I have recently installed a Venmar HRV. The control panel for this unit offers an Automatic setting where the unit will stop for 40 minutes and run for 20 minutes each hour. I would like to connect the HRV to my furnace so that it turns the furnace fan on for this 20 minute period. How can I best accomplish this?

The control for the HRV is right next to the thermostat. Is it possible to use a relay at the controls to activate the furnace fan when the HRV starts? Or is there a better way? If so, what sort of relay would I need?

Thanks in advance for your suggestions...

Derrick

Their can interlock contact can do that. Terminals labeled F & F. Terminal numbers could depend on model. He Insructions I looked at were terminals 6 & 7. http://www.venmarces.com/literature/iom/206815-hrv6-7-12-iom.pdf

6 could go to G on the thermostat AND

7 could go to (Rc/Rh or R). The roles of 6 or 7 can be reversed.

A wire between terminals G and (Rc/Rh or R) on the thermostat will cause the fan to run. Therminals 6 and & provide that wire.
See PDF page 16 of the reference.

Sorry - I didn't realise that Venmar have a number of different models. Mine only has 4 wires to the control. It is the HEPA 3100 model that uses the 40415 wall control.

See if you can provide a link to the manual.

There are a couple of ways to approach this problem.


1. Through a contact closure provided by mfr.

2. Purchase a different thermostat with a ventillation option (i.e. it runs the fan periodically). Some Honeywell Vision Pro models have this.

3. Use current sensors (about $80) to sense whether the unit is drawing power (wraps around one of the power inputs). ( Might not come on at the right time)

4. Contact manufacturer for their suggestions.

I found the manual here: http://dl.owneriq.net/a/ae615b20-3601-4c0c-a4e6-664e08b0c5d2.pdf

There is a connection to the G terminal (runs the fan). Don't know if it's an input or an output.

There is NO electrical information at all. Not even power reqirements.

I really do suggest giving them a call.

I can elaborate on my thoughts if necessary.

[QUOTE=KeepItSimpleStupid;2080401]I found the manual here: http://dl.owneriq.net/a/ae615b20-3601-4c0c-a4e6-664e08b0c5d2.pdf

There is a connection to the G terminal (runs the fan). Don't know if it's an input or an output.

There is NO electrical information at all. Not even power reqirements.



I was kind of surprised that there is no info on the electrical side of it either. I will give Venmar a call to see if they can provide any more info.

Thanks very much for your input. I will likely ask some more questions when I have more info... :o

I agree.

For the time being, I'll add this link to a current sensor. http://www.ssac.com/catalog/ECS01A01.pdf, so at least you'll know what I'm talking about.

All you have to ask is, is it permissible (i.e. makes sense) to fun the furnace fan in all operating modes of the unit.

Documentation for their current units is better, but it's still lacking. The initial one I found had multiple fans.

Believe it or not, I never completed this project... I have just been running the furnace fan constantly. Decided to go another route, thinking it would be easier (silly me :)) - I bough a current sensing 120 volt relay and installed it on the furnace fan power supply. I then ran the power supply to the HRV through this, thinking that it would work fine (turn the HRV on when the furnace fan came on). Wrong... the HRV draws about 5 amps, and this appears to be enough that my GA51 relay will turn it on, but the load is enough that it won't consistently shut off. Dang!

So I went out and bought a regular 120V AC relay - this one... http://www.ieknox.com/catalog/download/finder/S66EN.pdf
How should this be wired? I need to supply power from the furnace fan to one of the coil terminals, and the power supply through one of the Normally Open set of connections. How about the 2nd terminal for the coil circuit - what should this be connected to?

Sorry - stupid question, but I have visions of frying my furnace control board... Thanks in advance for your help!!