maintenance of a Hot Water recirc system tyhat was once a steam system

Koan

A friend has a steam system converted to hot water.

Their system:
circa 1910 with American Radiator radiators. Main feed is 3" supply! furnace is a gas fired Balderus with 1&1/2 inch copper for the first 10 feet going into a 25' long steel 3" main. 3" section is insulated (asbestos), but initial copper is not - is in a basement, was clearly originally a steam system. 2 floors of radiators, a couple rads on second floor do not get hot all the way.

They have lived there for 4 yrs, never bled radiators. I assume that is the first task.
Does the 1& 1/2" diam copper going to a 3" main pose an issue?? - hopefully not.
I would think not insulating the first several feet would be more of a concern.

I am more familiar with steam than circulating hot water. As they have done absolutely NO maintenance what should be the first order of business in maintaining the system?

I know one does not blow down and refill a hot water circulating system, are there any kind of anode rods?
at this point all I can suggest is to bleed the top rads first when the pump is running and insulate the furnace output pipes.

Does one ever drain and refill this type of system or is it best not to ??

What should the temp and pressure gauge read?? (up to what amount)
I can get some pics later.

Grateful for the input, I just want to point them in the right direction.

Jamie Hall

One does not drain and refill hot water systems.

If there are radiators which are not heating properly, they may need to be bled -- otherwise, no need.

Temperature -- whatever is necessary to heat the structure. 180 is about the max. You don't say what kind of boiler; if it is the condensing variety, you can go quite low on the returns. Otherwise, stay above 140 to 160 to prevent condensation in the boiler.

Pressure -- two stories? 15 feet above the boiler? 12 psi will probably work. 15 psi is ample. Check the expansion tank -- the pressure shouldn't vary more than a pound or two between hot and cold.

Steamhead

If bleeding doesn't cure it, the problem may be return piping that was fine for steam but totally inadequate for hot-water.

Look at the Hoffman system in your own house and note how much smaller the return lines are. On a Vapor system they don't have to be so big, since the steam shrinks 1700 times when it condenses back to water. But on hot-water, you need the same flow capability in the returns as you do in the supply mains. On Vapor systems, the supply mains can carry enough water but the returns often can't.

This is one of many reasons we don't convert these systems.

Koan

@Jamie Hall @Steamhead
You guys are tops!!! Thanks so much.
FYI --- Not a condensing boiler.

Koan

@Jamie Hall
Just want to make sure I understand, you explained 140-160 for a non con boiler. Is that the temperature of the return water going back into the boiler measured at the inlet?

Thanks

Jamie Hall

the return water. Don't go below that for a non-condensing boiler. (Except, obviously, for the brief startup times!)

Koan

Thanks!!!