Decisions, Knight, TT or EVO a tough choice

BoilerGuy

I am getting ready to replace a boiler room in a 1940's 10 unit brick apartment building. With new windows and some insulation inprovements the heat loss should be around 160K + domestic hot water

I plan on 2 boilers, the number 2 will be a WM CGI-6 167 input

My top 3 choices for the lead position in no piticular order will be a Knight KBN150, a Hamilton EVO 180 or a TT175. The domestic hot water will be a 120G-TT indirect connected to the lead boiler

In my area the Lochinvar are the most popular and cheaper.

It appears the EVO and TT have better warrenties.I like the design of the fire tube HX on the TT

The EVO has a built in flow switch and secondary high limit and a set of contacts for a secondary heat call (the WM when needed) it also has some nice service frendly features

I would not even consider a alumunin boiler

Any thoughts appreciated

CMadatMe

Why?

Why are you installing 2 boilers? Is this going to be a redundant system or are you looking for different boilers to quote? From your post looks to me like you are designing a hybrid system. Why for such a small load?

kcopp

I would agree...

Why the two? I would do the TT175 and call it good.

BoilerGuy

I like redundant

The WM is my back up boiler if the lead cant pull the load or in case of a failure, This is a personal project, I bought this building through a foreclosure. The boiler that is there is a 450,000 btu WM and a 199,000 BTU AOS tank type direct fired water heater. The copper piping has been stolen. whats left is a monoflo system, all 10 system pumps were hanging from there wires. The building currently is vacant, with NO insulation and single pane steel framed windows. I plan all new vinyl windows and blow in insulation in the walls and ceiling should get R25 in the ceiling and average R10 in the walls, the building Measures 33x84 x3 stories high located in Michigan

I am optimistic at a heat loss of 160K so I want the back up boiler not to mention the peace of mind. I have spent to many nights and weekends in boiler rooms because the one and only boiler was down and it was 10F outside. the second reason is I all ready have the WM with little invested

joel_19

Or.....

IMHO boilers that just sit without ever running have a tendency not to start when needed,creaky ignition stuck pump etc.

I'd consider a smaller TT with the intent that under high load for domestic or extreem cold the WM will run some,get some hrs on it.

that  way the TT will not short cycle as much in milder conditions when only a few of those 10 zones are running.

Agree 100% no aluminum!

Gordy

2 Mod/Cons

If you are dead set on 2 boilers, and mod/cons are in the choices. Why not use 2 smaller modcons in stage. You increase your modulation, and second boiler is not sitting there stagnet as a backup. Or is the CGI 6 an already purchased unit.



Gordy

CMadatMe

Hybrid System

Okay. Now that I understand your application. How about a small mod/con for the warmer months of the heating season when your btu output requirement  and water temps are less so you can take advantage of the condensing features of the boiler and have the Weil fire on those days that are close to design and you need that little extra push. Hybrid type systems are nothing new to small light commerical applications and will give you a nice system.

SpeyFitter

Also - "zoning"

If you got the $$$ in your budget, replace all those pumps with zone valves and use a Wilo Stratos = electricity savings $$$$$

BoilerGuy

Hybrid

Hybrid is what I have in mind, I just need to use the modern terminology

I bought the WM as a new scratch n dent for $500, 1 hour with a body hammer and it looks good, not a scratch on the Cast iron.

In my mind if I size the condensing boiler right the WM will run +/- 50 hours a year, I do agree any machine, boiler,pump needs to be used (exercised) to keep it in good working order.

I have considered a smaller lead boiler, I will be getting a detailed heat loss done before I make a final decision.

one other interesting bonus is the convectors will all be over sized with the better insulation and windows, This will keep me in lower water temps, thus more time in full condensing mode.

I looked at a new install today in a small 6 unit apartment building, the contractor installed a KBN210. The outside temp was 30F and water temp at 150F, with 1 zone open the boiler was cycling (no storage) with 2 zones open it ran at 20% I am thinking the 150 would have been plenty of boiler, maybe even the 110. I will not make the bigger is better mistake.

I plan to go with 2 system pumps and zone valves, 6 of the units are piped with monoflow on 1 pump and the other 4 I have to repipe and will do reverse return, they are all convectors with 1/2 inch pipe.