impeller

Jim_5

What causes impeller on the new little pumps to just totally disenegrate, They just turn to dust. You can flake the material off. I've had 3 do it on different applications.

hr

What are you pumping?

type of pump, size of pump, temperature and quality of fluid, pressure on system?

Cavitation can cause a pump impeller to erode quickly, look for causes. Try this link for some good info on causes.

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,4270,00.html

hot rod

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Jim_5

impeller

Just water, one was in a lennox completeheat, another was a outside woodburner, and the other was just a regular hot water boiler.

hr

Bronze or

plastic? What brand of pump?

Outdoor non pressurized boilers are plagued by pump problems. Seems most manufactures ship them with high head pumps. These non pressurized wood boilers often don't have enough pressure to prevent the pumps from cavitating. Also they ten to get overheated from time to time. Too much fire with not enough load. Temperatures up to and at boiling combined with little or no NPSH is a big problem.

When you say Complete Heat is this the Polaris combined open system application where the domestic HW tank provides both potable and heating, via an air handler? Again this could be an oversized pump issue.

If these are bronze impellers I'd check the ph of the water being circulated in the boiler system.

Contact the pump manufacture for more info, but I suspect it is an application problem more so then faulty components.

In any pump application you need to calculate the gpm and the head, or resistence through the piping and components, to properly size a circulator. otherwise you are just guessing. This generally leads to oversizing and potentially the problems you indicate.

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Glenn Harrison_2

If it helps any,

I've had three Lennox Complete Junk (er, I mean Heat) units that had the Taco impeller break down. All of them were on city treated water. My other customers with Complete Junk (there I go again) units on private wells have never had an impeller problem. My thought, is chlorination of the city water causing a reaction with the impellers at high temps, and high head.

hr

Gosh that would

have to be a really high level of chlorine, maybe over dosed swimming pool levels??

Never messed with complete junks, don't they run @ 140°? I wouldn't guess 140° and usual city water chlorine levels would make the difference.

But seeing is believing... think I would switch pump brands just for a comparison. I think the Grundfos hi heads still have stainless steel impellers.

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Glenn Harrison_2

Hot Rod, I'm completely open to suggestions...

on this. My idea is just that, an idea.

The three problem units are all running 130 to 140 degrees, so maybe HOT water was a poor thought. Maybe more along the lines of hot constant fresh water through the pump. These are plastic impellers in bronze 006 pumps.

Can't change the pump either, special impeller housing, that would require a major amount of retrofit possibly outside the confines of the unit (everything neatly PACKED inside of unit now).

It's a mute point anyways, as Lennox has completely discontinued the Complete Heat program and is now replacing warranty tanks with a furnace and standard water heater or a boiler and storage tank if conditions are met.

John White

iMPELLERS GONE

I am not able to go in to the whole issue of disintegrating impellers right now, and I'm not really qualified to anyway. But I would encourage a phone call to Joe Matiello or Doug Bird at Taco. There has been a lot of work done over the years to understand the issue. Generally, it has to do with hard water conditions.
I believe that, in regards to one of the above comments, all wet rotor manufacturers are using composit impellers. Maybe I'm wrong, but don't assume what you read was 100% accurate. These polymers are prone to unusual problems with different waters. In fact, very seldom in the large scheme of things, but nontheless an annoyance if you are the one with the issue.
Again, call Joe or Doug at Taco(401-942-8000) for some further discussion.
John White jr.