pumps

siggy

Steve,

Are the circulators installed in vertical piping with the integral check valves at the top? If so the problem may be an air pocket trapped under the check valve, and extending down into the volute. Bushings eventually run dry and the circulator ceases. Be sure there's a good microbubble air separator upstream of circulators, and that all circuit are well purged. I like to see these circulators mounted horizontally or with the check valve down to prevent the possibility of a large trapped air pocket.

siggy

Steve Minnich_3

losing pumps and baffled.....

Two years ago I installed a radiant heating system in a very large home, about 12,000 square feet.

It's fairly straight forward with two Buderus GB142's and a Triangle Tube indirect. There are seven circulators with 16 zones------client insisted on that many.

On the garage zone I've lost 4 pumps. No other pumps have failed. I used Grundfos 15-58FC pumps on this job and have always had a good track record with them.

Here's what I know...the voltage and amperage have been consistently on target. The zone does not have any leaks and as far as I can tell, none of the loops or the supply and return home runs aren't restricted in any way. The pump has not been airbound and the flow check doesn't seem to be sticking.

So I tested the ph balance of the water when I drained that particular zone. I used a basic swimming pool tester and it was above 10. Way too high right??? But could that possibly be the source of the pump failure?? If yes, why aren't the other pumps failing?? The only thing that makes it any different is that it is the garage zone and runs much more than the others. They're keeping the Audis nice and toasty.

Am I on the right track?? I'm having a little trouble nailing this one down. It should be easy but has proven to be anything but.

Any help or input would be greatly appreciated. Thanks.

jp_2

not telling us

what actually fails on the pump? rotor freezes? impeller poops out? leaks? burns out?

Steve Minnich_3

Bearings screaching like there's no tomorrow..........

Brad White_185

Stray

iron or minerals in the system? Treatment chemicals coming out of solution?

Have you done an autopsy on a removed circulator?

Weezbo

i have seen this with air being taken on somewhere within the

system...

that usually indicates a leak somewhere...

thermostatic three way proportional valves sometimes go defunct why who knows ...however if you have a few you might simply go around to each and open them with a supply call and dial them down beyond where they were set and open again to see if they might be be the source of contention emanating from the circulators...

just a thought...

Steve Minnich_3

No I haven't. Forensic investigation...I like it! What should I look/test for??

Brad White_185

Remove the

volute casting from the rotor/stator housing. Four screws usually, sealed by an o-ring.

The rotor should come out and any debris within it would be evident. A good magnet will weed out the ferrous particles, if any. May be a solder bead, Jimmy Hoffa's nose hair, anything.

Grundfos had an issue many years ago with their 15-42F line where they would seize up from systems that were less than clean; I cannot be more definitive than that but others I am sure have far more experience than I do. The Super Brute was, I believe in part, a response to the issue.

Now, I am not saying that this is another spate of that same issue, just that it rings familiar. I use and specify a lot of 15-58's and have not had a problem.

Steve Minnich_3

Thanks Brad......I know, the 15-58's have been very reliable for me too. I'm trying to think way outside the box here because it doesn't seem to be something obvious.

Steve Minnich_3

Yes and yes. No pumps w/IFC in vertical position?? I never would have thought of that. I see it all the time and do it all the time. There is a 2" Spirovent in the supply piping right after the boilers with the circ's pumping away. I have a feeling it may be gunked up. I'll check that when I return Monday. Can that be pulled aparrt and cleaned?? I've never had to do that in the past.

Thanks for the help.

hot_rod

This seems to be a new issue

with IFC circs. Makes me wonder if a small pin hole in the check would prevent the air lock in the volute?

hot rod