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#1
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Central A/C cooling fine but humidity seems high
CBHvac wrote:
"Bob M." wrote in message ... About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. 2 tons on 800SF...wow.. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. ("With proper sizing, probably should be running most of the time when Out Door temp is in the mid 90's.") The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. Bingo.. Problem. That 3 speed fan, isnt to go play with, its to allow for duct issues and blower curves... sniped the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Partially right..its not allowing the air enough time on the coil Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Slow the fan down, however when you do this, the current charge in the unit may not be enough... I would type more on this, but my helper took my fingertip off in an accident today, and typing is real fun right now.. Thanks. Bob M. If the latent load is high enough it may call for a 2 ton unit. Don't know what his conditions are, but sounds like a 1.5 ton on that cooling coil might do more of what he wants in respect to humidity, if there is not sufficient continuous run time with the 2 ton unit. I know some in S.W. WI that are cooling 2000 sq ft homes with 2 ton condensing units. However, that's what the heat load is in those cases, so doesn't mean anything for other conditions. "What is the Design Temp? With proper sizing, the unit probably should be running most of the time when Out Door temp is in the mid 90's." Slow the fan down, however when you do this, the current charge in the unit may not be enough... I take it that the increased latent heat load on the evaporator will vaporize the refrigerant faster requiring an increase demand for liquid (R.) which will increase the heat load on the condenser increasing the pressure which will increase the flow on an orifice or cap tube cooling coil which might require a little more refrigerant. A TEV would open more to keep the Super Heat in the correct zone. Or, is your explanation different? Hope your finger heals like new! D- -- Get the Cooling Capacity and Efficiency you Paid for - http://www.udarrell.com/air-conditio...city-seer.html http://www.udarrell.com/air-conditio...tent-heat.html |
#2
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Central A/C cooling fine but humidity seems high
"Bob M." wrote in message ... About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. 2 tons on 800SF...wow.. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. Bingo.. Problem. That 3 speed fan, isnt to go play with, its to allow for duct issues and blower curves... I'm wondering: could such a fast fan speed be literally blowing the air and moisture right off the coolihg coil, and not giving it a chance to condense the moisture so it drains out? I can lower the fan speed (I have 4 to choose from) but before I get into that, I wanted to at least see if my theory made sense. I figure if the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Partially right..its not allowing the air enough time on the coil Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Slow the fan down, however when you do this, the current charge in the unit may not be enough... I would type more on this, but my helper took my fingertip off in an accident today, and typin is real fun right now.. Thanks. Bob M. |
#3
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Central A/C cooling fine but humidity seems high
Bob M. wrote:
About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. I'm wondering: could such a fast fan speed be literally blowing the air and moisture right off the coolihg coil, and not giving it a chance to condense the moisture so it drains out? I can lower the fan speed (I have 4 to choose from) but before I get into that, I wanted to at least see if my theory made sense. I figure if the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Thanks. Bob M. 800 sq. feet and 2 tons seems like too much a/c for the building....... if you dont want to turn the fan speed down then call out a tech and get him to check it out and see whats wrong with it.. not the same guy who put in the second unit for you... he will never find his own mistake... |
#4
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Central A/C cooling fine but humidity seems high
"D-" wrote in message ... CBHvac wrote: "Bob M." wrote in message ... About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. 2 tons on 800SF...wow.. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. ("With proper sizing, probably should be running most of the time when Out Door temp is in the mid 90's.") The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. Bingo.. Problem. That 3 speed fan, isnt to go play with, its to allow for duct issues and blower curves... sniped the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Partially right..its not allowing the air enough time on the coil Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Slow the fan down, however when you do this, the current charge in the unit may not be enough... I would type more on this, but my helper took my fingertip off in an accident today, and typing is real fun right now.. Thanks. Bob M. If the latent load is high enough it may call for a 2 ton unit. Don't know what his conditions are, but sounds like a 1.5 ton on that cooling coil might do more of what he wants in respect to humidity, if there is not sufficient continuous run time with the 2 ton unit. I know some in S.W. WI that are cooling 2000 sq ft homes with 2 ton condensing units. However, that's what the heat load is in those cases, so doesn't mean anything for other conditions. Well..there is part of the problem..we dont know where he is at...and that is an issue.. "What is the Design Temp? With proper sizing, the unit probably should be running most of the time when Out Door temp is in the mid 90's." You got that right.. Slow the fan down, however when you do this, the current charge in the unit may not be enough... I take it that the increased latent heat load on the evaporator will vaporize the refrigerant faster requiring an increase demand for liquid (R.) which will increase the heat load on the condenser increasing the pressure which will increase the flow on an orifice or cap tube cooling coil which might require a little more refrigerant. A TEV would open more to keep the Super Heat in the correct zone. Well..around here, with the high humidity, we go for the lower fan speeds, and as we all know in the trade, that you design to med fan speed in most cases, and use high or low depending on the situation, but here, we go for the lowest possible.. When you do that, as long as the static is fine, you tend to find that the superheat changes, and 9 out of ten times, you add a bit of refrigerant to get things back in order, due to the lower fan speed, and slightly less airflow over the coil.. Or, is your explanation different? Hope your finger heals like new! D- Thanks...typing is bad enough...cant wait to go work in the rain tomorrow..LOL -- Get the Cooling Capacity and Efficiency you Paid for - http://www.udarrell.com/air-conditio...city-seer.html http://www.udarrell.com/air-conditio...tent-heat.html |
#5
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Central A/C cooling fine but humidity seems high
I live in southern CT. The house also has a poorly insulated 2nd floor. When
the first system was installed, there was NO insulation in the walls and the house was painted brown. Sucked up a lot of solar heat. There's also a half-finished basement, but the HVAC system attempts to heat and cool the entire house. So in actuality, the house is much bigger than the 800 sq ft would imply. When the temp is in the 90s outside, the unit does run for hours at a time. During those periods the condensate pump will come on once in a while (maybe every 15 minutes). The system will bring the house down from 78 (daytime setback) to 74 regardless of outside temp in about 2 hours. On the previous system, the fan speed was adjustable by changing the pulley size on the motor. I had fooled with it at one point and it was set to work very nicely in both winter and summer seasons without change. The new system has four fan speeds but uses a direct drive AC motor on the blower. The lowest speed is used when the thermostat's FAN ON/AUTO switch is set to ON and the system is not calling for heating or cooling. Just moves a little air around so you don't get that stuffy feeling. The highest speed is for cooling, and one of the other two is used for heating. The contractor who replaced the system did nothing but that, manufacturing new plenum pieces where necessary. As long as it heated and cooled, his job was done. He didn't install the original system, and when a friend with a similar house called these same people in to add AC to his system, they refused, saying they'd need a lot more return ducts to the 2nd floor (which they could not add), and other problems. Would have cost him like $10,000 to do it "right" so he just bought a few window units and saved a lot of money. I had a similar experience when I added AC to my old system, but the contractor wasn't as insistent and was able to install one return duct to the 2nd floor in my house. I don't think it does much good, but it's there anyway. I will get much more cooling when I replace my roof and add insulation to the 2nd floor walls and ceiling. As it stands now, upstairs reaches 90F in the summer and goes down to 50 in the winter, so you can imagine how little insulation there really is up there. I will try changing the fan speed to see if that helps at all. One thing that seems unfortunate with this unit is that they give you four speed wires from the motor, and only three active terminals and one "place holder" to connect them to, so you can't have one speed for both heating and cooling, or the same speed for FAN ON and heating and cooling. I am going to check the possibility of making some form of jumper that will allow me to have one wire go to multiple terminals while leaving the others disconnected. I'm good with electronic and electrical stuff so I'll take precautions first and measure twice before blowing something up. If I were designing this controller I would give the system more flexibility than it seems to have right now. Thanks for all the comments, suggestions, and agreement (in part) with my analysis. Bob M. ====== "jim" wrote in message ... Bob M. wrote: About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. I'm wondering: could such a fast fan speed be literally blowing the air and moisture right off the coolihg coil, and not giving it a chance to condense the moisture so it drains out? I can lower the fan speed (I have 4 to choose from) but before I get into that, I wanted to at least see if my theory made sense. I figure if the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Thanks. Bob M. 800 sq. feet and 2 tons seems like too much a/c for the building....... if you dont want to turn the fan speed down then call out a tech and get him to check it out and see whats wrong with it.. not the same guy who put in the second unit for you... he will never find his own mistake... |
#6
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Central A/C cooling fine but humidity seems high
"Bob M." wrote in message ... I live in southern CT. The house also has a poorly insulated 2nd floor. When the first system was installed, there was NO insulation in the walls and the house was painted brown. Sucked up a lot of solar heat. There's also a half-finished basement, but the HVAC system attempts to heat and cool the entire house. So in actuality, the house is much bigger than the 800 sq ft would imply. Then....the information we had, that you gave was wrong...another reason why we always tell people that we cant see it from here... When the temp is in the 90s outside, the unit does run for hours at a time. During those periods the condensate pump will come on once in a while (maybe every 15 minutes). The system will bring the house down from 78 (daytime setback) to 74 regardless of outside temp in about 2 hours. I have news for you....at 90F or higher in your area, you can expect it to run all the time, since the design ttemp in your area is less than that...and the TD during design is 20F.....so..so far, it all sounds like it was sized correctly, and perhaps better than you expect..but again...we cant tell from here. On the previous system, the fan speed was adjustable by changing the pulley size on the motor. I had fooled with it at one point and it was set to work very nicely in both winter and summer seasons without change. The new system has four fan speeds but uses a direct drive AC motor on the blower. The lowest speed is used when the thermostat's FAN ON/AUTO switch is set to ON and the system is not calling for heating or cooling. Just moves a little air around so you don't get that stuffy feeling. The highest speed is for cooling, and one of the other two is used for heating. Depending on the setup and original design from factory of the unit, low speed is ALWAYS for heating, and higher speed is for cooling...however, with a 4 speed motor, you have more options and the highest speed may not be needed.... The contractor who replaced the system did nothing but that, manufacturing new plenum pieces where necessary. As long as it heated and cooled, his job was done. He didn't install the original system, and when a friend with a similar house called these same people in to add AC to his system, they refused, saying they'd need a lot more return ducts to the 2nd floor (which they could not add), and other problems. Would have cost him like $10,000 to do it "right" so he just bought a few window units and saved a lot of money. I had a similar experience when I added AC to my old system, but the contractor wasn't as insistent and was able to install one return duct to the 2nd floor in my house. I don't think it does much good, but it's there anyway. I will get much more cooling when I replace my roof and add insulation to the 2nd floor walls and ceiling. As it stands now, upstairs reaches 90F in the summer and goes down to 50 in the winter, so you can imagine how little insulation there really is up there. Umm..kinda vaugue there....we are building homes with R40 in the walls and ceilings, and they can drop to freezing if the temps outside are low enough, and there is no heat in the place... I dont really understand what you are trying to get at here, but the R and U values are important, but they play a huge part in the Manual J and D calcs... something it sounds like has not been properly done. I will try changing the fan speed to see if that helps at all. One thing that seems unfortunate with this unit is that they give you four speed wires from the motor, and only three active terminals and one "place holder" to connect them to, so you can't have one speed for both heating and cooling, or the same speed for FAN ON and heating and cooling. Unless its a heat pump, you dont want that...low for heat, and a higher speed for cooling... I am going to check the possibility of making some form of jumper that will allow me to have one wire go to multiple terminals while leaving the others disconnected. I'm good with electronic and electrical stuff so I'll take precautions first and measure twice before blowing something up. If I were designing this controller I would give the system more flexibility than it seems to have right now. I suggest that unless you understand thermal dynamics, how this will affect your comfort and your systems performance and life, and things like temp rise, superheat, subcool, and the like, you leave it alone, and get a company out that can set up the unit properly, and not hack it in.. What you are talking about doing, sounds great in theory, but in actual use, can create even more issues.. Thanks for all the comments, suggestions, and agreement (in part) with my analysis. Bob M. ====== "jim" wrote in message ... Bob M. wrote: About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. I'm wondering: could such a fast fan speed be literally blowing the air and moisture right off the coolihg coil, and not giving it a chance to condense the moisture so it drains out? I can lower the fan speed (I have 4 to choose from) but before I get into that, I wanted to at least see if my theory made sense. I figure if the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Thanks. Bob M. 800 sq. feet and 2 tons seems like too much a/c for the building....... if you dont want to turn the fan speed down then call out a tech and get him to check it out and see whats wrong with it.. not the same guy who put in the second unit for you... he will never find his own mistake... |
#7
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Central A/C cooling fine but humidity seems high
The information I gave you was not "wrong", it was just incomplete. There's
a big difference. I did not think it was important to go into all the details with the first message, so I left somethings out. They were obviously of use to some people, while it may have been useless to others. Back in 1951 when this house was built, they used 2x4 construction with rock wool bats in the roof. The basements and 2nd floors (actually attics) were unfinished. The original homeowner finished the 2nd floor but did so as inexpensively as possible; this included no additional insulation and used doors. Apparently some ethnic groups are just plain cheap. When I added A/C in the late 1980s the contractor did the best he could given the situation in the house, stating it would not be effective on the 2nd floor. Fine. I've lived with it that way and am happy the main floor was comfortable. When the furnace was replaced, none of us expected there to be any difference in operation besides going from oil to natural gas heat, and reclaiming several square feet of basement floor space. Whether the system (heating and cooling) was working properly or at its most efficient settings is really immaterial if the house is comfortable and the homeowner is not complaining. Well, now I'm thinking of complaining and decided to pose the question here. I had no problem adjusting the pulley size on my old furnace, and I have no problem playing with the fan speed on my new system. If the ducts are inadequate for the air volume at the highest speed, then slowing it down is my only option besides ripping everything out and starting all over again. It was easiest with the old furnace to find one fan speed that was a compromise and leave it alone. May not have been the best setting, but it did the job. Kind of like driving a car in 2nd gear all the time. It may be a bit hard to leave a stop sign, and it may wind the engine up kinda fast on the highway, but at least you don't have to worry about shifting. So, if you are stating (not recommending) that the lowest speed is usually for heat, and higher speeds for cooling, I can go with that. I'll see what I can do to take the fan speed down one or two notches for cooling and see if that helps with the humidity extraction at all. I'm not going to fry the system or cause anything else to go wrong. As it is, the air temperature coming off the fan on the compressor unit outside has never been more than a few degrees above ambient temp anyway, so I've known all along that it's not pulling out as much heat as it could from inside the house. Maybe that's why it's been working as well/poorly as it has all these years. You've given me food for thought. It's my choice whether to cook it and eat it, or throw it away. I thank you for all the advice, suggestions, warnings, caveats, etc. Bob M. ====== "CBHvac" wrote in message ... "Bob M." wrote in message ... I live in southern CT. The house also has a poorly insulated 2nd floor. When the first system was installed, there was NO insulation in the walls and the house was painted brown. Sucked up a lot of solar heat. There's also a half-finished basement, but the HVAC system attempts to heat and cool the entire house. So in actuality, the house is much bigger than the 800 sq ft would imply. Then....the information we had, that you gave was wrong...another reason why we always tell people that we cant see it from here... When the temp is in the 90s outside, the unit does run for hours at a time. During those periods the condensate pump will come on once in a while (maybe every 15 minutes). The system will bring the house down from 78 (daytime setback) to 74 regardless of outside temp in about 2 hours. I have news for you....at 90F or higher in your area, you can expect it to run all the time, since the design ttemp in your area is less than that...and the TD during design is 20F.....so..so far, it all sounds like it was sized correctly, and perhaps better than you expect..but again...we cant tell from here. On the previous system, the fan speed was adjustable by changing the pulley size on the motor. I had fooled with it at one point and it was set to work very nicely in both winter and summer seasons without change. The new system has four fan speeds but uses a direct drive AC motor on the blower. The lowest speed is used when the thermostat's FAN ON/AUTO switch is set to ON and the system is not calling for heating or cooling. Just moves a little air around so you don't get that stuffy feeling. The highest speed is for cooling, and one of the other two is used for heating. Depending on the setup and original design from factory of the unit, low speed is ALWAYS for heating, and higher speed is for cooling...however, with a 4 speed motor, you have more options and the highest speed may not be needed.... The contractor who replaced the system did nothing but that, manufacturing new plenum pieces where necessary. As long as it heated and cooled, his job was done. He didn't install the original system, and when a friend with a similar house called these same people in to add AC to his system, they refused, saying they'd need a lot more return ducts to the 2nd floor (which they could not add), and other problems. Would have cost him like $10,000 to do it "right" so he just bought a few window units and saved a lot of money. I had a similar experience when I added AC to my old system, but the contractor wasn't as insistent and was able to install one return duct to the 2nd floor in my house. I don't think it does much good, but it's there anyway. I will get much more cooling when I replace my roof and add insulation to the 2nd floor walls and ceiling. As it stands now, upstairs reaches 90F in the summer and goes down to 50 in the winter, so you can imagine how little insulation there really is up there. Umm..kinda vaugue there....we are building homes with R40 in the walls and ceilings, and they can drop to freezing if the temps outside are low enough, and there is no heat in the place... I dont really understand what you are trying to get at here, but the R and U values are important, but they play a huge part in the Manual J and D calcs... something it sounds like has not been properly done. I will try changing the fan speed to see if that helps at all. One thing that seems unfortunate with this unit is that they give you four speed wires from the motor, and only three active terminals and one "place holder" to connect them to, so you can't have one speed for both heating and cooling, or the same speed for FAN ON and heating and cooling. Unless its a heat pump, you dont want that...low for heat, and a higher speed for cooling... I am going to check the possibility of making some form of jumper that will allow me to have one wire go to multiple terminals while leaving the others disconnected. I'm good with electronic and electrical stuff so I'll take precautions first and measure twice before blowing something up. If I were designing this controller I would give the system more flexibility than it seems to have right now. I suggest that unless you understand thermal dynamics, how this will affect your comfort and your systems performance and life, and things like temp rise, superheat, subcool, and the like, you leave it alone, and get a company out that can set up the unit properly, and not hack it in.. What you are talking about doing, sounds great in theory, but in actual use, can create even more issues.. Thanks for all the comments, suggestions, and agreement (in part) with my analysis. Bob M. ====== "jim" wrote in message ... Bob M. wrote: About 800 sq ft Cape Cod style house with forced warm air heat. Added 2-ton York central A/C in 1989. Due to plenum shape, they put in a horizontal coil rather than an A-shaped coil. Worked well once I blew insulation into the house. Always felt very comfortable. Replaced the furnace in 2000 with a Lennox gas unit, and they installed a new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same York compressor unit. The system will cool the house down quite nicely, but the humidity seems uncomfortably high at times, like over 50% even with the temp down to 74F. On days when it's in the mid 90s the system will bring the house down to the mid 70s and keep it there, cycling on and off as need be. The condensation pump runs, but not nearly as often as it did with the old setup. Cold air comes out of the ducts at about 58 degrees, so the system seems adequate for "cooling" purposes. The fan speed was factory set to the highest speed. I'm wondering: could such a fast fan speed be literally blowing the air and moisture right off the coolihg coil, and not giving it a chance to condense the moisture so it drains out? I can lower the fan speed (I have 4 to choose from) but before I get into that, I wanted to at least see if my theory made sense. I figure if the air moves slower across the coil, the moisture will condense and drip down and out. Never had this problem with the old horizontal coil. Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I run that unit to cool the room down to 74, then leave it to go back into the main floor, there's a noticeable increase in humidity and the room feels clammy and uncomfortable. It's this comparison that's got me thinking the central system isn't removing the humidity like it used to. Any thoughts or suggestions? Is my analysis sound? I don't see any moisture around the furnace, so I'm fairly sure the condensed water is going where it's supposed to. When the thermostat shuts the system off, the condensate pump usually comes on a few seconds later to pump the water out. That's why I almost think it's saving it until the fan slows down or stops. Thanks. Bob M. 800 sq. feet and 2 tons seems like too much a/c for the building....... if you dont want to turn the fan speed down then call out a tech and get him to check it out and see whats wrong with it.. not the same guy who put in the second unit for you... he will never find his own mistake... |
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