steam boiler replacement

Mark Bagdon

I have a wonderful old two pipe system in my 1935 house. This magnificent boiler works fine, but it is huge and takes lots of time to make steam. I hate to replace the monster, but am wondering how much gas I would save with a new properly sized boiler. It does have a cheap conversion burner on it firing at about 150 MHB. I figure a new boiler with 125 MBH input should do the job. I have finned tube recessed convectors, no radiators (see photo). Any thoughts would be appreciated.

Mark

Unknown

Wow , shes a big one

How many convectors are connected to that monster ?

Mad Dog

Ron's right Mark

Don't make any assumptions on sizing...you need to measure up your connected load (all the radiators). In Lost Art of Steam Heating it tells you how. Also, most guys who know better WILL NOT make any guesses on your projected fuel savings. It can be calculated fairly closely, but there aree so many different factors that are variable. Most guys don't want to quote any numbers because they WILL be held to them after next heating season. Will you save some fuel witha properlt sized and piped steam boiler??? YES! you PROBABLY WILL, but no promises on how much. Mad Dog

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Mark Bagdon

I did a fairly detailed calculation of BTU output of the convectors. The fin configuration does not match any of my catalogs (2" x 6" with three 1/2" pipes through the fins)but I based it on the area of each fin and number of fins per inch. I came up with about 70 MBH which matched the heat loss I calculated with a Carrier load program for the house. Then: 70 / 0.8 eff x 1.33 pickup gave me 125 MBH. There are 17 convectors of various sizes connected to the systems. I would imagine that the pickup with the convectors would be a bit lower than cast iron radiators but did not try to correct for that.

Steamhead

and

the boiler is only part of the efficiency situation. Once the boiler has generated the steam, its job is done. From there, the system must move it to the radiators. The usual problems I see on Vapor systems like yours are bad traps and air vents.

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Mark Bagdon

Steamhead

The system works fine. I replaced many of the trap elements over the past two years. I just think the AFUE of that monster must be pretty low. The combustion efficiency isn't bad about 79%. The other concern is how many more years I will get out of it without springing a leak. It is 68 years old!

Mark

Stemmer

steam vs hot water

Just an idea that MAY work. Get a proper heat loss done for the home. I'm sure many upgrades have been done. Now caculate the output of each convector based on steam and 180 degree hot water. If the output of the rads based on water meet or exceed your heat loss you are a conversion canidate. IF the supply and return lines are large enough, you may be able to convert your old system over to hot water without much work. In some cases you may have to change the return lines from the rads only. This may not be possible due to concealment. I would suggest that the fuel savings will be a pleasent surprise.
Stemmer

lisa

conversions

I wouldnt do it.Don't count on saving any money. The steam system works and is reliable.

Mark Bagdon

Hot Water Conversion

> Just an idea that MAY work. Get a proper heat

> loss done for the home. I'm sure many upgrades

> have been done. Now caculate the output of each

> convector based on steam and 180 degree hot

> water. If the output of the rads based on water

> meet or exceed your heat loss you are a

> conversion canidate. IF the supply and return

> lines are large enough, you may be able to

> convert your old system over to hot water without

> much work. In some cases you may have to change

> the return lines from the rads only. This may not

> be possible due to concealment. I would suggest

> that the fuel savings will be a pleasent

> surprise. Stemmer

Mark Bagdon

Hot Water Conversion

I have considered a conversion. I think that the returns are sized OK and the output would be sufficient. Issues are:

1. Possibility of freezing risers to second floor with HW. Its a brick cottage with original stucco inside walls - poorly insulated on the first floor. Thinking of blowing cellulose in the first floor, but it will look like swiss cheese since the stucco pattern is unique. Second floor is cedar shakes and well insulated. Three of the risers run up outside walls.

2. Could be tough removing the traps. Convectors are built into the wall and access to the traps is a bit tight. I meant to check if the Trane B-1 I have has a removeable seat. That might give me enough flow for HW, but I would still be worried about potential freezeup. I am in Albany NY. Pretty cold up here.

3. I suppose if I bit the bullet and insulated the first floor properly, I would get certainly see savings. but my wife would kill me if we can't patch it to match.

Mark
Mark

Boilerpro_3

Flow area for returns

If you only have a small orifice in the trap, you probably will be OK. Here's a converted one pipe radiator I did... The return is connected to the radiator with an 1/8 inch nipple in place of the air vent before it goes into the 1/2 inch return pipe.

Boilerpro

Steamhead

I'd stay with Vapor

especially since you've already invested in some upgrades, and since it will never freeze.

Also, fin-tube radiation on hot-water generally needs a greater flow rate than cast-iron. On hot-water you can feed cast-iron radiators up to about 90 square feet with 1/2-inch pipe. The same output with fin-tube baseboard or convectors would require at least 3/4-inch and someimes 1-inch pipe.

I love those old Tranes. Does yours have the Direct Return Trap that looks like a metal jug?

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Mark Bagdon

Trap Orifice

I just measured the trap orifice and it is exactly 1/4". The biggest convector needs about 0.8375 gpm if I assume 20 degree drop. I did not have the right books at home, but I figure the pressure drop though the orifice is quite low (0.75 ft), but the velocity is high (5.5 ft/sec) and ASHRAE seems to indicate that I could get cavitation through the orifice above 5 fps, which would be noisy. Any thoughts/ I could drill it out to reduce the velocity, but the small orifice would provide some nice self balancing. (It is a reverse return).

Mark Bagdon

Direct Return Trap

Steamhead:

Sure do. I am not sure if it is working since there is no sight glass, but the system is quiet (now that I replaced the trap element at the end of the dry return). If I do replace the boiler should I keep this jug in place? Do I need it if I have enough dimension "A"?

Mark

Steamhead

Yes, keep it

that's a "B" dimension at the end of the dry return, not an "A". The new boiler will probably have a lower waterline and should have a Vaporstat, but the DRT can stay as a backup.

Also consider upgrading your air vents if you haven't already. I like to use Gorton #2 vents on those old Tranes.

www.gorton-valves.com

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Mark Bagdon

DRT

> that's a "B" dimension at the end of the dry

> return, not an "A". The new boiler will probably

> have a lower waterline and should have a

> Vaporstat, but the DRT can stay as a backup.

> Also consider upgrading your air vents if you

> haven't already. I like to use Gorton #2 vents on

> those old Tranes.

>

> www.gorton-valves.com

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 157&Step=30"_To Learn More About This Contractor,

> Click Here to Visit Their Ad in "Find A

> Contractor"_/A_

Mark Bagdon

DRT

Thanks for the advice:

"A" "B" - I misplaced my copy of the "Lost Art..." and can't keep things straight. It got to be around here somewhere.


I guess I should invest in a vapor stat if I stay with the steam. There is a cheap pressure stat on there now that is not at all accurate at the low end.

Mark