Furnace ventilation

Highbeam · Dec 25, 2005

So let me try and summarize. You have a furnace with it's own intake and exhaust. Sealed deal, it falls out of the equation. So you have a room with a water heater in it. Traditional gas fired so it has a chimney. The water heater is no different than an old style fireplace with no flue and whether the fire is lit or not you will have room air being sucked out through the chimney all the time. As the air is sucked out of the room, something has to replace it. The fresh air ducts provide this makeup air. The 24/7 draft is a good thing for safe operation of the waterheater since just like that fireplace, a lack of draft will leave you with a smoke filled room. The only difference will be an odorless, colorless, poisonous smoke. The 24/7 draft is a bad thing for the energy efficiency of the home since the heated house air is being sucked out. Which is also a problem with fireplaces and is why they are so danged inefficient and have pretty much been phased out.

Leave your ventilation alone. It is safe the way it is. The one improvement I could see is to mount those vents very close to the burn chamber of the water heater to try and get the fresh air to go right up the chimney instead of heated room air but I got to tell you, the cold fresh air is not as good at going up a chimney as the warmer room air. When you replace that water heater, consider alternatives that do not require a 24/7 drafting chimney.

My automated gas burning appliances are in the garage. Beside my bed is a carbon monoxide detector just in case. I also use the CO detectors in RVs. When sleeping, you can't really tell you're being poisoned by CO until you die. If you're lucky enough to be awake, you may feel the symptoms in time. The detectors are only somewhat more expensive than smoke detectors.

Egon · Dec 25, 2005

The newer "make up air" systems I have seen only work when there is a negative inside presure differential.

They are very simple. A pipe enters the basement and has a downcommer the terminates in an open top container. Cold air in the container prevents any air movement untill there is a pressure difference. This is basic explanation. There will be screens ext. added to the proper commercial unit.

Egon /forums/images/graemlins/grin.gif

bebster · Dec 25, 2005

You could install an indirect hot water heater that gets its heat from the furnace. Assuming the furnace has a hot water output, you could tap into that and run that thru a hot water tank. You would need to put in the right valves to give that branch priority so that hot water tank gets the heat when needed (and space heating resumes when not). This would eliminate the venting issue you have since the furnace is adequately vented. In Michigan your furance probably has enough BTU's to handle the hot water too, but you should verify that.

Jstpssng · Dec 25, 2005

</font><font color="blue" class="small">( Everyday I see more combustion problems caused by lack of fresh or make-up air in these new tighter homes. )</font>

OK, what about gas fridges? We are using a new company camp which is relatively airtight; running the gas lights for more than a couple hours will set off the CO detector. Yet the propane company says it isn't necessary to vent the fridge. We usually keep a window open, but that seems like a hit-or-miss approach.

Scary part is that if I put in a long day and get extra tired, there is a good chance the detector won't wake me up.

Sigarms · Dec 25, 2005

It would probably be easier to instal a direct vent water heater.

I have three gas appliances (two furnaces, one water heater) in my mechanical room, all direct vent with no problems.

turbo36 · Dec 25, 2005

Even with a direct vent waterheater you still need the 4" makeup air duct due to the possibility of a negative pressure condition if you run the clothes dryer or kitchen exhaust fan (or bathfans). Leave it alone and you will be safe and happy in the long run.

Highbeam · Dec 25, 2005

For an appliance to put out CO it has to be burning rich. The appliance will be burning rich because it has already consumed a large portion of the oxygen in the room and is now unable to burn clean.

There are some appliances like ventless gas fireplaces, the gas oven and range, gas fridges and lights (though less common) that somehow people think are OK to run inside without ventilation. I don't think so. You are burning up your oxygen and releasing the exhaust and water vapors into the room. Why not roll the LPG barbecue inside? You need to either provide more ventilation for that fridge and lights or get rid of them.

I like the propane fridges but think they need ventilation, maybe move it outside or into a garage. Your CO detector going off is all the evidence you should need. Last I heard, CO is one of those poisons that accumulates in your system causing long term effects.

kenmac · Dec 26, 2005

A direct vent W.H. brings it's combustion air in from outside around the exhaust vent much like a mobil home FAF.It has a sealed chamber so to speak, so it dosen't need outher make up air.A gas appliance that uses outside air for combustion ,doesn't need nor require additional air.

kenmac · Dec 26, 2005

that fridge only burns about 3 CFH . not much more (if any) than a pilot light. If your fridge is putting off C.O. you need to service it. Dust in the air shudder or a improperly adjusted air shudder is a common cause of a gas appliance producing C.O.An appliance is allowed to produce a certian amount of C.O. such as a standard gas range .It will burn approx. 65 CFH with all burners on .If adjusted properly it will produce about 20-25 ppm of C.O. If you buy one of the commerical ranges that designed for home some of these require a range hood ,because they produce more C.O. than is allowed . We use to have alot of nat. gas fridges. & gas A/C/ units down here ,but they are all nost gone now. There are a few fridges. left ,but no gas A/C units left .EPA made us stop repairing these units due to the ammonia solution used as the cooling agent

Sigarms · Dec 26, 2005

If the issue is two holes in the basement bringing in outside air, you can install a ventilation control system at various prices (some are not that expensive).

Codes per local area and who follows and enforces them can be very interesting (particularly as to why).

If your contractor is "following" code (as he's telling you) your state may actually have an inspections department that you can call to verify what he's telling you.

In a perfect world, the contractor pulls a permit issued by the state, an inspector comes out to look at the work and passes it (or turns it down) after inspection.

Heck, "word on the street" from my local contractors is that in the near future EVERY RNC house MUST have a fresh air ventalation system.