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Another Rheem/Richmond hybrid water heater exhaust termination rant

drewintoledo | Posted in Energy Efficiency and Durability on

I just can’t understand why Rheem would sell an exhaust “termination kit” which includes an exhaust hood with NO DAMPER!   In fact, the exhaust hood is stamped: “FRESH AIR INTAKE” and will allow air and insects to enter.  Sure there’s a mesh that might prevent wasps, bees, etc., but what about ladybugs, stinkbugs, any other insects that are looking for a home?
I’m surprised I haven’t seen this rant yet.   How are others dealing with this gaping hole in their pretty good house?  I reduced from 8″ down to 6″ as that’s the smallest diameter Rheem suggests (they offer 8″, 7″, & 6″).  I wonder if the unit would operate just as efficienctly using a 4″ exhaust?   I called Rheem to discuss but was quickly frustrated as I was transferred around departments in a circular fashion until I made it back to the department where I started.
Anyway, I had to make my own damper so maybe this will help others.    I’m also adding an in-line 6″ damper to help reduce air infiltration.

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  1. MartinHolladay | | #1

    Maybe it's labeled "Fresh air intake" because that's what it's for. Perhaps you are the one who is mistaken when you called it an exhaust termination fitting.

    See the attached image from the Rheem HPWH installation instructions.

    1. drewintoledo | | #2

      I don't disagree! It boggles me why they'd use a fresh air intake in the termination kit and not supply a proper dampered unit such as this:
      I would have returned the parts and bought the above but the shipping and restocking fees did not justify.

  2. Expert Member
    Akos | | #3

    Unlike a bath or kitchen exhaust, when you have a closed loop system with both intake and exhaust running outdoors, there is no need for a damper. Unless the fan is running, no matter how much the wind blows, there will be no flow.

    If you look at the equivalent length calculation, a damper adds a lot of restriction, with an axial fan like the HPWH which doesn't have much pressure capability, the extra restriction will also hurt performance.

    Installers can and do mix up intake and exhaust (I've done it), connecting an intake to a flapper will result in zero flow. It is better to use an intake for both as it avoids this. ERV installs are always done with two intake hoods.

  3. user-5946022 | | #4

    @ Akos: you wrote "ERV installs are always done with two intake hoods."


    I did mine myself and used the panasonic EZ soffit vent, which is a product they recommend for the exhaust somewhere in their literature...

    In regards to the intake: Some of us live in climates that present issues with small flying insects. My ERV intake currently has this issue. I've installed screening behind the plastic intake louvers, but that is both insufficiently fine to keep the bugs out, and results in me needing to clean it out every few months as it starts to get clogged with pollen and whatever dust is in the air. I'd much rather clean at the intake than either have all this stuff in the intake duct, or worse, get into the working of my ERV or a HP Water heater.

    1. Expert Member
      Akos | | #5

      Same as above. Closed system, runs 24/7 (or should), the flapper only adds restriction.

      Bugs are always an issue, whenever I clean out my ERV filter, there always a lot of dead insects there. A screen can help as long as it can stay clean. In my case, I rather vacuum a filter than try to clean a screen 20' in the air.

      1. user-5946022 | | #6

        You make a good point - they do run 24x7 when the area they serve is occupied.

        I also put an insect screen on the backside of the EZ Vent grille to prevent wasps from building nests - they seem to LOVE to build at an exhaust - the constant airflow seems to attract rather than deter them. The screen is also there to deter any other insect that may fly up there when it is off.

        I'm wondering if I should remove the flapper on the EZ vent on the ERV that runs 24/7 when I am home? But that means if I go out of town and turn it off, I leave an open 4" hole ducted to the ERV. Thoughts?

  4. nickdefabrizio | | #7

    These ducting kits raise some interesting questions.

    I have an AO Smith Heat pump hot water heater (HPHWH) located in my basement, which is heated by a high efficiency, low temp Fujitsu mini split. The COP on my HPHWH says it is around 3.8, which is higher than the COP on my mini split; but I presume that is based on intake air coming into the HPHWH at room temperature or slightly below, not cold winter air....I presume the COP (i.e., the efficiency) -of the HPHWH goes way down if cold outside air is the intake air and under those circumstances, the HPHWH would not be as efficient as my Fujitsu low temp high efficiency mini split.

    Thus, in cases where a basement is heated by a high efficiency mini split with sufficient capacity, is it fair to conclude that the most efficient set up would be to not duct the unit to the outdoors-either on the intaske or exhaust side-and allow the mini split to take up the excess load (presuming that the mini split has the extra capacity)?

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