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Trouble wiring humidifier

Eperot
Eperot Member Posts: 3
Hi there,

First post so I will try to be as thorough as possible.

I just installed an Aprilaire 400 automatic humidifier on my ductwork, a replacement for an ancient Honeywell drum unit. This new unit is fully automatic and needs far more wiring. Seems simple enough but everything in the instructions calls for taking low voltage wires from a furnace terminal strip (typical R, C, W, etc..) and back to the humidifier control. BUT, I have a hydronic exchange system of a Triangle Tube boiler (solo 175) hooked up to an air handler. I cannot find any such terminal strip. SO,



This is what I have. A two wire thermostat hooked up only to R and W. If I trace those wires to the boiler, they first stop at a box containing a 24V transformer and a relay. The red from the R on the stat goes to the transformer, and the white from the W on the stat goes to a contact on the relay. It would seem then the relay triggers (A) the boiler to fire, and (B) the air handler to turn on.

Aprilaire states the following:



Power (R and C) on the humidistat should come from R and C on the furnace terminal strip. I suppose that means I should just hook up the humidistat terminals to the two terminals on the 24v transformer?



W on the humidistat should be hooked up to W on the furnace terminal strip. As there is no such strip, should it then be piggybacked off the wire that connects to the relay, from the W terminal on the thermostat?



G on the humidistat should be connected to G on the thermostat. There is no such wire. I can run one if need be.



Gf on the humidistat should be connected to G on the furnace terminal. (There is none. ) This one I have no clue about.



Two H terminals on the humidistat are hooked up to the solenoid on the humidifier, and a separate 24 volt transformer. They look fine.



There are also outdoor temp sensor wires, likewise hooked up fine.



So my questions stand about R, W, C, G, and GF. I didn't think it would be so different wiring up to a boiler system! I hope I did a good job explaining what I am working with and look forward to any replies. Thanks in advance!

Eric

Comments

  • TonyS
    TonyS Member Posts: 849
    Where are you getting 24v

    off of the Triangle. The Trimax is DC and the older mcba controlled units don't allow for 24 vac access. There must be some external relay that turns on the fan after it comes up to temp. I doubt the boiler and fan start simultaneously.You can just supply your own 24 vac tranformer and break the 24 vac through the humidistat and then an air switch in series. You could also add a dpdt relay or maybe there is already one there that pulls in when the coil comes up to temp. If they are using a 120v klix on switch just use the line coming from the klix on to the fan and pull in a RIB relay or you can just use one of those aprilaire inductance relays, expensive but less time consuming.
  • Eperot
    Eperot Member Posts: 3
    follow up

    Tony,

    in fact, yes...the circ. pump and boiler are on the relay the white thermostat wire (load?) attaches to. There is also another wire that leads off the relay and goes over to the air handler, attaching to another relay that triggers the fan. So they really do come on at the same time. Keep in mind, the boiler water is already very hot just standing and comes up to full heat insanely fast.

    I am not getting 24v off the boiler because as far as I can tell, Triangle Tube doesn't allow for any extra 24V hookups from the 24V board. Right now I am pulling the 24V off the same transformer that is supplying power to the solenoid on the humidifier. The Humidistat is all lit up and working, showing 14% humidity, but even in manual mode it won't get the solenoid to kick...although I backed the wires from the two H terminals out, touched them together, and the solenoid did work, so we can cross that off. It seems to me the W terminal (call for heat) line has to be hooked up in order for the humidistat control to turn the solenoid on. But that is my question, where should I connect it? piggyback it off the low voltage line from the thermostat connection to that first relay?

    And should it even matter that the humidistat control is powered up by the solenoid 24V transformer rather than from the boiler itself? It is always hot.
  • Slimpickins
    Slimpickins Member Posts: 339
    current sensing relay

    Just wire a 24v relay off your SSU to a current sensing relay clamped on a lead to the blower and then to the humidistat and back to the relay. Don't make it overly complicated.
  • TonyS
    TonyS Member Posts: 849
    It doesnt need to be

    connected to the boiler wiring at all. Keep it simple, like Slim said, use a current sensing relay or a sail switch in series with the humidifier circuit. Your just going to go from the R terminal on your transformer to the sail switch, then to your humidistat, to your humidifier then back to your C terminal. The sail switch will only allow current to pass if the blower is running. 
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