Vent/fan safety in a room with gas appliances

[fishguy306]

I know the humidity topic has been covered to death, and venting the fish room to avoid excess humidity, which I am attempting to do, however I'm running into an issue I don't often see brought up.

My fish room is in the unfinished half of my basement, a room that is about 26' long by 14' wide. On this side is the furnace, water heater and dryer, all gas powered. The furnace and water heater are at one end with the sump and ejector pumps, middle of the wall then has the washer/dryer and the other end is two 150 gal sumps, a 125 gal and four 75 gal tanks. The sumps will also be connected to a large tank on the finished side of the basement.

I'd like to set up a vent with a fan to kick on when humidity is above a certain level, say 45 or 50%, and just vent the air right outside. I'd even consider replacing one of the small windows down there with the vent to avoid drilling holes in the house.

But the issue I am worrying about it the furnace and water heater. I've heard that a big enough fan can pull the exhaust from these back into the room rather than up the vent. So question one is if this is something that can happen? My gut is telling me yes. Question two would be is there a workaround for this? I looked into splitting the water heater vent, so it would have two intakes, then adding the fan up the line so it'll suck in air from both, however from what I've seen that seems like a big no no.

Do I have any other options? I really would like to avoid a dehumidifier if I can at all avoid it, they are loud, expensive to buy and expensive to run. I've also seen the HRV and ERV systems and have looked into them, but once again they are very expensive. I'm also not crazy about bringing air below freezing into my basement in part of the exchange if I go without the heat recovery option. Further in the summer those units will just bring in humidity from outside. Chicago is such a lovely place.

 

[FamilyTank]

I quess theoretically,its possible. How big of a fan are you talking about? I've just installed a new 110 cfm bathroom vent fan, even 2 of them wouldn't concern me with pulling exhaust gases out and around the vent hoods of a water heater or furnace. What about walling off the appliances?

 

[fishguy306]

Honestly I was thinking I'm going to need something bigger. I was looking at something like a 4 or 6" duct fan rather than a bathroom fan, something like this-

https://smile.amazon.com/VIVOSUN-In...qid=1481910964&sr=8-14&keywords=duct+fan&th=1

I'm not set in stone on my course of action yet, but something like that is my plan. That said that is a ton of air I'd be blowing out with not much coming back in. So it would concern me it would be too much for the gases to escape properly.

 

[jccaclimber]

There may be issues tying in to the existing vent from a gas appliance, I would think a call to the local code office or an HVAC place would answer that. I remember the home inspector frowned on that (water heater and furnace sharing a vent) when he was inspecting my last house. My understanding was that the vent had to be big enough to handle both devices, but couldn't be so big as to let air cool moisture condense in it when only one was running. You also don't want it recirculating in one appliance and out the other, although I would think some sort of check valve would be possible.

As for outside air, you're either paying to pull the moisture out of the air (dehumidifier, house A/C), or paying to put heat back in. Also consider the power consumption of the fan when comparing to a humidifier. In the summer external venting wouldn't work for me because the outside air carries more water than the air I would need to vent.

I wouldn't think that an exhaust fan for a 4-6" vent would overpower the powered vents in other appliances, but something like a gas water heater that does not have a powered fan on the exhaust stack could be an issue. I also don't know how well sealed your place is, and make-up air has to come from somewhere. As a safety precaution, my gas furnace has a pressure switch to make sure the inducer fan is working, so at least there wouldn't be a safety issue there.

Personally I put lids on all of my tanks and sumps which significantly cuts down on evaporation as well as the cost of heating them. The house A/C keeps things dry in the summer, and with some luck it hasn't been an issue so far in the winter.

 

[ericarenee]

Honestly I was thinking I'm going to need something bigger. I was looking at something like a 4 or 6" duct fan rather than a bathroom fan, something like this-

https://smile.amazon.com/VIVOSUN-In...qid=1481910964&sr=8-14&keywords=duct+fan&th=1

I'm not set in stone on my course of action yet, but something like that is my plan. That said that is a ton of air I'd be blowing out with not much coming back in. So it would concern me it would be too much for the gases to escape properly.

I am not sure about your issue But in my basement in the summer time humidity tries to climb .I to have all gas appliances that connect to a brick flu that goes above my roof.. Across the same open area is where my sump and refugium tanks are I put a double 8 inch fan in that window one blowing out one blowing in... I have used this setup in the winter time once in a while and i see no issues . The hot air of a older furnace or water heater rises up the flu quite fast.. Newer equip and cloths driers the air is Forced out with a fan..

The above fan is the same as i use for air purification on Job sites.. I have them mounted in a wood frame box 10x x24x24 with a Furnace filter grill on the box . the hose i ran out thru the customers home to the exterior and terminate in another box that i can put filters inside of if needed..

This is now A REQUIREMENT thanks to LEAD PAINT Removal laws The fans are Great..

 

[fishguy306]

There may be issues tying in to the existing vent from a gas appliance, I would think a call to the local code office or an HVAC place would answer that. I remember the home inspector frowned on that (water heater and furnace sharing a vent) when he was inspecting my last house. My understanding was that the vent had to be big enough to handle both devices, but couldn't be so big as to let air cool moisture condense in it when only one was running. You also don't want it recirculating in one appliance and out the other, although I would think some sort of check valve would be possible.

I've done a bit more looking into this, the topic actually seems to come up with growers a lot, they set up grow tents in their basements and need to vent the heat. From what I have seen it is a big no no to tie it into the vents for water heaters, especially unpowered ones. It can cause the gases to be pushed back into the room. So it appears that idea is out.

As for outside air, you're either paying to pull the moisture out of the air (dehumidifier, house A/C), or paying to put heat back in. Also consider the power consumption of the fan when comparing to a humidifier. In the summer external venting wouldn't work for me because the outside air carries more water than the air I would need to vent.

That is true, however for me gas is a whole lot cheaper than electric, so I'm using it to heat my system as well as the room. I'm not sure what size dehumidifier I would need, however this smaller unit-

https://smile.amazon.com/50-Pint-De...8&qid=1481914212&sr=8-9&keywords=dehumidifier

draws 530 watts running, the fan posted before is only 120 watts. That said you bring up a good point, I'm not sure how well blowing air outside will work if it is even more humid outside in the summer than in my basement. In the winter I suspect the fan would work great, but not sure about it otherwise.

I wouldn't think that an exhaust fan for a 4-6" vent would overpower the powered vents in other appliances, but something like a gas water heater that does not have a powered fan on the exhaust stack could be an issue. I also don't know how well sealed your place is, and make-up air has to come from somewhere. As a safety precaution, my gas furnace has a pressure switch to make sure the inducer fan is working, so at least there wouldn't be a safety issue there.

I assume my furnace has a powered vent, however I'm not sure as it is pretty old. The water heater does not. My place is also not very air tight, I feel like air leaks in just about everywhere, including in the room where this equipment will be. Not sure if it would let in enough air or not to avoid issues. I could put an intake vent on the wall to the finished side to let more in. Probably not a bad idea anyway considering 1000 gal of the water will be on that side.

Personally I put lids on all of my tanks and sumps which significantly cuts down on evaporation as well as the cost of heating them. The house A/C keeps things dry in the summer, and with some luck it hasn't been an issue so far in the winter.

I will be covering most of the tanks, the sumps the best I can, however I'm not sure how well I will be able to cover the main tank. Right now the plan is for the back half of it to be covered then the front half covered with netting.

I am not sure about your issue But in my basement in the summer time humidity tries to climb .I to have all gas appliances that connect to a brick flu that goes above my roof.. Across the same open area is where my sump and refugium tanks are I put a double 8 inch fan in that window one blowing out one blowing in... I have used this setup in the winter time once in a while and i see no issues . The hot air of a older furnace or water heater rises up the flu quite fast.. Newer equip and cloths driers the air is Forced out with a fan..

The above fan is the same as i use for air purification on Job sites.. I have them mounted in a wood frame box 10x x24x24 with a Furnace filter grill on the box . the hose i ran out thru the customers home to the exterior and terminate in another box that i can put filters inside of if needed..

This is now A REQUIREMENT thanks to LEAD PAINT Removal laws The fans are Great..

Thanks for the tip! I have looked at fans similar to those, it would solve the negative pressure issue for sure, however I'm not sure they would move enough air to accomplish what I need. That said I'm not sure how much air movement I'll need yet anyway, guess I probably wont know until this summer when it starts getting humid.

 

[stage3-s4]

The first thing you need to find out is if your water heater and/or furnace are direct vented or atmospheric. This basically means it will pull combustion air from within the house (atmospheric) or from outside (direct vent). Sounds like you know the difference. If the water heater and furnace are connected to a common chimney stack usually made out of brick in older homes, most likely they are atmospheric. You would need to find a way to make up that 440CFM of air you plan to exhaust. That becomes tricky because then you are dealing with raw air from outside. You could try a small window fan as mentioned. You want to watch for the color of the flame in your furnace as this will be a good indicator of proper combustion (Should be blue in color). If they are both direct vent connected, you shouldn't have an issue.

 

[fishguy306]

I would assume both are atmospheric, the house is 30 something years old, the furnace might still be original and the water heater is 10+ years at this point. Honestly I expect either one to crap out any day now.

But yeah, that is my thought too, I will need to bring outside air into the room or I will have some issues. I guess figuring out how to do it is the difficult part. HRV units are expensive and just bring in humid air in the summer, though in the winter it would help keep the area warmer. I guess it is something to think about.

 

[stage3-s4]

yup thats always the fight I have with building owners. They hate spending money on large make-up air units just to temper outside out to make up for the air exhausted. But its code. Nothing you can do.

 

[fishguy306]

Very true. God knows I've spent enough money on the rest of this system. I'd be more for the HRV, but I don't think it'll solve my summer humidity issues.

 

[laverda]

It would seem to me that the water heater, furnace & dryer are going to help keep the humidity down as they all heat and draw air out of the house. I would think that would be enough to keep the humidity under control to a large extent. However that air being from saltwater is going to shorten thier life span a fair bit, so a dehumidifier would make the most sense I would think.
Also your talking about a pretty large basement, so I would not expect it to get that humid, unless your using a lot of fans to cool the system in the summer.