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Laars JVS50 with a 26-96 pump

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Matt_67
Matt_67 Member Posts: 287
I came across a laars JVS 50 boiler with a Grundfos UP 26-96 pump on it. It's a single zone system with about 100 ft of 3/4" pipe on it and fin tube baseboard. It's been this way since installation 15 years ago. Any ideas why such an oversized pump may have been used?

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  • hot_rod
    hot_rod Member Posts: 22,157
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    Laars did suggest a high head circ with long loops or small diameter loops. That circ sounds a bit large from what you are describing.


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kcopp
    kcopp Member Posts: 4,432
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    Teledyne laars was one of the first boiler mfg to really push primary secondary piping. If the installer tried to just use a 007 to do all that and the boiler it probably would hammer like mad due to poor flow.
  • hot_rod
    hot_rod Member Posts: 22,157
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    Exactly, high head circs were often swapped in after the installer realized the typical low head circus just didn't cut it.

    Over pumped in some cases no doubt, but the lesser of two problems. Also as those tube type HX start to get some build up, the high head circs would assure you didn't get the dreaded copper tube moan, percolation, hammering, and high limit tripping. That velocity increase would scour the tubes :)

    When you called tech support for some of the copper tube boilers back in the 90s the reply was often "It's not our fault, and you need a bigger pump" Probably spot on advise in many cases.

    If only low loss headers had been around in those early copper tube days. Properly piped, copper tube boilers are excellent heat transfer boilers, copper is a much better thermal conductor compared to stainless or aluminum. Some brands had two stage or modulating gas valves and would run fairly smoothly on zoned systems.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Matt_67
    Matt_67 Member Posts: 287
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    Just got finished fixing leaks in the crawl space and thawing frozen lines. Tried a 15-58 - had a 47 degree delta t. Ended up with a 26-99 on speed 2 with a 20 degree delta t. System is a mix of copper and pex with some pretty restrictive insert fittings. I'm still having trouble believing the .2 foot of head loss with a 4 gpm flow through the boiler. It looks like there have been some leaks in the past - maybe the heat exchanger has some scale? No popping or unusual noises at the boiler though.
  • hot_rod
    hot_rod Member Posts: 22,157
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    It's surprising when you start installing flow meters on pumped circuits, how the flow in not exactly what you expected.

    I've added Quicksetters to all my piping on the solar, and hydraulics to check flows.

    One that really surprised me was a 1" pex loop from a buffer to solar tank. It's only about a 50' run maybe 10 insert fittings.
    I expected the circ to me moving 10- 12 gpm, but on speed 3 only 5! Must be a lot more flow restriction to insert pex fittings that I expected. Sounds like you may have the same situation.

    Or else a flow restriction in the piping somewhere? Kinked pex perhaps? Again, I would have guessed a 15-58 on speed 3 would provide enough fizz.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Matt_67
    Matt_67 Member Posts: 287
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    I didn't see anything on the piping that looked suspect but there were a couple of virtually inaccessable areas so I guess it's possible. I was surprised at how restrictive the pex fittings were - it's relatively early ( for USA ) late 80's stuff. Seems to be in ok shape though. Some more research showed the boiler is actually 17 years old - I'd like to rework it with primary/secondary but it doesn't make sense at his point in the boilers life.