Whole house ventilation controls

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tom baker

tom baker

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Looking installed a motorized damper to bring outside air into the furnace return air plenum.
The damper would have a timer control and would turn on the furnace fan to bring fresh air into the house.
This type of control must be common in newer homes.
And it seems like there should be an control from the range hood or bath exhaust to open the damper when those are turned on.
The above would be a simpler installation over a air to air heat exchanger.
Any recommendations on timers, dampers, etc. I would have an HVAC company do the install.
 
tom baker said:
Looking installed a motorized damper to bring outside air into the furnace return air plenum.
The damper would have a timer control and would turn on the furnace fan to bring fresh air into the house.
This type of control must be common in newer homes.
And it seems like there should be an control from the range hood or bath exhaust to open the damper when those are turned on.
The above would be a simpler installation over a air to air heat exchanger.
Any recommendations on timers, dampers, etc. I would have an HVAC company do the install.
Click to expand...
Broan has a makeup air kit that works with a pressure switch. But I've seen them with a current sensor installed on the hood circuit. Dumps into return air duct

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Not sure if this company can work for your application. I have used their products in the past for power venting on pool heaters and any gas fired appliances.

Tjernlund Products, Inc. | Ventilation & Exhaust Solutions Since 1938

Tjernlund Products specializes in high-quality mechanical ventilation and exhaust solutions for residential and commercial applications. Trusted since 1938 for energy-efficient HVAC products.
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A word of caution. Most of these systems also have pre-conditioning for fresh air introduction. Had a customer who someone added fresh air ducting into the heating system that had no pre-conditioning, when it got real cold, 10deg to 20 below, (as it does mid winter here) the furnace couldn't keep up and would run without stopping and not really heat. So either your system would need to have pre-conditioning or have a means of temperature sensing that restricts operations below a certain outside temperature. With houses getting tighter, the use of makeup air is becoming more common. A HVAC supplier should have the correct equipment to accomplish this. But likely similar to this:

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Now if your desire is simply for fresh air in summer without AC, your furnace should be setup with seperate fan mode or "summer mode" that operates from the thermostat. The baffle system design is usually controlled by the furnace not the baffle controlling the furnace blower. Similar to this:
www.supplyhouse.com

EARD8TZ - Honeywell Home EARD8TZ - 8" Round TrueZONE Motorized Fresh Air Damper

Honeywell Home EARD8TZ - 8" Round TrueZONE Motorized Fresh Air Damper - The EARD is a round damper with a 24 Vac powered-open/spring-closed motor. It is used for fresh air intake for ventilation or for combustion makeup air. <ul><li> Adjustable damper position range stops. <li>Single-blade...
www.supplyhouse.com www.supplyhouse.com
 
tom baker said:
I could use a current relay for the range hood, someone remind me who makes them, Functional Devices?
Click to expand...
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I don't think I would go in the direction you're indicating with a one off custom build.

You're talking about fresh make up air to balance the house exhaust air, furnace combustion, kitchen and bath exhaust, plus extra fresh air for the recirculating ducted air, two different jobs.

If the house is so tight that it cannot balance exhausted air by itself, usual mitigations are cracking a window, dedicated OA combustion makeup air vents for the furnace, and a DOAS, dedicated outside air supply / heat recovery ventilator.

For the ducted air, commercially you would see a rooftop unit with an economizer package. The board that controls it is an (outside air) enthalpy control, open the damper to let fresh air in and exhaust air out.

Key in those two scenarios is for the passive venting it responds to demand, furnace running exhaust fan running, with no control needed, and for the DOAS, it responds to outside air conditions, optimized for low humidity moderate temps, and can close off for bad outside air conditions. It's a Honeywell green something board that does that for about $300., the fresh air economizer control. It does not care if the kitchen fan is running. It triggers for good outside air conditions.

I've been running with a window cracked all winter. The step beyond that I would be looking for is a DOAS with the outside air enthalpy control.
 
If you're going to intentionally bring in outside air, an energy-recovery system should be installed.
 
Larry I have been looking at an air to air heat exchanger. Cracking a window is simple. Climate near Seattle is fairly mild, not below 20 in winter, and above 90 in summer. Need to have combustion air for gas water heater and dryer.
Economizer is a good option, some buildings here used to open up outside air at night to cool off inside during summer.
It would work to use a current relay on bath fan and range hood to open up outside air damper.
 
tom baker said:
Looking installed a motorized damper to bring outside air into the furnace return air plenum.
The damper would have a timer control and would turn on the furnace fan to bring fresh air into the house.
This type of control must be common in newer homes.
And it seems like there should be an control from the range hood or bath exhaust to open the damper when those are turned on.
The above would be a simpler installation over a air to air heat exchanger.
Any recommendations on timers, dampers, etc. I would have an HVAC company do the install.
Click to expand...
Presuming house is very air tight, if you want to bring fresh air in you pretty much need to exhaust same quantity of air somehow or you won't really be bringing much in. Which is what an ERV does
 
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