Results 1 to 7 of 7
  1. #1
    Join Date
    Feb 2012
    Posts
    12

    HRV/Furnace Tie-in

    Hello Everyone!

    I found this site doing some research and decided to join to get more info. Ive recently purchased my home (15yrs old) and found it to be a mechanical mess. Everything was either not working or needed maintenance. Here is the list:

    HRV: Changed main board (blown transformer) and cleaned fans/motors . Installed inline fuse as per Vanee recall. Had to rewire control panel since they just randomly terminated it. I initially wired it like it was and rewired when proven not functional.

    Furnace Electrostatic Filter: Needed deep cleaning, Im assuming the vacuum sensor was clogged.

    Gas fireplace: Still not working. It used to go on (once) and stay on but after turning it off it wouldnt turn back on. After waiting 30mins it would turn on again. Im thinking its the thermopile pilot is OK. (Side Topic)

    Just to let you know, Im an Industrial Instrumentation Technologist. So I know my way around but Im not a HVAC tech, which is why Im here. Just like any process control, in principle it is simple but there is nothing simple about it.

    My system: High Efficiency Furnace, Trade 150 HRV. HRV has independent air return ducting fed from kitchen and three washrooms and the air supply is tied into furnace air return ducts (about 5 feet from furnace).

    So my questions:
    1) Is it required to interlock my furnace fan with my HRV with this setup?

    2) I have the Basic(VT1W) panel and it behaves like this:
    a. Dehumisdistat Dial: Does nothing
    b. MIN: Fan speed is low while in the MORE humid range and goes on HIGH mid way in the comfort zone and throughout the LESS humid range
    c. MAX: Fan speed stays on HIGH regardless of the dial position

    I would have thought the dehumisdistat dial would operate the HRV to control humidity depending on setpoint and the MIN/MAX would override the dial?

    3) Do furnaces need a fresh air supply? I realize the air intake/exhaust for the burner core. That said, is the burner core a closed circuit?


    I have to say Ive gained a great interest in HVAC and home comfort! This is a very interesting field of work.

    Please let me know if you want me to clarify or want pictures.
    Cheers,

  2. #2
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    An HRV is NOT a humidity controller. It simply exchanges enthalpy between air being drawn from the home and air that's being infiltrated into the home. Normally the ERV is run on a time schedule scheme that is established by first establishing the natural leak rate of the home and then calculating how much forced air ventilation needs to be introduced to get the home to the proper exchange rate.

    As far as combustion appliances are concerned, each one needs to have sufficient air to provide for good combustion. Many products today can meet Category IV venting requirements and therefore have their own combustion air source as connected to the great outdoors. This requires 2-pipes from the appliance to the outdoors, one for exhaust and one for intake. The room air blower on a furnace does require air but that air enters the blower from the returns in the treated envelope, runs through the heat exchanger without mixing with combustion air and thence onto the treated spaces of the home.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  3. #3
    Join Date
    Feb 2012
    Posts
    12
    Thanks for the reply

    Well an HRV certainly cannot control humidity during the summer, however in the winter it does a great job, it holds my house at 45-50%RH. So why have the MORE/LESS humid dial? just for the HRV to run more during the winter and less during summer? I do understand the purpose of the HRV, house are built air tight and don't breath so air needs to be replaced. My intention is to calibrate my system so I make sure I'm not an adding additional load on my furnace during the winter and not bringing excess humidity during the summer. I will look into changing the jumpers to have it run intermittently. I'm going after the min air exchange requirement. I'm a set it and forget it type of guy.

    So do I need to interlock my furnace fan with my HRV? I'm assuming I should since it will bring that dry winter air right to the windows and help condensation. (This is the reason I fixed my HRV, windows where sweating like crazy and once I got it fixed that resolved that.)

    Thanks for answering my furnace fresh air supply questions. Reason I asked this is because my father told me he has a 4 in insulated flex pipe ran from outside to behind his furnace... He has an oil furnace so I'm assuming it's different then my natural gas furnace. Will look into it out of curiosity.

    Cheers

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,642
    In a air tight home like yours, operate the ERV on low speed year around when the home is occupied. A plug in digital timer works well. With a duct connection to the return, the fresh air will push throughout the home exiting the throughout the random leakage points of the home. A Aircycler could be added to the furnace fan to cycle the fan 5 min every 30 mins. A adequately ventilated occupied home is dry when the outdoor dew points <50^F and damp when the outdoor dew points are +55^F. You need a 2-4 lbs. per hour of dehumidification to provide <50%RH when the outdoor dew point is high and the home is occpied without much cooling load. The Ultra-Aire whole house dehumidifier is the ultamite addition to this type of home.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  5. #5
    Join Date
    Feb 2012
    Posts
    12
    Thanks TB, those are the kind of answers I'm looking for!

    I wont be interlocking my furnace fan, it was nice to confirm and I happy to avoid that additional energy cost.

    So yesterday I ran my HRV for 24hrs and the house dropped to 35%RH... It was on avg -17*C & 62%RH outdoors. This is why I haven't been running it all the time. This still leaves me confused that the HRV is not controlled by a RH setpoint during the winter. I think most ppl would rather not dry out their house then to ensure they have ~60cfm of fresh air... You mentioned the plug in digital timer, this would work well, but I'm afraid I would always be changing the duty cycle depending on outdoor Humidity and temperature.

    FYI: I live in Sudbury, ON Cadada

    Thanks for the info
    Cheers,

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,642
    Quote Originally Posted by Tallicon View Post
    Thanks TB, those are the kind of answers I'm looking for!

    I wont be interlocking my furnace fan, it was nice to confirm and I happy to avoid that additional energy cost.

    So yesterday I ran my HRV for 24hrs and the house dropped to 35%RH... It was on avg -17*C & 62%RH outdoors. This is why I haven't been running it all the time. This still leaves me confused that the HRV is not controlled by a RH setpoint during the winter. I think most ppl would rather not dry out their house then to ensure they have ~60cfm of fresh air... You mentioned the plug in digital timer, this would work well, but I'm afraid I would always be changing the duty cycle depending on outdoor Humidity and temperature.

    Cheers,
    Outdoor %RH means nothing! It is about outdoor dew point. The outdoor dew point is -23^C. When -23^C dew point air is warmed to 20^C, the %RH is 12%RH. You are adding enough moisture to the dry that is passing through your home to raise the dew point to 4^C. Humidifying 60 cfm from -23^C outdoor dew point to 4^C indoor dew point removes 1.2 lbs. of moisture per hour.

    Fressh air is needed to purge indoor pollutants/renew oxygen when a home is occupied not when the outdoor air wet or dry. Humidifier or dehumidifier is used to provide the desire inside %RH.
    During most weather, the %RH is highest at 6:00AM and lowest mid-afternoon, while the dew point changes little throughout 24 hours.
    100%RH is very dry air when the dew points are low. 50%RH is wet air when the outdoor dew point is +60^F.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #7
    Join Date
    Feb 2012
    Posts
    12
    Alright I'm getting what you are saying. Haven't looked at this stuff since school... so sorry for the ignorant questions. HRVs are really meant for air ventilation and not humidity control. In some cases it can help... but this is just a byproduct.

    I will let the HRV run at low speeds and see what happens with the humidity overtime. I do want to rent equipment and see what the HRV is ventilating at since I'm sure it wasn't commissioned properly and I want my house to be under a slightly positive pressure.

    And if Humidity control is a problem I will invest in something like the Ultra-Aire or maybe just run the one I just purchased. Last summer it got so bad that the doors started swelling which is what brought this to my attention.

    Thanks for the info
    Cheers

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event