Aprilaire 1850 Dehumidifier with Prestige IAQ - Standalone


Old 07-27-19, 05:04 AM
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Aprilaire 1850 Dehumidifier with Prestige IAQ - Standalone

Good morning,

I just installed a Prestige IAQ thermostat to a simple setup: forced air natural gas Lennox Elite furnace, air conditioner.

I've just bought a whole house dehumidifier (Aprilaire 1850) as the summer is massively humid and our basement is very damp.

I'm having trouble with hooking up the Aprilaire to the IAQ EIM as a remote. The dehumidifier is pulling from a dedicated return and pushing into the furnace supply plenum with a Y duct and manual damper to direct some of the dry air into the basement as shown in installation manuals.

I've connected the DH and DH terminals to the U1 and U1 terminals on the EIM and set the Aprilaire 1850 into remote mode, but I'm getting an WE communication error on the Aprilaire. The manual for the Aprilaire show hooking up a wire to a remote "model 76" and connecting R and C wires (supposedly to power the remote stat), but I didn't do this (only have the DH-U1 AND DH-U1 mentioned above) as I was under the impression that those were only two power the remote thermostat, and the IAQ EIM doesn't need any additional power. Have I just misunderstood what those are for?

My goal is to dehumidifier the basement, and also provide a bit of supplemental dehumidification to the rest of the home.

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Old 07-27-19, 10:39 AM
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Welcome to the forums.

If using a Model 76, Model 8910, or Model 8620 as an external control or other third party external control, such as a thermostat with dehumidifier outputs, use the UP or DOWN arrows to select ENABLED and press MODE to go to the dehumidification with air conditioning (DEH W/AC) screen selections.

It looks like just a contact closure on DH will start the unit. It also looks like unless you use a float switch... there needs to be a jumper on the float switch terminals.

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Old 07-28-19, 05:42 AM
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I have connected a few Aprilaire dehumidifiers to Honeywell Prestige IAQ's and I am pretty sure that "Remote" is a different option from "External".

The display should say "External".
Old 07-29-19, 05:05 AM
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Houston, you are correct! I did not make the distinction between remote and external. And now no longer getting to e3 error. Thank you!
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