New Boiler

Damon

Hello, Great site! I currently have a 21 yr old Utica M150AGB water boiler 150,000 input, 123,900 output, 107,800 IBR in need of replacement due to minor leaks between all 4 sections on the front/input side. It leaks only during cold startup and cool down. It does not leak cold or hot. It has been providing sufficient heat for the 11 years I have been in this house. I'm in Chicago in a 1923 bungalow with a 1077 ft3 basement whose walls are concrete 3 ft below ground and brick 4 ft above. 1st fl is 1407 ft3 brick with plaster walls and 8'-9" ceilings. 2nd fl is 839 ft3, has stucco/plaster walls and 8'-7" ceilings. The majority of the walls are not insulated. Nearly all windows are original single pane wood with storms that have been weatherstripped. 2nd fl ceiling is below a non-accessible/vented attic with some cellulose insulation (I'm assuming 3"). The basement is a recently added and rarely used zone since the overhead pipes take the chill off the basement depending on how cold it is outside. Everything above ground is on one zone. Big CI radiators above ground and copper fin/tube baseboard in the basement. I have used HVAC-Calc to yield losses of 111,000 BTUH including the basement and 95,000 BTUH above ground. My questions are:

1) Utica tells me the old boiler is about 78% efficient but 123,900/150,000=82.6%. Am I missing something such as the AFUE being seasonal and the boiler plate ratings being steady state/continuous?

2) As one example, I'm looking at a Peerless MI-05 with the following ratings Input:140,000 Output:115,000 IBR:100,000 and the MI-06 which has 175M, 143M, 124M ratings. Which should I select considering that I don't use the basement much and I work at home and always have to heat above ground?

3) Due to the HVAC calc descriptions being vague, I used an infiltration rate of 0.7 which is based on the more descriptive, and ACCA approved, selection available in the trial version of Elite RHVAC. Is this right for my type of house?

4) I'm also looking at a WM CGa-5. Which I notice has a very small water content (2.7 gal vs the 7.28 for the MI-05). Does this make a difference?


I'm a chemical engineer and am getting some less than analytical info from some of the local contractors so hence my questions (and my level of detail).

Thanks for your assistance.

Steamhead (in transit)

All the boilers you mention

are atmospheric gas units. These aren't terribly efficient since they are wide open at the base, allowing lots of air infiltration and radiating heat into the basement floor (ever wonder why you can't install these units on combustible floors?).

Since the Utica units are pretty well made I suspect yours is leaking from either a lot of makeup water (due to a system leak someplace) or the flue gases condensing which can cause an acid rainstorm inside the boiler and chimney. You cure the latter with either a thermal bypass or primary-secondary piping, both of which allow the return water (and the boiler sections with it) to quickly heat up past the condensing point.

If you have a place to vent one of the newer condensing boilers (which are made to condense the flue gases) that meets Code, consider one of these. Or consider a wet-base, oil-designed boiler with a power gas burner. This will not only move more heat into the water rather than into the basement floor, but will allow you to burn whatever fuel is cheaper per BTU by having a pro swap out the burner. Not all manufacturers support running their oil-designed boilers this way, but the Solaia (a re-badged Biasi) and Smith #8 boiler lines are both supported for use with gas burners.

Here's a shot of a Solaia we installed with a HeatWise power gas gun.

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Damon

Thanks for the quick response. I'm running dino farts. The local guys are quoting $9,000 for HE units so I'll pass on those for now since the atmospheric units are in the $3200 range. With a $1700 heating only gas bill last year the payback on an HE unit at those prices is absurd. Do you have some realistic price differences between atm. and condensing units? I don't have a bypass now but I guarantee there will be one on the new system since I agree that contributed to the problem. The boiler never gets much above 160F normally but I have seen it at 180 - 185 when it's below 0 outside for several days. There's been no makeup water other what's needed to bleed the sealed expansion tank (history on the new install) and the system was drained ~3 years ago to add isolation valves and the basement zone. I'm sure there's no leaks other than the sections which are prety small. Here's a pic of the leaking sections after cleaning and unfortunalely before I discovered the leaks. It was probably leaking for a while which I figure is where those black marks are from but it didn't drip and sizzle and get my attention until I cleaned the junk off the sections, spent $275 on a custom made flue collector and fired her up

Steamhead (in transit)

You can still run

dinosaur methane with that Solaia. And the quality of the iron is first-class.

You could also pipe the new boiler primary-secondary instead of using a bypass. This would be a great way to leave room to add an indirect later.

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[Deleted User]

What if I have condensation and not a leak???

Can you tell from the previous pic which was taken 2 weeks ago just after cleaning and this one taken today if this is condensation or a leak? Both pics are of the return side with the drain valve on the right and the return line coming in on the left. I do have pics of the supply side which has minute "leaks" compared to the return side. Remember no bypass and large volume system with old CI radiators and the temp gauge on the boiler has only been running 120-140F recently which should be causing condensation. Also, I always close the cold water fill shutoff valves and never need to add water unless I drain the sealed expansion tank. If it's just condensation and not just small leakes would it pay to just add a bypass, outdoor reset and vent damper and hope it will last another 10 years or should I go for the new install?