Heat Loss In Furnace Exhaust

[Jmholb57]

A lot of heat comes out of exhaust of furnace into atmosphere. Is this normal?  Seems to be a waste of heat and fuel. Thanks jmh

[wildebill308]

Yes it is normal. Home gas furnaces have made big gains in efficiency over the years. RV furnaces not so much. 

Bill

[bm02tj]

If the furnace exhaust is to cool it will condense and corrode the internal parts.

As a rule of thumb more than 84% you start to get acidic moisture  inside.

 

[manholt]

Yeah, not something you want in a Oasis or Aqua Hot system!

[Jmholb57]

Thank you for answers. Helpful. 

[wildebill308]

Thanks for checking in.

Bill

[rayin]

The average RV furnace efficiency is around 60-65%. I now forget where I read that though.

[alflorida]

That is why we use a catalytic heater.  About 99.5% efficient.  Also, quiet.  We don't have to listen to the fan noise.

[wolfe10]

49 minutes ago, alflorida said:

That is why we use a catalytic heater.  About 99.5% efficient.  Also, quiet.  We don't have to listen to the fan noise.

 

But, they sure add moisture (a normal byproduct of combustion) to the interior.

[richard5933]

Catalytic heaters (Or any type of LP heater which does not vent the exhaust gases to the outside and supply outside air to the burner) run the risk of 1) depleting the O2 in the RV, and 2) causing a dangerous situation with carbon monoxide. The extra moisture would be the least of my worries sleeping inside a closed space with one of those running. A carbon monoxide monitor would be a must. Hopefully the unit itself has a low-O2 shutdown built into the control.

[abyrd]

 

50 minutes ago, richard5933 said:

Catalytic heaters (Or any type of LP heater which does not vent the exhaust gases to the outside and supply outside air to the burner) run the risk of 1) depleting the O2 in the RV, and 2) causing a dangerous situation with carbon monoxide. The extra moisture would be the least of my worries sleeping inside a closed space with one of those running. A carbon monoxide monitor would be a must. Hopefully the unit itself has a low-O2 shutdown built into the control.

We have used our previous MH for snowmobiling for extensively and we always used catalytic a catalytic heater as our primary heating source. We always left a window partially open in each end of the motor home and we also had O2 monitors.

We found the heat were comfortable and we could spend day without running the generator.  I would install one in our current MH if we had a place to install on.  With the four slides there is no wall space to accommodate a catalytic heater.

Jim

[manholt]

Been around for a long time, as long as you use common sense and protect yourself against the accumulation of Carbon Monoxide, it's a good heat source.  I leave a window and a vent slightly open for all heat source.

Now I use AH on electric and if cold enough on diesel for my heat....a lot more quiet than heat strip/pump in AC system!  I also have an enclosed electric oil recirculate heater, that I will try this winter....works good in garage!   

[alflorida]

On 11/17/2017 at 2:31 PM, alflorida said:

That is why we use a catalytic heater.  About 99.5% efficient.  Also, quiet.  We don't have to listen to the fan noise.

Since I started the conversation about catalytic heaters I should add a few details.

--  I installed our first one in 2004 in a 33' TT and have used them extensively as our only heating device unless we have free elect hookups.  I have installed the heaters in a 5th wheel, diesel pusher, 26' Class C and now our 29' Class A. 

--  About needing wall space for the heater.....I always install a quick disconnect propane gas connection and use a flexible hose to the heater.  This also allows me to aim the heater to where we want the heat. 

--  We also love to travel in the fall, winter and spring so we experience quite a bit of cold weather. Including one night that it was below freezing by 4pm and 12* at daylight the next morning.  Lots of frost on the inside of the windshield that morning

--  We use lots of blankets on the bed, so have only left the catalytic heater on while we slept 2-3 times in the last 14 years.  When we do use the heater while we sleep we slightly open a window by the bed.

--  Always, while the heater is on, the ceiling vent is open, usually at least half way.  

--  Needing to have the vent open usually brings a response about how much heat you loose with a partially open window and ceiling vent.  Well, just go outside and stand by your forced air furnace while it is running.  You are probably loosing a 100 times as much heat from the furnace than I loose through the ceiling vent and a window slightly open.  

--  We have two CO (Carbon Monoxide) detectors, one in the living area and one by the bedroom.  You should have one installed even if you don’t use a catalytic heater.

--  The catalytic heaters produce almost no CO.  The gas cooking stove produces many, many more times as much CO as the heater. 

--  The heater does produce quite a bit of CO2, hence the need for ventilation. You also need the ventilation for the water vapor produced by the heater to escape as much as possible. 

Anyways, that is my 13 year experience with catalytic heaters in a RV. We love their quiet efficient operation.

A couple of additional comments.

I have read many form topics over the years. There seems to be two sides to the issue of using catalytic heaters. Those of us who use them extensively and love them and are aware of their potential dangers. Then there are those who warn of dire circumstances that will happen with their use. I really doubt that those who are convinced we will have horrible consequences, by using them, have ever used them.

If you dry camp or boondock in cool weather the catalytic heater is indispensable.

 

 

 

[wildebill308]

The only problem with using auxiliary heat Sources is with out the RV gas furnace running you are getting NO heat to your basement.

Bill

[bm02tj]

Any non vented heater uses the O2 and when that is gone it makes CO  both not good 

unless designed for non vent use with a sensor to turn it off do not use in your motor home 

It could be unhealthy or deadly 

[richard5933]

Everyone is free to heat their RV as they see fit. There are pluses and minuses of all the methods of heating any enclosed space. I am glad that some have had success using a non-vented heater to keep their RV warm, but just because things have gone well up to this point is not a guarantee of future success.

From my reading, the current RVIA code does not permit non-vented propane appliances other than cook tops. Many states have adopted codes to prohibit the use of non-vented appliances. There are reasons for these restrictions. People die each year due to CO poisoning.

All that said, we each take whatever risks we feel comfortable with. My advice would be to be sure to research the subject as much as possible and be sure to take all required precautions for heating your RV. Electric, vented, non-vented...there are risks associated with each and the best way to mitigate them is to know what they are.

[manholt]

That goes for regular homes and log cabins also, you got to have fresh air in and stale out.  Do believe that is what Al wrote above!

bm, did you read all of what Al said?  Any of us?

[alflorida]

20 hours ago, WILDEBILL308 said:

The only problem with using auxiliary heat Sources is with out the RV gas furnace running you are getting NO heat to your basement.

Bill

Absolutely.  If you are in a location where the temps are well below freezing for many, many hours, (12 to 36 hours or more) you must make sure to get heat to where your water pipes are and your water and waste tanks are located.   However if the outside temps are above freezing at 1am and the temp only drops well below freezing through a couple of hours after sunrise, usually your basement will be fine.   Every RV is different so you MUST educate yourself on the configuration of your RV.  

A couple of years ago in our Class A we were camped overnight just outside Gallup, NM.  The temps were right at 32* about 7pm and dipped to 9* right at sunrise.  I had a remote thermometer in my water fill compartment.  It was down to 27* with the outside temp at 9*.  No problems.  The 27* for 2-3 hours was not going to freeze the water in the pipes. I did kick on the forced air furnace to put some heat down there when we got up.  

Something a lot of folks forget about.  If the outside temps are down to 20* or well into the teens for 6-12 hours, you better open up the cabinet doors beneath your sinks so the air from inside the RV will circulate to the pipes along the outside wall.  

18 hours ago, bm02tj said:

Any non vented heater uses the O2 and when that is gone it makes CO  both not good 

unless designed for non vent use with a sensor to turn it off do not use in your motor home 

It could be unhealthy or deadly 

Yep.  Be sure to open a window a couple of inches and the ceiling vent 2-3 inches for ventilation.  All the heaters I have seen have ample warnings about ventilation.

15 hours ago, richard5933 said:

Everyone is free to heat their RV as they see fit. There are pluses and minuses of all the methods of heating any enclosed space. I am glad that some have had success using a non-vented heater to keep their RV warm, but just because things have gone well up to this point is not a guarantee of future success.

From my reading, the current RVIA code does not permit non-vented propane appliances other than cook tops. Many states have adopted codes to prohibit the use of non-vented appliances. There are reasons for these restrictions. People die each year due to CO poisoning.

All that said, we each take whatever risks we feel comfortable with. My advice would be to be sure to research the subject as much as possible and be sure to take all required precautions for heating your RV. Electric, vented, non-vented...there are risks associated with each and the best way to mitigate them is to know what they are.

Yep.  The RVIA code is one of the things why RV shops will not install an unvented heater.    I am not sure why the CO (Carbon Monoxide) keeps being talked about with the catalytic heaters and everyone ignores the CO2 (Carbon Dioxide) which is primary reason for the ventilation requirements.   I have never had my CO detectors register a high level of CO or have the alarm go off with the use of a catalytic heater in about 14 years of use. 

Absolutely, everyone should research the proper use and ventilation before using a catalytic heater.  That also means not just accepting comments from people stating "Don't use them!" Or comments from others saying "No problem. They work fine. No worries."   Do your research, read the info in the owners manuals for the heaters.  Manuals for most heaters are available on line.  Then make your own decision.

[wildebill308]

I know about the temperatures dropping in NM. We were at the top of Raton pass it was 55  during the afternoon but the park owner came around and alerted us to a cold front coming through and to shut off outside water. (they had drain back freeze protection) before going to bed. As we were leaving the next day I added water to my tank and drained my holding tanks and made ready for travel and just left the electric connected. Glad I did it was -5 when we got up and sleeting.  It took a while to get the solid sheet of ice (inside and out) better known as the windshield clear enough to leave.

Bill

[bm02tj]

If you are using unvented heater without sensor you could have high co2 and low O2 with out tripping co sensors it is so unhealthy and possible deadly 

do not use  even with an open window 

[TimeTraveler]

I would like to add this note. I don't remember where I read of it but someone put a small catalytic heater in their wet bay to keep it from freezing. The exhaust naturally found it's way to other compartments as well  the inside of the coach. I don't remember the outcome but it wasn't that good. Just about everyone or some anyway faced with the sever cold will put a light bulb a severe duty bulb in a drop light into the service bay. If they are still around the polymer coated sever duty bulbs, don't use them. They give off a deadly gas when hot.