95% Efficient Gas Furnace & Venting for a Sealed Foamed Attic
HTML-код
- Опубликовано: 23 авг 2009
- In this video my HVAC contractor Gilbert Rosipal from AirRite shows us the inner workings of a 95% efficient gas furnace. You'll see the concentric pipe used for the sealed combustion chamber and the pvc vent pipe through the roof. We'll also discuss why we like to hang our units from the rafters rather than sitting them on the attic floor. -Matt Risinger Principle of an Austin Texas based High Performance Builder and Remodeling Company www.risingerhomes.com
Wow, I just ran across this while searching for information on exhaust ducting for high efficiency furnaces. A young Matt Risinger!
Thanks for your kind words! I get kinda geeked out on the HVAC systems in my houses. Matt
stumbled across this Vintage video.... I'm enjoying your HD production videos now!
you can tell these guys are pro's. These are the guys who you call, they come and fix or install, and then you never have another problem again...
Great question. I'm actually not sure if they have a technical name. My HVAC contractor gets them from the AC Supply House. I've been using them in all my houses for 8 years without any issues. I don't think this small amount of vibration will affect structural framing. Your method seems solid if you're worried about this small vibration though. Best, Matt Risinger
One beauty of these 95% gas furnaces is that the venting is all PVC. That allows you run horizontal flue pipes and locate the unit in places that won't work for an 80% furnace. I don't know for certain about your application but it seems likely. Best, Matt
@mack70214 Good question. I don't believe it would burn hotter. The unit we're showcasing in this video is natural gas powered and is very efficient as it turns 95% of the gas into usable heat and 5% is lost to inefficiencies. Typical Gas furnaces are 75-80% efficient. I've never installed an oil fired unit but I would guess that they make some equipment that will use the oil more efficiently too. Hope that helps.
This unit isn't particularly loud when operating. If it's in a crawlspace you would not hear it in rooms above. Best, Matt
Yes indeed. This furnace is much more efficient than the standard 75-80% efficient models you see in most new homes. BUT, equally important is that it's a power venting model. The flue is PVC and stays cool. It doesn't use combustion air from the attic so we can use this furnace in a foamed & conditioned attic space. Plus, no worries about combustion gas spillage into your house (meaning no carbon dioxide worries). I recommend these to all my clients.
Matt Risinger Carbon monoxide is the real concern
@ILoveLucyE68NY YES, for sure. This video was made during the install and the piping wasn't done. With a fully sealed and foamed attic you MUST provide piped in fresh air and exhaust for the sealed combustion. The clients got their first month's energy bill in June and it was $37 in electricity for a HOT month!
Are additional high low vents required through the roofline to provide combustion air on a 95% installed in a foamed house/attic?
I had a Trane furnace installed last year. They vented it outside and also piped a fresh air pipe but tyey never connected that pvc pipe to the furnace. They left it near the furnace and said the furnace would draw the fresh air from that pipe there. I had to put a pvc elbow on the furnace where this pipe should be because it got clogged,the furnace room has a cat litter box in it and that may have clogged the opening. Should we add more pvc pipes to connect this fresh air vent to the furnace ?
Ha ha guess what U2 brought me 12 years later ha ha ha ha ha awesome Matt
I am interested to know what the spring hangers are called (maybe "spring hangers" lol). Smart. I won't connect to the rafters the way that this was done though. I'd worry about the vibration eventually loosening the cross brace nails. I'll run eye bolts horizontally through existing rafters (5/8 inch) and connect to the spring hanger with another eye bolt and S hook.
aww you look so young.
My furnace is vented through the roof. It had a tee on the exhuast. They replaced the roof and put an elboy on it, Is that ok. My condensation pump runs more. about 6 times a day if not more.
It depends on the building envelope; if you have an older house that is susceptible to infiltration through the walls you are okay. If you have a newer home that has been engineered to have a "Tight" building envelope then the furnace will require a combustion air pipe from outside. High efficient furnaces have a closed burner compartment and when a two pipe system is used the furnace will be using fresh clean air from out side to mix with the fuel for combustion apposed to dirty air from house.
he is used a concentric it's a double wall pipe the inside of pipe is for exhaust and the outside of pipe is the combustion air so you don't burn oxygen out of house
I'm hesitant to comment because I'm not exactly sure which pipe you are calling "fresh air". If you mean the combustion air then that's not good if you have a modern spray foamed and tight construction house. I would get another trusted HVAC contractor to check this install and see if it's done correctly. Best to be safe when it comes to Gas appliances. Matt
With the exhaust vent upright in a roof penetration how is water drained from rain and snow melt?
90 percent furnaces have drains built in. They can get clogged. Recommend tune ups to clear drain lines and even drain the water from inducer if you hear it gargling. The flue gas is warm enough to melt snow. In high wind areas if a 45 or 90 was put on top it can give a pressure switch issues if wind is to excessive. Screens have been known to ice up. Just make sure the flue is higher then the snow level of your state and you should be ok.
High efficiency furnaces have drains built in to drain through multiple drain lines. Pvc needs to be sloped properly or you will have pressure switch issues.
Correct me if i'm wrong (and i'm no HVAC guy) but the reason there is a plastic (or PVC) vent isn't because of low heat but because of Carbonic Acid. Carbonic Acid is formed when Carbon Dioxide mixes with water after the combustion process and would be very corrosive to a metal vent or drain. Pretty much why everything condensate in a furnace like this, is PVC or plastic. But I do have a question on this, does the PVC vent have to be insulated? I've had an inspection on my home and the inspector is saying that it need insulated. Why?
Did he mean the refrigerant lines or the duct. Depending on location the duct needs to be insulated. I can't speak for code in other states but never heard of pvc being insulated.
One penatracion nice that's what my wife had before we got married and had my son 9 months later
Hi, I have uploaded this video so that you can see which unconnected air inlet I am talking about. When I had my home inspection done at the time of home purchase. The home inspector said it should have been taking air from outside of the house. But he did not mention that as concern. Can you please have one of your tech have a look and see if this is not something to be concerned about. Thanks
If the room is big enough and is getting plenty of fresh air intake some furnaces in the installation manual actually have pictures of 3 inch pvc intakes being vented into the gas buner box assembly. Flue gas should always be exhausted out side. Look at the installation manual and you will get your answer. You can download a pdf online by using information on your furnace data plate
Don't leave the cat litter box in the furnace room. The ammonia from the cat urine will eat away at the furnace heat exchanger and reduce the life of the furnace. Also don't store any chemicals even in closed containers, especially chlorine for pools.
In our furnance, the contracter never connected the fresh air inlet to any pipe, so basically it is drawing air from the basement. Will this cause any problem?
Avoid HVAC attic installations unless the environment is temp controlled or the attic is finished. Attic temps can exceed 140 and you are trying to cool the house. Expect to lose 10% cooling and run the risk of leaks that will bring attic dust into the house.