HRV & Geo - A problem

Discussion in 'General Discussions' started by Di2009, Jan 13, 2009.

  1. Di2009

    Di2009 Member

    HRV & Geo - A problem

    I UNPLUGGED my HRV for the last 48 hours and saw a significant drop of electricity usuage of over 40KwH per 24 hours!!

    So i know that the HRV is one of the culprits for my Geo's weird behaviour as it was it's jumping from Stage 1 to 2 to Aux constantly as well as part of the excessive electricity usuage!

    My Geo has stayed constant on 22C and has not waivered off Stage 1, since i unplugged the HRV and we are heading for a cold snap.

    The geo and hrv were installed by different contractors in isolation of each other, but i can't find anyone that knows enough about both!!

    Does ANYONE out there know why this is happening? What is the successful receipe to have them working together?

    The thermostats are next to each other on the wall, could the HRV dehumistat be interferring with the Geo theremostat?

  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I am not an expert on HRV's, my guess is that the HRV was pulling too much heat out of the house and the Geo was struggling to replace the heat.

    I doubt if the stats are interfering with each other.

    Maybe we can both be enlightened.:D
  3. Di2009

    Di2009 Member

    HMMMM, i hope so!! I need to run the HRV as my house is R2000 tight and lack of fresh air is not going to be good!

    Question on the Geo stat - does the location of the stat effect the effectiveness of the furnace? in most houses i have seen the stat located directly above the furnace location one floor up? mine is the opposite side of the house to where the furnace is?
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Not usually.

    If the stat is on an outside wall or close to a door that would provide drafts, then your furnace would run more. Is there is temp difference from one end of your house to the other?
  5. Di2009

    Di2009 Member

    not hugely noticeable if there is one, but going to buy some manual thermostats and place them around the house to see. Yes stat is near a door but have deliberately not being opening that door to ensure no interference!

    What were your thoughts on the ice build up on the Water in/Out points on the furnance? I never once saw that happen on my previous Geo in 6 years.
  6. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Once the loop temp drops below 32°, ice will form on the exposed metal parts. Since your loop seems to have been designed to run with temps in the 20's, ice cannot be avoided.

    I am guessing your previous geo loop never dropped below 32°.

    The heat pump can still work with loop temps below 32°. It will shut off with temps close to 20°. We will just have to wait and see what happens.
  7. Di2009

    Di2009 Member

    How do i test/know what the actual loop temperatures are?
  8. hardchines

    hardchines Member Forum Leader

    Great thread! Whats a HRV??:rolleyes:
  9. rw1995

    rw1995 Member

    I've done a moderate amount of research on HRV/ERVs for my recently installed WF 4ton.

    I went with an ERV from Renewaire, as they seemed to be quite efficient as far as retaining heat and moisture.

    The 40kwh drop is most likely not from the operaiton of the HVR alone. The one I bought is 157 watts running 200cfm. If it is tied to your furnace blower, kicking it on, it will draw more obviously. My blower is GE ECM blower, drawing less than an amp on low. This equates to less than 400 watts with the blower and ERV running. If it ran 50% of the time, it would still be under 5kwh per day.

    Non ECM blowers will draw much more energy, but I can't see one drawing 40kwh per day. My bet is the HRV you have is not too efficient, and its requring your system to work much harder to maintain the temps. The Renewaire is 75%+ efficient.
  10. nile

    nile New Member

    funny you should mention this

    hi all

    i had a 5 ton tranquility system intalled in the spring in my house
    3 closed wells at 250 per well for a total of 1500 feet
    this is 30 kms north of toronto
    worked well for ac in the summer
    then this dec when the heat pump was beginning to really work i noticed frost on the pipe to the loop
    then i had error codes appearing and the aux system would turn on
    my installer said it was faulty thermistors and came and replaced them
    seemed to work fine until i noted frost on both brass fitting at the unit
    the system seemed to be working ok until it got a little colder
    some mornings i got up and the unit was on aux heat and it was only minus 4 c outside
    i bought an infered temp gauge and found the temps were ewt of 26f and return of 22
    i called the installer and the canadian distributer and they said that was fine
    this past week end i visited a friend up north who has the exact same unit except hee has a horizontal system
    i checked his return temp and it was 38 f
    this had me worried
    so i did a google search and got this site and poked around a bit
    this got me alot worried that a might have short looped
    so i went back downstairs to have a llook at the system and rack my brains
    return air was 68 exiting at 85
    brass pipes wer still frozen up
    aux was on
    i was pissed
    went up to vent to my wife and call the installer for some response
    went back downstairs to think again and leaned up against the return air duct work and it was freezing
    measured the entering air temp and it was 45 f
    the insulated hose from the air exchange unit was -4 c
    needless to say i took the front off the air exchange unit and poked around abit
    decided to unplug it and block the pipes with some towels and closed her up
    this am no aux heat and ewt is 40f
    tonight its -13c ewt is 40 f
    man was a relieved and pissed at the same time
    no one inspected to old air exchange unit and if i had to guess i dont think its working too well

    the installer is coming thurs to discuss the matter
    so good so far

  11. Di2009

    Di2009 Member


    Ok, so the HRV is definitely one of the culprits (even though it's unplugged) the air is still entering and being -20C out here today, the duct work from HRV to Geo is ice cold and the Geo is now running Stg 2 Aux. So did "niles" stuff towels trick in the HRV to stop the cold air flow for now!

    But DOES ANYONE have an optimal design for in/out pipe for the HRV and the duct pipe to the geo?? I had two different installers for HRV and Geo and neither understands the other side!! :(
  12. Di2009

    Di2009 Member

    new stats after flush

    Installer was here today and flushed the loops, here's the current stat's would like to know your thoughts on them:

    Loop Temp In 34 and Out 27.8
    Loop Pressure In 50 and Out 44 PSI
    Heat Rise temp In 68.8 and Out 90

    Electric Heat with fan draw on electricity 78.1 & 16.1 for the compressor

    Are these good?

  13. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    they look OK. why did they measure power with the electric heat on?
  14. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Could HRV or its ducts be too big

    ASHRAE calls for something like 15 CFM per person or 0.35 ACH (check these numbers - I'm guessing) I believe the document is ASHRAE 62.2.

    You may need a damper that closes off outside air when HRV is off.

    Here in frigid north Florida I had chilly bathrooms on cold (well, maybe COOL) days - realized outdoor air back feeding through fans - bought three $12 soffit vent grilles from Lowe's. Fan pressure opens them, springs close them. This is a detail the installers overlooked.
  15. rncbraun

    rncbraun New Member

    Hello. I am new to forums in general and read with interest your discussion on HRV and Geo Thermal heating. We are about to install an HRV unit, as our house is "airtight", and I am wondering if there is an HRV Unit that incorporates its own heat pump, since there seems to be a significant heat exchange. We are on Gas heating at the moment. I would love to use Geothermal in the future, though. I have to admit however, I don't fully grasp the concept of a heat exchange pump...

  16. geoloop

    geoloop Member

    Why do you have an HRV? Is your house really that tight? they are simply to avoid elevated levels of carbon dioxide in the home. it should be on a timer at least that cycles it for a couple of minutes every 3 hours or so.
    This will not be popular with the crowd here so I apologize guys but take a tight house and turn the darn things of and monitor CO2 levels for a week or so. You will see that they are snake oil in most cases.
  17. IdahoGEO

    IdahoGEO Guest

    Nice take. Sounds like an HRV could be more trouble than it's worth...
  18. Farmboy

    Farmboy New Member

    I'm planning for on-demand ventilation with a CO2 sensor. Would be interested in real world examples of CO2 monitoring in a "tight" home. Do you or does anyone have any?
  19. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    For air-tight homes

    We use the SKUTTLE 216 out door air intake. Visit their site. We have never had a problem with clean outdoor air piped to the return of a system out stripping the demand for conditioned air, and the ability of a system meeting design day loads.

    There is no electrical connection so it will not mess with the KHW load.
  20. Lucky

    Lucky New Member

    Look up where it's connected

    I'm installing that kind of equipment and I very often see mistakes in the installations (of my competitors of course !).
    Usually, the air exchanger is connected to the central system but many installers take off from the main trunk of the furnace to exhaust the air (witch you just paid to heat up) and through it outside. Instead, the exhaust air from the house is supposed to be taken in the return air to the furnace (witch is at room temperature) about 6 feet before the fresh air intake from outside (witch is also in the return air duct going to the furnace). This is, of course, if your air exchanger has its own ventilation system. If you have a static air exchanger (the ones with only the recuperation cube) you can't connect this way. Your only alternative would be to stop it when it's too cold outside if you want to save on utility bill. But then it's like trying to breath with a plastic bag over your head (if you house is that tight) !

Share This Page