Insulate return lines or not?

chuck_6

I've heard mixed messages on this subject, but should return lines be insulated or not? We have two return lines, one that goes through a crawl space that is not insulated. The second return line starts in our garage, and goes through a semi-finished basement area back to the steam boiler. The return in the garage is insulated, but not in the basement. Does the insulation cause a slow return of water back to the steam boiler or clog up the returns?

Brad White1

Insulate the returns

I would insulate the return lines in the crawlspaces and inaccessible areas for a couple of reasons: To control the heat lost to unoccupied spaces and to prevent or at least deter freezing should there be a hang-up on that particular leg. This last scenario is not too likely, but still I would insulate. Where controversy has crept in is at the near-boiler piping. I always specify the insulation on the steam side of course (above the waterline) but not below, to promote a final flourish of condensing. I have seen jobs insulated fully without a problem, but and old timer (now Dead Man) gave me the bare return story. If personnel may have contact, yes, insulate for burn protection.

Another part (not knowing your background) is not to use foam but to use moulded fiberglass on steam lines. Check your local energy code. Forget that 1/2" stuff from Home Depot.

For 2" iron pipe here in Mass. the code says for temperatures from 201-250F (low pressure steam is in this of course), the insulation should be 2" thickness, and for lesser pipe sizes, 1.5" thickness. Only below 200F can this drop to 1" so perhaps condensate (return) would fall into this category.

Constantin

I would insulate but only if its safe

I second Brad's recommendation to insulate everything with the appropriate insulation materials. Ideally your piping will not lose heat on its way to the rooms in need, this will maximize the responsiveness of your system. If the crawlspace is not insulated well, then I'd take a look over at the Building Science Corporation web site for more info that is appropriate to your specific climate. Their climate-oriented line of builders books is neat also.

The only good reason I can think of why the return lines in the basement are not covered is to ensure that they are meant to lose a certain amount of heat to keep the place warm. Are any water pipes down there and if so, how cold does it get on a design day down there?

And now for an amusing yet sad example of how experience is what you get, when you didn't get what you wanted: Relatives of mine had some returns running underneath the ceiling in a glass-roofed solarium. During the energy crisis they decided to save some energy by insulating said exposed pipes, which was followed by a terrific crash during the next snow-storm. With the passive snow-melt system insulated out of commission, the roof had caved in, ruining the solarium.

DanHolohan

Insulate

The cooler the condensate gets the more it's liable to absorb carbon dioxide and go acidic on you. The low pH of the condensate eats the return lines. Keep the condensate as hot as possible and the returns last longer.