50s Boiler Pump Advice

bhaves · 6:15PM

I have an old gas boiler "National - U.S. Radiator" with a rated output of 126,000 BTU/HR. I believe it is in a Monoflow loop configuration. From what I can tell the boiler dates back to the 50s, but still works fine. When I moved into the house it had a Bell and Gossett 100 series pump on the return line, I am not sure if the pump is original or not.

It worked fine for 2 heating seasons before I noticed a water leak which appeared to be around the pump/bearing shaft despite oiling before each season. Since the leak started during the heating season I did a quick fix and bought a box store Taco 007 and ran that for the season.

This season I tried to restore the old pump with a new bearing assembly and coupler from B&G and oiled it with the included oil per directions. It has run for about a week, but now every time the boiler fires the coupler section makes a loud rattling for 5-10 seconds before smoothing out to quiet operation. Another coupler has the same issue.

I am not sure if maybe the new assembly is bad or if the motor is also going or mounts. I am wondering if it is better at this point to replace it with a newer style wet rotor pump since disassembly again would mean fully draining the system (no isolation valves). The Taco 007 got us through, but I am not sure if it has enough flow long term. Can anyone advise if the Taco 007 would be suitable for a replacement or should I be looking at something else? Taco 0010 or Grundofos UPS15-58, etc.

System Info:

National - U.S. Radiator : 126,000 BTU/HR output Boiler
12 Cast Iron Baseboards
80FT single copper loop around basement (Monoflow)
B&G 100 pump

Jamie Hall · 6:18PM

Before you go off the deep end here, check the alognment of the motor and the pump shafters. A coupling is not designed or intended to make up for any misalignmnet — angular or off to one side etc. — and a misaligned assembly — even a little bit — can not onlly make a racket but damage things.

bhaves · 6:22PM

Thanks Jamie, There isn't too much play where the motor meets the housing when the 4 bolts are slightly loose. Any tips to get perfect alignment? It's in a tight spot between the boiler and chimney.

Grallert · 7:42PM

With those pumps there's not anything you can do about the alignment. So if the shaft on either end is out you will go through couplings assemblies and pump seals. You are better off using a modern pump. They use less electricity as well as being less expensive than any single part on those B&Gs

bhaves · 10:15PM

Thanks Grallert. I was able to find a local supply shop that had the motor mounts in stock and replaced them along with adjusting the mounting bolts every possible direction I could think of, but still the same behavior 5-10 seconds of rattle before smoothing out.

I think at this point I'm done sinking money into this old pump, but I'll run it for now to stay warm.

Are there any new replacements that would be similar to the B&G? I started looking at pump curves / flow charts, but I still don't know what I would need. Old posts here for similar swaps say the Taco 0010 is almost a direct replacement while looking at the chart, others say the B&G is oversized and a 007 should work. No preference to Taco, it just seems popular

If any more info is needed about the system, let me know

Grallert · 10:31PM

A 007 will very likely work just fine and will fit in the original flanges. Also very common. Grundfos Alfa is another and my personal favorite.

hot_rod · 10:32PM

You need about 12 gpm to move the full output if that boiler

If you need 126,000 Btu the 007 may be a bit small

While the 0010 might be closer match they are $$

I would go with an ECM before the 0010 for about the same money

The Grundfos Alpha 26-99 covers a wide range of gpm and head

50s Boiler Pump Advice

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