Cost of Insulating Steam Pipes worth it?

SunRad

I have a 3 unit rental property with a huge, grossly oversized Weil-Mclain LGB-6 steam boiler. The house was built in the 1920s with two pipe steam. There are two steam mains running eeeeealong the basement with only about 20% covered with asbestos pipe insulation. I'm not looking to touch that part but I've been wondering if the cost of purchasing pipe insulation for the rest of the exposed pipe would be worth the cost. To cover the two mains (without fittings) I would need 42 ft for 3 inch pipe and 70 ft. for 2 1/2 inch pipe. Plus 4 ft. of 4 inch pipe for near boiler pipes. Based on the prices on I see, it would cost about $700 to purchase all this insulation in 1" fiberglass. (Some sites charge more and have free shipping, some charge less but have insane shipping costs.)

The goal of insulating the pipes would be efficiency (reducing my fuel costs) and perhaps it would help with the water hammer I hear when the system turns on before all the water gets pushed out of the steam mains into the return. At such a high cost, it doesn't seem to be worth the investment but I'd like to hear other peoples opinions.

Here's a pic of the boiler and near-boiler piping.

This is where one of the mains end. The steam main is the larger pipe below and the pipe to the left is the dry return. No F&T trap in this system.

Below is zoomed out from above picture. You can see the steam main ends and connects to the dry return from above (pictured above) and also ties in to the wet return below.

The is the end of the other steam main (the longer one). This one is in 3 inch for the first 40 ft then is reduced to 2 1/2 for the next 35 ft. It runs through this wall hung radiator and connects to the wet return by means of the radiator. It does not appear to tie to to the dry directly.

Pressuretrol:

I added the Gorton #2. Originally the system only has the Gorton #1. This being a two pipe system, I believe this is only means of air removal from the system.

EdTheHeaterMan

Since it is grossly oversized then insulating your pipes will make the short cycling more of a problem. You are already overpaying for the heat you need, what is a little extra insulation going to do for you?

After you come to replacing that boiler, years from now, with the proper size boiler, then I would look into insulating the pipes then.

Just an opinion, not based on facts.

Jamie Hall

In terms of return on investment, I would have to say it's a tossup. However, there are other benefits to insulating the mains — and efficiency is probably the least of them. The most important is that insulating the mains increases — sometimes substantially — the speed with which steam reaches the length of the main from a cold start. The means that it is much easier to get a good balance for the heating in various parts of the building, and it also means that the total run time of the boiler will be less. How much less? Hard to quantify.

There is also the benefit of reducing heat loss from the mains, of course. Whether that is a plus or an actual disadvantage depends on what, if anything, the basement is used for and how well it is connected to the rest of the structure. I warn you that there is a rather lively debate on this aspect…

In my opinion, insulating the mains is worth the cost — but some of the benefit will not be apparent to strict bean counting.

In another topic. The crossover trap and rip which you note are essential to correct operation of the system. Assuming that the crossover trap is working, the sole main vent at the boiler is ample. The other main which goes to the large radiator (sometimes referred to in old literature as a condensor), and it was thought to help speed up steam flow to the end of the main) should also have a crossover trap. It would worth figuring out where it might have been, and replacing it. Without it air removal from that main will be dependent on venting through the radiators. This is adequate, but slower than it might otherwise be — and limits the extent to which you can throttle radiators on that main, should you wish to do so.

I wouldn't be at all surprised to discover that this system was intended to operate on less than 1 psig, possibly as little as 8 ounces gauge. Depending on the radiator fittings (inlet and outlet) it is quite likely that it will operate more evenly and more efficiently if the pressure is limited to 8 ounces gauge.

The system should not water hammer at all. Water hammer is very rarely to be expected, but is almost always related in older structures to sections of main or runouts which have inadequate — or even reverse — pitch. It would be worth investigating and checking the full length of all the mains and runouts to ensure that they are, in fact, still pitched properly. Pay attention to sags.

And to this before you insulate!

SunRad

Thanks @Jamie Hall for your response. Great point about the reasons for insulating. In this case, the basement is used primarily for storage although one tenant does their laundry there. However as you can see there is no insulation in the ceiling between the basement and the first floor.

Regarding the crossover trap, are you saying the current crossover trap is sufficient (on the main that has one) or do you recommend getting a crossover trap that has a means of venting air? I was under the impression the current trap in place only prevents steam from passing but does not have a means of venting air.

I'm not sure if water hammer is the correct term but as the system fires up from a cold start (and maybe even not such a cold start) I can hear the water in the pipes whishing around and being pushed to the end of the main accompanied by some banging. Since the main is so long and the sags appears to be in a few areas, I can't imagine how it can be fixed without replacing a large portion of the pipe?

109A_5

Kind of makes me wonder if this trap was placed over the dry return it would work better, usually the steam comes into the capsule side port not the valve port.

Insulation is a one time cost. Fuel is every month. At the time of a new boiler is the insulation going to be less expensive ? Do you need the heat in the basement ?

Larry Weingarten

Hi, A question for All… Is there any way to downfire the boiler? Remove part of the burner or ??

Yours, Larry

Jamie Hall

A crossover trap does vent air. In fact, that's what it's there for. The air goes into the dry return. There is no need for any other vent there — assuming, of course, that the dry return is vented. In fact, in most vapour systems there must NOT be a vent there!

That particular trap is plumbed oddly. In fact, backwards. It should, however, still work — though it will be much more prone to damage from excess pressure.

On the water hammer. I doubt that you will have to replace any pipes, unless you have a section which is completely bananaed. You'd be surprised how flexible a long section of iron pipe really is — so measure from one end to the other of a while length and make sure that the end to end slope is adequate — then set up a good laser level or something like that and go from hanger to hanger pulling the pipe up into alignment. Add hangers as needed.

SunRad

@109A_5 I don't really need heat in the basement, as long as it stays above 55° or so.

@Larry Weingarten I didn't know down firing was even an option. Perhaps a professional can chime in if it actually is. The house has 3 floors with 5,500 sq ft. Insulation is probably poor since it was build in the 1920's. I was told by the plumber that installed this boiler (prior to my ownership) that he went with this size because the 3rd floor didn't get warm on the older boiler.

@Jamie Hall Thanks for the clarification on the venting. This system does have vents on the dry return as pictured above. I will try to find a local stream contractor that can help with adjusting the mains. If anyone has any leads I would appreciate it. The house is in NEPA, specifically Luzerne county.