EK DHW indirect vs. storage tank with flat plate heat exchanger

thomase00

I am getting close to pulling the trigger on an EK Resolute. I currently have an oversized 33 year old Weil-McLain with 3 hot water baseboard zones and a 40 gallon Mega-Stor indirect on priority.

Installer wants to use my existing indirect, but I have read that there are disadvantages compared to EK's solution. In another thread, it was suggested that the existing indirect can be used as a storage tank with the internal coil disconnected, which seems to have all the advantages of the EK system without needing to buy the new tank (although I don't really understand what the advantages are). However, Roger Marran himself seemed to recommend against this, although I don't really follow the reasoning.

It would help if someone could help me understand exactly how the EK system works. It sounds kind of like an aqua booster, where a circulator moves DHW through the boiler's tankless coil and back into the storage tank. My guess is that, instead of a tankless coil there is ANOTHER circulator running boiler water through the flat plate heat exchanger. Am I on the right track?

Can someone help elaborate the pros and cons?

On a totally separate topic, my installer says my system is simple enough that I don't need primary/secondary piping. Does that make sense?

Robert O'Brien

Yes, there is a boiler side pump and dhw pump. It's really all about the ability to purge residual heat from the boiler to the DHW tank. Using an indirect doesn't allow this and using an indirect as a storage tank probably won't allow

thomase00

Did your reply get cut off mid sentence? You were talking about why the indirect can't act like a storage tank (i.e. with disconnected internal coil).

Why can't you purge heat from the boiler into the indirect via the indirect's internal coil? Does it have to do with the case when the boiler is still "hot", but below the temperature of the indirect? If so, how does the flat plate heat exchanger not have the same problem?