HVAC Load Calculator for Oil to Gas Conversion Suggestions?

PilotPat24

Hi Guys,

I am looking to convert a house on Long Island, NY from Hydronic Baseboard Oil to Gas. Does anyone have a recommendation of a Free HVAC Load Calculator to determine to BTU requirement?

Thanks,

Pat

Jamie Hall

Are you replacing the boiler? Or installing a gas conversion burner in the existing boiler? Very different projects.

You have two load conditions -- one is what the capacity of your existing radiation -- the baseboards -- is. The other is what the house needs. Whichever is less limits the maximum size of the boiler wanted -- most likely the house load. That can be calculated with the Slant/Fin calculator, here: https://www.slantfin.com/slantfin-heat-loss-calculator/

STEVEusaPA

How many gallons did you burn in the last 12 months?
What equipment do you currently have, make/model #, and do you use your boiler for domestic hot water?

PilotPat24

STEVEusaPA said:

How many gallons did you burn in the last 12 months?
What equipment do you currently have, make/model #, and do you use your boiler for domestic hot water?

Hey Steve,

2021 - I had 665 Gallons Delivered
2022 - I had 375 Gallons Delivered so far. In the fall, I'm sure I would have another 225 gallons delivered which would be about 600 gallons for this year.

Thanks,

Pat

PilotPat24

Jamie Hall said:

Are you replacing the boiler? Or installing a gas conversion burner in the existing boiler? Very different projects.

You have two load conditions -- one is what the capacity of your existing radiation -- the baseboards -- is. The other is what the house needs. Whichever is less limits the maximum size of the boiler wanted -- most likely the house load. That can be calculated with the Slant/Fin calculator, here: https://www.slantfin.com/slantfin-heat-loss-calculator/

Hi Jamie,

I am not sure what I want to do yet. I currently have in this house a Peerless WBV boiler that has to be about 25 years old. Your thoughts?

Thanks,

Pat

Steamhead

Those are good boilers. If that were mine, I'd clean it out thoroughly, install new firebox refractory, replace the oil burner with a Carlin EZ-Gas burner matched to the boiler and the oil barometric with a gas one, and add a blocked-flue switch. It's not unreasonable to expect this setup to last another couple decades.

Hot_water_fan

I like using usage:

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

That's probably placing your heat load around 40,000 btu/h without DHW and 30,000 btu/h with DHW, which is probably about half of your current capacity.

STEVEusaPA

PilotPat24

Hot_water_fan said:

I like using usage: https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler That's probably placing your heat load around 40,000 btu/h without DHW and 30,000 btu/h with DHW, which is probably about half of your current capacity.

Well the boiler only supplies baseboard heat which is 102,000 BTU's.  I have a Toyotomi on demand HWH for hot water.  I am sure the boiler is way oversized.  It's a 2000 ft/sq house.  

I'm guessing people's thoughts is that I should stick with oil?  Would it be worth it for me to have a properly sized system?

Pat

Jamie Hall

Before I even began to consider switching from oil to gas, I'd ask what the relative cost is going to be. First question, obviously, is do you already have natural gas run to the house? Is the service big enough? If you do, what is the cost of gas per BTU vs. the cost of oil per BTU? But even then, with that low an oil usage, what can you really save? Would it pay for a new boiler in the 10 years or so a new boiler would last (the saying "they don't make 'em like they used to" comes to mind). Probably not -- but it might pay for the conversion burner which @Steamhead suggested.

Eventually that Peerless will give up, but with any care at all it will be a while -- and by then the choices and reasons for them will have changed.

In_New_England

I used the Weil McLain worksheet.

The slant/fin app looks great, but a bit complicated.

I also looked at my oil consumption for Jan/Feb (150 gal) and got a rough estimate of my average BTU during that period. There is a way of working out the heat demand more precisely using outdoor temperature charts for that period.

I also used the slant/fin baseboard charts to estimate my baseboard output. A quick rule of thumb is 580 BTU/hr x feet of baseboard if it is driven at 180F.

STEVEusaPA

In_New_England said:

I used the Weil McLain worksheet.

The slant/fin app looks great, but a bit complicated.

Too many 'rules of thumb' in the calculations, I'd think it might oversize. Actual usage would seem to be more accurate, and much easier.

Dave Carpentier

I found the SlantFin app for the phone to be pretty cool. You still have to measure and define things of course, but the app was well designed for even an amateur to use.

Jamie Hall

I have heard people say the Slant/Fin app is too complicated. It's not. You do, however, need to exercise enough to get reasonable inputs. With reasonable inputs, it gives reasonable results -- and they are almost as accurate as a full scale Manual J. Actual usage can also be reasonably accurate -- no better and no worse -- but you again need the correct inputs. Without them, it's worse than useless.

PilotPat24

Jamie Hall said:

Before I even began to consider switching from oil to gas, I'd ask what the relative cost is going to be. First question, obviously, is do you already have natural gas run to the house? Is the service big enough? If you do, what is the cost of gas per BTU vs. the cost of oil per BTU? But even then, with that low an oil usage, what can you really save? Would it pay for a new boiler in the 10 years or so a new boiler would last (the saying "they don't make 'em like they used to" comes to mind). Probably not -- but it might pay for the conversion burner which @Steamhead suggested.

Eventually that Peerless will give up, but with any care at all it will be a while -- and by then the choices and reasons for them will have changed.

I do not have natural gas currently at the house. It is currently in the street and National Grid would run it to the house providing I switch one of the appliances over to gas.

I will take a couple of pictures of my current configuration and see if anyone has any recommendations to improve anything the way it is currently set up.

Thanks,

Pat

ChrisJ

You're going to find there's a few on here that are against natural gas no matter what.

I converted from oil in 2011 and I'd never go back.

PilotPat24

This house is a rental and I pay for the heat. I'm just trying to figure out what fuel would be cheapest to heat the house with and if it would be worth it to switch over to gas over the long term.

Pat

pecmsg

Cost per BTU/h between Oil and Gas is always fluctuating always changing. Some years Oil is cheaper some Gas. I highly doubt you'll ever see a return on investment converting, it's more a personal choice.

Tightning the envelope and properly sizing the equipment WILL give you a return-on-investment year after year.

PilotPat24

pecmsg said:

Cost per BTU/h between Oil and Gas is always fluctuating always changing. Some years Oil is cheaper some Gas. I highly doubt you'll ever see a return on investment converting, it's more a personal choice.

Tightning the envelope and properly sizing the equipment WILL give you a return-on-investment year after year.

Understood. I will begin to gather all of the specs on my house and my system I currently have.

PilotPat24

pecmsg said:

Cost per BTU/h between Oil and Gas is always fluctuating always changing. Some years Oil is cheaper some Gas. I highly doubt you'll ever see a return on investment converting, it's more a personal choice.

Tightning the envelope and properly sizing the equipment WILL give you a return-on-investment year after year.

You don't think it would be worth converting to Natural Gas with Fuel Oil Prices being $5.50+/gallon? I don't see fuel oil prices coming down anytime soon.

Jamie Hall

Natural gas spot prices are going up, too. Unless artificial controls are established, I believe that you will see the various fuel prices per BTU even out again, but at a much higher level than before. Fuel oil prices are more volatile, as the level of government control is less.

ChrisJ

Jamie Hall said:

Natural gas spot prices are going up, too. Unless artificial controls are established, I believe that you will see the various fuel prices per BTU even out again, but at a much higher level than before. Fuel oil prices are more volatile, as the level of government control is less.

So.
That's a bad thing, no?

Jamie Hall

ChrisJ said:

Jamie Hall said:

Natural gas spot prices are going up, too. Unless artificial controls are established, I believe that you will see the various fuel prices per BTU even out again, but at a much higher level than before. Fuel oil prices are more volatile, as the level of government control is less.

So.
That's a bad thing, no?

That is a political question... not going there.

It is worth noting, though -- without getting off into the weeds too far -- that natural gas (and town or manufactured before that) is what the economists call a "natural monopoly" -- one where a single entity controls the market in an area naturally, since installing competing infrastructure is excessively costly. Other natural monpolies include electric power, cable television, hard wired phones... that sort of thing. Fuel oil or LP, or coal, for example, are not. There are no natural barriers to make competition difficult.

ChrisJ

Jamie Hall said:

Natural gas spot prices are going up, too. Unless artificial controls are established, I believe that you will see the various fuel prices per BTU even out again, but at a much higher level than before. Fuel oil prices are more volatile, as the level of government control is less.

So. That's a bad thing, no?

That is a political question... not going there.

Less stable fuel prices seems like a bad thing to me.   Not to mention you basically already went there my friend.

Erin Holohan Haskell

No politics here. Thanks!

fentonc

Oil has basically always been a globally-traded commodity, so the price has historically been much more sensitive to world events / markets than gas. Gas has mostly been supplied via long-term contracts, and was difficult to ship around the world, so there have been big long-term price discrepancies in NG prices between different parts of the world (Europe is ~10x the USA right now, for instance). In the last few years, the US has built a lot of LNG export capacity, and with the current Ukraine/Russia situation (and thus sky-high prices for LNG in Europe and Asia), NG prices in the US have been increasingly volatile because more of it can be exported when someone else is willing to pay a higher price. Prices have basically doubled since March, for instance. Anytime you're directly exposing yourself to volatile commodity prices, you're kind of making an investment decision/bet about the future price of those commodities.