Can I add-on to my existing HRV?

[mhorts]

We live in Seattle and have a 24'x17' media room in the back of the house over the garage. I have a projector hung from the ceiling and a stack of equipment, etc. in the back of the room. It gets kind of warm in there. Like most folks in Seattle, we do not have or really need air conditioning.

I used tinfoil to cover the two floor heating grates in the front and back of the room. We have forced air gas heating. The media room never needs heat, as you can imagine. It is warm in there even tonight, when it's ~40 degrees outside and raining. To solve the issue, we just leave the big north-facing windows open to some degree in there almost all the time. Maybe I can leverage most of what I already have to pull that warm air out of there...

Here's my thought...
We have a Honeywell R8421 Home Ventilation unit hanging in the top of the attic with ducts leading to each bathroom and the laundry room. I think you experts call this an "HRV." I leave the HRV on low throughout the year, from the master control, and then the individual ducts are controlled individually when you turn on the timer in the bathrooms. There are five round grille-things in the ceiling, one in each bathroom, one in the laundry room, plus one in the master bath sink area.

Question:
Could I tap into one of the ducts in the attic and run another duct to the ceiling of my home theater room and use the HRV to pull the warm air outta there? Everything is easily accessible up there. I have a recessed ceiling can light in the media room that I no longer use and it looks to be the same size round hole, so I figure if I buy some round soft ducting like what's up there and a metal sleeve and a plastic grille thing, I'm in business. Unlike the bathrooms, I could get away with not using a timer. I would just set the master control to high downstairs beofre I go upstairs to watch a movie.

Is this possible?
Also, is this a DIY project?
Any help would be appreciated!

Thank you,

Doug S

[JAMES 3528-old]

If you are going too pull air out of that room then air has to go back in. Will this be filtered and treated air? If not you may want to put in a small ductless split system in the are. Isn`t Seattle kind of wet? Collin a member of this board, I think lives near there in Canada. If he can not help you, he can sell you a Bar- B- Que grill.

[Maddog]

I'm not familiar with that product, are you sure it's an HRV and not just a central vent fan? If it is a vent fan only, you're just a well off with the open window. Maybe one of the other members knows what this is. Good luck.

[Maddog]

I did a search on Honeywell's site, couldn't find that number. All of their current units start with "HR". I guess it could be an older model that is no longer listed.

[Collin]

You get snow last night? We woke up to a sprinkling.
Doesn't quite sound like an HRV because there aren't any supply air outlets. Sounds like a central exhaust system. You could probably take air from the media room though, maybe from above the equipment if that is where the heat is coming from. Now how are you going to get fresh air into that room? Probably the window.

[mhorts]

Hi Collin:

More soon... going skiing, yes we got a little snow here at 500 feet! It is definitely a HRV, I just didn't describe it completely cause I'm not too swift when it comes to HVAC... compare to Honeywell HR150...

Gotta go, wife mad...
How to cut the duct? get the parts? she's pulling me out the door... arrrrrggghhhhh

Doug

[Collin]

So how far would the run be? If you were to run the pipe through an attic space you would probably use insulated flex pipe. Problem is HRV's aren't designed to move a lot of air. By adding another return run you may diminish the ability of the unit to exhaust adequately. Kind of one of those gotta see it scenarios. Can any of your friends recommend a local contractor? Or do you have a ski chalet I can borrow after I do the job?:D

[mhorts]

I went up into the attic and measured and looked around. Here is the deal... The unit is a Honeywell ER90 B1003. I believe that means it is an ERV (energy recovery ventilator), NOT an HRV as I stated earlier. Honeywell's Web site only lists an ER150 and ER200. This house was built in 1997.

There's a main intake to bring in outside air, and an exhaust that blows out the stale air, both venting to the roof. There is a duct that blows conditioned air into the house. There are three ducts coming out the side. Two of the three have larger ducting, and are split into two runs of Class 1 Flexible Duct, for a total of five runs of class 1 duct. Two go to the master bathroom, one to the kids bathroom, one to the downstairs powder room and one to the downstairs laundry room. The laundry room is the only room without a timer. Instead, this room (actually a hallway leading to the garage) has the master contol, which is variable speed and has a red LED light. Even if this "master" switch is off and a bathroom timer is turned on, the red LED will glow, and the unit will turn on.

To add the home theater room it will take about a sixty feet run. The room is upstairs and there is an existing hole I could use that now houses an unused recessed can light. I could probably use the downstairs laundry room run since we have never even turned on the ERV to vent that room when doing laundry -- we have never needed to or even thought about it. It's a hallway and gets plenty of ventilation as is.

OK, that's what I know -- any ideas? This has to be a DIY... Thanks!

[Collin]

An important issue is how many cfm's the unit is rated for. I am not familiar with that particular unit, but have done a few different hrv's. My guess is the most you'll get out of it would be 30-50 cfm. This amount won't make any difference in cooling down the room without continuing to open the window.

[mhorts]

Collin:

No, I don't have the manual, but the unit is rated at 90cfm, thus the model number ER90. I spoke to a technician on the phone today who asked the same question, and he looked it up and told me it's rated at 90cfm.
Here are the dimensions of the rooms that are being vented now:
Downstairs rooms, 10 foot ceilings:
Laundry room hallway = 5.75 x 9 x 10 = 518 cf
Powder room = 5 x 9 x 10 = 450 cf
Upstairs rooms, 8 foot ceilings:
Master bath water closet = 2.5 x 6.75 x 8 = 135 cf
Master bathroom = 10 x 14 x 8 = 1120 cf
Kids bathroom = 5 x 12 x 8 = 480 cf
So the total cf of these rooms = 2703
Am I correct in saying that the 90 cfm machine I have now is replacing the air in these rooms every 30 minutes?
2703cf / 90cfm = 30 minutes
Then, the upstairs media room is 12 x 22 x 8 = 2112 cf
for a total of 4815 cf / 90cfm = 53.3 minutes
How do you guys rate these things?
If this acceptable?
Remember when we're watching a movie, we're not running the fan timers in all the rooms throughout the house. You said you had done a few of these, does the timer close the vent when the timer runs out?
I don't mind keeping the window open, I just think this would take a lot of extra heat out of the room.
For the cost of 60 feet of duct and a palstic grille, I think it may be a pretty good solution. What do you think?

[Collin]

But I'll give it a quick shot. Trusting your math you have a total of 2703 cubic feet. Add the media room of 2112 less the laundry/hallway of 518 leaves a total of 4297 divided by 5 runs = 860 divided by 90 cfm equals 10 cfm per run IF they are all equal.
So the media room at 2112 cubic feet divided by 10 cfm = 211.2 divided by 60 = 1 air change every 3.52 hours.
HRV's are sized for 1/3 air change per hour. Not sure about ERV's but I think you will be grossly undersized. Do you have dedicated bath fans in addition to the ERV? If not don't do it!

[mhorts]

Collin:

OK -- you talked me out of it. Plan B: install a duct from the recessed can light hole to the attic vent grille, and put an exhaust fan up there that turns on when the equipment is on.

Does the fan go in the ceiling end of the duct or at the attic end of the duct? Fan noise is a factor.

Know of a good Web site to buy exhaust fans like this?
http://howelltechnologies.com/FE657DD0940C295F7F2959E07C19EA5D/default.html

Is too epensive...


Thanks -- Doug

[Collin]

http://www.fantech-us.com/fx.htm
Sounds like you have quite the killer system:chill
How hot does it get around the equipment?