Boiler gas usage

Curtis572

Hello, I was hoping someone may be able to assist with getting a general idea of what a new boiler's gas consumption may be versus an old boilers consumption.
I know doing the upgrade is going to be beneficial due to the age and size of the old boiler but I am just trying to get a ball park idea of what to expect from a new boiler set up.

The old boiler is a superhot ss360 from 1980 and has no flame modulation, where the new boilers in question are NTI FTVN150. Based on the size of the house and the heat loss that has been calculated by my contractor he figures up to 300,000 BTU may be needed through the winter at times still as we see -40 Deg C, it is an 1980 house and has a sizeable foot print. He quoted 2 due to the fact that a single unit large enough to heat our home goes into the commercial class and is more expensive.

As I said I am trying to just get some sort of an idea of the consumption that the new boilers may use and am wondering if this can be done somehow off of past gas usage?

Any insight on this would be greatly appreciated, thank you to any one that has any idea on this in advance

Hot_water_fan

How much gas did you use last year?

Savings cost be 5-50+%, it depends on so many factors. Some benefits come from modulation, others from right sizing, even more from condensing, and you can’t forget a proper installation! The biggest benefits would combine all of these: you’d be replacing a poorly installed behemoth with the proper sized boiler that is properly dialed in to use only the minimum temperature for the weather.  

I remember one guy posted that he was saving 25-30% and was pissed! He didn’t do his homework - the amount of money per year his installer told him he’d save was nearly his entire annual bill. Can’t expect miracles.

The Steam Whisperer

In larger installations I like to stage two, non condensing simple cast iron boilers with roughly 60% of the peak load in each boiler. For nearly the whole winter, only a single boiler will run at near full capacity, providing very high efficiency. When replacing an oversized single stage boiler, this configuration of heating plant typically saves about 30% on fuel usage, and gives you built in back up that can typically keep a building above freezing in most winter weather should one boiler fail. We've had as high as 70% savings.
Simple cast iron boiler, even atmospheric, keeps repair costs down and parts are not proprietary and life expectancy should be 30 years or more.

Curtis572

Hot_water_fan - I will have to check what the usage was, but I am fairly certain it was high. That SS360 is a behemoth of a boiler and of course has no flame modulation on it. With 6 zone valves in the house it seemed as though when it was cold out, like below - 25 Deg C that the boiler cycled on and off all day and night to meet the demand of the house heating requirements.

I thought about it more yesterday and for a base guess I wonder if simply comparing the efficiency ratings of the boilers and going off of the last years gas consumption if that will give me what one should hope to expect for a minimum savings. Basing this off of the boilers maximum output, which the new ones will modulate the gas usage where the old one does not, so it should be better that that.

Yeah there are so many factors for sure. For our house in general we are fairly consistent in our heat levels, had all of the window replaced and do not open windows in the house in the winter unless absolutely necessary. So in that regard we are fairly consistent. Now outside weather factors are a different story of course. On top of that we are going with a boiler heated domestic hot water tank as well so that will be another factor, I am hoping that this will be more efficient than the current tank that we have thoug as it sounds like a small jet engine starting up when it cycles on.

The contractor I am dealing with also seems to know what he is doing, he has done other work for me and people that I know and there is never a complaint with his workmanship or installs being inefficient. So thankfully I have ended up with some one that is good in this regard.

The Steam Whisperer - I will have to look into these style of boilers, I am new to boiler heat and all of the available products. Any in particular you would recommend?

EdTheHeaterMan

With all this very specific information:
Size of old boiler = "very big"
New boiler = "NTI FTVN150"
Design for new system = "up to 300,000 BTU may be needed"
Past gas usage = not provided
How do you use it? = "fairly consistent in our heat levels"
I can safely say that you will save exactly 36.829% on your previous heating energy consumption. However there is a margin of error of plus or minus 33.25%

The life span of a simple cast iron boiler with easy to find replacement controls and parts is double that of the NTI FTVN150. The repairs are less expensive and completed faster on the cast iron boilers. The boilers are usually less expensive. The fact that most of the time you will be operating on one boiler with longer operating cycles will provide you with the best all around performance. KISS is the acronym for Keep It Simple S... (salesman). I would recommend the Crown Aruba Boiler. if it is available in your area https://www.velocityboilerworks.com/product/aruba-5-awr/. Other companies like Weil McLain use specialized parts that are more expensive. Crown uses more generic parts for lower cost and ease of service.

Just my thoughts

Hot_water_fan

I thought about it more yesterday and for a base guess I wonder if simply comparing the efficiency ratings of the boilers and going off of the last years gas consumption if that will give me what one should hope to expect for a minimum savings.

That’s not a bad approach but the efficiency ratings are for comparing well installed boilers that fit the heat loss, which hasn’t been determined yet. 

hot_rod

How many square feet are you heating? 300,000 could heat 10,000 square feet of a mid level insulated home.

I’d get a complete heat load calc done.

Curtis572

Hot_water_fan said:

I thought about it more yesterday and for a base guess I wonder if simply comparing the efficiency ratings of the boilers and going off of the last years gas consumption if that will give me what one should hope to expect for a minimum savings.

That’s not a bad approach but the efficiency ratings are for comparing well installed boilers that fit the heat loss, which hasn’t been determined yet. 

Fair enough, the heatloss is definetely a huge determining factor in this situation.
Any recommended tools for determining this?

EdTheHeaterMan said:

With all this very specific information:
Size of old boiler = "very big"
New boiler = "NTI FTVN150"
Design for new system = "up to 300,000 BTU may be needed"
Past gas usage = not provided
How do you use it? = "fairly consistent in our heat levels"
I can safely say that you will save exactly 36.829% on your previous heating energy consumption. However there is a margin of error of plus or minus 33.25%

The life span of a simple cast iron boiler with easy to find replacement controls and parts is double that of the NTI FTVN150. The repairs are less expensive and completed faster on the cast iron boilers. The boilers are usually less expensive. The fact that most of the time you will be operating on one boiler with longer operating cycles will provide you with the best all around performance. KISS is the acronym for Keep It Simple S... (salesman). I would recommend the Crown Aruba Boiler. if it is available in your area https://www.velocityboilerworks.com/product/aruba-5-awr/. Other companies like Weil McLain use specialized parts that are more expensive. Crown uses more generic parts for lower cost and ease of service.

Just my thoughts

It is indicated that it is a superhot ss360 from the late 70's or 1980 when the house was built.
That boiler does seem to work well still but the gas consumption is excessive is all.

I do like the idea of easy to find replacement parts and more life out of the unit.

I will check into the crown aruba boiler and others if this is not available in my area.

Also are there any sites that are a good reference to check boilers efficiency ratings? I have looked but everything that comes up is just to sell me a boiler in the end and does not give an efficiency rating on the existing boiler

Thank you very much for the information.

Curtis572

hot_rod said:

How many square feet are you heating? 300,000 could heat 10,000 square feet of a mid level insulated home.

I’d get a complete heat load calc done.

I am heating about 4000 square feet with my garage included. I definitely want a heat loss calculation finished. I'll have to try and check this out.

Hot_water_fan

Fair enough, the heatloss is definetely a huge determining factor in this situation.
Any recommended tools for determining this?

One way is determine how much gas you used last year compared to the heating degree days.