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  1. #1
    Join Date
    Sep 2007
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    edmonds wa
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    I-pak Daytime warm up

    I am working with mod #SFHGD114P1447 that I am not sure why the heat will not come during the daytime. Unit is being controlled by a alerton type control system. unit runs fine in the summer time but in these temps the alerton controls will switch on the heat thru the changeover contacts .this shows up on the HI on the roof as heat at 0%. the bas shows heat on with set point at 68deg. The main problem is the dat can be way lower when the econo is at the 10 percent min or the co2 controls start to drive open the osa. On the gbas board it says the input voltage of 1.27v and that is about 68 deg.
    The morning warm up works fine when the mod burners, are not in lockout, another issue, but the control guy does not know what the 68 degree set point he has given the unit what it responds to IE return, mixed or dat. the bas switch's between the heat and cool commands, based on the number of boxes over a adjustable amount that need heat or cool. This 68 degree set point for the heat is the highest the heat is allowed during the day, that is programmed in the bas, why that temp no one knows, just the way it always been, but it can be adjusted higher.

    The way the daytime heat now is being done it is not working. the 4 unit's total between the two bld's basically stay in the heat mode all day long at these temp,s. I am sure there a better way to do this besides what the control co says ,it was designed this way and it's always been this way.

  2. #2
    Join Date
    Mar 2011
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    Long Beach, CA
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    What is your day time warm up set point?
    What is the day time warm up termination point.
    How are you determining the AREA average space temperature?

    Hopes this PDF helps.
    Attached Images Attached Images
    But I am still learning and looking for a new mentor.
    _______________________
    In a strict sense troubleshooting is not part of the repair..........understand the symptoms and you will find a solution.

  3. #3
    Join Date
    Sep 2007
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    edmonds wa
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    Thread Starter
    alcomech The rtu's have the trane 0-5 volt gbas panels in them.
    The alerton bas sends either a heat or cool call to the changeover contacts on 1tb5, wire connection 21 and 22 The hi shows this going to the heat mode at o percent. Now, the hi does not have the dwu enabled now and has the default temps of initiate at 67 and terminate at 71.

    The bas controls the set point for heat and cool by sending 0-5 volt signals to the gbas panel..The bas looks at the number of boxes that want cooling and of heating in the same way. at present, cooling is any more than 15 boxes, is a call for cool and 25 boxes for heat. the starting cooling set point is 68 and will slowly drop down to 55 if the boxes in cool start to increase. The heat cycle is set to heat up to 68 when the heat is set to be on. The mwu set point on the bas is set at 100 deg and this does come and work in the early morn hours by looking at the trends on the dat of the bas supply sensor.

    If the dwu is enabled on the hi, what sensor would it look at for control? The start up guide says it looks at the discharge air sensor to modulate the gas heat burner,if that's the case, is that the same sensor that the dwu initiate and terminate use for their set points? And would the dwu only come on with the change over contact calling for heat.

  4. #4
    Join Date
    Jun 2006
    Location
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    With the gbas you are sending occupied cooling and heating setpoints. Not daytime warmup. The occupied heat and cool work of the same controlling sensor. Not sure which sensor your units are using. You would have to look into Controlling Sensor Source>Occupied Zone Control on the HI.

    So your BMS system switches to heat. The unit looks at the controlling sensor and if it's above 68 degrees......the heat will not run. If it's below 68 degrees, then the unit will heat and regulate DA based on supply air heating setpoint. I bet if you look.....your controlling zone sensor is above 68 degrees.

    Daytime warmup works independent of occupied heating. You also can't change setpoints through a gbas. And it will only run when in the cooling mode.

    You mention your MWU setpoint is 100 degrees? Hopefully you meant supply air heating setpoint.

    Sounds to me you just need to raise your occupied heating setpoint.

  5. #5
    Join Date
    May 2004
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    SE Pennsylvania
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    When the GBAS changeover input is closed, the unit will use the heating supply air setpoint and will maintain that supply air temperature until the changeover input is opened. If the setpoint is 68 that's what supply air temp it will try to maintain. DWU initiate and terminate would use space temp if you have one connected. DWU and MWU will operate independently but would be 100% VFD command and 100% heat output.

  6. #6
    Join Date
    Sep 2007
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    edmonds wa
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    Thread Starter
    To both, good info and a place to start. I am thinking knowing what sensor being used for control and then setting up the current 68 deg heat set point, to see how one of the units respond. What started this was the number of boxes that wanted a heat increase, plus the dat temp the BAS was seeing was always colder than 68 deg. One of the units had a 54 dat because a over active co2 was driving the osa to 40 %.this has been quoted to replace.

    Another problem has been lockouts on the Honeywell modulating burner control. I have borrowed a keyboard display module and installed to try and narrow this down.
    The first code came up with a lockout code 19 and of course when reset all will run fine. These are new accounts, so I am thinking a lot of these issues have been ongoing for a while. Thanks to both for the help!!

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