______________________________________________________________________ Hi all. My folks down in florida have a device called a humidistat that runs the AC every now and again just to control the humidity. I live in Georgia. I’m a cheap a$$ and keep my AC set at 78/80 in the summer…and sometimes the humidity INSIDE gets kinda high because the AC does not run for a few hours… Can I find and hook up a humidistat like my parents have to my carrier AC units to have them run when the humidity gets too high? if you need a website visit host-my-site.com not the cheapest but the best service around. Replies: TechMaster “Re(1):humidistat” , posted Sun 18 Jul 14:22 ______________________________________________________________________ Bigjohn, the humidistat you chose was a 2 wire and will work just fine. You just break the R wire and wire it in series. As far as controlling the a/c, you can only run the system by temperature or humidity (not both) wiring it this way. If you want either one to put on the a/c, then you will have to do what Zenos said and wire the humidistat in parallel, but the wiring might get confusing. Normally in Florida people run the a/c off the humidistat so there house stays dry when they are away for some time. Keep Cool! rcktexas “Re(6):humidistat” , posted Wed 15 Sep 23:54: ______________________________________________________________________ > You just break the R wire and wire it in series. I just fried my programmable thermostat. Although it is battery operated, it appears that breaking the R wire (power) damaged it. I now wish I had combined the Y and G wires instead – that way the fan would not run continuously. I could have added a SPDT switch to convert back to heat. I will need a thermostat for the furnace so I just as well get one now. I am going to get a mechanical type thermomostat where presumably I can break the R wire without frying the unit. I don’t need the programmability. I am now running the compressor and fan together off the dehumidistat alone – it works just fine. [this message was edited by rcktexas on Thu 16 Sep 00:21] rcktexas “Re(6):humidistat” , posted Wed 15 Sep 11:52: ______________________________________________________________________ Now that I have some experience with a humidistat I would like to make some comments for your consideration: >the humidistat you chose was a 2 wire and will work just fine. You just break the R wire and wire it in series. Some thermostats require 24 volts to operate, in which case breaking the R wire (power) is not going to work. My thermostat is battery powered so I can break the R wire. If I had broken the Y (compressor) wire instead, then the fan would run when the temperature was above the setpoint regardless of the condition of the dehumidistat. The makers of dehumidistats need to provide DPST relay so you can break both the Y and G wires. For use when heating just set the dehumidistat to ON (lowest setpoint) and it will be on all the time. >As far as controlling the a/c, you can only run the system by temperature or humidity (not both) wiring it this way. Not quite true. With series wiring, if you set the thermostat on a setpoint above where the dehumidistat cuts out, then you are controlling on both the thermostat and the dehumidistat. If the humidity drops below the setpoint in the time between cycles, the compressor will come on when the temperature rises above the thermostat setpoint and the humidity rises above the dehumidistat setpoint. You can achieve this condition by playing with the thermostat setpoint right before the dehumidistat cuts off. >If you want either one to put on the a/c, then you will have to do what Zenos said and wire the humidistat in parallel, but the wiring might get confusing. As pointed out elsewhere, the risk of parallel wiring is that the dehumidistat will come on sooner than the delay to protect the compressor between cycles. However, based on the considerations above, the same can happen in series wiring. The delay built into the thermostat is based on the thermostat cutting off. If for some reason (abnormally low thermostat setpoint) the thermostat never cuts off, then the system is being run solely by the dehumidistat and it has no time delay to prevent bumping the compressor. HTH [this message was edited by rcktexas on Wed 15 Sep 11:54] bigjohn “Re(2):humidistat” , posted Sun 18 Jul 14:28 ______________________________________________________________________ Which wire to I “split” to wire it in paralell? if you need a website visit host-my-site.com not the cheapest but the best service around. TechMaster “Re(3):humidistat” , posted Sun 18 Jul 15:05 ______________________________________________________________________ You would need to run a 2-wire from the humidistat to R and Y on the thermostat. You won’t be splicing into any wires. When done there will be 2 wires on R and Y of the thermostat. Just remember either control can put on the a/c. You don’t want to short cycle the unit. You may want to install a time delay. Keep Cool! TechMaster “Re(1):humidistat” , posted Sat 17 Jul 14:08: ______________________________________________________________________ The humidistat needs to be wired in series with the (R) terminal from your thermostat. You want to wire the humidistat to close on humidity increase. If you want to run the system by humidity control, you would put the thermostat on COOL and to the lowest setting and set the %RH on the humidistat. In Florida we keep them set at 65%RH. Keep Cool! [this message was edited by TechMaster on Sat 17 Jul 21:15] bigjohn “Re(2):humidistat” , posted Sat 17 Jul 14:31: ______________________________________________________________________ Cool! Question 2… Where can I buy one! Most of the ones I see advertised say stuff about hooking them to control a humidifier… Also – does this need to be a separate wire-run to the unit or can I split off / tie in behind the thermostat? I’m a computer geek, not a HVAC guy… so details help! John if you need a website visit host-my-site.com not the cheapest but the best service around. [this message was edited by bigjohn on Sat 17 Jul 14:32] TechMaster “Re(3):humidistat” , posted Sat 17 Jul 21:13 ______________________________________________________________________ A Johnstone Supply should have one. There all over the U.S. Just tell them you want a humidistat to make on humidity rise. You can tie it in behind the thermostat by breaking the (R) wire. Keep Cool! bigjohn “Re(4):humidistat” , posted Sat 17 Jul 21:16: ______________________________________________________________________ would something like this work? http://rewci.com/huusfordecoc.html John if you need a website visit host-my-site.com not the cheapest but the best service around. [this message was edited by bigjohn on Sat 17 Jul 21:38] TechMaster “Re(5):humidistat” , posted Sat 17 Jul 23:20 ______________________________________________________________________ That would work just fine! Keep Cool! rcktexas “Re(6):humidistat” , posted Sat 4 Sep 17:38 ______________________________________________________________________ >>would something like this work? >>http://rewci.com/huusfordecoc.html >That would work just fine! Before I buy that unit I am still confused with all the technical jargon being used to describe installation. What is the acceptable method of installation – in series or parallel? I live in Houston where the humidity is oppressive. I am forever having to adjust the temperature setpoint manually by 1 degree to flush the humidity from my house. When the house dries out I raise the temp 1 degree to prevent it from overcooling. I use the famous t-shirt test to decide when humidity is too high – if my t-shirt is wet then it’s too humid. My first guess would be to control solely off the humidistat by setting the thermostat way high. But I want your recommendation based on my situation. Please include details on how to install this unit for a layman. I have installed a programmable thermostat before so I know the wires are coded by letters. But I do not know what they mean. Please elaborate. Thank you for your assistance. BTW, why not get a Carrier Humidistat and replace the thermostat? Xenos Webmaster “Re(7):humidistat” , posted Sat 4 Sep 17:44 ______________________________________________________________________ Just so we can get the jargon straight, its not a humidistat that you want its a dehumidistat and that link is to one. I would recommend connecting it in series with the Y wire and use the thermostat as a low limit. Xenos. The best way to escape a problem is to solve it. rcktexas “Re(6):humidistat” , posted Sat 4 Sep 19:57 ______________________________________________________________________ >Just so we can get the jargon straight, its not a humidistat that you want its a dehumidistat… Then I suppose a thermostat is really a dethermostat when used in the cooling mode. >I would recommend connecting it in series with the Y wire and use the thermostat as a low limit. I like the series mode much better than the parallel mode for a couple reasons. Is there any polarity involved? I believe someone mentioned connecting a wire to the ‘in’ side. Just out of curosity, why was connecting it in series with the R wire also recommended by others earlier? What’s the difference? Xenos Webmaster “Re(7):humidistat” , posted Sat 4 Sep 20:45 ______________________________________________________________________ Then I suppose a thermostat is really a dethermostat when used in the cooling mode. Technically yes however humidistats are used to control humidifiers to humidify or homes. In your case you want to dehumidify there for it need to operate differently. There is no polarity that you need to be concerned with. Y or R will work, disabling R will kill everything including heating, Disabling Y will only kill the compressor however the fan will sill operate. Xenos. The best way to escape a problem is to solve it. rcktexas “Re(6):humidistat” , posted Wed 8 Sep 09:34: ______________________________________________________________________ >… disabling R will kill everything including heating, Disabling Y will only kill the compressor however the fan will still operate. I finally got the significance of that statement. I really need to pay more attention, but this is new to me so I am slow on the take. Perhaps the term “run” would have made it easier for me to see things right away. Whatever. I wired Y and indeed the fan would not shut off. So I wired R instead and now the fan goes off. As far as the furnace is concerned I will have to turn the dehumidistat control to “ON” (low RH) since I do not plan to control humidity during the heating season. FWIW, I think the instructions that came with the Ranco dehumidistat could have been explicit about this little fan nuance. All they did was wire it with Y in series mode. I am going to shake down the system today and for those who may be interested I will post an update. In the meantime, thanks for all your help, even though I didn’t fully grasp it at the moment. [this message was edited by rcktexas on Wed 8 Sep 09:39] rcktexas “Re(6):humidistat” , posted Sat 4 Sep 21:46 ______________________________________________________________________ >There is no polarity that you need to be concerned with. Y or R will work, disabling R will kill everything including heating, Disabling Y will only kill the compressor however the fan will still operate. Then ‘Y’ it is. As far as the actual dehumidistat unit – I wonder if there is one available locally at Home Depot or Lowes – or even an hvac dealer? What would I ask for – a “dehumidity control”? Is this a common hvac item or is this a specialty item best purchased on that web site? bigjohn “Re(6):humidistat” , posted Sun 18 Jul 00:29 ______________________________________________________________________ Thanks for the help… and all I have to do is take the Red wire off the thermostat, attach it to the ‘in’ wire of the humidistat and the out wire of the humid. to the thermostat? So then the AC will run in either condition = humidity too high OR temp threshold exceeded?? Man this is QUITE helpful. If you need a website – visit my site and say who you are. Automatic 15% discount off my prices! You rock. if you need a website visit host-my-site.com not the cheapest but the best service around. Xenos Webmaster “Re(7):humidistat” , posted Sun 18 Jul 09:29 ______________________________________________________________________ Sorry Tech Master, Just though I would help out. Technically yes, but the humidistat has 3 terminals not 2. You need the common and the one that closes on a rise in humidity ( dehumidistat). As well make sure when it powers Y that the fan starts, 90% of the system will back feed the power to G however you may have the 10% nd may require a small relay. Xenos. The best way to escape a problem is to solve it. bigjohn “Re(8):humidistat” , posted Sun 18 Jul 10:37 ______________________________________________________________________ thanks xenos. My system is a 5 year old carrier system, if that helps. if you need a website visit host-my-site.com not the cheapest but the best service around. Xenos Webmaster “Re(9):humidistat” , posted Sun 18 Jul 11:34 ______________________________________________________________________ It’s easy eough to prove, just jump R to Y and see if the indoor fan starts as well. I’m sure it will on a 5 year old system. Xenos. The best way to escape a problem is to solve it. Xenos Webmaster “Re(10):humidistat” , posted Sat 4 Sep 21:49 ______________________________________________________________________ You need a humidstat ( sorry to add confusion) that closes on a rise in humidity otherwise known as a dehumidstat. Xenos. The best way to escape a problem is to solve it. rcktexas “Re(6):humidistat” , posted Sat 4 Sep 23:07 ______________________________________________________________________ Are there web site tutorials for how residential hvac control wiring is set up. It would be helpful to know what R and Y are doing. Xenos Webmaster “Re(7):humidistat” , posted Sun 5 Sep 06:12 ______________________________________________________________________ http://www.hvacmechanic.com/tstatwiring.htm Xenos. The best way to escape a problem is to solve it. rcktexas “Re(6):humidistat” , posted Sun 5 Sep 06:35 ______________________________________________________________________ Thanks for all your assistance. I will be checking with Home Depot and Lowes today to see what is available, and if I do not like any of it I will check with some residential hvac contractors Tuesday. rcktexas “Re(6):humidistat” , posted Wed 8 Sep 00:39 ______________________________________________________________________ I found a dehumidistat manufactured by Ranco at Johnstone in Houston – J10-0809. It comes with a horizontal wall mount enclosure. My cost was $28.67 plus tax. I prefer to buy things like this locally in case there is a defect. The enclosed literature warns about installing in parallel, so as advised here, I will install it in series. It comes with a wiring diagram for this specific application, namely, to use in conjunction with an existing thermostat. The literature did mention that you could use it in parallel mode if you wired in a second thermostat to protect the compressor. But for my purposes I am hoping the series mode will work. I ordered an inexpensive hygrometer which will arrive today so I will be able to monitor what is going on as I fine tune the dehumidistat/thermostat combination. I will report my experiences for those who might be interested in this trying this out. My only concern is that the unit will either cycle too much or not enough. There appears to be an internal adjustment hole in the unit possibly for setting the swing. I will call Ranco today to find out. After consulting with that web site mentioned on the other thread about A/C Efficiency, I discovered that my compressor/condenser was actually 44,500 Btu/hr and not the 48,000 Btu/hr implied by the 4 ton rating. That lowers the theoretical cost of running the unit per hour based on prevailing egergy cost, which in Houston is about 11.5 cents per kW-hr. If by all these maneuvers I am able to save 1 hour per day and not affect comfort, then over an 8 month air conditioning season (April-November), I will save approximately $120 per season. That buys lots of BBQ and beer.