Boiler Nat Gas Consumption (1 Viewer)

[chet]

I have a 500k btu boiler to heat my driveway and back patio. It runs on Nat gas. What's the max daily gas consumption of the boiler? It runs at 96% efficiency. Do you need any other info?

 

[jon_mx]

What kind of units show up on your natural gas bill? Never really examined the bill that closely.

 

[chet]

What kind of units show up on your natural gas bill? Never really examined the bill that closely.

Nat gas trades in units called mcf (1000 cubic feet). Last week an mcf traded below $3 in the spot market. I don't know if the utility uses mcfs on the bill though.

 

[BroadwayG]

Rough estimate 1,000 BTU per cubic foot

Assuming that's 500k input btu per hour on your boiler, you're looking at a max 12 mcf of gas per day if it runs constantly.

 

[chet]

Rough estimate 1,000 BTU per cubic foot

Assuming that's 500k input btu per hour on your boiler, you're looking at a max 12 mcf of gas per day if it runs constantly.

Thx. That confirms what my friend told me.

 

[chet]

Can anyone confirm that a 500k btu boiler that is 96% efficient will burn about 12 mcf of gas/day if running at capacity? Thx

 

[eoMMan]

Can anyone confirm that a 500k btu boiler that is 96% efficient will burn about 12 mcf of gas/day if running at capacity? Thx

Only if the carborater is running at 62% with the cut off valve modified with copper tubing.

 

[The Duff Man]

The boiler is not going to put out 500 BTU necessarily when it is running. That is probably the maximum heat output it is rated for. Your pumps circulate the liquid (probably a glycol mixture) through the system, and there will be heat loss associated with heating your space. That heat transfer amount is going to depend on a whole lot of factors but that is what will dictate gas consumption, not max output capacity of the boiler.

The actual BTU output will be calculated using the flow (gpm) through the system and the supply/return temperature. Your boiler will have efficiency curves that dictate the actual efficiency at the required operating point, which will vary at times depending on the load.

Most likely if your control system is good and you use an assumption of 500 BTU you will overestimate the consumption. In my experience engineers WAY oversize heating equipment. I would not be surprised if your boiler never outputs more than 400 BTU and that on the coldest day of the year. I have seen 500 BTU systems never use more than 200 BTU.

Sorry none of this probably helps.

 

[chet]

The boiler is not going to put out 500 BTU necessarily when it is running. That is probably the maximum heat output it is rated for. Your pumps circulate the liquid (probably a glycol mixture) through the system, and there will be heat loss associated with heating your space. That heat transfer amount is going to depend on a whole lot of factors but that is what will dictate gas consumption, not max output capacity of the boiler.

The actual BTU output will be calculated using the flow (gpm) through the system and the supply/return temperature. Your boiler will have efficiency curves that dictate the actual efficiency at the required operating point, which will vary at times depending on the load.

Most likely if your control system is good and you use an assumption of 500 BTU you will overestimate the consumption. In my experience engineers WAY oversize heating equipment. I would not be surprised if your boiler never outputs more than 400 BTU and that on the coldest day of the year. I have seen 500 BTU systems never use more than 200 BTU.

Sorry none of this probably helps.

It helps but I am trying to get a sense of the cost of running the boiler. Can you make an estimate for say the coldest day of the year (400 BTU in your example) and then an average day (200 BTU)? Thanks

 

[AAABatteries]

You heat your driveway and back patio?

 

[chet]

You heat your driveway and back patio?

sometimes