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AC question

Mike Thanks for all the good thoughts I should say that in the mean time I was able to get a good tech to charge and test my compressor It has been working like a champ for the last week. I took 3 different companies telling me it was dead and needed replaced. I'm sure that is true it is an old and non efficient unit However it was nice to have it 70 degrees during Dutch days ( one of the biggest retail days of the year in Hanover) I can't thank the tech. enough. He spent 15 min on the roof, told me the risks, and got-er-done. What is the concept for the economizer? Mine consists of a Honeywell remote (outside) T-stat. A set of louvers and a Honeywell drive moter. If it is connected to the ac unit or the air handler it is not built in or to a circuit board. If I had to guess it is a 1970s attempt to gain some efficiency. It also apears that the thing makes a choice by reading the outside temp as to where it gets its supply air. I know that you guys feed your kids from what you do. I wish that their was not so much mis information being spread by the local tallent. There are quite a few people from the Wall who have done or are in the process of doing work for me. I am not afraid of paying good people. I will recheck the lable on the connections. Thanks again T

Comments

  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398
    AC question

    Where should the t-stat wire connect in a roof top Commercial unit? Have 5 wires in the stat cable R W B G and B what is the conventional color/connection.
  • Tom_35
    Tom_35 Member Posts: 265
    Wiring connections

    The normal wiring connections are as follows:

    R---Red wire (one side of the control voltage)
    W---White wire (heating)
    Y---Yellow wire (cooling)
    G---Green wire (fan on)
    B---Blue wire (this can be used for a number of different applications, depending on the unit;

    Many commercial units have 2-stage cooling and 2-stage heating, with each additional stage needed another wire. When the unit has an economizer, another wire is generally needed.

    Hope this helps.

    Tom Atchley
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    Tom I am trying to rewire my control wiring I have an old trane roof top RA753R type 4340-9155 . The tech got me running (thanks to him). I was able to find the old stat wire that was cut off by the old owner when they moved out their fixtures. any way (I have an economiser) it uses a honeywell controll moter. is there a wiring diagram available for these systems? are they kinda the same? My roof unit has a single pair control wire that is a switch wire. It is curently connected to one pair of contacts on the contactor for the air handler. this hook up will not allow for (fan only) operation. What I have: 1- roof top unit (has its own contactor),1- air handler, 2- 24V transformers, 1- t stat, 1 honeywell economizer control moter (has 5 connections on it), 1 outside reading t-stat( has 2 sets of switch wires one is on when the other is off), and 1 contactor for the air handler. Do you have a diagram for a system like this . many thanks T.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Call A Pro

    Without looking at it, it can be wired a few different ways depending on the application. You are trying to tackle a problem that can possibly fry neumerous controls. 2 stg cooling is what you want since you have an Economizer. Econo acts as 1st stage when outdoor temps fall below Enthalpy setpoint. Mech. cooling will be the 2nd stage. If you are just using it for ventalation, ...Another ball of wax... no easy answer.
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    Mike thanks for the concern, I seem to be prety good at this stuff if pointed in the right direction. It apears that the "economizer" consists of an outside reading t-stat, a drive moter and the louvers. It lets the system draw air from the celing or the outside. I would figure that there is a prefered temp to set the out side stat to. the next question is the drive moter It is a Honeywell with 5 conections 2 are labled t-1 and t-2 ( would this be for t-stat ?) the other 3 would then be for power and what else? If all I wanted to do is draw the coldest air possible for return air how would I hook it up? Sorry Im hooked I just love this stuff. Thanks T.
  • don_144
    don_144 Member Posts: 27
    that too

    is respected furn guy.Thats why we do it, we enjoy it and we feed our family at the same time.

    I have to agree on the side of caution and say call a pro as well.

    First it not just about the wiring,you need to get into the designer head and see what his intention were,then only then
    will you be able to wire the system.

    Outside air intake and building pressurization is nothing to
    sneez at,no pun intended.

    Something simple as a freeze stat being overlooked can cause
    big time damages.

    Hope this helps.

  • Empire_2
    Empire_2 Member Posts: 2,343
    Read your reply

    Are you sure that the # begins with R and not M? "M" is the motor or actuator. I have a book on Honeywell but I cannot find the R designation. Most economizer control actually takes place internally through the wiring in the unit. I'm sorry I couldn't help you...
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Too Many Variables

    As I mentioned in the post on The Wall, I mentioned to you that, since a number of technicians have worked on your system (and obviously messed things up), it was in your best interest to call in a professional.

    I am in no way, shape or form doubting your technical abilities, but I do not think that it would be fair to have someone attempt to explain your system or its associated wiring to you sight unseen.

    For example, you may have two completely identical systems with the same model number and serial numbers that are only off by 1 digit. These units (about as similar as they can be) are most likely NOT wired or controlled the same. The addition of system accessories, different wiring startegies, etc. make them compltely different.

    The advice you are being given is not to prevent you from doing some of the work yourself, but to protect the very valuable equipment that you have on your roof. The loss of air conditioning in a commercial space will lead directly to lost business.

    Imagine a restaurant owner who attempts to fix his own air conditioning system and blows it up. Customers come in, feel the heat and walk out. In an attempt to save a few dollars on service, he ends up losing a ton of money in lost business.

  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    The economizer

    The economizer is a piece of equipment that determines the percentage of return air from the space and the percentage of outside air (the mixture referred to as mixed air) that will return to the system.

    The economizer reads outside air temperature (and sometimes heat content, or enthalpy) and deternies if the outside air can meet the system's cooling requirements. FOr example, if the temperature inside the structure is 80 degrees and there is a call for cooling, the economizer will introduce and filter outside air if the outside air is cold enough to provide the necessary cooling without having to operate the compressor. This is referred to as "free-cooling".

    Settings on the economizer can range from 0% outside air to 100% outside air deopending on the ventilation, fresh air and required system operating paramenters for commercial/industrial systems. For example, some structures require, by code, a minimum of 10% outside (fresh) air all the time, regardless of temperature.

    Since your particular system has been worked on by a number of different technicians whose expertise you obviously have doubts about, you might want to get a reputagle company in to make certain that the economizer is operating as desired and required.

    Keep us posted and thanks for your contributions to the board.
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    I was reading your reply and trying to apply it to my system. If there is a % of fresh air required It would need to be done with the mechanical part of the system. In other words the louvers would have to fall X % short of fully closed. My sensor is installed through a plywood covered window. It sits between the glass and the plywood. If you are drawing some outside air at each cooling call. Would it not be better to have the sensor just inside, of the outside air louver? If located here It would be reading the actual air temp. inside the fresh air supply duct rather than heat off the sun baked wall. What do you think?
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Yeppers

    The economizer controls obtain data points and determine the optimal louver (damper) positions based on them. Taking the temperature of the space between a piece of plywood and the window will not likely provide useful information.
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    I'm still thinking that your talking about a more complicated rig than I have so here is a picture of the control. I did trace the T1 and T2 wire back to the location where the outside stat and the air handler contactor is mounted. too bad it was disconected. The wire hanging in the picture is lost above a main duct and not near any power that I can see it has 3 wires, I cannot see where it is connected after it passes over the duct. Any ideas? Thanks again.
  • Rodney Summers
    Rodney Summers Member Posts: 748
    that's a pretty basic modutrol..

    i think these guys got it right when they say find a pro but you might be able to do some of the footwork upfront to move things along or even help yourself.
    if that unit is a trane & you wish to keep it, start by calling into or visiting your local trane parts office & order the technical / service manual for that unit (or what ever they got). check for a schematic & possibly a separate economizer label drawing glued to the inside walls of he unit. if they exist, make a copy of them on your xerox machine without tearing them off the wall. that modutrol motor is intended to hookup to what is now known as a series 90 modutrol controller. the t1 & t2 are for the externally supplied 24vac xfmr. the r,w,& b terminals are jumpered in different fashions (r-w, r-b, r-w-b, etc) to either rotate the vent fully open, fully closed, or a few open angles - that is all - nothing magic there. my guess is, like many of those old motors, the unit has probably seized by now & it may be tough to find an exact replacement unit. you will have to peruse through all the honeywell literature to find the closest thing. that unit was a m90xx series - they are now in the m94xx series. the easier thing to do is just remove the link rod & screw the louvers shut. although the economizer "sort of" works in conjunction as a 2nd cooling stage, it is usually engaged in parallel not series so once you've disabled the vent the mechnical cooling takes over & never knows the difference (you do lose the $ savings from not being able to take advantage of the outdoor temperature when cool). by parallel i mean that the indoor thermostat doesn't know & doesn't care about it. the modutrol is usually controlled independently [within the unit] by a simple temperature control sensor & that is it. the r/w/b wires would normally come back to a low voltage terminal board in near the control side & either would be discretely controlled or governed by some facsimile of an early series 90 controller. you can either look in there & see what you can see, or better, get the manual from trane (and make sure you hold on to it). the 3-wire cable is probably missing because some techs will rip it out once they discover that the motor is seized. it is not uncommon that in many installations the techs are instructed to disable the economizers because the motors fail - open vent - in the middle of the winter on a rooftop heatpump unit & thus kills the heat by diluting it with the outdoor air.

    long story short - get the book/schematic from trane - it has all the real answers.

    ss
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    Thank you!! I was thinking that the 3 wire was reading somthing in the main duct. that aside am I right in thinking that the outside stat is only deciding if the compressor should run or not depending on the outside temp?
  • Empire_2
    Empire_2 Member Posts: 2,343
    Reply

    Yes is sits under the hood and monitors outside air. Also looks like your damper motor will be a 2 position assembly, not a modulating one. Minimum position which is usually at 10%, ( just eye it) should be controled by actuual linkage setting unless there is a minimum position adjustment. some air should flow through the outside dampers not only for fresh air, but for continous movement across the temp control.
  • Rodney Summers
    Rodney Summers Member Posts: 748
    outside t-stat ?

    you lost me on the "outside t-stat" & switch. you'll have to electrically define that "t-stat" a bit better (or a picture). does this t-stat have a temperature adjustment? not clear on what it is, where it's located, & electrically what it's doing. is this really just a temp sensor control? if the economizer was only controlled by a very primitive temp mechanism and those switches you mentioned are simply mutually exclusive then they could serve to open & close the louvers with only 3 wires providing closure to either the r-w or the r-b. the sensor would have to "see" outside temp for this - usually mounted inside the unit near an outside vent.

    ss

  • Bill_57
    Bill_57 Member Posts: 2
    circulating hot water from steam boiler

    I have a steam boiler in the basement & a seperate hot water heater for domestic hot water . I want to tap into the hot water in the boiler( Crown Steam Boiler Rated172,000btu) by installing a 1/17 hsp circulator pump to pump hot water from reservoir in boiler(returned hot water from steam ) into 3- 6' radiators to heat the basement apt ( either low profile cast iron or baseboard ). Can I use flexible hose ( rated180 degree) to transport hot water to radiators & back to boiler ,single loop What size dia. hose will be best ?. I plan to install a low voltage thermostat in basement apt to control the temp there. What type of relay must i install inorder to have the boiler go on & the pump to circulate hot water to radiators when the thermostat calls for heat ? When I set the pump system up ,which direction do I pump the water (into the boiler ?away towards radiators? ) do I need an expansion tank?
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    This is a Honeywell stat with an outside sensor I believe that it tells the compressor not to run if the outside temp is below the call temp. of the room stat. The Modutrol works!! I connected t1 and t2 to 24v and reconected the r,w,and b wires to the terminals labeled same. The thing adjusts to a partal open position after it runs a while. seems to adjust every so often. I guess it is adding as much outside warm air as it can before the temp starts to rise in the main duct where the sensor is. If this is true it is more of a vent than an economiser. It is adding 90deg air to the system. I guess The savings will come if the outside air was cold enough to not run the compressor. I connected the compressor's contactor switch wire through the outside stat. If the air outside is below 70 the compressor circuit will remain open. What temp should the compressor not come on if the room is still calling for cool? room is set for 73F Here is a picture of the rest of the system and the outside stat. I think the think is setup. what do you think?
  • Rodney Summers
    Rodney Summers Member Posts: 748
    low temp limit...

    the low outside air temp limit would be up to tranes's design & there's usually a safety stat in there for just this reason. my guess would be around 60F (without an ambient control). is this a heatpump?

    also, the economizer may not be totally adjusted / operating correctly if the louvers are allowing any significant amount of 90F air to enter right now in the mid afternoon.

    ss
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    It's just an old AC unit. We have steam for heat. It is adding just a crack of fresh air. I was able to see the louver opening from the outside. It seemed like more looking at the moter arm. I will set the limit to 60 and see what happens. It will turn off the compressor if you set the low temp limit (stat) to 100+ . When the compressor was off it caused the louvers to shut tight. I reposted a picture on the last post. Thanks for the help!
  • Rodney Summers
    Rodney Summers Member Posts: 748
    louver control stat?

    that stat mounted there throws me.

    how many wires (just 2 spst or 3 with a spdt?) & where does it go?

    are you sure it just doesn't go to the modutrol?

    ss
  • Empire_2
    Empire_2 Member Posts: 2,343
    I think I got it

    Check it out. The stat in the building is a lo temp compressor cut out, That's all... Usually set at 50* or so. The modutrol connections on the outside hood actually act independently from the rest of the system. R-B makes on Temp rise/ R-w Break on temp rise. As your compressor is disabled, say it is 50 * outside, there is probably a relay which closes to operate the dampers to rely on outdoor temp only to provide no lower that 50*supply air. This is where the R-B-W contacts come into play. As the cooler air comes in through the outside dampers, the contacts on R-W/R/B make and break to introduce 50* air according to your discharge air sensor which I believe you said you have. Dampers will open and close to acheive this temp (50*) till the space is satisfied. If it was 30* outside the dampers would modulate more to the closed position because of the much cooler temps. I also believe that there is probably 2 sets of dampers. Indoor and outdoor.... Am I right?
    Hope I was able to help..
    Mike T. If anyone would like to call me I can talk faster that I type. 716-648-1763 Empire Mechanical or leave a # and I will call you......
  • Rodney Summers
    Rodney Summers Member Posts: 748
    what?

    it looks like 3 heavier gauge than 24v wires coming out of that t-stat. still seems strange that it would be adjustable & located inside - even with the capillary temp line.

    ss
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    Yes on the 2 damper. they are joined together( more outside means less inside air)I never found the sensor in the main cold duct but it seems to work. I have one set of wires going toward the rear of the building I have not traced so far what other kind of sensor might there be. I have a sendor in the main duct conected to the modutrol, one conected to the outside stat, the inside room stat, any ideas ? It could have been connected to the timer that is now disconected.
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    It is heavy wire and there are 2 more that went to the closed on hot side of the stat I am not sure of
  • Empire_2
    Empire_2 Member Posts: 2,343
    OK

    Remote bulb??? I cant tell you why they do it but it's Done!. Maybe an attempt at energy management? They exist and I see em all the time. Iagree that It would have been easier to mount other type in the unit, but hey, Im just trying to get to the bottom of the Q: Dont let it shock you so much.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Would be nice

    If we could all be there and get to the bottom of this... Probably a logical answer to all the Q: being thrown about:) I think we all have our theory on the application of this particular job.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Do I Hear Fieldtrip?

    Where are you located Mr. Furnitureguy?
  • soot_seeker_2
    soot_seeker_2 Member Posts: 228
    Do I Hear Fieldtrip?? \"hvacbusters\" !

    "Do I Hear Fieldtrip?"

    they should film it - "hvacbusters" & put it on discovery.

    i think he's on long island - nassau county?

    i don't remember but i think i've seen this post come up about 10 times in the last 3 or so months on all the boards.

    but i do think this thing has been pretty much put to bed if not for some silly wiring schemes & control placement. no?


    ss
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398


    Guys sorry for all the confusion I think that Mike has the skinny on this one. Please keep in mind that this unit is old school. I think the 60s or 70s. The good news is that it is working and it now has an economiser that is opening and closing by its self. The heavy wire on the low temp cutoff could be the result of a part pre-wired or pulled from another job. It has a green wire run through the pipe that is not conected on either side. I wish it was a cool night so I could see if the louvers open more as it cools down it's still bloody hot in Hanover PA. I was reading the first post and I really didn't know a screw driver from a monkey wrench about HVAC. Thank you all. I would like to know what other factors were monitored by old units. This would alow me to look for other sensors in the building that might be burried in the walls etc. I will let you know what happens with the louvers in the AM if it is cool. Thanks again T.
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