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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8164
Experience:  Furnace, A/C and heat pump specialist.
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There is a horrible odor coming from my hvac system. A technician

Resolved Question:

There is a horrible odor coming from my hvac system. A technician has come out with some bubbly water to look for a gas leak and found nothing. I don't know when it's going to happen. It seems to happen more often when it's raining or moist outside but today was a sunny day and just a sprinkling of a shower and the odor has returned. It's is extremely strong the closer to the unit you get. I am assuming it's the water heater (55-gallon tank) because it only happens when I have hot water running at the kitchen sink. I know this sounds convoluted but rain/moisture + hot water running at the sink equals an odor that makes my eyes water and makes it impossible to breathe. If you enter the room, your eyes will shut on you. If you're in the house, you only smell it a little bit and it's tolerable but you can smell it. It smells chemically with a bit of gas or something mixed in. It hurts the eyes. The water heater's exhaust pipe is joined near the top of the hvac exhaust pipe. I only noticed this 5 years ago when I had the HVAC unit installed but it's very hard to predict when it's going to happen. Rain and running hot water seem to be the trigger but when a HVAC tech is here, it usually won't reproduce itself. Troubling! Oh, I do have a carbon monoxide and smoke detector installed in the very same room as both units ("utility room") and it has never once gone off. It's brand new, $60 combo unit. I'd say the horrible fumes/odor is definitely not CO.
Submitted: 4 years ago.
Category: HVAC
Expert:  airheatman replied 4 years ago.
Hello.Sorry you are having problems. My name is XXXXX XXXXX I will do my best to help.Please wait to leave rating until we are finished.Arte you able to upload any pictures of the installaion? It sounds as though there must be a direct realtion to the water heater since you nly smell it when demanding the water heater to be on.
Customer: replied 4 years ago.
I should be able to upload a few. Can you tell me which parts specifically? I'll take some that I think will help but if you can direct me to pipes or labels that you're looking for, I'll include those as well. Thanks!
Expert:  airheatman replied 4 years ago.
The location of the water heater in relation to the return air grille for the ac system. The vent from the water heater and especially the water heater's exhaust pipe is joined near the top of the hvac exhaust pipe that you mentioned.Also the termination of each on roof or wherever they terminate.
Customer: replied 4 years ago.
Hey! Sorry, I have guests over for dinner so I'll have to pick this up later. I'll be back!
Expert:  airheatman replied 4 years ago.
No problem. Look forward to working with you at your convienence.
Customer: replied 4 years ago.
hvac 01

hvac 2

hvac 3

hvac 4

hvac 5
Customer: replied 4 years ago.
hvac 6

hvac 7
Customer: replied 4 years ago.
hvac 8
Customer: replied 4 years ago.
return is out in the hallway, there is a tight sealing door closing off the utility room
Customer: replied 4 years ago.
I'm leaving to go hiking and will return later.

Thanks for looking!
Expert:  airheatman replied 4 years ago.

Since your claim is that this odor seems to be at it's worst when water heater is in demand leads me to believe it is directly connected.After viewing the pictures, my opinion is that this issue may have something to do with whatever sealer that is on the vent pipe joints.Neither the furnace nor the water heater should require any type of sealant.However both should be ran out of double wall tpye B metal vent pipe(not single wall pipe). See images belowgraphicNo sealants of any kind should be required .It appears there are several places where your vent is not sealed well even with this sealant. Also around the unit are places where a small amount of surrounding air can enter the air stream such as furnace door, where furnace connects to coil, drain and refrigerant pipe openings on coil, etc .My suspicion is that as the vent pipe from water heater gets hot (as well as some heat escaping at the bad joints, this orange colored sealant may be producing the chemical odor and being drawn into the air stream.The only relation I can see about the rain is perhaps the single wall metal is cooler above ht roof line and perhaps have an effect on the amount of odor. My suggestion is next time you have the odor, go to the vent pipe and smell around the joints where the sealant is and see if it is strong there.(Of course not for a prolonged period of time, Don't want you inhaling fumes). If indeed it smells strong at that point, I suggest replacing both vents with type B double wall pipe with NO sealants. (really should be done anyway). Hope this proves to be helpful.

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Customer: replied 4 years ago.
I've always suspected that orange (red) sealant but the tech said that is high temp sealant that gives off no odors. I will look into having the exhaust redone. I wouldn't mind sniffing around next time but boy oh boy, I'll tell you what...when you open the door to the utility room and it's at its worst, you wish you could remove your eyeballs and wash them off with bleach. The pain would be a whole lot less.

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