Installing Aprilaire 700 to Carrier 58MCB

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Old 01-10-16, 01:02 AM
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Installing Aprilaire 700 to Carrier 58MCB

Hi z0d1ak1,

I'm installing Aprilaire 700 to my Carrier 58MCB furnace and it is so great to have someone already install Aprilaire 700 with Carrier furnace already.

Could you please give me the picture of the wiring on the furnace and humidifier?

Thank you.
 
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Old 01-10-16, 10:51 AM
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Installing Aprilaire 700 to Carrier 58MCB

Welcome to the forums.

Do you have the SAME exact model as the original poster ?
You need to supply the pictures for wiring help.

http://www.doityourself.com/forum/electrical-ac-dc/534445-how-insert-pictures.html


The top picture/diagram in post 2 is what you need to follow.
 
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Old 01-10-16, 04:06 PM
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Thanks for your reply, PJmax.

Below is the wiring diagram of my furnace.

Don't judge me but I absolutely have no experience with furnace and I don't know where to start.

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Old 01-10-16, 07:18 PM
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BTW, below is my Nest wiring. I just wonder if there is any option to install the Aprilaire 700 Manual with Nest. I prefer to control temperature and humidity in one unit.

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Old 01-10-16, 11:42 PM
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Not a problem. Actually a very basic wiring job.

First.... please make sure you have the gray cased Aprilaire 700 and not the almond one.

This is the wiring you'll be following.

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You will need an additional wire from the thermostat to the furnace. You are currently showing fives wires in the stat cable. See if there is an extra one. That will get connected to the * terminal at the stat and one of the brown wires at the humidifier. The other brown wire at the humidifier gets connect to the COM 24v terminal along with the white and blue that are already on there. That's it.
 
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Old 11-06-17, 04:18 PM
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Hi Pete,

Thanks so much for this forum and your guidance to the OP. I have the same exact setup with my Carrier furnace to a Nest 2.0 as the photos in Manh Vo's show.

I only have 18/5 running from Nest thermostat so I guess I need to replace with 18/7 to get an extra wire or should I just run an 18/2 to connect to the * terminal at the stat and one of the brown wires from the Aprilaire 700? Sorry for such a basic question but do I just use 18/2 thermostat wire to connect the other brown wire at the humidifier to the COM 24v terminal (which has the white and blue already on there)? Assuming I can use either wire color (ie. white or red) to connect.

Finally, I just want to ensure there is still no need for a relay with this setup as I don't want to end up burning out the board unintentionally during setup or prematurely down the road.

Thanks,

Eric
 
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Old 11-06-17, 04:53 PM
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Welcome to the forums.

Are you using the C connection as one of those five wires ?
The nest claims to run fine without a C connection but if I do the installation..... it gets a C connection or I don't do it.

If you aren't using the C.... you can use that wire to run the humidifier on the *.
Otherwise any type of #18 cable would be ok to use.

Wiring the humidifier up like this doesn't put any stress on the control board. The only item that could possibly fail is the 24vac transformer. If the furnace has a 40va transformer there will be no trouble. If it has a 20-25va one..... it could fail. As far as I know Carrier furnaces use a 40va transformer.
 
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Old 11-10-17, 07:13 AM
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I am also getting ready to install an Aprilaire 700 (a new one without the internal transformer) on a Carrier 58MCB (50MCB080, my circuit board is slightly different than the one pictured above but of course the terminals are the same). I was going to post here to confirm that I can power the humidifier from the 40VA furnace transformer (through the R and COM terminals) but PJmax has already answered that for me -- thanks! I figured it would be ok since there is a 24V 0.5A HUM terminal on the board that I won't be using so there must be some extra capacity there. I hope it's ok to add a question here rather than starting a new thread.

I'm going to be using an Ecobee3 in single wire mode, wired as shown here in another post from PJmax; the Aprilaire controller won't be used at all:
https://www.doityourself.com/forum/a...mostat-bee.jpg

I already have 2 wires on the COM screw terminal on the furnace board, for the thermostat and outside A/C unit. I will need to add a third wire. Is it ok to have 3 wires on one screw terminal, or do I need to pigtail them?

If I need to pigtail them, should I use a heavier gauge wire for the pigtail, or is 18 AWG sufficient since the current is limited by the transformer output (in other words, the pigtail doesn't have to carry the maximum ampacity of the three 18 AWG wires it's connected to because the transformer can't supply that much anyway)?

If I need to pigtail, would it be better to do the pigtail connection in the rather cramped compartment pictured above where the circuit board is, or below in the blower compartment where the thermostat wires feed in from? Neither seems like a great choice to me in terms of neatness.

Thanks!
 
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Old 11-10-17, 12:24 PM
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There shouldn't be a problem putting three wires under one screw terminal.
If you want to tie them together with a tail... that's also fine. #18 would be ok for the tail piece.
 
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Old 11-10-17, 01:00 PM
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Hi Pete,

Thanks for the welcome and the quick response!

The C connection was being used by one of the 5 wires so I tried to fish a new #18/7 (this is before I saw you had responded), but was too much trouble as I guess the wiring is running through some pretty narrow holes through the house and/or through some 2 x 4's (arrgh) ... doubt I'm gonna find someone who will sign up just for that job (although would be nice) so I guess I'm sticking with the original #18/5 and not using the C connection.

Attached is my current setup and info on the furnace and transformer appears to be 40va so I think I should be alright.

Appreciate your help!

Eric
 
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Old 11-10-17, 01:05 PM
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Sorry, I guess I'll ask one more q, since you're much more knowledgeable than myself or my research has proven, but do you agree that I should not tap into the tankless hot water line when installing the humidifier? (with concerns there won't be enough water draw from the humidifier to activate the tankless unit?)
 
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Old 11-10-17, 02:10 PM
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I agree.... there would probably not be enough flow to activate the tankless.
 
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Old 12-18-17, 09:55 AM
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Smile Thanks for the diagram, saved my manhood!

This diagram worked perfectly for me when hooking up my Aprilaire 700m to my Nest. I did however set it up a differently to start, using an external relay based on a youtube video and the nest pro setup pdf. I had it setup with an external relay, but then figured out that the 700 had an internal relay than handled the 24v directly. Thanks again.

Signed
Happy Camper who saved big $ installing myself
 
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Old 12-18-17, 11:20 AM
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You're welcome.

The 700 came as two distinct models. The older model, usually almond colored, had it's own self contained 24v power supply and only required a contact closure to operate.

The newer model is gray and requires 24vac applied to its input wires to operate.
 
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Old 01-27-18, 01:43 PM
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Talking Thank you for this thread!

Thank you to everyone that contributed to this thread. I've been lurking and checking out your diagrams for a few days. Today, I took the plunge and got everything wired up!

Thanks again!
 
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Old 01-28-18, 12:35 AM
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Welcome to the forums and good job.
 
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