grundfos pump body material

archibald tuttle

got a grundfos UP26-99BF in a heatmaker 9600 HWG that needs a new pump. it needs the pump body as well as cartridge. i'm trying to figure out if I can just buy UP26-99F and use the pump on the bronze body. i'm guessing the pump housing on the one I have is aluminum. i don't know if that's standard and how much it matters. cause the UP26-99F is, of course, half the price of the BF and i don't want to go through the grief of pulling the flange body out of those tight quarters anyway. anyone who has any knowledge of the pump material and compatibility between the F and BF of this model, would appreciate them sharing.

brian

RobG

I'm confused, do you need to replace the cartridge or the entire pump? The F is for a closed system and the BF is for an open system. The body dimensions are the same and the cartridges are the same.

hot_rod

The BF is a bronze body circulator. Yes the motor and rotor assembly from a iron body should fit into the volute.

It may be painted silver? I've never seen aluminum, although most newer DHW circ pumps are now a forged or cast stainless steel, maybe it has been swapped recently?

archibald tuttle

hot rod,
thanks for that fancy word to help me clear up the confusion i left for RobG. So I need the whole motor and rotor assembly but i don't want to replace the volute. I know that means i need to buy a whole new pump and then throw away the volute but just wanted to make sure the (unless anybody needs one . . . as to the aluminum, i'm talking about the outer material of the motor rotor assembly, not the volute. (in case that was also confusing.) but magnets don't stick to the outside housing of the motor but, although it is painted bronze color paint, you can quite clearly see where it is machined that it is not bronze. so i'm guessing aluminum. just didn't know if that was the standard material for motor shell.

there is modest dielectric separation between the housing and volute with the rubber gasket although the four cap screws obviously cross between the two pieces. although this is a DHW model, it is in heating service. This is a four story building that always liked to air up on the fourth floor and the higher pressure ratings means we can run the system at 30 psi with a 45 psi blow off (i think its actually rated to 120 but the indirect hot water tank is limited to 45 on its boiler water side. anyway, never get any fan coils aired up any more.

thanks,

brian

hot_rod

Yes, the motor housing is aluminum no doubt. If this is a closed system there is no need for a bronze pump? There is probably plenty of other steel in the system, piping, expansion tank, boiler?

Once a system is filled and purged the small amount of O2, remember air is mostly nitrogen, about 21% O2, in the system is "consumed" as it oxidizes any metal it contacts. Once this is completed corrosion from O2 cannot exist.

Now it is possible air is getting into the system via float type air vents if you have certain conditions, like pumping towards the expansion tank.

archibald tuttle

there is an imperfect crossover with the chiller that introduces air every year. and there are ghost leaks that are never enough to see water anywhere but there is make up. still nothing like an 'open' system.

as i said, we didn't get bronze pump models for the corrosion issue, although the flow switches on the heatmakers are chocked right up after 15 years (admittedly small passages). we got the bronze pump models because they are rated to run at higher pressure.

of course, assuming relatively little water exchange and the new microbubble venting technologies, this should have reduced airlocks high in the system, but the chiller has a length of pipe that doesn't purge well and reintroduces air into the system every year as well and past experience drove me nuts trying to keep circulation in parallel piped units on uppermost floor.

there is no steel or cast iron in the system (maybe that explains why the brass and copper bits of the airflow switch appear to have been the sacrificial spots). so i just favor the higher pressure. i just never have any airlock issues up on the top floor of this four story adventure running the system at 30 that we used to get running it at 15 (admittedly with an old style air scoop and open rotor pump).

so the bronze volute is in place and not only wouldn't i want to go through the trouble of getting it out of there, but the heatmaker volutes are tapped for 1/16" pipe (who knew there was such a thing) and so i'd have to machine a new volute unless i wanted to buy an OEM one another doubling in price . . .

so amperage is the only other mystery. i though looking at the old pump it said 1.06 or somthing but the 115V UP26-99F is speced at 2.15. when i was trying to figure out what was going on i put an ammeter onto the old pump and it was drawing right around 1 amp. now, as it turns out, that was no load because the impeller had come loose from the shaft, so if the 2.15 is locked rotor, maybe the 1 amp i got is completely unlocked rotor, so to speak.

i gotta look at the fine print on the old pump again. maybe it had figures for both the 240 and 120 V configuration and I didn't notice that when thinking that the nameplate amps were 1.06 or thereabouts (which corresponds to the 240V version).

RobG

Why not just buy a new cartridge and leave the body/volute in place?

archibald tuttle

because the body is damaged rust from leak. but the volute is fine. if you read the fine print on the cartridge replacements they give you the conditions where new cartridge alone is not appropriate. and they don't sell the intermediate stage, which would be the entire motor but not the volute . . .

Dave H_2

The manufacturing of the cartridge is different from one model to the next. If one is designed for an open system and the other for a closed system, yes they will all fit and seem interchangeable.
However, I do know here at Taco, that a cartridge for a bronze circ is different than one for a cast iron. We place a stainless steel sleeve over the cartridge to eliminate corrosion to the cartridge in an open system.
Not sure about the manufacture of the UP circs, though.

Also, microbubble eliminators only eliminate air bubbles from the system, however, they do not remove the entrained oxygen in the system which will continue to create rust and havoc on a system.

Dave H.

archibald tuttle

dave,

grundfos, it seems, only offers a single cartridge replacement for this line. i believe the sleeve is stainless steel. maybe hot rod can come back online here and say . .

agree with you about oxygen and the long run. any system i'm going to own or maintain i put in stainless or bronze these days. that said, if they are 007 style standards, i keep cast iron around and just consider them throwaway after a decade.

that said, more trouble in most systems with modest corrosion but failure to exercise. we need more pump exercise software built in to relays (and antifreeze software overriding nighttime setbacks to circulate at regular intervals when the temp is below a user settable threshold).

on the corrosion side, i opened up a system that was well vented and indirect separated from the boiler circuit with maybe 120 max water, but is not entirely barrier tubing on the radiant loops (half the tubing is from the poylbeautiful days . . . so there is going to be more oxygen than in a closed copper system or barrier pex system, and the cast iron pump was the most sacrificial element in the whole system because there wasn't one other piece of steel or cast iron.. just put in a new one after 7 years, its just chock full of corrosion. can't really complain about that . . . just sayin . . .