Oversized boiler suggestions

What’s the EDR load connected to the boiler? You need to measure your radiators to determine their output to figure out the proper boiler size. Depending on the boiler model you may only need to have sections removed to right-size it. Caping off the burners while maintaining the same volume of water isn’t going to improve efficiency in the slightest.

You have to be very careful here.

1. Combustion Analyser experience
2. Gas Pressure Manometer
3. Extensive experience derating equipment.
4. You may very well void the warranty too!.
5. In the past, I have installed smaller gas jet orifices, but the adjustments can take countless hours to hit all your parameters, especially CO.

Mad Dog

Maybe that's what they had on the truck.

The other important question is where you are located, as that obviously affects your house's heat loss, and therefore cost.

In a well-sealed 1920's Victorian with new replacement windows and attic insulation, you could be quite similar to our 1920's or 30's four unit apartment house in the Boston area. We also have upgraded windows and 10" blown cellulose in the attic. Our heat loss is just under 20 BTU/hr/sq ft on a zero-degree design day.

So for comparison, in December we burned 254 gallons of heating oil for 4800 sq ft of living area. Your living area is a bit more than half that at 2500 sq ft. But close to half. Half of 254 gallons is 127 gallons, which at $3.50 per gallon is about $444 to heat your house with oil in December (if it was in the Boston area, assuming similar heat loss to ours).

You can calculate the BTU equivalent of your natural gas, and what that would have cost you. Oil prices are going down, and natural gas prices are going up, at least around here, so it could well have cost us $500 or more in December to heat your floor area with natural gas.

So $500 for December heat may be par for the course, if your climate is similar to Boston.

But if you're much farther south, of course that's different, and you'd have to scale for the milder climate.

your gas bill was 500$. Do you have gas water heater ? Gas cooking ? Gas dryer ? If so what was the gas bill in summer when the boiler is not running. You say it’s oversized . How long are heating cycles ? There are real tests a tech can do that you need done to figure out if it’s oversized. A room getting to hot is an unbalance system and thermostat issue, in my opinion. If all radiators are closed down and a few rooms are too hot , an idea is open up venting on other rooms or further cut down the hot rooms. There are ways to cut down hot rooms . Top venting , smaller vents , radiator covers , and more . If it heats to fast , I would figure out is a tech can reduce gas input . I know how I would do it , but I’m sure it isn’t the “correct” way. Have you had or experienced any record cold like in the past? I don’t think so. The boiler was probably sized for that. It will happen again.

@jesmed1 oil prices may be coming down while gas prices are rising, but natural gas is so much cheaper than every alternatives you can’t compare them.

• A gallon of heating oil has 137,381 BTUs
• One therm of gas has 100,000 BTUs.

As I said, I paid under $0.75 per therm including fixed service charges. Doing the math (and assuming equal efficiency) fuel oil would have to be $1.04 or so to be equally efficient.

You mentioned you paid $3.50.

Natural Gas is the cheapest heating fuel (even over heat pumps) and it isn’t close*.

*Except geothermal when you ignore installation costs.

Edit: at a cursory glance I suspect that the fuel use per boiler is not linear - I.e. a 2x size boiler doesn’t use 2x size fuel.

Does anyone thing with most of the air vents choked down because the rooms get too hot will cause the burner to run and constantly cycle on pressure trying to satisfy the thermostat?

Is the thermostat located in the freezer?

So the question is if the rooms overheat why the stat isn't shutting the boiler down?

Seems like you're operating with basically no air vents which as everyone knows will drive up the fuel bill.

You want to run low pressure vent the mains quickly and the rads as quickly as possible while still maintaining some balance of temp between rooms and locate the thermostat where it will satisfy

I didn't mean to derail the thread into a debate about the cost of different fuels. I don't know where you live, but in Boston, natural gas is now close to parity with heating oil on a per-BTU cost basis ($2.40/therm vs $3.40/gal.)

You probably live in a region near natural gas fields where transportation costs are low, which makes natural gas massively cheaper than it is here in Boston, so your math would be different, obviously.

So if the OP has natural gas prices closer to yours, then yes, obviously he is burning a lot more BTU's than we are per sq ft. Which means his house is leakier than he thinks.

Bottom line is the OP had a baseline energy cost (with natural gas) that he expected to lower with energy retrofits, and unfortunately it didn't turn out that way. Maybe some tweaks to the heating system can help.

Cab you take a picture of your pressure controls and main air vents? Ditto for the piping directly above the boiler.

Your boiler is the correct size. If it is overheating before satisfying the thermostat that points to an air venting problem affecting the balance of the system. A lack of venting could also be causing pressure to build causing the boiler to shut down on pressure. If the pressure control is set too high, the pressure damages air vents making the problem worse.