Reverse Flow

Tom_133

As many of you know Vermont took on some water this summer. So been doing a lot of flood repairs. The last one I need to deal with is an older oil fired HB smith. It's a 2 zone radiator, with mono flow loops. I went to get a parts list together and noticed the boiler is piped backwards. The return goes in the top. I talked to the installer cause I bumped into him by chance. He said thats how that company has installed them for the last 25 years, because it fixed all air problems putting the circs on the return pushing toward the system and away from the boiler. I agreed I saw the logic in that but asked if he felt it hurt the efficiency and he said, No. My question to all of you is do you think this hurts the efficiency ? Also, I am moving the new boiler 10' higher to the first floor, and its going to be a mod con, with a HEAVY outdoor reset, since the radiators are huge, and double the size needed! Should save some money.

Intplm.

Well..... it's probably piped that way because it was shipped that way from the manufacturer. (Circulator on the return.) Am I understanding you correctly? Or is it piped as explained in the next paragraph?

The best way to pipe a hot water boiler is to pump away from the expansion tank. That means having the circulator on the feed side and not the return side of the boiler, and again, away from the expansion tank.
This is the point of no pressure change I believe that is what I learned from the Author and creator of this sight many years ago @DanHolohan.

You should read his books. They are entertaining and offer a lot of common sense practical knowledge that will help to make the best of your business. And make your life a whole lot better too. No B.S. !

@Tom_133 Why are you installing the mod cons 10' high? And why mod cons? Is this part of Vermont prone to flooding? I thought that this was a rare act of nature. I'm in New England and have some friends that helped out there.

hot_rod

It depends somewhat on the boiler. With high pressure drop style, the coil Sermeta type boilers they like to see the pump on the return, pumping into the boiler.

I'm not sure I see the logic in flowing backwards through a cast boiler? Pumping into the top? If that is what you are describing.

Tom_133

What I am describing is the returns are pumping back into the top of the boiler, and the supply comes out of the bottom of the boiler. Backwards from with the manufacturer label supply and return.   Pumps are placed on the manufacturers return but pumping to the system, NOT the boiler.  

hot_rod

I recall this on other posts over the years. I suppose the boiler transfers hear in either direction. The boiler designers may have a reason for cold in the bottom, hot out the top. Certainly easier to trap and catch air at the top, where air vents are often screwed into the block.

We have also seen flow through cast radiators backwards over the years here on HH

All I know is water knows to follows the arrows on whatever the product

retiredguy

I only ever saw one large school with 3- H B Smith 650 boilers piped this way. I can not remember the school district that these boilers were in but it was piped that way because the heating engineer specified that in the drawings. Buy the way it worked great and heated well.

EBEBRATT-Ed

@retiredguy

Did you ever see a Smith 450 or 650 piped with the return water coming in to one of the bottom headers and the supply coming out of the bottom header on the opposite side? Top header not used for piping. I seem to recall a few of those