Humidification Control

electriKyle

I am an electrically inclined project manager at an MEP design firm. our mechanical engineering group specified several Nortec RH2 Humidifiers for a high end luxury condo. Regrettably we did not specify the associated controls. Now the walls and ceilings are up and the contractor is asking for a big change order to put in the controls we are recommending( please don’t come back with responses saying I bet your spec or the contractors contract covers it… I checked, it does not)- 1) a hi/low limit switch 2) an air proving switch 3) a modulating humidistat
would greatly appreciate some insight in terms of what control equipment we really need, ripping up walls and ceilings to place the hi/low and air proving switch would not be a good look
thanks ahead of time

EBEBRATT-Ed

@electriKyle

I assume from what your saying that you don't have access to the ductwork to install the controls?

As far as air proving instead of an air switch you could use a current sensor on the air handler blower motor. This is commonly done.

The modulating humidistat would be wall mounted like a thermostat. I don't see any way around this one. Unless you have a wall mounted thermostat somewhere that by chance has extra wire in it's cable. It could be mounted in a return duct if the fan is run 24/7 or on a humidity call and interlocked with the humidifier.

The high limit humidistat has to be duct mounted and should be around 10' downstream of the humidifier in a straight duct no way around that one. Reason being on a dry day the wall mounted stat calls for humidity. Without a high limit humidistat to limit the humidifiers operation the humidifier can flood the duct


Unfortunately failure to install these controls (especially air proving and high limit) will lead to duct flooding and ceiling replacement.

ratio

You can use a Honeywell TH8321R with a wireless indoor sensor for on/off humidifier control (make sure to select the remote as the humidity source). The thermostat can be mounted out of sight with the humidifier.

I imagine it could be done with a cheaper TH8110 by fancy programming & overloading an output terminal, since it doesn't have a universal relay output.