Bypassing on/off button on window air conditioner

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  #1  
Old 11-12-07, 01:08 PM
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Using central Thermostat to control window AC

I have bought a window unit (Panasonic CWXC103HU) to cool a single room in my basement. I already have a thermostat connected in there which I currently have wired to a duct fan leading into that room coming from the upstaris system. That has worked quite well until now. Now we're using mostly heat instead of ac upstairs but the basement room continues to get too hot because of lights and equipment in there.

I would like to control this unit with my existing thermostat which is a digital honeywell. After some advice from the forum here, I was able to make it work with the duct fan just fine using a relay but this is different. I was hoping that the controls on the window unit might be 24v like the thermostat but that doesn't appear to be the case.

I've worn myself out trying to find schematics or a service manual so I could figure this out but no luck.

I've taken out the controls and have tested some of the wiring. The controls seem to be DC and less than 2V. The other wires seem to be AC and much higher 115v. I'm sure this can be done but I need to know where else to look.

I already have a return that I will connect to this unit and I will connect the output to the ductwork.

So should I be looking at the 115 wires or should I find another low voltage source and use relays?
 
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Old 11-12-07, 07:06 PM
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hmmm I did not run the specs on that window shaker but a lot of the newer window shakers actually have electronic controls with a built in thermostat that will cycle the unit to the set temperature without having to add a remote t-stat. Is it to late to return this one?
 
  #3  
Old 11-12-07, 07:45 PM
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There is really no way to make it work with lot of these newer units..

YOu could put a relay on the 115v, say the plug.. but most electronic units I've seen will not reset when the power come back on.. You'll have to turn the system back on by hand.

Is the in a single room? What rooms surround this room? Why not put a fan in the wall to exchange the air from this room to one of the surrounding rooms?

Also, the These windows unit are not made to run when outdoor temps is below 40...
 
  #4  
Old 11-13-07, 06:36 AM
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Originally Posted by Jay11J View Post
There is really no way to make it work with lot of these newer units..

YOu could put a relay on the 115v, say the plug.. but most electronic units I've seen will not reset when the power come back on.. You'll have to turn the system back on by hand.

Is the in a single room? What rooms surround this room? Why not put a fan in the wall to exchange the air from this room to one of the surrounding rooms?

Also, the These windows unit are not made to run when outdoor temps is below 40...
You're right. It doesn't reset on it's own. Can you think of a way I can defeat that? Surely I could put a jumper somewhere to keep a circuit closed all the time that would keep it on.

I was thinking of using a relay to trigger the fan and compressor individually. But would I have to trigger the start and run on the compressor separately?

It is a single room... well actually 2 rooms. What surrounds it is unfinished basement so the outdoor temp wouldn't be an issue. The unit itself would be in the unfinished basemement part.
 
  #5  
Old 11-13-07, 06:43 AM
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Originally Posted by Mr Fixit View Post
hmmm I did not run the specs on that window shaker but a lot of the newer window shakers actually have electronic controls with a built in thermostat that will cycle the unit to the set temperature without having to add a remote t-stat. Is it to late to return this one?
I bought this one used. It does have a thermostat but the unit is not going to be in the wall of the room where I need it(the walls are solid concrete) It will be about 20 feet away. That and the need for quiet(it's a studio) are the reasons I need to duct it. Also, I already have a thermostat in the wall in that room running to the area where I'll need to put it.

I also have the ductwork run from the previous setup as well as a 12" return in this area that feeds back to my central. I plan to reconnect that return to this window unit to close the loop.
 
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Old 11-13-07, 12:51 PM
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I would think that you could disconnect the existing control panel completely and wire in a relay and a remote t-stat without to much trouble . Use your multi meter to double check but you should be able to simply backtrack from your compressor leads and fan motor leads to see which leads on the unit need to be energized with 115 volts (I assume this is a 115 volt model?) to turn on the comp and fan(blower fan will be set at one speed motor your blower motor probably has three taps?) you will also need a transformer to power your t-stat. The transformer could power off the unit feed also. All you have to do is buy a normally open 120volt/24 control voltage relay. Wire the comp and desired fan speed hot lead to one side of your relay and bring the feed hot lead to the other side and tie neutrals together. Now hook up your transformer hot and neutral to the power feed and then run 24 volt power and transformer common back to your t-stat and then send back 24 volts and common to the relay coil on a call for cooling thru the t-stat and you should be good to go. Sounds like fun.
 
  #7  
Old 11-13-07, 02:06 PM
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Originally Posted by Saturn View Post
I would think that you could disconnect the existing control panel completely and wire in a relay and a remote t-stat without to much trouble . Use your multi meter to double check but you should be able to simply backtrack from your compressor leads and fan motor leads to see which leads on the unit need to be energized with 115 volts (I assume this is a 115 volt model?) to turn on the comp and fan(blower fan will be set at one speed motor your blower motor probably has three taps?) you will also need a transformer to power your t-stat. The transformer could power off the unit feed also. All you have to do is buy a normally open 120volt/24 control voltage relay. Wire the comp and desired fan speed hot lead to one side of your relay and bring the feed hot lead to the other side and tie neutrals together. Now hook up your transformer hot and neutral to the power feed and then run 24 volt power and transformer common back to your t-stat and then send back 24 volts and common to the relay coil on a call for cooling thru the t-stat and you should be good to go. Sounds like fun.
Go for it! That's what I like to hear! I was afraid I would get a bunch of "Can't be done" or "that would be too hard" kind of answers. There are actually 5 wires to the fan on this one - So 1 for each speed and a common, but what's the 5th one for?

The compressor has 3 wires. Would one of them be for start and the other, run? If so, how would I wire that?

I've tested the unit a little bit and I've traced 3 leads back to the control board but they all show 115vac at all times when the unit is turned on even before the compressor comes on. I sure wish I had schematics for this thing. Would it help if I took pictures of the wires, etc. and posted them?

I can use the 24v feed off my central air handler that it's currently connected to. The window unit will sit right next to it anyway.

I like the suggestion too of connecting the 115vac relay to the plug but he was right. The on/off button will get me. Do you know how I could wire around it?
 
  #8  
Old 11-22-07, 06:29 AM
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Bypassing on/off button on window air conditioner

I have a window unit air conditioner (Panasonic CWXC103HU) that I am connecting to a standard 24v central thermostat. I have the thermostat wired and a relay to turn power on and off to the AC unit. Problem is that this unit has a panel of control buttons on the front...one of which is on/off. When you turn off the power to the unit(i.e. relay turns off or I turn off the breaker) it defaults back to the "off" position. So in order to use the thermostat as it is, I would have to go to the AC unit and push the "on" button every time the thermostat comes on.

I'm looking for a way to bypass this on/off button so that the AC unit comes on every time power is supplied or it's plugged in.

I've looked high and low for the schematics with no luck yet. Maybe someone can help me in this department. I can post a picture if that helps.

I've posted a thread about this in the HVAC forum but they ran out of suggestions when we got to this part and someone suggested that I post it here.

Can anybody help me figure this one out?
 
  #9  
Old 11-22-07, 08:10 AM
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Sounds like the unit has an electrinic control. A mechanical control would stay on. If you take the cover of the unit it should have wiring diagram.
You are probably going to need to tap into the compressor and fan circuits to turn it off from there instead of the on/off switch.
 
  #10  
Old 11-22-07, 09:12 AM
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[The following is based on a 120v AC, 240v may need modification of method] The fan probably has two or three speeds. Simplest would be choose the speed you most often use and treat the fan as a single speed fan. Determine by examination which lead of the fan is neutral. By experimentation determine which of the remaining leads is the one you need for that speed. One lead to the compressor is neutral one is hot. Determine which is hot. Connect the fan hot and the compressor hot to the relay. All other leads on the fan (except neutral) disconnected and capped.

No guarantee the above won't damage the AC but it should work because basically you are just bypassing the electronic controls. If you want multiple fan speeds that is possible but more complicated. If you want the fan to run when the compressor is off which would reduce temperature swings the fan would be wired through a mechanical switch or perhaps a second relay depending on your thermostat.
 
  #11  
Old 11-22-07, 09:19 AM
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In addition to what was already suggested...

I'm assuming you've tried the obvious: If you hold the power button down while applying power to the unit, does it power up in the 'On' setting and stay there? If so of course all you'd need to do is jumper that little button.
 
  #12  
Old 11-23-07, 08:37 AM
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Originally Posted by ray2047 View Post
[The following is based on a 120v AC, 240v may need modification of method] The fan probably has two or three speeds. Simplest would be choose the speed you most often use and treat the fan as a single speed fan. Determine by examination which lead of the fan is neutral. By experimentation determine which of the remaining leads is the one you need for that speed. One lead to the compressor is neutral one is hot. Determine which is hot. Connect the fan hot and the compressor hot to the relay. All other leads on the fan (except neutral) disconnected and capped.

No guarantee the above won't damage the AC but it should work because basically you are just bypassing the electronic controls. If you want multiple fan speeds that is possible but more complicated. If you want the fan to run when the compressor is off which would reduce temperature swings the fan would be wired through a mechanical switch or perhaps a second relay depending on your thermostat.
I'm with you on the fan and I think that the high setting would be fine all the time.

The compressor, however, seems to have 3 leads which are labled S, R, and C(Start, Run, and Common?) Is this like a refrigerator in that the start power is applied and then the run power? If so, I'm not sure how I could just hook up the relay to the compressor and make it work.
 
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Old 11-23-07, 08:54 AM
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Originally Posted by core View Post
In addition to what was already suggested...

I'm assuming you've tried the obvious: If you hold the power button down while applying power to the unit, does it power up in the 'On' setting and stay there? If so of course all you'd need to do is jumper that little button.
No, actually, it gives a short beep and then nothing. If I let go and push it again, it comes on, etc. It has a thin touch pad so it's just a momentary switch I guess instead of an on/off type switch. The back of the pcb button panel is labled so I jumpered the on/off button... same thing. So does that mean I need to jumper it somewhere else? The button panel is connected by a ribbon cable to another pcb.
 
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Old 11-23-07, 09:48 AM
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If it helps, I found the specs on my compressor which include a wiring diagram.

http://www.lge.com/products/componen...pdf/QK156C.pdf

I don't see any reference on it to hp but I'm wondering if I couldn't use a refrigerator compressor start relay to start and run this compressor. ???
 
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Old 11-23-07, 11:29 AM
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You need to look further back in the wiring to the point where 'line' connects. If you look at the drawing in the lower right of that sheet. One of the connections is going to be at the capacitor. The other at an overload protector.
 
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Old 11-23-07, 11:30 AM
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I just found a schematic on the back side of the control area...

http://www.flickr.com/photos/[email protected]/2057947672/
 
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Old 11-23-07, 11:41 AM
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At the bottom RY-COMP is the relay contact to turn on the compressor. You need to connect after the ry at the 4 contact. Looks like it might be a blue wire (BL).
Near the center of the drawing is the fan control relay. Two speed are present fro ry-low and ry-hi. Note this is after the fuse so you should note the fuse value and install fuse in the line.
 
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Old 11-26-07, 04:17 AM
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core posted a link to a schematic in a different thread that may work well here: http://www.oldradio.com/current/cont2mom.htm

Use the relay's contact closure across the on/off switch. Power the relay's 12v transformer off the switched AC circuit. When the thermostat kicks the circuit on, the relay pulses the on/off switch to turn on the unit. When power is cut, everything resets.

If it doesn't work the relay is probably firing too early (before the unit's processor has a chance to boot). You may need to add another RC to delay the relay pulse when the circuit is powered.

No modification to the high-voltage side of the unit is needed, so its built-in overload protections are still in place.
 
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Old 11-26-07, 07:46 AM
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Originally Posted by Rick Johnston View Post
core posted a link to a schematic in a different thread that may work well here: http://www.oldradio.com/current/cont2mom.htm

Use the relay's contact closure across the on/off switch. Power the relay's 12v transformer off the switched AC circuit. When the thermostat kicks the circuit on, the relay pulses the on/off switch to turn on the unit. When power is cut, everything resets.

If it doesn't work the relay is probably firing too early (before the unit's processor has a chance to boot). You may need to add another RC to delay the relay pulse when the circuit is powered.

No modification to the high-voltage side of the unit is needed, so its built-in overload protections are still in place.
Ok, I think I'm following you. Could I just connect the 24v relay to the thermostat, then the RC, and then across the contacts across the on/off switch leaving the power to the AC unit connected the whole time?

The RC causes the relay to pulse instead of staying closed the whole time it is supplied 24v right?

Can you tell me exactly what I'll need to put the RC together?
 
  #20  
Old 11-27-07, 04:04 AM
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If the unit is powered all the time the circuit gets much more complicated because you have to pulse the on/off switch's relay a second time to turn it off.

The schematic shows a switch. It's not needed. Plug the 12v DC power supply (wall wart) into your switched leg -- the same as the one for the unit. A 10k ohm 1/4 watt resistor and a 1000 microfarad 25 (or 50) volt polarized axial electrolytic capacitor will connect next to each other in parallel to the zero volts side of the wall wart. Make sure the cap is connected with the proper polarity. The other leads of the resistor & cap connect to one side of the relay coil. The other side of the relay coil connects to the + side of the wall wart.

Connect the leads from the on/off button to the normally open contacts on the 12v relay.

The RC causes the relay to pulse instead of staying closed the whole time it is supplied 24v right?
Correct.

Could I just connect the 24v relay to the thermostat
I think you might need the slight delay that the extra wall wart will provide. (And maybe even a second RC network in parallel with the coil to delay the turn-on pulse even more.) Besides, it's always better to buffer different circuits so they aren't directly connected to each other. The second relay will accomplish that.
 
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Old 11-27-07, 04:51 AM
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I am not sure why you would want to do this.

The addition of electronic controls to a window shaker has improved them greatly.
Many have anti-short cycling, freeze protection, more accurate temperature control, humidity control, on-off timer and can adjust the fan speed according to cooling load.

You might find that the fast reacting nature of a wall thermostat may cause the breaker to occasionally trip.
 
  #22  
Old 11-27-07, 06:30 AM
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Originally Posted by GregH View Post
The addition of electronic controls to a window shaker has improved them greatly.
Many have anti-short cycling, freeze protection, more accurate temperature control, humidity control, on-off timer and can adjust the fan speed according to cooling load.

You might find that the fast reacting nature of a wall thermostat may cause the breaker to occasionally trip.
The reason I need to do this is because this is for a basement room that is not adjacent to unfinished space. More importantly, even if it were, the walls are 10" concrete all the way around making it more or less impossible to cut any decent size hole, not to mention the noise and ruining the aesthetics of a really nice studio.

I made a big improvement for this room a while back by installing a duct fan(I do have a single 10" duct running to this room from my upstairs unit) which I control with a thermostat that's already installed in the room. This cools plenty well but one problem is that the central unit wasn't always on when I needed it. Also, now that it's getting cold outside, my heat pump is on in the central unit instead of the AC and the studio still gets too hot at times because of all the electronic equipment in there... never too cold.

So since I already had a thermostat, I thought it might not be too difficult to connect a window unit and connect it to the existing duct as well(there's also a return for this area)
 
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Old 11-27-07, 10:40 AM
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Ok,
Not exactly sure how you would connect this unit to a duct or where you would discharge the heat from the condenser side.

You may have a thermostat in the room for the duct fan but you would need to set up relays to have it control the a/c unit.

You also need to keep in mind that the fan that is in a window unit does not have the capacity to force air through a duct.

This looks like a perfect application for a ductless split unit.
 
  #24  
Old 11-27-07, 11:23 AM
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Originally Posted by GregH View Post
Ok,
Not exactly sure how you would connect this unit to a duct or where you would discharge the heat from the condenser side.

You may have a thermostat in the room for the duct fan but you would need to set up relays to have it control the a/c unit.

You also need to keep in mind that the fan that is in a window unit does not have the capacity to force air through a duct.

This looks like a perfect application for a ductless split unit.
I'm sure it's a great application for that but I'm afraid that wouldn't accomplish my other objective which was to spend almost $0 on this.

The unit will be in the unfinished basement area to discharge the heat. The air (hopefully) will travel through the duct via the built in fan and the duct fan together. The relays, etc. are exactly what I'm here to discuss.
 
  #25  
Old 11-27-07, 05:26 PM
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Wait ... you have a window air conditioner in your recording studio? The noise of that thing running will clearly be heard in your recordings!
 
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Old 11-27-07, 06:12 PM
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I have merged your original thread on this project with the one you posted in electrical.
We do not get the whole scope of the project when you shop around for better answers.

Yes, I know you asked about relays but those who do not wholeheartedly support the idea of your project do so from a different knowledge base.

I have to tell you that even if you were to get the electrical part running that window unit will not blow into a duct that is fed from a different fan.
In the furnace duct you will have a positive static pressure that will be pushing against the fan in the window unit.
This only has to slow the air flow in the window unit slightly for it to freeze up.

I would suggest that you get the window unit running and at least try it in the duct before you mess with a remote stat.

In a previous post you talked about having a run and start winding on the compressor to deal with.
Have you pulled all the wiring off the a/c?
If so in order to get it running you will need to look at the schematic for the unit and reconnect the run capacitor and start relay if it as one.
 
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Old 11-27-07, 07:25 PM
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I must not have been clear in my description. The duct is currently connected to the central trunk line. When I get the window unit working, I will disconnect it from the trunk line and connect it to the window unit. I will also connect a dedicated return to the window unit air intake. It won't be connected in any way to my central.

I haven't pulled any wires off at this point. I posted a link to the schematic in a previous message. I'm not positive if it has a start relay. I could use a little help there.
 

Last edited by GregH; 11-29-07 at 10:29 AM. Reason: Not necessary to quote entire previous post.
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Old 11-28-07, 09:59 AM
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Heat dissapation ---

Is it possible you could ventilate an enclosed area with a vent-slot cut in the floor above your studio?

I ask this because if you could, it may be possible to construct a vertical "box" , floor-to-ceiling , say 2ft in depth, and 3ft in width.

At the top of the box would be a rectangular opening in which the window AC would be set-in-place. The heat dissapated by the condensor coil would have to vent upwards thru the floor above , and could possibly add heat to the room when the AC is operating in cold weather.

An HVAC pro might be able to provide an "induced-draft" fan which causes an up-wards air-flow.

You could you the space below the AC unit for shelving and storage.

If it's necessary to prevent the AC unit from operating when you are cooling the house , well, you need another control-circuit.
 
  #29  
Old 11-28-07, 12:25 PM
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Originally Posted by PATTBAA View Post
Is it possible you could ventilate an enclosed area with a vent-slot cut in the floor above your studio?

I ask this because if you could, it may be possible to construct a vertical "box" , floor-to-ceiling , say 2ft in depth, and 3ft in width.

At the top of the box would be a rectangular opening in which the window AC would be set-in-place. The heat dissapated by the condensor coil would have to vent upwards thru the floor above , and could possibly add heat to the room when the AC is operating in cold weather.

An HVAC pro might be able to provide an "induced-draft" fan which causes an up-wards air-flow.

You could you the space below the AC unit for shelving and storage.

If it's necessary to prevent the AC unit from operating when you are cooling the house , well, you need another control-circuit.
I see what you're saying and I guess that would work except that the ceiling is solid concrete. This room is under the garage.
 
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Old 11-28-07, 04:01 PM
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I looked at the schematic for your unit and you could redirect the compressor and fan circuit to external relays.
The problem is that I will again say that the performance of the a/c after you install it will be nil to zero.

As I already said the fan that is in the unit, both evaporator and condenser are not designed to force the air through more that the coils of the unit.

There was the suggestion to add a booster fan and there could be a possibility of this if you set it up correctly.
For the size of your air conditioner you would need a fan to move the cool air that was capable of moving air in a duct at a rate of 400 cfm after allowing for restrictions.

You could also move the warm air out of the back if you used a fan that could move about 700 cfm after restrictions.

Dealing with the electrical is the easy part.
The mechanics of making a contraption like this work, refrigeration wise is the challenge.

You would be able to test the concept by temporarily hooking it up, allowing the unit's controls to run it and see if you can remove heat from where you want to.
 
  #31  
Old 11-28-07, 06:33 PM
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Greg,
Please add some insight into the audible noise a rig like this would generate and what it would take to silence it. If it's going to be used in a sound recording studio, it has to be silent. (And chad, don't tell me you won't use it while the music is being recorded. That's the time you'll need it most.)

As I understand it, a duct has to take several right-angle turns to quiet the air source. It also has to be made of some kind of sound-absorbant material like fiberglass, correct? But is also starts with a unit that's designed to be quiet to begin with. Window AC's aren't the quietest things in the world.
 
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Old 11-28-07, 08:13 PM
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As planned it wouldn't cool so it wouldn't be used and not a problem for recording.

To make airflow silent you need low velocity which you get by oversizing the ductwork and grills.
Oversizing the blower and using it at the lower rpm of its capacity range will lower the tip speed making less fan noise.
Lining the duct with acoustic insulation, a couple of 90 deg bends as suggested and locating the air handler as far from the quiet room as possible will also lower the sound level.
 
  #33  
Old 11-29-07, 09:33 AM
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Originally Posted by GregH View Post
I looked at the schematic for your unit and you could redirect the compressor and fan circuit to external relays.
The problem is that I will again say that the performance of the a/c after you install it will be nil to zero.

As I already said the fan that is in the unit, both evaporator and condenser are not designed to force the air through more that the coils of the unit.

There was the suggestion to add a booster fan and there could be a possibility of this if you set it up correctly.
For the size of your air conditioner you would need a fan to move the cool air that was capable of moving air in a duct at a rate of 400 cfm after allowing for restrictions.

You could also move the warm air out of the back if you used a fan that could move about 700 cfm after restrictions.

Dealing with the electrical is the easy part.
The mechanics of making a contraption like this work, refrigeration wise is the challenge.

You would be able to test the concept by temporarily hooking it up, allowing the unit's controls to run it and see if you can remove heat from where you want to.
I do have a booster fan in line with the 10" duct I'm going to use which I believe operates at 650 cfm.

Based on the schematic, can you tell me how you would go about the wiring?
 
  #34  
Old 11-29-07, 09:39 AM
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Originally Posted by GregH View Post
As planned it wouldn't cool so it wouldn't be used and not a problem for recording.

To make airflow silent you need low velocity which you get by oversizing the ductwork and grills.
Oversizing the blower and using it at the lower rpm of its capacity range will lower the tip speed making less fan noise.
Lining the duct with acoustic insulation, a couple of 90 deg bends as suggested and locating the air handler as far from the quiet room as possible will also lower the sound level.
That makes sense. Do you think 10" ductwork would be considered oversizing in this case? Also, can you reccommend something that will work for acoustic lining?

The unit will be about 20 - 30 ft. away based on the way the duct will run.
 
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