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Old 10-27-2011, 10:36 AM   #1
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fresh air/makeup air dampers


I'm thinking about installing some fresh air dampers for our furnace and was wondering what the best were? Our furnace has one 6" inlet from the outside for combustion air that runs down to the plenum, and then one 6" makeup air vent that simply dumps in to the room. When it's cold outside that can make that room and our entire downstairs cold awful fast.

Not really sure, what is best... I've been looking at thermostats with electric damper controls. I could then run one of these:

http://www.iaqsource.com/category.ph...?category=2128

or

http://www.drillspot.com/products/50...torized_Damper


Or there is the Skuttle products that are all passive. Not sure which is best?

http://www.skuttle.com/makeupcontrol.html


All in all one product might be good for the combustion air venting and another might be great for that makeup air vent? I'm not sure how the passive dampers work except for vacuum from combustion? I'd think for combustion air I would want to go with an electric damper? I appreciate any feedback and ideas...

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Old 10-27-2011, 11:12 AM   #2
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fresh air/makeup air dampers


What size furnace & hot water tank is the fresh air feeding? Is it larger than you need?
&
You can also make a simple air trap to limit the temp driven air dumping into the furnace room. The units can still draw as much air as they need but the air spilling out of the fresh air vent won't be driven by the cold air dropping down the vent.

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Old 10-27-2011, 12:42 PM   #3
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fresh air/makeup air dampers


Hot water heater is just a standard 50 or 55 gallon one, I think...

Furnace was said to be way larger than needed for our house, but I'm not sure. Would a model number or something help on that?

By simple trap do you mean the 5 gallon bucket trick? I thought about doing that, but pretty sure the wife will veto it for aesthetic reasons, so I was looking for other solutions that looked more official and professional...
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Old 10-27-2011, 11:54 PM   #4
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Yeah, a 5 gal bucket will do but try using a larger vent pipe in place of the bucket.
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Old 11-02-2011, 10:53 AM   #5
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fresh air/makeup air dampers


Ok, here is better info....

Here is the 6 inch vent that dumps in to the room...




On the right is the makeup air vent that dumps in to the room, on the left is the combustion air vent. It's 6inches and runs to the plenum of the furnace, no damper.





Here's the furnace, picture is too low to see combustion air hooking in to the cold air return...





And the exact model...




More info:

House is 1800 sq ft of heated space. Additional 500 sq ft is unheated that I've thought of sending venting to....

Furnace room also has water heater and electric dryer.

Exhaust venting in the house includes:

- fireplace (damper closed but not sealed)
- dryer venting
- kitchen range venting
- one bathroom venting (other 2 are on exterior walls)
- furnace and water heater exhaust

Just wondering what I can do with the fresh cold air coming in... I thought about the bucket, or bigger vent pipe trick, with the makeup air, but wondering if that really works that well. I've seen the Skuttle devices as well...

Also considered an electric damper for the combustion air?
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Old 11-02-2011, 11:07 AM   #6
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fresh air/makeup air dampers


i would block that window with a sheet of 2" styrafoam and pack with insulation that opening for the winter..you have enough atmospheric air to run 5 boilers in that room....that air in the dead of winter must drop like a rock into that room so that air gets heated furnace and HWH and vents out after the burn?it cost less to heat 60F-70F air in a room then 30F air dropping into it..that is over killing only common with commerical boiler roomsi see you taped over that return air grill on the furnace that didn't take to long....i would tighten up on the double elbows coming off the top of that flue keep the bottom one remove the other and turn that remaining one to marry it up for a better rise..just a suggestion

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Old 11-02-2011, 11:19 AM   #7
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fresh air/makeup air dampers


Yeah, we taped over the grill in the cold air return because code is no return air grills within 8' of the plenum or something like that. We were told it's an explosion hazard...

I'll block off the makeup air dump in to the room.

I'll also investigate changing the flue pathing, I know that was just changed by the company that installed our AC.

What about installing an electric damper on the 6inch combustion air venting so it only gets cold air when it's running?
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Old 11-02-2011, 11:43 AM   #8
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thats a static vent right not Induce Draft with a sepreate fan within the furnace... looks staic sure adding a auto vent damper would hold the balance of the heat on the exchanger after the stat shut the furnace from setpoint. check local Grainger for availibility...#1H805 item for 6" flue call the installer to see if that style furnace will accept a flue damper wire harness tap.if installed the damper will become the first R to W action to move when the stat calls for heat..watch the flue duct screws on install damper has to swing 180 degrees to make the switch and run the heat...but definitly call the company to see if it will take one... NOTE on tht venting the furnace gets its air to burn from the room and the burst gas goes up that flue it's not supply it same on HWH...quick test on either in the off cycle light a match near the flue or hat on the HWH and it should full the flame even make it go out and watch the smoke drag up the flue...
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Old 11-02-2011, 12:14 PM   #9
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fresh air/makeup air dampers


Thanks for the responses. I'm on my own as far as the installer goes... we bought this house 3 years ago and the furnace was installed long before that... The furnace itself has stickers from 3-4 different HVAC companies that have worked on it....

I have the model number of the furnace and could also look at the control board to research the part you suggested. I know when the AC was installed this year they did some "trick" that makes 2 thermostat wires in 4. It looks like it's simply jumpering a couple connections, but our thermostat only had 2 wires when we were on heat, now with AC it has 4 or 5 and they never ran new wire...

As far as the match trick, help me understand... Inside the furnace I have the combustion fan, it sits over the combustion chamber and is then screwed to the flue and exhausts up out the chimney. Would I remove the combustion fan venting to test with the match? It looks like a sealed system otherwise... I can take more pictures...
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Old 11-02-2011, 01:39 PM   #10
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OH,seeing that flue piping made me think it was staic with no Induced Draft motor but that changes the install of the flue damper...maybe somebody will kick in with adding one to a unit with induced draft.forget the match trick its for furnaces and HWH with staic flue venting..forget i mentioned it....if you don't have an induced draft motor on the HWH the match test will work there.just light it and hold it up to the hat the vent pipe connects to to see if it goes out and th esmoke drifts up into it.....like i mentioned the flue damper is controlled by the stat call for heat when added,but right now the ID is the first thing to run from a stat heating call...somebody will add to this..or just start a new thread asking about "adding a flue damper to an induced draft furnace?
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Old 11-02-2011, 02:42 PM   #11
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fresh air/makeup air dampers


Ahh, so I misunderstood... if I didn't have an induced draft furnace I could have added that damper to the chimney... can you add a damper to the combustion air intake? I think that would help tremendously, right now it's a 6 inch pipe directly from the outside to plenum... it sits there wide open letting cold air come in and fill the basement 100% of the time... the makeup air vent isn't helping either, but I may plug that as you suggested and redo the chimney piping to be less horizontal...
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Old 11-02-2011, 03:04 PM   #12
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on the draft from the chimney even in the summer.as long as that metal is warm to hot from either the furnace or HWH cycles the air will rise from the basement up keeping the draft rising...even ieith both off residual heat on the metal causes a drfting up...on the add on i did one on a new weil-mclean boiler i did in 90' when i change my boiler just walking in as you did to a home.... adding one to a furnace with induced draft is the question somebody else needs to tell you...if i had a 60watt light bulb in that 6" flue pipe for and example....the heat from the bulb would cause a heated draft to rise up into the chimney doesn't take much even maybe the air in the room being 65F in the winter...heat travels to cold

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