As I discuss below, it appears to me that I have no choice but to replace my boiler. This is a major expense which I cannot afford; however, neither can I live with the problem identified. So:
1. I want to get second opinions on my analyses and conclusions; and,
2. If I do replace the boiler, this will entail a major expense, and, I only get one chance to get it right. So, I am seeking information, recommendations, suggestions.
I. BACKGROUND INFORMATION:
My current boiler was installed in 2000 for the previous home owner. I purchased the house in 2010. The boiler contractor made numerous significant mistakes in the original installation and in subsequent work. (Some of which are detailed in previous postings by me.)
I was ultimately able to get the contractor to correct the “fixable” problems that he created (completed in early 2015). Without going into the details of the mistakes/resolutions, the outcome is that, with one important exception, the system is finally operating wonderfully.
The noted exception is that I now get hammer. But ONLY under a very specific condition: when the water level in the boiler falls below the 1 inch level on the sight glass. This, in turn, only occurs for a brief period at cold start (boiler hasn’t fired for something more than 2 hr). The hammer is annoying when it occurs during the day. It wakes me up when it occurs during the night.
With regard to the cause of the hammer, my conclusion is that it is caused by an undersized boiler. It turns out that the contractor undersized the replacement boiler by 25%. I discovered this when I performed my own EDR/boiler sizing calculation.
The cold-start hammer had never manifested itself prior to the recent system corrections. This is due to the fact that one of the other major installation mistakes had “masked” the hammer. (To wit: the system had an open-to-air vent associated with an unnecessary and incorrectly installed condensate return tank/pump combination. I had this removed.)
Also, I have noted that when the boiler reaches steady state, the water level stays between 2 and 4 inches below the “set” water level (i.e., often only 1 inch above the bottom of the sight glass). I assume that this is too low. This suggests to me that even under steady state operation, I am overtaxing the boiler’s ability to make steam.
1. My EDR is 491 ft sq. This equates to a “Net I=B=R Steam Rating” of 118,000 Btu/hr (240 Btu/hr per sq ft of EDR). It appears that when specing boilers, most people refer to the “Input” Btu/hr. How do I derive the “Input” rating from the “Net” rating?
1A. When seeking replacement boiler quotes, do I spec the EDR, the Net rating, the Input rating, or, all of the above?
2. Boilers are available in a limited number of capacities, and it appears that that different boiler manufacturers offer slightly different capacity boilers. This makes it unlikely that I will get quotes for a boiler that matches my EDR exactly. How “sensitive” do I need to be when choosing a boiler size? Do I have some leeway, whether up or down? … Is it better to be a little high or a little low?
My gut tells me that for my system, I would be fine with a “somewhat” undersized boiler. My logic goes as follows: The “only” problems I encounter with a 25% undersized boiler are: i. hammer occurring at a cold start; ii. low steady-state boiler water level; (and possibly, iii. getting “full heat” out of the one 3rd floor radiator that I have). This suggests to me that I have some leeway; e.g., 5%, 10%? Any thoughts?
3. Related to the preceding question: Generally, are there other issues or sizing “pitfalls” I need to consider related to up-sizing my boiler?
a. E.g., issues related to a 90 year old heating system that was designed to accompany a larger-capacity boiler tank and a system that heated more slowly. I.e., modern boilers make steam more quickly than the old boilers, and, a larger boiler will only exacerbate any associated issues (e.g., shorter cycling).
b. E.g., Could there a reason, other than incompetence, that the contractor installed a 25% undersized boiler in 2000?
4. Boiler brand options: any suggestions re brands, or brand review sources/articles?
5. Re: ball park est: I’ve been told that for this size boiler (~ 190,000 Btu/hr), a general replacement estimate is in the $4-to-$6,000 range (Upstate, NY). Is that accurate?
One-pipe steam. NG fired. 2100 sq ft heated space.
Utica Boiler PEG150C (150,000 Btu/hr Input) connected to 491 sq ft of radiation. Operating press 0.5 psi.