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(More customer reviews)This is the new and improved Aprilaire #58 humidstat control. This replaces the RP #56 control they previously used in the model 700, 760 etc. The 56 worked fine for me for a few years before it got fried. It was automatic and could be used with the outdoor temperature sensor. The new one is much improved. It has a cleaner, neater design that incorporates an lcd display, three indicator lights which signify humidifier operation, water panel replacment and one to signal for dealer service in the event of failure. Upon inspection it seems to have a redesigned circuit board with surface mounted relays (quieter than the older model I may add)and adds the ability to interface with Aprilaire thermostats namely the 8570 which allows the thermostat to communicate with it and relay indoor humidity and outside temperature as well as control it without having to go directly to it. This is nice because in most application installs the humidstat is located near the humidifier on the return plenum.
Sometime in 2006, Aprilaire redesigned the humidifers and removed the 24volt control inside the humidifier(#4238)and changed the color from almond to grey and slightly changed the case styling. This helps in determining whether a customer/user has an older or newer unit. There is an A/B switch inside the humidstat that must be set to B if one owns an older humidifier and damage could result if that switch is in the wrong position, so before powering on everything make sure of that.
This humidstat also differs from old models in that it requires 24volt power (2va to 10va) depending on the model of humidifier you own. You can use your furnace terminal accessory board or heat pump air handler board but instead I opted for a plug in 24v 40va transformer. By interlocking the humidifier with a relay in a box and an existing air flow switch on the return and using a plug in transformer I was able to totally bypass messing around inside the the air handler. The previous installation job consisted of using an aprilaire #50 current sensing relay and this is what failed. I would definately recommend using a plug in transformer, a relay in a box (aprilaire rebadges one #4851)and if necessary an air flow switch. The advantage is that the relay will allow the humidifier to run anytime there is a call for humidity not just during the heating cycle. The current sensing relay is only rated for 50 watts while the #4851/RIB is rated much higher. Using an external transformer makes the install easier and allows for anyone to replace it if it goes bad. Strip two thermostat wires and crimp around the terminals and tighten. Plug in and your done. There is a little screw terminal that controls the panel time replacement indicator and for the 700 it should be turned to C. Make sure you follow the directions related to your equipment. In my case Heat pump. Since I did not use the 24volt strip inside the handler I had to jumper the WG/CF to common. Be sure to download the RP-58 Addendum as this has additional information to help with your install. This humidstat has changed and the same configuration cannot be copied and used on this one as the terminal designators have changed as well. I would recommend hooking up the outdoor temperature sensor if feasible as this would make it truly automatic and one would probably never have to make any adjustments at all.
Once in operation it is quieter, has a nice lcd blue backlit display which displays the relative humidiity and the level of humidity as you turn the dial (1-7) and an illuminated led that shows humidifier operation.
If you own an older model (remember almond color) aprilaire humidifier 700, 760 and even 400 - 600 series (check compatibility before buying) and you are in need of a new humidistat or want one with automatic control then this is the one you should buy. It might be slighty more expensive than a RP-56 but it is worth it and comes with a 5 year warranty as all of Aprilaire products now do. These guys are great btw, they know indoor air comfort and can easily be reached by telephone and email, unlike Honeywell.
Be Well My Friend!
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Aprilaire RP-58 Humidistat Control #58The new Aprilaire #58 automatic humidifier control works in conjunction with your furnace to control the operation of the humidifier. The control senses indoor RH and outdoor temperature and automatically adjusts the operation time of the humidifier to provide the optimum humidity level in the home. The digital readout on the control displays the RH level inside the cold air return. Can also be used in manual mode when it is not possible to run wire to outdoor sensor. This controller mounts on return ductwork.New lighted display includes indoor relative humidity readout, service indicator light, water panel change light, and indicator light. In order for the humidifier to operate, the furnace blower must be running and the humidifier control must be calling for humidity. NOTE:control must be continuously powered for proper functionality - separate 24 volt transformer may be required.Includes:ControlOutdoor SensorManual Mode ResistorManual Mode StickerInstallation InstructionsOwners ManualFor use with models: 110, 112, 220, 224, 400, 440, 445, 445A, 448, 500, 550, 558, 560, 560A, 568, 600, 700, 760, 760A and 768Unit dimensions - 5 15/16" W x 4 1/4" H Requires round 3/4" hole for duct mounting.
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