Old Vacuum (vacu-stat?) two pipe steam system. New Boiler

914ml

We have a two pipe steam vacuum (vacu-stat?) system in our home that was built in 1937. It was originally an oil system but was converted to gas at least 25 years ago. We had a carbon monoxide leak and have to replace the boiler (Peerless?) which is 240K BTU. We have been told that current boilers are fast firing and pressure while our system is based on a slow firing gravity (not pressure)system, and that the replacement boiler will almost invariably lead to knocking in the convectors. Our convectors are all built-in and would require major construction to gain access to them.
Our plumber is recommending a Burnham boiler replacement. He says that there is nothing available today that would replicate the slow firing vacuum gravity system. If so, is there anything we should buy to prevent (or at least minimize/cure the knocking).
Do we have any choices?

gerry gill

this doesn't make sense..

install a boiler, install a vaporstat, run very low pressure, replace any air vents, perhaps valves and traps..you should then be set..what kind of system do you have? any identifing names, like mouat, broomell, veco etc.? and you say originally oil,,are you sure it wasn't coal? i can help you out more if it was coal fired..

Steamhead

Good chance that

> We have a two pipe steam vacuum (vacu-stat?)

> system in our home that was built in 1937. It

> was originally an oil system but was converted to

> gas at least 25 years ago. We had a carbon

> monoxide leak and have to replace the boiler

> (Peerless?) which is 240K BTU. We have been told

> that current boilers are fast firing and pressure

> while our system is based on a slow firing

> gravity (not pressure)system, and that the

> replacement boiler will almost invariably lead to

> knocking in the convectors. Our convectors are

> all built-in and would require major construction

> to gain access to them. Our plumber is

> recommending a Burnham boiler replacement. He

> says that there is nothing available today that

> would replicate the slow firing vacuum gravity

> system. If so, is there anything we should buy

> to prevent (or at least minimize/cure the

> knocking). Do we have any choices?





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Steamhead

Good chance that's a Trane Vapor system

They made a lot of this type of system. I've seen them with traps (round things with hexagonal caps) on the convector returns and also with orifices on the convector inlets. Dunham and Webster made similar ones.

Either way, the new boiler should be run at less than 1 pound using a Vaporstat. A properly sized, properly piped modern boiler will work fine.

Have you located any manufacturer's names on the convectors, valves, traps or any hardware in the piping near the boiler? This would help us identify your system. Also post some pics here if you can.

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914ml

Now that you mention coal, I do remember one of the engineers telling me that it was coal fired and then converted to oil and finally to gas.
As to brands, I went back and looked for all the markings and labels I could find:
On one of the two large pipes coming from the top of the boiler, there is a large vertical wide chamber that has the name No. 210 TRANE
DIRECT TETURN TRAP
PAT'D JAN 3 1918 embossed on it
with #405 on the other side.

The Gauge on the front of the boiler says
RETARD INTERNAL SYPHON GAUGE
with numbers going from 0 to 30. VAC. on the left side
and PRESS. on the right side of the face.

On the outside of the right side of the boiler there is a gas meter going into the boiler that has
PITTSBURGH EQUITABLE METER CO.
APPLIANCE REGULATOR
SIZE 103-12 embossed on the top.

On the back of the boiler there are several items that I have identified:

A round cover that has a vertical pipe with both ends rounded to the side of the boiler. On the pipe
TACO 647 is embossed.

There is a small box with a Honeywell label that contains two wires and a mercury switch. On the side of the box are two slide adjustments: One labelled CUT IN POINT in LBS and KG/cm 2.
The second labelled DIFFERENTIAL also in LBS and KG/cm 2.

There is a MINNEAPOLIS HONEYWELL REGULATOR CO.
IMMERSION TYPE L165A1X1
AQUASTAT
SERIES 10 CONTROLS

There is a MCDONNEL NO. 369
LOW WATER CUT OFF

The gas burner is a GORDON BYDAND
on the side the label says
ROBERTS GORDON APPLIANCE CO.
BURNER NO. 84X (OR 34X)
SERIAL NUMBER 57917
20"
MAX BTU 210 PER HOUR.
Inside the burner cover is a
HONEYWELL ELECTRIC GAS VALVE
V 155
MAX PRESSURE 8 OZ

I could not find any writing on the vents at the convectors.
I hope this information is helpful to you.

914ml

Conference: HeatingHelp.com's The Wall
Forum: The Wall (for Q&A)
Topic: Old Vacuum (vacu-stat?) two pipe steam system. New Boiler

Date: November 02, 2004 12:59 PM
Author: 914ml (mjl8@columbia.edu)

Now that you mention coal, I do remember one of the engineers telling me that it was coal fired and then converted to oil and finally to gas. As to brands, I went back and looked for all the markings and labels I could find: On one of the two large pipes coming from the top of the boiler, there is a large vertical wide chamber that has the name No. 210 TRANE DIRECT TETURN TRAP PAT'D JAN 3 1918 embossed on it with #405 on the other side.

The Gauge on the front of the boiler says RETARD INTERNAL SYPHON GAUGE with numbers going from 0 to 30. VAC. on the left side and PRESS. on the right side of the face.

On the outside of the right side of the boiler there is a gas meter going into the boiler that has PITTSBURGH EQUITABLE METER CO. APPLIANCE REGULATOR SIZE 103-12 embossed on the top.

On the back of the boiler there are several items that I have identified:

A round cover that has a vertical pipe with both ends rounded to the side of the boiler. On the pipe TACO 647 is embossed.

There is a small box with a Honeywell label that contains two wires and a mercury switch. On the side of the box are two slide adjustments: One labelled CUT IN POINT in LBS and KG/cm 2. The second labelled DIFFERENTIAL also in LBS and KG/cm 2.

There is a MINNEAPOLIS HONEYWELL REGULATOR CO. IMMERSION TYPE L165A1X1 AQUASTAT SERIES 10 CONTROLS

There is a MCDONNEL NO. 369 LOW WATER CUT OFF

The gas burner is a GORDON BYDAND on the side the label says ROBERTS GORDON APPLIANCE CO. BURNER NO. 84X (OR 34X) SERIAL NUMBER 57917 20" MAX BTU 210 PER HOUR. Inside the burner cover is a HONEYWELL ELECTRIC GAS VALVE V 155 MAX PRESSURE 8 OZ

I could not find any writing on the traps at the convectors.
What make or model VAPORSTAT should I look for and will it work with a Burnham boiler?
I will try to post some pictures tomorrow or the next day.


I hope this information is helpful to you.

Thank you very much.

gerry gill

steamhead nailed it-

thats a trane vapor sytem..get rid of the pressure switch and install a vaporstat at just a few ounces..

Steamhead

Trane Vapor System

You are one lucky guy. The Trane Vapor system was one of the best.

This type of system is covered in chapter 15 of "The Lost Art of Steam Heating", available on the Books and More page of this site. Look under the heading "The Boiler Return Trap (and the Alternating Receiver)". The system they illustrate in detail is a Dunham, but your Trane works in the same basic way. The main difference is that Trane used standard air vents on the dry (overhead) returns instead of a Float Trap/Air Eliminator, and they didn't always vent the steam mains thru standard radiator traps. Don't confuse this with the earlier Trane system elsewhere in the chapter.

If your system has no way of venting air from the steam mains except thru the radiators, you will need to add main vents. These are sized by measuring the length and diameter of each main and calculating the amount of air therein.

The Taco is a tankless water heater that was used to heat your faucet water. If it is still in service I'd suggest switching to a tank-type indirect heater that gets its heat from the hot boiler water. The Aquastat maintained a minimum boiler water temperature so the Taco would work.

The small Honeywell box with the mercury switch is the Pressuretrol. The Vaporstat you want on the new boiler is also made by Honeywell, and cannot be set higher than 1 pound.

If this is the typical Trane setup, you may only find something like "B1" on the sides of the trap bodies. Trane cast their name into the top cap, around the hexagonal "nut" that you can put a wrench on. These traps should not pass any steam into the dry return, but should pass air and water. If the dry return gets steam-hot, follow the heat back to the leaky trap.

I've worked on a bunch of these systems, and when properly maintained thay're hard to beat.

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914ml

traps

I looked at the traps and did find B1 embossed on them. Would we have to change all the traps when we change the boiler?
If we have to change the traps, are these Trane traps still available or are there replacement parts or will we have to look for different companies? What do you suggest. As I said originally, almost all of the convectors are built in and would be hard to access without breaking walls.
If the traps seemed to work fine with the old boiler, should we expect them to continue working well with the new boiler, or would we have to expect changing all of them?

Steamhead

You might have to replace the insides of the traps

but that's pretty easy, and you don't have to remove them from the convectors. Both Tunstall (www.tunstall-inc.com) and Barnes & Jones (www.barnesandjones.com) make replacement Capsule or Cage units for your traps, and both sites have online catalogs. Your contractor should be able to get these parts thru his supplier.

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