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  1. #27
    Join Date
    Jan 2004
    Posts
    164
    Just a guess but if you slow the fan down (hope fully you have adjustable sheaves to get your attained 90 degree split) will your building temp come up to temp. If not take something and block the air flow into the unit to get the 90 degree delta on all three and see if the building temp comes up then you know your moving way too much air. And if you try this and the air temp comes up then you will know what the problem is and you can figure if the calucations are incorrect. I am old school and I always try to prove why!
    If you find it bad 3 different ways- ~its bad~

  2. #28
    Join Date
    Oct 2012
    Location
    Torrington CT
    Posts
    82
    but if you take down the CFM going. I think they need that much air going in. If you block the air coming in it would raise temp but you would not have the air you need.

  3. #29
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    449
    So he needs to check air velocity and verify air flow using the equal friction method, or perform an air balance and confirm the delivered air. Although it is very unlikely that he is moving that much air to over come the required temperature rise.

    Again this is a completely sealed combustion which requires 100% outside air. Combustion air is normally delivered by an inline fan and draft by a roof ventilator. It's very common that there is a VFD for both combustion air and draft, however the OP has not stated actual configuration.

    Draft will normally be set at a slight negative say -0.10" WC as an example and combustion air at 0.00 " WC. This is a basic design for start up but will need to be corrected based on his design criteria.

  4. #30
    Join Date
    Feb 2009
    Location
    Wisconsin
    Posts
    310
    Verify design gas pressure. Measure with all units running and check static pressure. The design of the ICE heat exchanger requires some static to scrub the exchanger. What kind of discharge duct is there?
    You have to fight through some bad days to earn the best days of your life.

  5. #31
    Quote Originally Posted by Betabass View Post
    Are your AHU making up the exhaust air by bringing outdoor air back into the building??

    no, there is no makeup air on the AHU's besides the one but the dampers are closed completely.

  6. #32
    Quote Originally Posted by hvacrmedic View Post
    Is this unit is pulling 100% outside air?

    The unit is using zero percent outside air as a make up air. the only outside air that the units use is for the sealed combustion and they need to use that due to the negative pressure of the building.

  7. #33
    Join Date
    May 2000
    Location
    Salem, WI US
    Posts
    61
    I would Perform a combustion analysis on the units and compare/ review manufacturers specification on readings, there is something causing this reduced temp rise.

    Beta

  8. #34
    Join Date
    Oct 2005
    Location
    B.C. Canada
    Posts
    854
    I remember doing startup on a very similar unit with the tech from ice and he mentioned that these units have a very low temp rise, like 20 to 30 on high fire....mabey the units are opperating correctly and just not being used for the right application. Have you talked to ice about this? Im thinking this might just be a possibility

  9. #35
    Join Date
    Mar 2007
    Location
    Sterling Heights, MI
    Posts
    141
    coolerik
    View Profile View Forum Posts Private Message Add as Contact View Forum Threads

    Professional Member Join Date:Oct 2005
    Location:B.C. Canada
    Posts:387I remember doing startup on a very similar unit with the tech from ice and he mentioned that these units have a very low temp rise, like 20 to 30 on high fire....mabey the units are opperating correctly and just not being used for the right application. Have you talked to ice about this? Im thinking this might just be a possibility
    My experience with ICE units is similar. We had about a dozen non-Icecon controlled units which worked great, and they are high temp. rise units. The four newer units controlled by Icecon boards are low temp. rise. You should check with ICE to determine if the settings on the Icecon are proper, as they were the only ones who could program the boards and match them to the unit application. I had to purchase an extra board to keep a unit running when I returned the old board to ICE for service which took a long time. They said not be interchange the board with other units too. These type of units worked best in enclosed areas where minimal cold air entered the zone, not as air turnover units in a large factory setting with the big doors opening or where there was a lot of exhaust. The software to communicate with the board would only work if the board was 100% functional. If there was a malfunction, you could not cummunicate with the board to aid in service. If we need any new units, nothing with an Icecon board is coming in again.
    Better Service Through Knowledge...
    RSES, The HVACR Training Authority. www.rses.org

  10. #36
    Join Date
    Feb 2013
    Location
    Minnesota
    Posts
    2
    Quote Originally Posted by breegle1313 View Post
    There is a software that you have to plug a laptop into the board on the unit and you can read the rpm of the combustion blower and the percent of gas at all six stages. They are all where they are supposed to be. I am thinking that the heat exchanger might be getting clogged because of the draft reading of the flue and the lack of the transfer of heat from the heat exchanger. My coworker swears that it cannot be the heat exchanger being clogged because there was no black soot coming from the flue.
    I dont mean to post incorrectly, but I cant find a way to private message.
    You mentioned the software, is it possible to get a copy of that software? Totally unrelated topic as I am taking over a unit with a BMS and need to verify some settings but I cant seem to find the software they talk about in the documentation to be able to do so.
    Thanks in advance!

  11. #37
    Join Date
    Mar 2007
    Location
    Sterling Heights, MI
    Posts
    141
    Look at these google searches:

    www.ice-ww.com/HTDM%20Installation%20Manual.pdf see page 27


    http://hvac-talk.com/vbb/showthread....etup-questions


    Sorry, that software, laptop and special cable was left behind at the location those units were at. Happy not to have any of those HTDMs. Ours all ran stand-alone with an on board thermostat. Can’t see how a BAS can help anything. Some of your problem may be that the BAS control setup was not done for real life conditions, and again these are low temperature rise units that are supposed to run continuously.
    Better Service Through Knowledge...
    RSES, The HVACR Training Authority. www.rses.org

  12. #38
    Join Date
    Feb 2013
    Location
    Soon I will be in NE
    Posts
    16
    I have never touched an ICE unit - but they seem to be in the same category as an EVAPCO system, where they do custom design for each application. That being the case (along with my usual disdain for mechanical engineers - sorry guys!) I would check the design of the system itself - Board is calling for 100% - 10v dc output - valve is open - but is the valve the right size? Is there excessive pressure drop through the gas train? If you know your airflow - then you can also know the Btu's needed to get the temp rise you need - then cross reference the Manufacturer's specs on the valve to be sure that it will be able to deliver. If you need help double checking the sizing on the gas train - I have a reference that will help with that.

    Also check that the gas pressure doesn't drop when the system fires - sometimes the pressures look good until the system starts.

    I had an EVAPCO that was delivered with an undersized TXV because Evapco did not account for the pressure drop across the distributor. When the weirdness starts - do not assume anything is right on a custom system.

  13. #39
    What type of program is hooked up to the systeam?

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