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  1. #1
    Join Date
    Jun 2009
    Location
    Ontario, Canada
    Posts
    1,029

    need help on lennox beast :DMS4 w/ honeywell motors.

    Need an old timer lennox expert.

    I kinda take over a converted old hotel renovated in the late 70s with two of these beast on the roof, 24 zones each. system is from 1979, still in full operation. the building now is an office complex that has been diced up and cut up through out the years. found a board room that's fed by two different zone, I endup fixing all the t-stat to the same temp to combat those zones cancelling each outher out. I found some info on it, but still don't understand it. another company used to take care this building, they're not getting called in for whatever reason, and the tech that works on this bldg is now at another company. I do have a way of contacting him if I need to, but I don't know him that well, only met several times so far.

    - would someone explain to me in plain english on how this system work?
    - what's turning the fan and heat/cooling on and off? what's controlling the temp/demand for cooling/heat?
    - how does this cold deck/hot deck shebang works?
    - is the zone control powered by the unit or is it on different power source?
    - I'm also looking for service bulletins/manuals on how to tackle this if any body has some pdf.

    thx for your help.
    Parts Changer Extraordinaire
    ------------------------------------------------------
    Have tools and gauges, will travel.

    RIDGID|YELLOW JACKET|UEI|TESTO|STANLEY|CPS|VETO| KLEIN|MILWAUKEE|MASTERCRAFT|

  2. #2
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    5,476
    Quote Originally Posted by blitz View Post
    Need an old timer lennox expert.

    I'm also looking for service bulletins/manuals on how to tackle this if any body has some pdf.
    I'm an old guy, but not a Lennox expert.

    I emailed you all I have on this unit.

    Hope it helps.
    Instead of learning the tricks of the trade, learn the trade.

  3. #3
    Join Date
    May 2013
    Location
    Florida
    Posts
    120
    Good Luck..... Replace it.... your looking at 34 years old.. hate to see the electric bill.... if you replaced it .. it would probably pay for itself just in Elec.

  4. #4
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,269
    I'd say time to replace, and have the hydro bill cut in half, eh?

    Translation for Americans:

    I'd say that the service life of the unit has ended, and a new unit should be installed soon. The electric utility bill would be about 50% of the current charges, due to increased efficiency. Do you know what I mean?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  5. #5
    Join Date
    May 2013
    Location
    Utah
    Posts
    57
    I was a Senior Mechanic taking care of about 8 DMS4 units of varying tonnage in Dallas, Tx. around 1997. At the time I had a full library on my truck for most of the systems I took care of that warranted keeping information at hand. If you can contact Lennox and get some of this literature you will find it helpful.
    The wiring diagrams and sequence of operation are critical to really understanding them. Here are a few things that may help:
    The zone controls are proportional and are operating your face and bypass dampers of the hot and cold decks. Failed zone controls can sometimes give you full damper. There are some molex plugs in the zone section you undo which will cause all dampers to go full heat or the other way. Usually I address the heating cooling operation first, but damper operation eventually has to be verified. Many but not all have return air fans. The evap coil and condensers as well have to be definitely clean. Its common to lock out the heating function on outside air temp once cooling season is in swing. This can sometimes be done incrementally depending on what kind of heat the system has and how many stages. I always started on those units by cleaning up all previous bad work and hack jobs and addressing the basics first. Compressor section should always be washed clean of oil from past leaks. The lead stage compressor usually had an accumulator on the other side of the blower section. Most of those replacement compressors had oil EQ ports on them which allow for removal of excess oil after a compressor change. These are critical.
    See how the system stages up and down. The supply and return air fan and economizer have to behave as they should. Cooling and heating setpoints typically have to be adjusted at certain points when the weather is changing.
    If it has been compromised on the control section you have to break it into logical repair steps based on the way it was originally supposed to be.
    IN 97 it was still practical to repair them and parts were available. They can however be time bandits as many medium and larger commercial systems can be and if the customer can go replacement, that can be done with retrofit multizone equipment of a similar nature. I have seen around the same time, a Carrier Multizone dropped on a transitional curb to replace a DMS4.
    If you have one to tame it can be a rewarding experience to learn something about that style of unit. They are one of a kind.
    Even in Texas at that time there were not many Techs who were good at that model, or cared to be.

    SC

  6. #6
    Join Date
    Jun 2009
    Location
    Ontario, Canada
    Posts
    1,029
    thanks for the info
    Parts Changer Extraordinaire
    ------------------------------------------------------
    Have tools and gauges, will travel.

    RIDGID|YELLOW JACKET|UEI|TESTO|STANLEY|CPS|VETO| KLEIN|MILWAUKEE|MASTERCRAFT|

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