliary controls for some reasons all required line voltage. And it was unclear what advertised auxiliary controls would actually be available.

Based on my past experience, I was not in the mood to bet all my money on one horse. Diversifying my investment seemed to be a safer path to take. So I ended up ordering one Panasonic FV-20VEC1 and one Broan ERV200 ECM to replace the two failed Recoupaerator 200 DX.

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Failure of Recoupaerator 200 DX

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The pandemic brought a kind of perfect storm for many of us. In our case, it was ventilation related. Two of our ERV’s broke down – right when we really needed to rely on good ventilation. Although, considering what other folks had to endure, ours wasn’t really a perfect storm but more of an inconvenient breeze.

We had three Recoupaerators 200 DX Energy Recovery Ventilators by UltimateAir in our building, one for each apartment. And as mentioned in the past, these ERV’s were one of my favorite green building gadgets.

Six months into the pandemic, the ERV for the garden unit broke down, followed by the one on the 1st floor. You may be asking: “What is the big deal? Just get replacement parts, or a new unit”.

I tried. I contacted UltimateAir, and got crickets chirping. I eventually found out that UltimateAir went out of business at the beginning of the pandemic.

I was now sitting on three ERVs with no tech support or good way of obtaining parts or even a replacement unit. That this was a disappointing experience is an understatement. I loved the setup, effectiveness and efficiency of these ERVs from UltimateAir.

But it looked like it was time to let go and research alternative products that I could use as replacements. And that had its own challenges because of the supply chain issues that reigned during that time.

We did the only thing that we could do: Ventilated the old fashioned way by opening windows, tried not to think too much about the associated energy penalty, and remained hopeful that the supply chain would eventually unclog.

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Chiberia 2019 – ERV hibernation

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Two aspects of our mechanical system fell victim to the Siberian express that ran over us during the last week of January. One of them was the Energy Recovery Ventilator (ERV).

The ERV typically operates down to 10 degrees Fahrenheit (-12 degrees Celsius). Below that, the enthalpy wheel freezes up, and a temperature sensor in the ERV shuts the unit off. That meant that we were without mechanical ventilation for three days.

That’s not too much of a problem, as we could crack open a window or two to get fresh air into the building. The down side was the big energy penalty when opening the windows.

I can report that it didn’t get stuffy despite the presence of two human beings and two dogs, and that humidity levels stayed under control as was evident by the minimal condensation at the bottom of the windows during the early morning hours.

Our ERV is an earlier model of the RecoupAerator 200DX. With the current model, temperatures below 10 degrees Fahrenheit (-12 degrees Celsius) should not be an issue as the unit comes with a pre-heating element.

The element is built into the fresh air intake and is tied to a temperature sensor which pulses it on and off as needed to maintain the incoming air at 12 degrees Fahrenheit (-11 degrees Celsius) to prevent the enthalpy wheel from freeze up. This allows the unit to operate at outdoor temperatures below 10 degrees Fahrenheit (-12 degrees Celsius). And if combined with a solar PV array, it can even operate at a low carbon footprint.

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Fanning over efficiency

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There are several useful tools in the cyberworld that can assist with making energy efficient decisions. One of those tools is the Energy Star website with its Product Finder section.

But there is also a cautionary tale here – hidden in the fine print, if you will. I recently ran into this head on, while looking into ceiling fans.

One of the big home improvement stores had a sale on ceiling fans that I wanted to take advantage of, because it included a number of Energy Star certified products. I went to the Energy Star Product Finder to look up the performance specifications of the fans that were currently on sale.

Well, the dichotomy between ceiling fans that meet the minimum efficacy levels and ceiling fans that seem light years ahead of those levels is quite remarkable!

The minimum efficacy levels set forth in the product criteria are as follows:

  • At low speed, fans must have a minimum airflow of 1,250 CFM and an efficiency of 155 cfm/W
  • At medium speed, fans must have a minimum airflow of 3,000 CFM and an efficiency of 100 cfm/W
  • At high speed, fans must have a minimum airflow of 5,000 CFM and an efficiency of 75 cfm/W

A ceiling fan sized 43” to 60” meeting the above criteria, in addition to the luminair requirements, will carry the Energy Star label. And most of those fans may exceed those standards by a factor of about 1.3.

Yet there are ceiling fans on the market that leave those requirements in the dust. Take the Emerson Midway Eco (CF955) that I researched and purchased for our 1st floor:

  • At 561 cfm/W at low speed, it is 3.6 times more efficient than the minimum requirement
  • At 475 cfm/W at medium speed, it is 4.75 times more efficient than the minimum requirement
  • At 336 cfm/.W at high speed, it is 4.5 times more efficient that the minimum requirement

On the extreme end, the Home Decorators Collection – 60in Aero Breeze at 1447 cfm/W at low speed, exceeds the minimum requirements by a factor of 9.3.

Bottom line: Look for the Energy star label on products, but don’t buy just yet! Do your research first, because there may be a product that blows those Energy Star requirements out of the water – and saves you money down the road.

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Wet duct insulation!

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Let’s stick with the ventilation subject for a moment, dear readers, because I need help with a hack. I hope that some of you can point me in the right direction. Here is the problem that needs solving:

The duct insulation in the flex ducts that connect to my ERV is getting wet every winter.

Why do I have the flex duct in the first place?

The purpose of the flex duct is to stop vibration transmission from the ERV to the rigid ducts.

Why does the duct get wet?

During the winter month the fresh air intake carries cold air and the exhaust duct from the ERV to the building exterior does the same. This cold air often cools down the duct below the dewpoint. That causes any moisture that is lingering in the flex duct or that gets past the duct sleeve to condense on the flex duct core. It is subsequently absorbed by the fiberglass insulation around the flex duct. Theoretically, this should not happen. The outer duct sleeve should prevent any air, and with it moisture, from getting to the flex duct core.

The weak points in this system are where the flex duct connects to the rigid duct, and even more so, were it connects to the ERV.

I use sturdy duct zip ties and even have the tool to zip them as tight as possible. But even with utmost diligence, it appears impossible to make these connections airtight.

An added complication is that the ERV needs occasional maintenance, which in some cases requires me to disconnect the flex ducts from the ERV. The zip tie system makes disconnecting and reconnecting fairly easy, but apparently fails to get it 100% airtight. I am also concerned that handling the duct during the maintenance operations may lead to breaches in the duct sleeve.

Solutions?

Is there a product out there that would be better than flex duct but still provide the vibration isolation? Or is there a better system for connecting and sealing the flex duct to the ERV?

Whatever a better and air tight solution may be, it must allow for easy disconnection and reconnection of the duct to the ERV.

Any suggestions? Who’s going first?

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