Big pipes

JerseyJon

I have what appears to be a former gravity hot water heating system in a 102-year-old house. It has big cast iron or steel supply lines that transition smaller as they run out to the last loops in the opposite corner of the basement. At some point it was retrofitted with a circulator so there's copper in and out of the boiler that connects to the big ol' pipes. The house and hydronics are both 2-years new to me. I'm trying to better understand the system before deciding what I can do to make it more efficient. I've heard and read different opinions about big gravity feed pipes. The only thing I'm certain of is that these suckers are giant heat emitters. My basement is toasty. I either need to insulate the pipes or replace them.
So far, the arguments for keeping them are: If it ain't broke don't fix it. And the idea that the boiler and circulator are sized for the existing pipes and it's unwise to change just one piece of a fairly balanced system. One guy compared the pipes to a flywheel on an engine that stores energy. The reserve of hot water prevents short cycles, he said.
The other argument is that heating the extra water and iron slows down the system so it takes longer for heat to reach the radiators on the floors above.
Should they stay or should they go?

JohnNY

You've got unnecessary mass in your system and you seem to know it. If I were you, and looking to save money not necessarily spend it, I'd insulate the heck out of those big pipes and address their diameter when you have to. Like if something should spring a leak, or when you go to change the boiler. You may never recoup the expense of having them changed on their own.

JStar

Or install a mod/con and let that mass work for you, not against you. High mass = high efficiency.

Jamie Hall

Step one: insulate those big pipes. Odds are that at some point they were insulated -- with asbestos. And someone got panicky and took the insulation off but didn't replace it. I'd suggest 1 inch fiberglass. It's easy to get, easy to apply, and effective. And not expensive.

Step two: Then when I had the money I'd follow Joe's advice and install a nice mod/con to go with the system.

Don't bother to mess with the pipe size until you absolutely have to -- such as, as JohnNY says, you find you have a leak.

icesailor

"" I either need to insulate the pipes or replace them. ""

You need to insulate the pipes first.

Understand your gravity system.

When it was total gravity, the wall thermostat started the burner, No matter what the outside temperature, the boiler water and the inside temperature reached a balance between the heat being lost to the outside and the heat slowly being added to the inside. Along came Mr. Pump. He could make the water go through faster than the house could loose heat. So the equilibrium was lost. You can get it back with controls.

Depending on what you are willing to do, you can have a slick system. But for every dollar you spend on insulation and weather stripping will be paid back to you in lower fuel bills, regardless of what you do to the heat system. Once you've done that, whatever you decide to do later will show. If you don't insulate, you may spend more on "improvements" and never get a ROI. You will with insulation. If you're handy, you can put up pipe insulation. "Any Fool Can Do It". as a good friend always said. He is right.

JerseyJon

Thanks. This is all helpful. I just feel like I need to better understand how the system works before I can make good decisions on how to make it work better.
It's interesting that the extra mass could help with efficiency if I go the mod con route. It means I probably need to wire brush and then paint them before I insulate.
I don't know if they ever had asbestos insulation. There are still some stretches wrapped in newspaper. I can see if there's a date to know if that was the original insulation.

Ironman

Unless the pipes are heavily rusted on the outside, I see no value in wire brushing and painting. Just simply insulate them and the condensation that forms in the summer when they're cool won't be an issue any more. If they're gonna rust out, it will be from the inside out.
As long as there are no leaks on the system and air is properly bled, they won't rust out from the inside.