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Posted by HeatPro on July 28, 2006 at 16:46:40:
In Reply to: Expansion Tank Location for LAARS Endurance boiler #EBP-110LP posted by Ruth on July 28, 2006 at 15:16:20:
+++ A very interesting question. From time to time, I've found factory technical writing teams confused by insufficient field experience.
That has the result of making more confusion among installers who have even less experience. The problem comes from trying to use 'one-size-fits-all" reasoning. The industry expert is now someone who has no field experience actually installing units, nor teaching experience to get a vocational teaching certification, so must ask engineers who are sometimes confused between commercial-industrial and residential applications.
The intent of your question is to decide between general 'pump-away' caution and what is happening inside the Endurance boiler. It is apparent that the circulator inside the boiler is 'on the return' which has been provided in magazines as the wrong thing to do. So the question is what to do about a situation where the factory (whose instructions are code) seems to have a conflict between putting the circulator on the supply pumping away from the expansion tank on the supply. The instructions do say to put the expansion tank and air scoop on the supply, then it also says to put a circulator to pump away from the scoop and expansion tank 'if needed.' The poorer part of the technical writing is that it doesn't define what might cause that necessity. (It seems more like a CYA if they're wrong than a useful instruction.)
It is less than apparent that many boiler companies are advising installers to place the boiler circuit within a separate system circuit that has its main circulator on the heating circuit. Another way to say it is that the instructions for piping the Endurance show that the heating circuit supply and return mains are joined so the boiler is connected with tees about 12 to 18 inches apart into the main.
With only about ten feet of pipe between the Endurance boiler supply and return there is no significant piping drop to be concerned about having the 'pump away' configuration. If the expansion tank is on the return coming from the main, only miniscule flows would be affected by it being there. However, it is better to be on the safe side of advisement; especially when answering a question that might ASS U ME the idea that someone could pipe the boiler into the system in the older 'traditional' supply from the boiler and return to the boiler without the loop-subloop idea (possibly to save the cost of another circulator.)
In summation:
DID YOU PIPE THE SYSTEM LOOP-SUBLOOP as instructed in the installation instructions? If so, there isn't much concern. If you didn't pipe as directed then you MUST use the pump-way piping as directed, or the warrantee is void.