# HRV Wiring Run With Furnace Fan



## lenaitch (Feb 10, 2014)

I'll let the HVAC folks answer your specific question, but I'm wondering why you wouldn't run your HRV all the time? If you have a reasonably tight house, you're living in the same air all the time. They consume minimal electricity and I think I read they are about 90% efficient for recovering heat from the exhaust air.


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## user_12345a (Nov 23, 2014)

In theory you can use the electronic air cleaner terminals but check the rating.

When furnace fan comes on it could trigger a relay which turns hrv on. 

I disagree with setting up an hrv this way.

Your need for ventilation will not correlate with furnace fan operation in auto mode.

In fact the colder it is, the more the house will leak and the less ventilation will be needed. You'll dry out the house when it's -20c and not have enough ventilation in the spring and fall.

It should be the other way where a demand for ventilation gets furnace fan to run at low speed.

HRV may have terminals for this but depends on the model.

Demand for ventilation should be based on indoor humidity. If you have a push-button with no humidity control, that's okay; you can get a second control which turns on the unit when humidity is higher than lets say 45% or whatever.

Now, if your hrv is set up to draw stale air from the house directly and the fresh air gets put into the return, there is no need to run the furnace fan for hrv to work.

If your sub did it the cheap way and it's drawing stale air from return, you'll need the fan on. doing it The cheap way saves the contractor money but costs you more.


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## 123pugsy (Oct 6, 2012)

Wiring diagrams attached.


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## 123pugsy (Oct 6, 2012)

user_12345a said:


> In theory you can use the electronic air cleaner terminals but check the rating.
> 
> When furnace fan comes on it could trigger a relay which turns hrv on.
> 
> ...


Of course 2 on the return duct.
I really don't give a hoot about this device. It's something I've been legislated to install.

Ok, so I can turn it on with my wall switch and it can command the furnace blower to run?

I just need it when the cooking starts stinkin up the house.


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## user_12345a (Nov 23, 2014)

can't advise without install manual. have a link?

i see a separate connection for a dehumidistat - i advise getting one and connecting it with 18/2. gives good moisture control, prevents overventilation compared to on/off swich. just set it 5 to 10% above humidifier setting if they installed one. shouldn't need hrv in house that needs humidifier though.


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## user_12345a (Nov 23, 2014)

> Of course 2 on the return duct.
> I really don't give a hoot about this device. It's something I've been legislated to install.
> 
> Ok, so I can turn it on with my wall switch and it can command the furnace blower to run?
> ...


looks like you can, but would have to see the install manual.

Until you've lived in the house you won't know if the hrv is needed or not. 

If you did a good job and it's tight, you may need it to control moisture.

A shame it's code mandated because you may not need it; i'm guessing you payed around 2 grand installed. i suspect the codes are good for and designed big builders where they like to cut corners but don't really suite individuals doing custom build.


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## 123pugsy (Oct 6, 2012)

PAGE 33


https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjQqr-6ovzQAhUsxoMKHbu9DREQFggaMAA&url=http%3A%2F%2Fcms.www.summeraire.com%2Fassets%2Fuploads%2Fdocuments%2FX_NW130_140_160_220_260_INSMAN_EN_REV45_WEB.pdf&usg=AFQjCNHVpbg4xcsFHx4GkjNYMA5xUrAbQw&sig2=edZ1rpjiXh9WT46hzw-0DA&cad=rja


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## yuri (Nov 29, 2008)

I have never seen a HRV not run off it's own 120 volt dedicated circuit and it probably would not meet the elec code running off the furnace.

The EAC /electronic air cleaner terminals or ACC accessory terminals are only meant for low amp uses not motors. The EAC has a fan motor.

Lifebreath has a dry contact where they can close a switch thru G on your furnace circuit board and start the furnace fan. Yours appears to do that also. You take G from your thermostat and run it a contact on the HRV and then from there back to the furnace G.

When the de-humidistat turns it on then it starts the furnace fan. Not sure if you have a continuos low speed fan in the HRV.

Lifebreath does and some people run it all year round for ventilation. 

Follow the wiring diagram you have and find the G on the thermostat on the diagram and go from there.


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## user_12345a (Nov 23, 2014)

i said EAC terminals to isolation relay which would switch a low voltage hrv signal, yuri. not powering directly - that would be dumb.

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Well, it shows interlock with W-heat and Y-cool, etc which is weird. don't know what those do.

There's zero explanation in the manual on sequence of operation - how it interfaces with furnace or air handler. 

Looks like it has the dry contact mentioned above however...

*To be sure...

You would have to run the hrv and check between R and G at the hrv with a multi-meter in ohms. 

if it closes when hrv is on, opens when hrv is off you can run an 18/2 wire to the HRV and connect it to those terminals. At furnace connect to R and G on the board.

Hopefully that's all you need and other terminals don't need to be connected.

it should turn on furnace fan with demand for ventilation, not other way around.


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## 123pugsy (Oct 6, 2012)

yuri said:


> I have never seen a HRV not run off it's own 120 volt dedicated circuit and it probably would not meet the elec code running off the furnace.
> 
> The EAC /electronic air cleaner terminals or ACC accessory terminals are only meant for low amp uses not motors. The EAC has a fan motor.
> 
> ...


Thanks.

I have a receptacle on the wall right beside the unit.

So, pull the wall switch upstairs and install a dehumidistat?
Hook those wires up to COM and D/CT on the HRV.
Pull an 18/5 from HRV to furnace? or 18/2?

This is where it gets fuzzy.
Do I pull out the wire from the thermostat that goes to the furnace terminal strip and splice it to the wire that goes to the HRV G(com)?
Then take another wire and shove it into slot G on the furnace terminal strip and attach it to G(N/C) on the HRV?


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## 123pugsy (Oct 6, 2012)

user_12345a said:


> i said EAC terminals to isolation relay which would switch a low voltage hrv signal, yuri. not powering directly - that would be dumb.
> 
> ----------
> Well, it shows interlock with W-heat and Y-cool, etc which is weird. don't know what those do.
> ...


Thanks.

Now I'm really confused....aarrrgghhhhh.

How can I make it turn on and off with a wall switch?


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## user_12345a (Nov 23, 2014)

Leave the wall switch alone. Use it to cycle the hrv on for fresh air.

I'm assuming u have a push-button switch.


You can add an optional dehumidistat if you want to cycle the hrv based on humidity.

The dehumidistat connection is a separate one on this hrv in manual.

Page 10.



This unit seems to have a lot of features and can be run in continuous low mode.

if it was me, i would want it to stay off except for when you push the button to turn it on. (or if u go for a dehumidistat)

I would want it either completely off or on in high speed mode as needed. continuous will dry out the house.

they've made these things too complex and insufficient documentation.


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## 123pugsy (Oct 6, 2012)

Ha, what control did they give me?
They left a piece of 18/2 wrapped around a 2x4 at the center of the house.
I hooked up an on/off switch.

Can I hook up this basic on/off light switch to make this thing run?
I need to test it and at least have it running for occupancy inspection.


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## user_12345a (Nov 23, 2014)

which terminals is it connected to on the hrv?

it appears that the controls are all digital and not just on/off switches.

you may be able to use a light switch on the dehumidistat connection but not 100%. what does the unit do when u turn that switch on?

check terminals first because you do not want to touch lcd w terminal and pcb terminal. those are for the electronic controls.

might as well put a dehumidistat or mechanical bathroom fan type timer rather than a switch and have some more functionality.



hopefully someone familiar with this unit will post here. i'm just going off the manual.

In the manual it shows that you can select mode with push button switch on the unit itself.

"off/auto" sounds right for operation only when there's a call for it.


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## yuri (Nov 29, 2008)

Look at the Shepherd control wiring in your wiring diagram next to the thermostat wiring.

Trace where those 2 wires connect at the HRV and hookup your switch there. It looks like the Guardian optional control is the de-humidistat control which they should have sold you and supplied you. Or the basic wall mount dehumidistat which is also in the manual.

Most people have a 20 minute timer in bathrooms if they are using it in place of a bathroom exhaust fan.

I would expect most inspectors would want to see at least the basic dehumidistat.


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## 123pugsy (Oct 6, 2012)

yuri said:


> Look at the Shepherd control wiring in your wiring diagram next to the thermostat wiring.
> 
> Trace where those 2 wires connect at the HRV and hookup your switch there. It looks like the Guardian optional control is the de-humidistat control which they should have sold you and supplied you. Or the basic wall mount dehumidistat which is also in the manual.
> 
> ...


That's where I hooked them up.

I will check again tomorrow.
Where does one buy a dehumidistat?


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## 123pugsy (Oct 6, 2012)

user_12345a said:


> which terminals is it connected to on the hrv?
> 
> it appears that the controls are all digital and not just on/off switches.
> 
> ...


Timer, dehumidistat, Sheppard , all no voltage devices, are simply just switches, no?

I hooked up to the LCD W and Com.

Did I fry something?


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## shawnmstout (Dec 18, 2016)

whatever you do, pick up a multimeter and test the voltage yourself. They are very cheap and you would know for sure the voltage. No matter what you do, before hooking anything up, double check


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## user_12345a (Nov 23, 2014)

The hrv has devices that are not on/off switches. 

lcd-w is wrong. you may have cooked something.

Check the wiring diagram.

There's a separate terminal for dehumidistat or windup timer.

you go between that and common.

jump the right terminals before wiring anything to make sure it does what you want it to do.


I don't know why your hvac sub didn't do the final wiring.

If you want a dehumidistat that closes circuit when humidity is above setpoint, you can get one at rona ->https://www.rona.ca/en/dehumidistat

lowes or home hardware may have as well. check stock b4 going because it's not a common item.


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## supers05 (May 23, 2015)

That hrv uses communicating Controls. A standard switch probably won't work in the sheppard terminals. 

Cheers!


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## 123pugsy (Oct 6, 2012)

user_12345a said:


> The hrv has devices that are not on/off switches.
> 
> lcd-w is wrong. you may have cooked something.
> 
> ...


Thanks.

I'll try a jumper across COM and D/CT.
This should get it spinning I would imagine as the stat is the same as a switch.


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## 123pugsy (Oct 6, 2012)

supers05 said:


> That hrv uses communicating Controls. A standard switch probably won't work in the sheppard terminals.
> 
> Cheers!


Thanks. I should have used the dehumidistat terminals, DOH!


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## 123pugsy (Oct 6, 2012)

shawnmstout said:


> whatever you do, pick up a multimeter and test the voltage yourself. They are very cheap and you would know for sure the voltage. No matter what you do, before hooking anything up, double check


Thanks.

I have a good multi meter.
I may still hook up to the 120 output when the blower runs if it's available. I'm sure the HRV is very low amperage. I will check the data plate.


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## 123pugsy (Oct 6, 2012)

Damn!
I hooked up the switch as required and it still didn't work.

Then, I saw a sticker on the side showing LED lite patterns. I couldn't see any LED lites anywhere but I did discover a sticker that said "push".
Pushed it three times til the top lite lit up and she started to go. Lites are hiding under the sticker.

The temp difference from air in to air that gets sucked into the duct is amazing. It really does work well.


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## 123pugsy (Oct 6, 2012)

So the unit draws 1 amp and my buddy said the 120 output when the blower runs is 1 amp max.

Where is this 120 volt output located?
Yuri mentioned electronic air cleaner I believe?


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## yuri (Nov 29, 2008)

It may draw 1 amp when running at full speed ( mine uses 1.4 ) BUT it should draw quite a bit more when it is starting. Maybe 2-3X more. I am sure they did not design the EAC or ACC accessory terminals for high amperage draw and I would not use them.


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## 123pugsy (Oct 6, 2012)

Thanks.

I need a simple method for this.
Current sensing relay for when the blower starts up?


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## yuri (Nov 29, 2008)

Actually a simple Honeywell sail switch in your return duct would do it.

Have the 120 volts go thru the sail switch and then use whatever low voltage controls you want.

In theory you could tell the inspector you are running it off the LED controls in the HRV, that is legal. Mine even has a de-humidistat in the HRV so no external controls are needed. Not sure if they will agree but it is worth a try.


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## 123pugsy (Oct 6, 2012)

Thanks.

That's very cool Yuri.
I could use one for my humidifer as well.
But not the same one I guess.


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## user_12345a (Nov 23, 2014)

It makes zero sense to cycle the hrv based on furnace run time.

wire it to cycle on the furnace fan when the hrv runs. it won't cost much - if i recall your furnace has an ecm motor.

There has to be a way to cycle the hrv based. 

Did you have it in off/auto mode? not just off?

you'll want some kind of wall control to govern operation - ideally based on humidity.


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## yuri (Nov 29, 2008)

123pugsy said:


> Thanks.
> 
> That's very cool Yuri.
> I could use one for my humidifer as well.
> But not the same one I guess.


No, but they are not that expensive. Graingers/Acklands sells them and we have them in Canada.

Ideally you want to have a de-humidistat to turn it on if your house humidity is too high in the Winter to prevent window sweating or mold. However some houses don't have that problem. Mine does not and I run a bypass humidifier.

Then you want a 20/40/60 minute timer to use it for occasional ventilation/ I have that. But your economy brand 20 min timer only goes for 20 minutes and does not have the extra 40/60 if you push the button 1-2 more times.

Point being you need to decide when and what you want to use it for. 

The bldg code just says you need one for ventilation. Not sure if it specifies you need a de-humidistat. In theory you can just turn it on with the LED control and let it run forever.

If you just want to run it with the furnace fan? that does not make sense.

You need to interlock it to the fan thru G so it starts the furnace fan. That is why they have that contact.

Not sure what you want the HRV to do or when you want to use it.


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## 123pugsy (Oct 6, 2012)

Thanks guys.

It's simple.

I want it to run when the furnace comes on to get fresh air into the house.
I want it simple. I don't want to think about it. I don't want to set dials and knobs and push timers. 

To each our own, I guess.

I may need to shut it down half the time in the summer. Too much humidity coming in I would imagine.
In winter, the humidifier will have to fight the dry air.

I'll try it like this. If humidity is too low in winter and too high in summer, only then will I try to change the control system.

Finally found the HUM and EAC terminals.
I got the humidifier's transformer moved to the furnace with supply voltage taken off the HUM aux terminal.


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## yuri (Nov 29, 2008)

I would run it off the sail switch and figure out a way to get a wall switch to turn it on in place of the de-humidistat.

Turn on switch and once the unit starts with the furnace fan you are golden.


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## 123pugsy (Oct 6, 2012)

Thanks Yuri.

Now that I finished the humidifier, it's absolutely dead.
Aprilaire 700 wired up for manual operation.
I have 28 volts at the control and the screen is blank, no lights, nothing.
Is polarity a factor for the wires that are hooked up to the transformer feeding this thing?


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## user_12345a (Nov 23, 2014)

If you run the hrv in intermittent mode and interlock it with the furnace fan, it will do what you want, bring a controlled amount of fresh air in.

Poor control, like running it whenever the heat is running will result in over-ventilation.

You need to regulate runtime some how, either with a dehumidistat or by the unit's internal timer.

You mentioned a humidifier.

You should know that if you did a good job on the house, the humidifier won't be necessary. People automatically put humidifiers on furnaces out of habit but tight houses do not always need them.

In fact if you do need one in january, you won't need the hrv at the same time.

If you ended up with a dehumidistat, you would have to set the hrv higher than humidifier, otherwise hrv will run constantly with humidifier replacing the moisture. Like putting foot on the gas and break at the same time.

The main purpose of hrv is to control moisture, co2 and odours if the house doesn't leak enough. 

If you don't control it properly, it will waste energy. My preference is humidity based control but the internal timer is good too.


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## 123pugsy (Oct 6, 2012)

user_12345a said:


> If you run the hrv in intermittent mode and interlock it with the furnace fan, it will do what you want, bring a controlled amount of fresh air in.
> 
> Poor control, like running it whenever the heat is running will result in over-ventilation.
> 
> ...


I got the humidifier to light up and it was showing 42%.

I turned on the hrv to see what would happen and it started clocking downwards instantly and stopped at 39%.

Why is it a new tight house wouldn't require a humidifier?
Is 42% enough? I'm sure it will be less in the middle of January.


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## 123pugsy (Oct 6, 2012)

Humidifier issues:

http://www.diychatroom.com/f17/aprilaire-700-wiring-manual-mode-456313/#post3805441


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## user_12345a (Nov 23, 2014)

A lot of new houses are tight enough that the moisture put out by showering and cooking is enough to offset what's lost by air leakage.

In your new house you also have materials that need to dry out, perhaps concrete that's still full of moisture from when it was poured.

If it's 42% without showering or cooking, it will go up when you move in.

Depending on the quality of your windows and outdoor temp, you'll need to maintain no more than 25 to 45%. 

In summer no more than 60% with 50 or less being ideal.

Too much and u get condensation.


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## yuri (Nov 29, 2008)

123pugsy said:


> Thanks Yuri.
> 
> Now that I finished the humidifier, it's absolutely dead.
> Aprilaire 700 wired up for manual operation.
> ...


There is no polarity. Not sure what you did.


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## 123pugsy (Oct 6, 2012)

yuri said:


> There is no polarity. Not sure what you did.


Thanks.

Hooked up 24 volts when the furnace runs and nothing.

See the thread in the link above.


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