Replies

1. GBA Editor
   Kiley Jacques | Dec 28, 2020 11:41am | #1

   I’m going to give your question a bump in hopes that an HVAC expert will chime in. Meanwhile, take a look at this related Q&A thread: ERV—combined one or two vs independent one or two?

2. 
   jrpritchard | Dec 28, 2020 12:01pm | #2

   I would not suggest trying to tandem the ERVs. While it may be possible and acceptable to do that if it were presented to me as a contractor I would suggest giving each a defined purpose such as one for bathroom/laundry ventilation, with another tied into your air handler for continuous ventilation. There are also plenty of good options for a single stand alone model capable of doing your required CFM that have similar ECM motors and features as the Panasonic model that you are referencing above.

1. 
   toothman2020 | Dec 28, 2020 05:27pm | #3

   Jrprtichard

   What units do you have in mind?
   I need something that is good building zone 7. The only ones I’ve seen that are good are Vanee and Vanmare.

3. Expert Member
   Akos | Dec 28, 2020 06:34pm | #4

   There is absolutely nothing wrong with combing two units. You connect them in parallel and upsize all connection from there for the combined flow rate of the two.

   You can also have the two units run independently to different sections of your house, this would work well if you have a larger footprint with many bathrooms.

   You can even have them share the same exterior connections saving extra holes through your walls.

   You do have to do your homework and design the ducting to make sure that losses are bellow the limits of the units. These auto balance and maintain the flow set point provided the static pressure is within their operating range without issues.

1. 
   toothman2020 | Dec 28, 2020 07:49pm | #5

   Akos,

   Thanks for the insight. Particularly, that one exterior connection is appropriate if two units are connected in parallel. I understand this design strategy complicates my ventilation needs. Especially, compared to using one larger unit. However, these Panasonic ERV units appear so well made that I want to use them.

   Can you go into a little more detail regarding ductwork design and losses are below the limits of these units?

   Thanks.

1. Expert Member
   Akos | Dec 28, 2020 08:47pm | #6

   If you look at their PDF, the auto balance works up to 0.4" WG pressure. This includes both ducting going to outside as well as to the house. To be on the safe side, I would design for no more than 0.3". If you are doing a main trunk+branch setup to each room, this would work out to probably a 7" rigid (8" flex) shared trunk.

   Just thinking about it, the cost of two units and extra ductwork, you are probably near the cost of a larger ERV, might as well go with a Zehnder ComfoAir 350 or a Vanee G2400E ECM.

1. 
   alanferg | Sep 24, 2023 10:35am | #8

   Something to think about... I calculated the equipment purchase and annual operation (electricity and filters every 90 days) for two Intelli-Balance 100 ERVs to be less than one Intelli-Balance 200 ERV. Presently, I'm getting ready to install my two IB 100 ERVs, so real-world experience will have the final say.

1. 
   DennisWood | Sep 25, 2023 09:43am | #12

   You mentioned filters every 90 days. The Panasonic filters are on the pricey side. You'd be far better off using an inline filter box with larger filters and removing the Panasonic supply filters altogether. This would increase efficiency (the ERVs use less power when you decrease static restriction) and also improve efficiency. If you use a filter like 18x18x4, replacement costs will be a lot less, and you'll be 6 months likely between changes.

   Akos, in this parallel setup, I'm assuming you'd also need to wire your boost switches etc. to both units correct? What would prevent one unit in boost to reverse or stop flow from it's twin unit?

   With regard to efficiency, the Panasonic 200 (and based on the HVIC database numbers for a the 100 vs 200) for a given air flow, the 200 would likely be using less power overall vs two 100s. Given the long term outlook, and 24/7 use, it's something that should enter into a comparative analysis.

2. 
   alanferg | Sep 24, 2023 10:46am | #9

   Akos, in a situation with two ERVs each with dedicated roles, are you saying a single fresh air duct from one exterior hood can be Y'd to serve two ERVs? Further, can the exhaust air from the ERVs be merged to a single duct? I'd like to minimize exterior penetrations. I was looking at getting two Panasonic Wall Caps (FV-WC04VE1, https://na.panasonic.com/us/iaqsupport?series=596&product=4636) to keep air streams for each ERV dedicated resulting in only two exterior wall penetrations. However, the product isn't designed for flow above 50 cfm.

1. Expert Member
   Akos | Sep 24, 2023 02:59pm | #11

   Combining the ducts only works if the two units are in a parallel. With two distinct ERV serving different parts of the house, you want dedicated ducting for each.

   The hood you linked to is really only meant for their small spot ERV (does work quite well for that). You can use the Lifebreath version which is rated for much more flow. The duct connections on that are a bit tight so make sure you put it in a place where you have good access.

4. 
   user-2310254 | Dec 28, 2020 10:00pm | #7

   Just out of curiosity, what are you basing your target CFM on?

5. 
   AndyKosick | Sep 24, 2023 12:08pm | #10

   Panasonic makes a 200

   https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/energy-recovery-ventilators/intelli-balancer200-balanced-air-solution-60-200-cfm