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DIY diesel heater.....
Spruce:
--- Quote from: a900 on December 14, 2018, 11:43:06 am ---Haha. Better start trying to work out how to get these photos uploaded. Somehow I can upload PDFs.
For anyone interested. First one shows the size of the heat exchanger I used. I used one this size because I didn’t want one that was 2 small and not knowing what would be 2 small. So basically looked for one that was the same size as a Webasto plate heat exchanger or larger. When I add a second it will be much smaller to fill a gap on my board. As I really think it’s larger than needed but for the main hose I wanted to make sure I got the hottest temperature I could.
I’m working on a recirculation that switches the pump to a low speed the same as 11 on my controller and diverts the water back to the tank. So when I finish a job and drive to the next one or get distracted chatting with customers I can keep the heater idling so it doesn’t shut down. (Learnt they use less fuel this way) This will be on a switch for now but might use a wireless fob and control the electric reel with it too. https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F131730091890
This will save me time turning my pump down and plugging the reel hose in to recirculate every time the van is moved.
Frostat to come. Which will use most of the circuit set up for the recirculation but use a little board that you can get for £2 that can turn the pump and heater on and off at whatever temp I set. https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F283139826056
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It would also help you to have a bigger header tank as it becomes a heat reservoir and extra heat buffer. It takes more water to heat up and gives you more flexibility in that half heat mode window.
a900:
Spruce that’s something I’ve been thinking about. It’s quite a small reservoir really. It does have its advantages. Should result in faster warm ups. But in reality to heat the extra 5l or something isn’t going to be long.
Although I have thought about this and I’m not sure how much different it would make. I’m still taking out the same energy from the reservoir whatever the size through the heat exchanger. So a larger reservoir would just result in less temp dip but same energy back in to get to the shut down level. Surely? Feel this one is confusing me 😂 sometimes like that then all of a sudden get it
How long does your take to shut off? Does it have any system to keep it running on idle?
a900:
--- Quote from: Smudger on December 14, 2018, 06:11:11 pm ---sorry, thick here - how does it work ? or are there other parts needed ?
Darran
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Put simply 2 water circuits
Heater circuit or loop. Water in the heater through to the exchanger fed back to a reservoir continues.
Pole Circuit. Water runs through the heat exchanger taking heat from the heater curcuit and heads down your hose and to your pole
windowswashed:
Basically the same principal as an indirect calorifier :)
Spruce:
--- Quote from: a900 on December 14, 2018, 10:17:00 pm ---Spruce that’s something I’ve been thinking about. It’s quite a small reservoir really. It does have its advantages. Should result in faster warm ups. But in reality to heat the extra 5l or something isn’t going to be long.
Although I have thought about this and I’m not sure how much different it would make. I’m still taking out the same energy from the reservoir whatever the size through the heat exchanger. So a larger reservoir would just result in less temp dip but same energy back in to get to the shut down level. Surely? Feel this one is confusing me 😂 sometimes like that then all of a sudden get it
How long does your take to shut off? Does it have any system to keep it running on idle?
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I don't have a diesel heater in the van atm. I'm going to fit mine when I get my 'new' van sorted. (I wish I had a bit of warm water on occassions this winter so far - I'm not liking the stiff hoses or the cold hands.)
I'm just making that observation on the size of the tank because HeatWave and Purefreedom use a 12 liter tank. They they also do recommend not to fill it fully.
Here is what the Thermo90 manual says;
When the water temperature reaches 72ºC, the heater will switch to a lower output. The combustion air motor speed and fuel pump delivery are reduced.
If the coolant temperature continues to rise by a further 10ºC, the heater will then automatically stop combustion, fuel delivery will cease and the flame within the combustion chamber will be extinguished. The heater will then commence a 180 purge cycle.
The heater is now in stand-by mode. The green operation light will still be illuminated and the water pump will continue to circulate the hot water. The heater will automatically restart if the water temperature falls by 15 C, going through the same start cycle as before.
If you have a bigger header tank it will take the same heat delivery from the Webasto longer to raise the water that extra 10 degrees before the heater goes into shutdown mode.
I have an additional 10 plate heat exchanger which I want to add into the heating circuit. This will be have its own pump controlled by a digital temperature controller. Hot water pumped through this heat exchanger will return to the van's tank. The idea is that the controller will be set to switch on this additional pump at say 80 degrees and switch off just before the heater would normally go back into full heat mode. (I don't know exactly at what temperature the heater is programmed to return to full heat mode, but on the Thermo Top C its 68 degrees.) I will also put a cheap PWM controller into the circuit to reduce the pump's flow rate. What I want to do is keep the pump kicking on and off to keep the burner in this half heat window.
My problem is that I don't find window cleaning very mentally stimulating, but I do love talking to our customers. This is why I need the automatic heat reduction included.
Yes, having a bigger header tank with more water will take longer to heat, but PureFreedom have suggested its best to start your heater before you get to your first customer. Most of our customers are a 10 to 15 minute drive away so starting the heater at home before setting off is what we would do. The van's alternator will also supply the initial current surge need to start the boiler.
Dazmond manually redirects heated water to his tank to keep his T90 running continiously. I want to do the same electronically.
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