WOW!!! unfortunately I see this way too often. people get caught up in the sales pitch of what appears to be a very simple product. The sad thing is the people selling it and making it are down right crooked selling a product that does not meet its claims. This can add up to a 30% loss of energy and bigger effect on total efficiency. Measuring delta T on your pipes without other known data can be very misleading. If you know the size of your pipe, the head loss, GPM or velocity of the water then you might be able to make somewhat accurate and usable figures. I've read many times that someone has Pump X and it flows upto 20 GPM but at what headloss? A 20 gpm pump can and does pump only 4 gpm in an application of high head. ( not elevation change but piping losses) An acceptable velocity standard figure when the pump & pipe are sized correctly is 3-4 feet per second for any water boiler. This is a much more important figure to know when calculating delta T from headers. If you have more than 5 degrees DT in 50' of pipe when the velocity is 3.3fps then there is a problem. I have seen a 0012 pump with 10' head that flows 24 gpm and a 0010 pump at 4 gpm at 10' head. Obviously the 12 is gonna show a far less temp drop but only because the water velocity is triple the speed and has less time to cool down in the same 1" pipe. High water velocity is not good in a boiler system, it can cause all kinds of problems, breaks, bangs, premature failure from errosion of pipes and heat exchangers. 1" pex can supply 54,000 btu/h with a delta T of 20 degrees from supply to return at the boiler. So you could be sending 50kbtu to the ground alone with a DT of 30-40 degrees in just the supply run. So on a 200 kbtu output unit , it lost 25%. So on a 50% efficient OWB half the wood could be heating the ground.
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