C7 Coolant Temp: Low at Idle in Cold Weather

[PNW_Steve]

Originally Posted by cadillackid

my DEV bus has air shutters... shutters closed and T-stat closed my Top radiator Hose will be pretty much cold if I let the bus idle for about an hour with the heasters inside on.. my temp gaige goes down to just off the 'C'. the DTA360 cant make as much heat as the heater cores are requesting..



my red bus auto-idles itsself up and down to maintain 165-170 coolant temperature.. it will go as high as 1450 and down to normal at 700.. it varies on its own when I have the Idle porogrammed in the computer to 'Auto'


-Christopher

My truck has a similar feature.

The first Winter that I had it, I started it one cold morning and went back inside for a cup of coffee while the truck warmed up. I'm sitting there sipping my coffee and hear the engine speed up. I rushed outside, pistol in hand, thinking that someone was stealing my truck. :

[Versatile]

Are you sure a window isn't closed properly?

[capnron]

I'm not sure if an aftermarket fix is possible, but many of the trucks I drove had thermostatically controlled shutters in front of the rad. It worked just fine and kept the temp steady even at idle.

[cadillackid]

They make em, my dev bus has them and they work well.. at idle though the engine just doesn’t make as much heat as your heaters are pulling off if you have a lot of them turned on.. I see busses with the shutters in junkyards.. FE and CE, never seen them for an RE

[Booyah45828]

They don't make/use shutters in an RE configuration. The shutters are there to prevent the ram air cooling that you receive in FE and CE buses. RE buses don't receive ram air cooling with having the radiator on the side, so no need for shutters.

Christopher has it right. If the heaters are maxed and it's cold out, you're simply pulling more btu's then what the engine is creating at an idle. Either bump it up to high idle, or turn some of the heaters off.

[PNW_Steve]

I hate to be contrary but I have seen several RE's with shutters.

I was in the TNM&O shop in Lubbock and from what I saw all of their buses had shutters.

There were a few times that I wished that I had had them on mine. Cardboard is a little tacky

[wrenchtech]

In the residential HVAC world there are now baseboard radiators available that are said to work better with lower temperature water. This is because the new high efficiency boilers run best at lower temps. The boilers operate with condensing technology that extracts so much heat out of the burned fuel that the exhaust is cool enough to vent with plastic pipe, but lower temp water output is part of the deal.

I was wondering if the radiators/heater cores in my bus are designed to heat with 190° coolant and just don’t have what it takes to heat when the coolant is at 140° or 120°. Of course, I also noticed that my floor mounted heaters are almost completely plugged up with dirt and dust. Perhaps that explains why they don’t heat so well.

I would like to design a heating system that uses a mini boiler to heat liquid for me to circulate in my factory installed heaters and to heat the coolant in the engine for cold weather starting. I was thinking that a propane fired tankless water heater might do the job. The hurdles are that most tankless water heaters are designed to heat the water no hotter than 140°, and again most hot water space heating takes place at around 180°. There are tankless heaters that are designed for commercial uses, like dishwashing in restaurants, that put out really hot water, but they are way over sized for heating a bus by 5x and require 120v to operate.

It would be much simpler to just use an RV propane furnace to heat my bus, but it kind of galls me that they are kind of low tech and only about 70% efficient while most residential furnaces are around 95%. In the meantime I’m experimenting with diesel fired truck heater’s, which are not all that efficient either, but which have the advantage that they can be fueled at the same time and with the same fuel that my bus uses, a safer fuel for spotting leaks and which won’t explode or combust spontaneously.

[cadillackid]

BTU ratings of heaters are based on a certain temperature of fluid in the pipes.. Bus heaters are generally rated at 180-200 degree water when you read the Spec sheets..



the newer units wrenchtech mentions for home use have higher fin area and often multiple passes of water.. they are desgined to reach BTU ratings with cooler water to match that of what the new boilers output..



low-temperature heating is being integrated into homes (and skoolie) builds more.. ie floor heating loops dont need (or want) to be anywhere near 180 degrees.. you have a Huge surface area of heated exposure.. your body feels warmer with more area heated to a lower temperature.. your movements around a room heat the air as well as natural convections..



Bus heaters are fan forced.. any kind of a fan forced heating appliance will have a certain temperature-rise across its coil. ie air-in vs air out.. generally the more air you blow through the lower that rise is.. the heat needs time to transfer from the copper pipe to the aluminum fin and from the fin to the air..



Bus heaters cranked on high with cooler coolant temperature results in cooler air which results in the occupants feeling cold drafts and uncomfortable. you may actually "feel" warmer if you run all your heater fans on low speed instead of huigh when you are parked and idling. for one you are getting more 'rise' across the coil so warmer air. and you are also pulling less heat off the engine so the coolant temp may go up a bit..



-Christopher

[cadillackid]

Originally Posted by wrenchtech

In the residential HVAC world there are now baseboard radiators available that are said to work better with lower temperature water. This is because the new high efficiency boilers run best at lower temps. The boilers operate with condensing technology that extracts so much heat out of the burned fuel that the exhaust is cool enough to vent with plastic pipe, but lower temp water output is part of the deal.

I was wondering if the radiators/heater cores in my bus are designed to heat with 190° coolant and just don’t have what it takes to heat when the coolant is at 140° or 120°. Of course, I also noticed that my floor mounted heaters are almost completely plugged up with dirt and dust. Perhaps that explains why they don’t heat so well.

I would like to design a heating system that uses a mini boiler to heat liquid for me to circulate in my factory installed heaters and to heat the coolant in the engine for cold weather starting. I was thinking that a propane fired tankless water heater might do the job. The hurdles are that most tankless water heaters are designed to heat the water no hotter than 140°, and again most hot water space heating takes place at around 180°. There are tankless heaters that are designed for commercial uses, like dishwashing in restaurants, that put out really hot water, but they are way over sized for heating a bus by 5x and require 120v to operate.

It would be much simpler to just use an RV propane furnace to heat my bus, but it kind of galls me that they are kind of low tech and only about 70% efficient while most residential furnaces are around 95%. In the meantime I’m experimenting with diesel fired truck heater’s, which are not all that efficient either, but which have the advantage that they can be fueled at the same time and with the same fuel that my bus uses, a safer fuel for spotting leaks and which won’t explode or combust spontaneously.

a condensing Combi-boiler is something you can use in a bus.. esp if you use a multi-mode heating system.. when i do a design i will try to keep the water flow as "slow" as possible and still keep minuimum rated flow across the boiler.. this allows you to send cooler water back into the boiler.. the water inlet is the coldest water which is what it uses to cool the secondary condensing heat exchanger.. the cooler you can make that exhaust and more moisture you can condense out, the more efficient system you have. I have designed more than one home system where the "Stale" (water thats circulated through fan coils or baseboard heaters) is then circulated through floor loops since cooler water is desired in floors than in primary radiant / advection units..



-Christopher

[wrenchtech]

Originally Posted by cadillackid

a condensing Combi-boiler is something you can use in a bus.. esp if you use a multi-mode heating system.. when i do a design i will try to keep the water flow as "slow" as possible and still keep minuimum rated flow across the boiler.. this allows you to send cooler water back into the boiler.. the water inlet is the coldest water which is what it uses to cool the secondary condensing heat exchanger.. the cooler you can make that exhaust and more moisture you can condense out, the more efficient system you have. I have designed more than one home system where the "Stale" (water thats circulated through fan coils or baseboard heaters) is then circulated through floor loops since cooler water is desired in floors than in primary radiant / advection units..



-Christopher

Radiantec is a company that has been around for more than 35 years, which promotes DIY radiant heat. They recommend a tank type hot water heater of the Polaris brand as a heat source for residential radiant. They also recommend Noritz tankless heaters. Noritz NRC66DVLP can put out between 15,000 and 120,000 BTUs and works with a flow rate of 0.5 - 6.6 GPM and can be run on LP gas (propane)II am investigating this for the possible heart of my heating system, which will heat the factory installed radiators that already exist in the bus and heat the coolant in the engine when needed.

[cadillackid]

The Navien lines are what I’m most familiar with.. the issue with tanks is depending n where you live the climate can change greatly morning to afternoon to night esp in spring and fall.. heating up a tank of water is a bit too d a waste even if it’s low temp for direct radiant loops.. my Navien unit can flow.25 - 11 GPM depending on the desired rise.. Naviens tend to be larger than others so likely overkill for a bus.. mine at home has a max input BTU of 199K on natural gas.. i think it’s similar on LP.. it’s burner and a designed to fire at minimum of the gas valve so it can provide small amounts of heat at low flow .. I haven’t read the specs yet on the ones you mentioned. A small tank is desirable as a ballast tank and so you don’t badger the heater which reduces efficiency

I guess my main point of a that installing multiple heat types allows you bus to adapt to the water temp you have available .. fan coils are great but need high temp . Floor heat is slow but works well from lower temp water.

[wrenchtech]

Under-floor radiant is not something that I’m considering. I’m not planning on doing a roof raise so I can’t afford to lose headroom by building up the floor beyond the 2 inches of foam that I’m putting in already. I am considering high-efficiency baseboard radiators or wall panels. A company called Smith’s environmental products has the baseboard radiator that looks pretty interesting. It is said to be able to heat with water temperatures as low as 100° and it’s $60 a foot, complete with back panel and cover. It might be something I can afford.

https://smithsep.com/wp-content/uplo...terature-2.pdf

I found some good information on the subject of hydronic heating with lower temperature heat sources here: a mechanical engineering website

I am seeing more benefits to a hydronic system. Besides my desire to be able to heat my engine for easy starting in cold weather, I’m also thinking that it will allow me to move my fresh water and gray water tanks into my underfloor storage without having to worry that they will freeze in cold weather. I could wrap each tank in a jacket of foam insulation and then run a simple loop of PEX tubing from the heating system through each tank to keep them just warm enough so that they don’t freeze.

I was thinking that I would have to keep those tanks in upstairs in the main living space in order to keep them warm. I’ll be glad if I don’t have to sacrifice that valuable real estate.

[Booyah45828]

Originally Posted by PNW_Steve

I hate to be contrary but I have seen several RE's with shutters.

I was in the TNM&O shop in Lubbock and from what I saw all of their buses had shutters.

There were a few times that I wished that I had had them on mine. Cardboard is a little tacky

No, please do so. Do you have any pictures of them, or could you get some? I'd love to see what they look like. I wonder if they're air solenoid operated like the shutters on most buses.

Cardboard is tacky, but ya gotta do what ya gotta do.

The shutters/cardboard are there to prevent the ram air cooling that you receive in FE and CE buses. RE buses don't receive ram air cooling like the aforementioned buses do with having their radiator on the side, so there isn't a real need for shutters. I wonder what their thoughts are by installing them.

[PNW_Steve]

Originally Posted by Booyah45828

No, please do so. Do you have any pictures of them, or could you get some? I'd love to see what they look like. I wonder if they're air solenoid operated like the shutters on most buses.

Cardboard is tacky, but ya gotta do what ya gotta do.

The shutters/cardboard are there to prevent the ram air cooling that you receive in FE and CE buses. RE buses don't receive ram air cooling like the aforementioned buses do with having their radiator on the side, so there isn't a real need for shutters. I wonder what their thoughts are by installing them.

No. I did not take pictures of my bus with cardboard stuck to the side of it. Trust me, it works and it looks tacky.

[o1marc]

Originally Posted by wrenchtech

Under-floor radiant is not something that I’m considering. I’m not planning on doing a roof raise so I can’t afford to lose headroom by building up the floor beyond the 2 inches of foam that I’m putting in already. .

Adding PEX for hydronic heating adds no height to the floor. Use a router to cut the recess in the top of the rigid board. Put your finish floor on top.

[Booyah45828]

Originally Posted by PNW_Steve

No. I did not take pictures of my bus with cardboard stuck to the side of it. Trust me, it works and it looks tacky.

lol, not the pictures I was after.

[wrenchtech]

Originally Posted by o1marc

Adding PEX for hydronic heating adds no height to the floor. Use a router to cut the recess in the top of the rigid board. Put your finish floor on top.

Yes, I get that, but only have 2 inches of insulation. If I cut a channel 1/2 an inch deep in my 2 inches of insulation I will only have an inch and a half of insulation between my tubing and the cold dark underside of my bus. In residential construction up here we like to see R-30 in a floor that is unheated on one side. Not realistic for a bus, but something to consider. Plus, I figure I will have a plywood subfloor and then the finish floor on top of that. Plain old plywood is not such a good conductor of heat. I'm thinking that in the contest to draw away my heat, the underside of the bus might win. I was thinking I might have 3 inches of insulation in my walls. If I could create a low profile wall panel radiator that was mounted completely inside the insulation it might work better.

Maybe I should stop designing for the Wisconsin winters altogether and just move closer to my brother in Arizona. But then again there is the allure of Colorado in winter.