Diesel Air Heater

[Stinky-ClassB]

I'm trying to imagine how these things are used. I'm imagining that once you start it up you probably leave it on low rather than letting it go out entirely if for not other reason than the juice to heat the glow plug. Not like an electric heater that goes to dead cold off when not heating. So if you're living in a bus full time it would run continuously for weeks? And if you're making miles maybe you would just fire it up at the end of the day and kill it in the morning?

 

[cadillackid]

they modulate.. the diesel air heaters anyway modulate up and down... they are temperature controlled.. just like a hating system in a house they shut off when they reach temp..


my heatimg system in my house modulates.. on days like today where its 17 outside and windy it runs most of the time at a really low rate.. but does still shut off..


the diesel heater for the bus is similar depending on how cold it is and how well imsulated your bus is

 

[Stinky-ClassB]

The furnace in my house shuts off except for the pilot. No fan no heat. But I can't see this working with these diesel heaters. Juice to heat the glow plug. Damage from heating and cooling of the screen. Seems to me they must be designed to keep a minimum flame going constantly. But I don't have any direct experience so it's a mystery.

 

[cadillackid]

If your furnace at home is so ancient to have a pilot then it definitely doesn’t modulate .

Like I mentioned the diesel heaters modulate but at some point you will make too much heat and it gets too hot inside so it shuts off. Upon shutdown they turn the glow plug on to burn off any leftover fuel and the fan runs for a bit and then all stops until temperature drops then it comes back on.

Cycles aren’t inherently bad if you do them right. But you can’t run it full time unless you want it really hot ..

Even my modulating home furnace shuts off when the lowest modulation still warms the calling zone to setpoint. My furnace has a glow rod which glows to ignite the gas.

 

[Stinky-ClassB]

I love my ancient furnace. Never have to do the routine service. The heat exchanger is never going to crack. If the motor gives up I can find a replacement somewhere in my shop or buy one for $20 on Kijiji. Thanks for telling about modern modulating miracle furnace. Reminds me how lucky I am. Anyway, I'm getting the impressions that these little diesels aren't meant to turn off. That they just dial down to a Bic flame so the basket stays hot. I guess the pump just slows down to a drop every few seconds. Is that the way of it?

 

[s2mikon]

@jackdebear, That is how my 2 heaters in the motor home work. If I set it to 72 degrees it will run full tilt until it gets to 72 and then it goes to its lowest setting and continues to pump heat. The one I put in my darkroom has additional modes that allow me to use it manually, and a high altitude mode in addition to thermostat mode. But it never turns off. It was purchased recently. All of them have worked real well and I can't complain at all. Great bang for the buck.

 

[cadillackid]

Sorry but I’ll take my 98% effficient heating system and keep my house 75 cheaper than others who have to shiver with sweaters and 65.

I replaced plenty of those units with cracked heat exchangers.. a testo 320 test should be in order in it.. and it does need serviced for safety and to keep the burners cleaned and the air / fuel adjustment is optimal and gas pressure is correct.. yes sir it does matter


Now back to the diesel heater. The typical air heater uses a dosing pump. Each time the pump clicks it pumps a measured amount of fuel . The frequency is raised and lowered according to demand. Along with the fan speed to maintain optimal air fuel ratio. So it’s easy for these to modulate up and down.. this is also how they start up. High glow plug and small amounts of fuel till you get the chamber hot then you can burn more fuel and efficiently without smoke.

Now if you use a webasto coolant heater for heating coolant loops like the standard school bus model it uses a burner style like a home fuel oil boiler. Which uses a nozzle, a high pressure mechanical pump and a spreader. Those don’t modulate, they kick in and off.. using a spark igniter as opposed to a glow plug ..

 

[Hiyu]

We have two scenarios when we use ours, if we're boondocking and it's freezing cold, we run it 24/7 at a hz rate comfortable to us, if it gets too warm, we crack open a window to regulate the heat. We normally keep it on the low hz, if that's not good enough, we amp it up til it suits us. When we're on shore power, we use our oil filled space heater which is okay for our Wa state weather during our avg winter temp. If it gets too cold we supplement with the CDH, but have always secured the CDH at bedtime and do well enough with the space heater. When we wake up, we fire up the CDH for a bit.... hope this helps

 

[cadillackid]

whats a CDH?

 

[Hiyu]

Chinese Diesel Heater

 

[dbsoundman]

I purchased an Afterburner controller for my diesel heater (highly recommend) and so it will actually shut off once it reaches a set temperature plus a certain margin, all user configurable. I think I have mine set to shut off when it's +5 above the set temperature and turn on when its -2 below the set temperature. It does obviously consume more battery power that way, but it also saves some fuel (I think, though this is not yet proven).

Most of the basic controllers have something called "linear Hz mode" where you basically control the speed of the dosing pump only, so the heater is always running if you turn it on, but it stays at a certain pump speed (and regulates the fan to match). This is definitely useful to keep the thing from ramping up and down all night, and then it's easy to estimate fuel usage because the fuel consumption rate is locked in.

The Afterburner controller gives you a good web interface so it's very easy to switch between modes. Mine is on thermostat mode with the margin right now so the heater only comes on when the bus is really cold and the mini split heater can't keep up, but next time I go camping in the cold I may opt to use Hz mode instead and see how I like it.

 

[Rucker]

I purchased an Afterburner controller for my diesel heater (highly recommend) and so it will actually shut off once it reaches a set temperature plus a certain margin, all user configurable. I think I have mine set to shut off when it's +5 above the set temperature and turn on when its -2 below the set temperature. It does obviously consume more battery power that way, but it also saves some fuel (I think, though this is not yet proven).

Most of the basic controllers have something called "linear Hz mode" where you basically control the speed of the dosing pump only, so the heater is always running if you turn it on, but it stays at a certain pump speed (and regulates the fan to match). This is definitely useful to keep the thing from ramping up and down all night, and then it's easy to estimate fuel usage because the fuel consumption rate is locked in.

The Afterburner controller gives you a good web interface so it's very easy to switch between modes. Mine is on thermostat mode with the margin right now so the heater only comes on when the bus is really cold and the mini split heater can't keep up, but next time I go camping in the cold I may opt to use Hz mode instead and see how I like it.

Nice tip-thanks!

I've read a bit about aftermarket tweaks to the diesel heater controls-to let it run slower, in particular, and how that might clog the assembly. Makes me curious if the long-term operation with this thermostatic device might introduce problems.

As far as I can tell from the terrible instructions that came with my diesel heater, there is no thermostatic control on the device. H1, H2, H3 up to about H5 I think for low, medium, high. Works consistently well.

Kind of like a wood stove-you crank it up, then damp it down as needed. I haven't done a 'cold overnight' yet so not sure how troublesome it will be to adjust.

 

[dbsoundman]

Nice tip-thanks!

I've read a bit about aftermarket tweaks to the diesel heater controls-to let it run slower, in particular, and how that might clog the assembly. Makes me curious if the long-term operation with this thermostatic device might introduce problems.

As far as I can tell from the terrible instructions that came with my diesel heater, there is no thermostatic control on the device. H1, H2, H3 up to about H5 I think for low, medium, high. Works consistently well.

Kind of like a wood stove-you crank it up, then damp it down as needed. I haven't done a 'cold overnight' yet so not sure how troublesome it will be to adjust.

There’s some debate as to whether or not running on low will cause the heater to soot up, but it seems like now people are trending away from that conclusion. It seems like it may have more to do with running at different altitudes with the wrong air/fuel mixture.

 

[matthews2001]

NOISE LEVEL?

thats my question regarding interior or under bus install for a CDH!

I like quiet mornings looking out all my front windows (but its cold up there). CANNOT STAND my RV propane furnace (that I installed ) because of its noise level!

 

[Iceni John]

Most (but not all) CDHs have motherboards and controllers that allow one to fine-tune their air/fuel ratios. My Warmtoo XMZ-D2 5kW heaters came out of the box with too low fan speed and pump Hz setting when on Low, so I increased them slightly to prevent a slight rhythmic pulsing from the exhaust with puffs of smoke: I increased the pump's minimum Hz from 1.4 to 1.5, and increased the minimum fan speed from 1450 to 1750 RPM. It now burns absolutely cleanly on Low with no smoke at all, even at 4000 feet ASL; what's more important is that it now always maintains greater than 120C burner temperature on Low to prevent incomplete combustion and soot buildup. After running all night there is now no soot at all inside the exhaust pipe, and there is no measurable CO on my CO alarm/meter. If your CDH's burner temperature drops below 120C it will accumulate soot inside the burn chamber. I did not change the upper pump Hz or fan speed, just the lower ones. Most "experts" say that to adjust for higher elevations one should reduce the pump Hz, but I strongly disagree: if there's less air, isn't it logical to instead increase air (by increasing fan speed)? This is exactly why turbocharged engines perform better than NA engines at higher elevations: their fuel is certainly not turned down! One person said that CDHs' fuel should be reduced by 4% per 1000 feet, but if you did that at 12,500 feet there would be a 50% fuel reduction which is plainly insufficient to maintain any combustion, let alone clean complete soot-free combustion.

I don't think that the Afterburner controller will save an appreciable quantity of fuel by shutting the heater completely off when the room temperature is reached. If using a standard pump that moves 0.022 ml of fuel per stroke, in one hour at a pump rate of (hypothetically) 1.5 Hz it will have moved only 118.8 ml (only about 4 fl.oz in USA-speak), a completely inconsequential amount of fuel! More to the point, if the glow pin is heating up every time the heater restarts, this will appreciably shorten its life and consume much more power from the battery.

John

 

[cadillackid]

Most (but not all) CDHs have motherboards and controllers that allow one to fine-tune their air/fuel ratios. My Warmtoo XMZ-D2 5kW heaters came out of the box with too low fan speed and pump Hz setting when on Low, so I increased them slightly to prevent a slight rhythmic pulsing from the exhaust with puffs of smoke: I increased the pump's minimum Hz from 1.4 to 1.5, and increased the minimum fan speed from 1450 to 1750 RPM. It now burns absolutely cleanly on Low with no smoke at all, even at 4000 feet ASL; what's more important is that it now always maintains greater than 120C burner temperature on Low to prevent incomplete combustion and soot buildup. After running all night there is now no soot at all inside the exhaust pipe, and there is no measurable CO on my CO alarm/meter. If your CDH's burner temperature drops below 120C it will accumulate soot inside the burn chamber. I did not change the upper pump Hz or fan speed, just the lower ones. Most "experts" say that to adjust for higher elevations one should reduce the pump Hz, but I strongly disagree: if there's less air, isn't it logical to instead increase air (by increasing fan speed)? This is exactly why turbocharged engines perform better than NA engines at higher elevations: their fuel is certainly not turned down! One person said that CDHs' fuel should be reduced by 4% per 1000 feet, but if you did that at 12,500 feet there would be a 50% fuel reduction which is plainly insufficient to maintain any combustion, let alone clean complete soot-free combustion.

I don't think that the Afterburner controller will save an appreciable quantity of fuel by shutting the heater completely off when the room temperature is reached. If using a standard pump that moves 0.022 ml of fuel per stroke, in one hour at a pump rate of (hypothetically) 1.5 Hz it will have moved only 118.8 ml (only about 4 fl.oz in USA-speak), a completely inconsequential amount of fuel! More to the point, if the glow pin is heating up every time the heater restarts, this will appreciably shorten its life and consume much more power from the battery.

John

I wish mine had that ability!! i havent found any adjustment on my coolant heater... the electronic control protocol was rather easy to hack but there's no manual ability in it i have found yet to set the pump to fan ratios.. the air heaters seem to have a lot more Hackability than the coolant heaters do

 

[Rucker]

Most (but not all) CDHs have motherboards and controllers that allow one to fine-tune their air/fuel ratios.

<snip>

More to the point, if the glow pin is heating up every time the heater restarts, this will appreciably shorten its life and consume much more power from the battery.
John

Thanks John-this is exactly the kind of thing I was wondering about.

My heater draws 8.3 amps when it fires up, and drops to about (I think) 3.5 or less when running on medium heat. Assuming the thing would cycle off for 30 minutes or greater (depending on the cold and how much insulation you have), it's overall less battery draw to cycle the heat rather than leave it on.

By there's no question in my mind it will accelerate wear on the heater. You'd need to balance the fuel and battery savings against the risk of premature heater failure. I'd say if you really, really need to control air temperature, or absolutely maximize fuel or battery usage, and afterburner it an option; perhaps in those cases, for optimum happiness, have a spare diesel heater to swap in.

 

[cadillackid]

8-9 amps is about right .. the glow plug on mine is rated 85VA , the heater ramps it up slowly I’m guessing to help save it’s life. Burns impurities off without damaging the surface of it..

And most of the heaters use the glow plugs twice per cycle . It turns on when the heater shuts down to burn off any residual fuel and keep the plug clean. So lowering cycle numbers sounds like a good idea

 

[dbsoundman]

Good points on the cycling. I’ll see what I can modify to prevent doing that too often. I suppose the fuel consumed when starting up might negate the benefit of shutting it off entirely?

 

[Rucker]

NOISE LEVEL?

thats my question regarding interior or under bus install for a CDH!

I like quiet mornings looking out all my front windows (but its cold up there). CANNOT STAND my RV propane furnace (that I installed ) because of its noise level!

My diesel heater is directly under the bed. It is not a problem.

The biggest noise factor is the impulse pump, and there are a lot of videos on how to dampen/quiet the clicking.

I have a bumper extension with a metal toolbox, and the diesel tank and pump are in that. The biggest challenge I had was when I first installed the heater I couldn't tell if the pump was working unless I opened the rear window and listened for it, so, these can be installed to be super-quiet.

edit: I just noticed this is my thousandth post! do I get a prize? :-')