# Hood fan interlock with make up fan/heater



## PokeySmokey (Nov 14, 2017)

You want a method to interlock the Hood Fan with the (conditioned make up air) Heat Recovery Unit (HRV) / Energy Recovery Ventilator (ERV) so as the Hood Fan speed changes the HRV/ERV speed will change to replace the air removed by the Hood Fan. This is to keep the building from going into a negative air pressure condition relative to the outside air pressure. There are devices which you can install to start manually the HRV/ERV when the Hood Fan is started.


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## wildernessbob (Dec 11, 2020)

PokeySmokey said:


> You want a method to interlock the Hood Fan with the (conditioned make up air) Heat Recovery Unit (HRV) / Energy Recovery Ventilator (ERV) so as the Hood Fan speed changes the HRV/ERV speed will change to replace the air removed by the Hood Fan. This is to keep the building from going into a negative air pressure condition relative to the outside air pressure. There are devices which you can install to start manually the HRV/ERV when the Hood Fan is started.


it's actually not the HRV. it's an inline fan with a mechanical damper to retain airtightness when the fan is not in use. the fan is to provide make up air so the house does not depressurize as you note when the hood fan is turned on. so the control not only needs to interlock with the hood to turn the make up air fan on and off, i need it to also control the speed of the make up air fan. the hood has three speed settings and the max is 650 CFM. i believe the make up air fan will provide the same volume, but what we don't want is to have the hood on low and the make up air fan on max, potentially pressurizing the house.


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## HertzHound (Jan 22, 2019)

Probably to late if you already have the fans, but these guys look like they have a controller.



https://www.hvacquick.com/catalog_files/HVACQuick_Balanced_MUAS_Catalog.pdf



I did two ANSUL systems last year, after not doing one for quite a few years. I couldn't believe how advanced they became. The exhaust and makeup air fans on the roof had built in VFD's. They were controlled back to the control unit with cat5 cable. Even the relay panel that shut off power under the hood was interconnected with cat5, although the customer cheeped out and didn't get that option. It probably cost them more for us to put in an eight pole contactor for the remedy?


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## wildernessbob (Dec 11, 2020)

HertzHound said:


> Probably to late if you already have the fans, but these guys look like they have a controller.
> 
> 
> 
> ...


yep, too late for that system. all i really need is a speed control for the fan, the heater will take care of itself and can be connected with a simple relay. i'll keep looking.
Thanks


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