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(Commercial) Your opinion on replacement boilers
I have a customer that wants new boilers. They currently have an old Kewanee firetube, 5 million btu, and two 2 million btu condensing boilers. The boilers never condense. They run their domestic hot water off a shell and tube heat exchanger. They have to send 160-180 to the heat exchanger to make hot water year-round. The DHW load is so small that one 2 million btu boiler short cycles all summer to maintain it. These condensing boilers have a 20:1 turndown, even at 100,000 btu input at low fire they short cycle during the summer.
My original suggestion was lets gut this and re-do it all. Install water heaters so that we could actually use condensing boilers or a hybrid condensing/non-condensing boiler setup. I was informed that they want to go as cheap as possible, no exceptions. They have listed a few different boiler brands that they want, all of them are condensing boilers and all of them only have a 5:1 turndown, which means even more short cycling during the summer.
Since removing the DHW heat exchanger isn't an option, what would you do in this situation?
I am leaning towards two cast iron sectionals. Added mass would hopefully limit summer short cycling. They'd last a lot longer than condensing boilers and cost less to maintain.
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