Lochinvar Knight or WM evergreen, 399btu

acaciolo

Hello!
You guys have given me some great advice in the past, and now I am starting anew house that I need a little help with. I am a custom home builder and have a great partner/hvac company that is super knowledgeable.

I am starting my personal house and looking at either the WM evergreen (readily available locally) or Lochinvar Knight using Natural Gas. I like the remote connectivity of the Lochinvar and their control system seems awesome, but I have heard about a bunch of heat exchanger issues (not sure if it is blown out of proportion or not.) Lochinvar doesn't have a terribly strong presence in our area, but parts etc. won't be a problem. My installer is more familiar with WM, but has done a few Lochs and liked them. My current house had a 16 zone, tekmar controlled very complicated system with a mix of radiant and hot water. I am looking to simplify in this new house...

It will be powering 4 hydronic coils in 5 ton air handlers and a radiant zone. It will also do DHW. I searched the forum and found lots of opinions. Anybody have advice either way? Cost is about the same.

thanks!
tony

GroundUp

Might I ask how big this house is? 399k seems like an awful high heat load, did the installer perform a load calc? I am not familiar with the WM, but I have installed hundreds of the 400k+ Knight boilers in commercial settings and they've been fantastic as long as water chemistry and HX is properly maintained. A lot of the failures you hear about are due to low flow and lack of maintenance, we've had terrific luck with them when properly installed and maintained.

acaciolo

It is about 9000sf and there is a 3000sf garage that is heated too.   Plus a heated basement of about 3000sf.

The 399 sounds big but it actually just about right. Thanks! 

mattmia2

you might think about cascading 2 smaller boilers too. it will give you a higher turndown ratio and some redundancy if one fails.

Gary Jansen_4

I'm partial to the Lochinvar.
But, if you were me, and the budget can handle it, I would do either 2-199's, or a 199 and a 285.
Greater turndown, less cycling, better matching the output to the loads, redundancy, more efficiency.
Cascade them together.
If you did the 2-199's, you would match your total theoretical load, and if you lost one boiler, you could possibly keep the system at a reasonable temp, maybe not comfortably, but enough to somewhat maintain the space.
If you did a 199 and a 285, then the 285 could conceivably carry the building on its own.
Good luck, Gary

acaciolo

great advice. I did consider that, but since natural gas is so cheap in my area, I was having trouble justifying the extra expense. The main A/C units are actually heat pumps, so I do have that in case the boiler goes down. I did like the new weil mclain eco boilers, but they can't be cascaded yet.