Garnification said:Northwoodsman said:LeonMSPT,
Thanks for the overheating explanation!
That scenario is exactly why/how I started my posting last month on tha fact that a circ. pump can be too much/large for a boiler (even though all the postings I had seen previously stated that's it better to have a little bigger pump.)
I have an EKO40 system (with 1,000 gallons of pressuized storage) with approx. 30' of 1-1/4" copper for the primary piping.
I had been burning it approx. 1.5 months (Nov/Dec 2008) before I realized (and then perfromed the calculations) that my pump was moving the water way too fast though my boiler and thus it was not removing the heat away from the boiler in an efficient manner.
I had a Taco 010 3 speed pump which I had been operating on HIGH (using approx. 125 watts of power).
After I did the calculations I found out that I had a system which only had 4' of head (due the large cooper tubing I used in the primary loop).
Thus, I immeditely changed the circ. pump to LOW speed (which operates the Taco 010 just like a 007 and uses approx. 75 watts of power) and my heat transfer into the tanks went from 52K BTU/HR to 103K BTU/HR.
I was able to prove the old saying that "you can't get something for nothing" is not true.
Actually, I was able to get 2X the BTU's for 50 watts less power
Hope this helps!
NWM
NWM, I agree with your figures and the bigger piping is a definite plus in these boiler setups. One thing that I am having a problem with in this post is that your circulator is moving water to fast through your boiler to extract heat from the boiler right? I got a few question to ask. 1. when you were charging/ heating on high speed, what was the burn like- was it cycling or burning full out? 2. do you have a temp gauges on the supply and return into the mixing valve or boiler and if yes what was the temp span between high and low flow?
I guess what I'm picturing is that its not a problem of moving water to fast through the boiler but a case of hot water cumming back to soon from storage maybe a short cycling problem in the plumbing
I know, correct me cause I am probably wrong. I burn a garn style so I don't do the burn/pump/charge.
Ummmmm........ BTU transfer is a function of pounds per minute x degree of temp drop. Thus........ 10 pounds of fluid dropped 10* is the same as 20 pounds of fluid dropped 5* or 40 pounds of fluid dropped 2.5*. What some people misconstrue as "moving too fast to drop off the heat" as I heard one old timer explain, is not exactly correct. Now, as Garnification has said, you can run into heat transfer problems if inadequate flow is causing the burner to shut down due to high limit scenarios but I guess I'm not following how too much flow causes a slowing down of heat transfer. More flow through a HX of a given size will simply mean a lower Temp rise but actually the same amount of BTU's. A classic example of this is a pool heat exchanger which typically has a delta T of only a few degrees on the pool side but transfers mucho BTU's because the pool side flow is maybe upwards of 40-50GPM. I'm going to quiz one of the techs at AIC the next time I talk with them.