Spruce. I was looking at heat exchangers out of combi boilers that are the same size or larger than the Webasto one. Like the gt017. I beleive the Chinese Kw rating should be taken with a pinch of salt
You said the exchangers you had resulted in cold hoses on the outlet side of the heater circuit. Shows that the exchanger is drawing all the heat out of the system well.
I planned to used silicon hoses and lag everything on the heater side
You say you made this set up 5 years ago. Still using it?
No I'm not. It was a 'test bench' I made up to see how efficienctly or inefficiently the system works. And those heat exchangers work brilliantly. They are perhaps too good for the application as I think we need something smaller or less efficient that will 'share' some heat with the other heat exchanger so at least both operators benefit.
In the early day when minbore hose became available to us window cleaners it was rather stiff. It was just manageable in summer but a nightmare in winter. (But it was better than the 1/2" garden hose we used before that.) So the original idea was to have a heater that just put enough heat out to warm the hoses enough to make them more manageable to use in winter.
My heat calculator said that raising the temperature from 9 degrees to 36 degrees at 1.5lpm of water required 2.65kw of heat. But as the outlet of the first heat exchanger was cold after zapping all the heat I concluded that I'm missing 2.55kw of heat; nearly half of the rated 5.2kw. When I started off I honestly believed that this 5.kw Webasto should provide enough heat for both operators so I was very disappointed when the results fell far short of my expectations.
I felt really upset that we have a respected German company advertising a product that isn't delivering what its expected to. When I worked for Bosch Power Tools, German regulations stated that they could underate a motors wattage but nothing more. In other words they could, for example, bring out a new drilling machine fitted with a 750watt motor. However, they could promote that product as having a 500 watt motor. Then further down the line they would then promote that same power tool with an upgraded 600 watt motor and then later on a 750watt motor. But they obviously couldn't advertise the drill with a 600 watt motor when it only had a 500 watt motor.
I see this 5.2kw, not as a 5.2kw unit, but as smaller because that extra heat going out through the exhaust is of no use to man or beast. I see this as the same as advertising that drill with a 750watt motor when its only 500 watt.
In my own mind I just couldn't justify loosing 50% of a liter of diesel in wasted heat, especially as diesel in those days was climbing to about the same price as it is now. Adding this heater would mean I would be using around £80 of diesel a month added to the £60 I spend filling the van's tank up. I just couldn't believe that the poor performance of this heater for our purposes was worth the running costs of an extra £500 a year for winter use just to have slightly warmer hoses.
I changed the minibore on my hose reel for something that was a little more flexible and hence manageable in the cold and that seemed a better solution.
As I stated earlier I didn't give up on the heated water idea and bought a 2 man Heatwave spares or repairs. I got it working but the second heat exchanger was leaking water so stripped it down. At the time I didn't expect my van to last as long as it has done due to rust so haven't made much of an attempt to set this one up in a van that would soon be scrapped. This system is still in my garage.
