Efficient Furnace? April 01, 2025, 09:48:20 am With the future now showing promise of more efficient RV appliances such as the inverter air conditioner, why is it taking so long to come up with a better furnace? Residential furnaces with in excess of 90% efficiency are common. The furnace at our cabin has no noticeable heat from the flue when running, eg, where the one in the LD feels like it heats up the forest more than the interior!Steve
Re: Efficient Furnace? Reply #1 – April 01, 2025, 11:47:43 am Hi Steve; I agree. They should at least have SEER ratings, but of course once built into a motorhome, you are sort of stuck with the footprint. Before LiF batteries I always wanted to put in a thermocouple assembly on the exhaust, so that waste heat could at least ameliorate the power drain from running the heater. Recently I almost had to abbreviate my visit to Jalama Beach. The temperatures were so cold, especially at night. The wind off the ocean at 55 mph one night and moisture laden (not to mention the salt), the heater ran a lot and I nearly ran out of propane. Only 8 gallons in a ten gallon tank. Almost a gallon a night. RonB 1 Likes
Re: Efficient Furnace? Reply #2 – April 01, 2025, 11:54:56 am The exhaust waste is a nod to safety when it comes to combustion appliances and carbon monoxide. It's clearly possible to build more efficient units, but you increase the small odds of having issues that cause occupants to never wake up.In the marine and van industries, diesel heaters are common and chinese knock offs are available. Webasto would be a brand name, and off brands are all over Amazon. Obviously, diesel makes more sense when the engine in the vehicle is also diesel (like many boats, or sprinter vans). It's also easier to engineer a safe combustion system when you have a relatively stable amount of atmospheric O2. Not the case when you change elevations frequently. There are people who have retrofitted these to gas powered RVs (with a small diesel fuel tank). https://www.youtube.com/watch?v=N0X0huHwoSY&t=14sI think it's an issue of fuel type and safety. Many do use a propane catalytic heater (Camco Wave) but wisely (IMO) only use it when they are not sleeping.Rich
Re: Efficient Furnace? Reply #3 – April 01, 2025, 12:17:14 pm Quote from: rich - April 01, 2025, 11:54:56 amThe exhaust waste is a nod to safety when it comes to combustion appliances and carbon monoxide. It's clearly possible to build more efficient units, but you increase the small odds of having issues that cause occupants to never wake up.Sorry, but I don't see how this is true. More efficient combustion does not increase the risk of poisoning. The heat exchanger prevents that.Quote from: rich - April 01, 2025, 11:54:56 amMany do use a propane catalytic heater (Camco Wave) but wisely (IMO) only use it when they are not sleeping.These are external combustion devices, so all combustion products are present in the living area. Any problem with the devices could cause poisoning.Steve
Re: Efficient Furnace? Reply #4 – April 01, 2025, 12:34:15 pm The one motor has a recirculation fan on one side, and a fan to propel exhaust out and draw in fresh air, on the other end. The object is to diffuse the exhaust and dilute it. I was parked once at a confined space campground, where the neighbor's heater exhaust was pointed directly at my side window. I kept the window closed (it was cold) and an eye on the CO monitor's display of below alarm threshold levels. The airtight integrity of any motorhome, is just so-so, even for a Lazy Daze. RonB
Re: Efficient Furnace? Reply #5 – April 01, 2025, 01:02:53 pm High-efficiency home furnaces have large, convoluted heater exchangers with increased surface area, giving the combustion gases more time to transfer heat. A better conventional RV furnace would need to be much larger.If looking for a better furnace, consider the combination water heater/furnace Truma Combi, it's advertises having 90% efficiency. Truma has been building the Combi units for years, and they are seen in European RVs and some domestic Sprinter RVs.Truma Combi eco | TrumaThe Combi has a lower BTU rating but should produce close to the same amount of heat as the furnaces in our LDs, due to its much higher heat recovery. Ron's small propane tank would last longer with a Combi..Another plus would be the extra space freed up by the small Combi replacing both the furnace and water heater.Better appliances are out there.Larry
Re: Efficient Furnace? Reply #6 – April 01, 2025, 04:00:27 pm This heater has been in business in the U.K. for European RV's use. Del City sells units and parts. I didn't see anything about efficiency ratings, probably there somewhere. Whale Heat Air: Lightweight, Powerful Heating Solutions for Your RV - Del... RonB
Re: Efficient Furnace? Reply #7 – April 01, 2025, 04:59:19 pm Quote from: RonB - April 01, 2025, 04:00:27 pmThis heater has been in business in the U.K. for European RV's use. Del City sells units and parts. I didn't see anything about efficiency ratings, probably there somewhere. Whale Heat Air: Lightweight, Powerful Heating Solutions for Your RV - Del... RonBFrom the link I listed above."Truma Combi eco Features:Near-silent operationLightweight and space-saving solutionMaintains constant temperature throughout the RVHighest available energy-efficiency over 90%"Over 90% is as good or better than most modern high-efficiency home furnaces, and it would be quieter too.It sure beats the low efficiency of the Suburban furnaces our LDs have...you will not be able to warm your hands on the exhaust.Larry
Re: Efficient Furnace? Reply #8 – April 02, 2025, 09:55:00 am Our Winnie Travato has the Truma Combi furnace/water heater. We've had the Travato for several years, having downsized for my health. So, point being, we've had some experience with it in cold and warm camping. Ours is the gas/electric model. (I would need to look at the manual to get the actual model number.) What I can say is the following: it can be run on gas, electricity, or both. As you would expect, heating is faster on gas. As I understand it, either the water heater or the furnace surrounds the other ( ie,concentric). So turning on one also helps with the other. However, either can be run separately (ie, you can run the furnace with no water in the water heater section). Also, in normal operation, either can be run separately, giving either priority. That said, the water heater has 3 modes, as I recall : eco, normal, and "I want it NOW, I mean NOW" (I can't remember the exact title for the last one, but...you get the idea). The 3 modes divert operation from the furnace, so if you are in "I want it NOW" mode, the heat is basically off. Heat can have a little trouble keeping up with fairly cold temps, like low 20's. We would set the thermostat around 55-60 at night, which it could keep, and do so without any noise, basically silent. Since the control was at the head of my bed, I could turn it up to 70ish while still under the covers, and the MH would be warm enough in 10 minutes. Remember, the Travato has the foot print of a full size pickup truck, so not large (we're about 22' long). The water heater tank capacity is only about 1 or 2 gallons, which means either the setting is "I want it NOW", or a short shower. Even on the high setting, it always seems to have trouble keeping up, especially in colder temps. So, bottom line...would I want one in a LD? Maybe. I would want to be sure the heating capacity was sufficient for the volume. (We had a mid bath, and the current Truma (meaning the one we have currently in the Travato) would never supply enough heat/hot water for that.) Is it more efficient? Definitely. I think our Travato is a 2020. Even with our tiny propane tank, we still haven't refilled it from when it was new. Obviously, usage dependent, however. We camped where we had hookups, so we often ran it on just electricity. Anyway, I thought I would give y'all a "usage data point". Have fun!KenFormer 2009 Mid Bath Owner 3 Likes
Re: Efficient Furnace? Reply #9 – April 02, 2025, 01:17:14 pm Hi Ken; Interesting data points, Thanks. The Truma only holds 2.4 gallons of water! They do have a a 'level one' size 7,500 BTUH and a 'Level 2' size nearly double at 14,300 BTUH. They spec 12V DC for power consumption, so the water heating is 12V and propane? Seems like it would be easy to run out of hot water. I don't find the noise produced by the heater fan that bad, but the 23.5' T/K has a smaller (lower BTUH) rating than the larger MidBath, and 31" LD's. So I suspect the bigger coaches may have more energetic fans. I don't have as many windows or surface area as the longer coaches either. The biggest problem with Jalama is that the county made the proprietor remove the propane filling station a few years back. So that leaves you with a circuitous 40 mile trip to Lompoc and back. With the rain and rocket launches viewing (spectacular watching the booster return at night twice!) the road was in good condition in a few repaired places, and not very good in many other locations.So at Jalama three other Lazy Dazes appeared one night at the high up view, hook up spaces. Was that you Larry? They were gone after the rain stopped the next morning. I was going to wander up there to see who they were. I was parked just a few feet from the surf, spot 55 and 59. RonB
Re: Efficient Furnace? Reply #10 – April 02, 2025, 02:15:12 pm Most of the time I find the most efficient way to heat my LD is with the Wave 3.If it's really cold I will run the furnace to heat things up a bit, then turn it off and use the Wave 3 to keep the temp inside livable.No fan noise and it doesn't use any 12v power. 1 Likes
Re: Efficient Furnace? Reply #11 – April 02, 2025, 03:03:12 pm We have been looking into Timberline hydronic heating system which is used on many Sprinter and Transit van conversions. They also make the heater hot water unit used in the Winnebago Ravel. The system is designed to be used in extremely cold conditions and operate with a glycol solution so it will not freeze if it is off and stored in below freezing weather. The main unit looks like it would fit where the LD domestic hot water unit is in our 98~MB. The heat exchangers can be placed where you need them with high efficiency fans built in, although you have to run the hot lines to the locations. In floor heat is an option but to retro fit it in a LD that would be quite an undertaking. The unit is fired by the vehicle's fuel, either gas or diesel models are available. For our 98~MB we would locate in-place of the DHW heater and leave the old furnace working in it's original place. We would have to add a fuel line from the fuel tank. The unit burns at 20BTU heat at about 1/4 gallon per hour of sustained burning. People we have me with these Timberline systems in their vans, talked about a half gallon of fuel for overnight heat in sub 20s in 20ft long sprinter van. Maybe that translates to about a gallon a night in our LD but you would be able to control the heat at each heat exchanger depending where they are located. Thus maybe heat the back lounge warmer then the rest of the LD~MBs and save some energy? I have contacted the Manufacturer and they are willing to work with builders and make some necessary adjustments to work out. Fortunately they re located here in Camus Washington so I plan on stopping in at their location to check it out. Last time I talked with Truma, they require a person to be a licensed and trained Truma installer and facility to buy a Truma unit. Karen~Liam 98 ~ MB NinAHome - Timberline Heat and Hot Water
Re: Efficient Furnace? Reply #12 – April 02, 2025, 05:39:11 pm Quote from: RonB - April 02, 2025, 01:17:14 pmSo at Jalama three other Lazy Dazes appeared one night at the high up view, hook up spaces. Was that you Larry? They were gone after the rain stopped the next morning. I was going to wander up there to see who they were. I was parked just a few feet from the surf, spot 55 and 59. RonBWe were not part of that group, I think they were the three LDs from Washington State, all family members, on their way to San Diego for a wedding. They were sampling the various coastal campgrounds, and they spent a couple of days at Montana de Oro SP after leaving MB and before going to Jalama Beach for the night.Larry
Re: Efficient Furnace? Reply #13 – April 02, 2025, 05:56:00 pm Quote from: RonB - April 02, 2025, 01:17:14 pmSo at Jalama three other Lazy Dazes appeared one night at the high up view, hook up spaces. Was that you Larry? They were gone after the rain stopped the next morning. I was going to wander up there to see who they were. I was parked just a few feet from the surf, spot 55 and 59. RonBWe were not part of that group, I think they were the three LDs from Washington State, all family members, on their way to San Diego for a wedding. They were sampling the various coastal campgrounds, and they spent a couple of days at Montana de Oro SP after leaving MB and before going to Jalama Beach for the night.Larry
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