Pump Reverse Rotation

Boilerpro_5

Yes, a pump will continue to pump with reverse rotation, but it is much less efficient and, I suspect, probably is not too good for the impeller.
Don't feel too bad, there is always something new which can be screwed up. It becomes a case of just how much do you check. If you try to check everything, you'll end of having to take everything apart and putting it back together. When walking into another contrator's mess, you never can tell whether they just don't know thier engineering (or the engineers didn't know) or they are just plain sloppy or both.
You can try your best with having lots of background and knowledge and you can still miss things.

Humans.....what can you do?!

Boilerpro


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Canuck_3

Reverse Pump Rotation

I'm curious to see if anyone has ever encountered this situation - and I need to vent!!

Some background: - We were called in to review the hydronic heating installation at a large commercial facility. To say the least, the installation was less than adequate (truthfully - it was a disaster). We provided a report, outlining deficiencies and items that the installing contractor was to correct. We returned to review the corrections and found that there were still a lot of deficiencies and that some of the remedial work had created more deficiencies; suffice to say that it was ugly. In the end, the owner and GC decided that we should correct the issues in the largest building, allowing the original contractor to make good on the smaller out-buildings; (of course our involvement was cutting into their bottom line, which was causing a lot of animosity). With work completed from our end, we had an inspection by the consulting engineers with no deficiencies indicated. The system was scheduled to be balanced, (by the original contractor), who indicated that they couldn't balance the system because the building pumps were operating in reverse rotation! I truly felt sick to my stomach when I was told of this. How could it be? The pumps are Armstrong 4380-2x2x8 operating on 240 VAC, single phase power. The building is configured in primary/secondary. Temperature/pressure in the system was always 'normal' for the layout, (returns were cooler than supply, suction pressure was less than discharge pressure, etc.)I went to the site that very evening to confirm the situation and found that the pumps were operating properly. When I made comment about this the next day, the original contractor stated that their balancing guy corrected the problem earlier the previous day. When I asked them how the system could have operated in this way - they answered that the pumps will push water when in reverse but efficiency is down by 30%.

I for one don't believe it, but I've never encountered this before. Lessen learned for an old dog like me though; I always check rotation on a three phase pump because it's easy to reverse, but rarely check rotation on single phase, especially if the unit is already in place and functioning. Not anymore - I never actually checked the pump because the system, although deficient, was operating - and now I can't offer my personal assurance of what the rotation actually was.

My question to you fellow Wallies: Has anyone ever heard of a pump that can develop head while rotating in reverse?

Ken_40

Since most

240VAC setups do NOT feature reversible rotation via "jumper" - but a very few do, the question you ask is: will a pump that has a reversing direction motor option, when run "backwards" run, and will it suck from the eye of the impellor, only at substantially reduced flow and push water out the supply end?

The answer I fear is yes. I do not recall the impellor design of that particular Armstrong, but if it's open vaned, yes it can pump in the correct direction when run backwards, perhaps at the 30% dimished flow meatball suggested.

If a closed vane impellor, the pitch would have to be very steep to allow normal flow, but I would not bet lunch he may be right on that score as well.

If you wanted to know for sure, switch the jumper setting and see for your self! Assuming it even has a switchable rotation option!

BAB

Watch Out Here

Did a project once where the new electrical contractor was determined to discredit the previous electrician. When rewiring the switch location for an exhaust fan he "discovered" the fan was rotating in the wrong direction. I & the previous electrician & the owner had just confirmed the fan's rotation a week or so before. Two of us were on the windy roof with cell phone until the rotation was correct. Incidently, the switch only operated the relay for the three phase. Regardless, he went on at length how he had corrected the rotation. It is a tough claim to dispute, espectially after the fact, ... he who wins is usually the biggest & loudest & shouts the lastest.

I have had experience with pumps & fans operating maginally when on the wrong rotation, ...3 phase, never sinle phase. Easy to check if the pump & rotation arrows are right there in front of you. But when trouble shooting, or starting up, a complex system it sometimes gets lost in the shuffle. You really have to count on your electrician. The jumper detail is interesting news to me.

Bromley

Dave Yates (GrandPAH)_2

web info

I just finished checking their web site and can't find any reference to the single-phase being switchable for rotation. If I were in your shoes, I'd call Armstrong and ask for something in writing. If it turns out the motor doesn't incorporate posts to change leads for direction, you'll have a 'got-cha'.

EBEBRATT-Ed

I have had too instances with a three phase Grundfoss pump and I still don't know what is going on.

This pump is a chilled water pump on a process machine(not that it matters).

I started the pump initially and after bumping it the rotation was wrong and we reversed it and the system operated ok.

While adding an additional pump to a second machine they claimed the first pump wasn't pumping. We assumed we got some air in the system (which we did) and started bleeding the first pump. It wouldn't bleed right so after several trys we shut it down and checked rotation and it was wrong. Thinking we must have screwed up we reversed rotation and started up and the system worked ok. It ran for 6 weeks with no problem.

Then we did some other work on the system adding an additional zone. Again they complained the first pump wasn't working. We checked rotation and it was wrong! We reversed it and all is well.

I color coded all the wiring and made a diagram so if this haoppens again I can see if someone is mesing with us.

At this point I just don't get it. Just have to wait and see. I have never had anything like this on 3 phase and nothing else coming from the same panel had to be reversed.
Hard to beleive but I suspest someone is messing with us.


ED

Weezbo

switch any two wires.

is an old rule And check rotation. that might seem trite so i go a little deeper...depending on the amount of leads from the motor ,some you must go back and check the connections in the motor leads abd the available voltage..

since the correct motors may not be available you might find an acceptable motor from Dayton that only has the correct voltage and rotation and quite a few less leads..and eh ..less expensive ...

Carol Fey is here ...she seems pretty swift to me. why not post this on her section...?

Come to think of it..to not to do so , is like, a begger sitting on a bag aof jewels complaining he has not a penny for food...*~/:)

Unknown

Pump Rotation

Here's the deal. Centrifugal impellers are designed to fling the fluid, not scoop it. Reverse rotation will still move water in the same direction but at less head, flow and effeciency. How much less, us pump manufacturers don't know (we don't test em running backwards). A great way to test reverse rotation on site if you can't see the shaft - do the shut off differential pressure test (or which ever shut off head pressure is higher that is the correct rotation).

To change roatation on three phase reverse two of the three wires (after shutting off the power of course - and probably by a qualified electrician). Once running in the correct direction do a load balance (as close to even amps across all three legs as possible).

To change rotation on single phase capacitor start motors, Baldor as an example have a sticker on the electrical box cover "for rev rot exchange leads 5 and 8". These are maretted together inside the box and effectively reverse the polarity of the Start capacitor, reversing the rotation.

Bottom line is the first rule of troubleshooting is look for the obvious first - I always recommend check rotation - it is the easiest to check and often overlooked.

Canuck_3

Canuck_3

Thanks for the input fellas

The general feeling I get from this forum is that flow is possible with reverse rotation. I did initially get the feeling that the original contractor was just out to discredit our work and it seems that some of you have also dealt with people playing the "silly bugger" game (sheesh - I really hate that game).

What's my fault is that I wanted to be in the place Bromley was, knowing full well that the pumps had been operating correctly, but I dropped the ball there in not checking initially. Well - lesson learned and not with too much pain - the owner and GC still loved the refit and put the whole 'pump rotation' incident down to sour grapes.

Thanks again guys!