Pumps

Brad White_27 · February 2006

> I have been asked a question about a pump problem 
> I have never ran into before. I have some ideas 
> but: I thought this would be an interesting one 
> for the Wall. The pump is being used as a 
> secondary pump feeding out to 15 fan coils all 
> equippped with half inch Honeywell three way 
> valves. The water temperature is normal heating 
> values. The primary pump is { one of two } 
> pumping at 20 psig and the secondary pump is 
> rated at 60 gallons at 33 feet of head it is a 
> Grunfoss horizontial 3450 rpm one horse. The guys 
> tell me that this is the third time they have had 
> the pump down for repair.They tell me the last 
> time they put it on line it { in thier words } 
> sreamed and made such horrible noises they shut 
> it off. Now I have been enlisted to reinstall a 
> new pump fresh out of the box -- you quessed it 
> the same pumpp only brand new. I say [ no one 
> will listen } this is not the way to happiness. I 
> feel that this is just plain --- well dumb. What 
> is happening to this poor secondary pump?? I have 
> my own ideas but this is something I have not run 
> into before so theory is wonderful but: experince 
> is the real teacher. Any ideas -- I mean really 
> tradesman / engineering theory ideaa I need some 
> intelligent help. Thanks I am really hopeful I 
> will know what is going on soon Jack Ennis Martin

JackEnnisMartin · February 2006

Primary Secondary Pumping

I have been asked a question about a pump problem I have never ran into before. I have some ideas but: I thought this would be an interesting one for the Wall. The pump is being used as a secondary pump feeding out to 15 fan coils all equippped with half inch Honeywell three way valves. The water temperature is normal heating values. The primary pump is { one of two } pumping at 20 psig and the secondary pump is rated at 60 gallons at 33 feet of head it is a Grunfoss horizontial 3450 rpm one horse. The guys tell me that this is the third time they have had the pump down for repair.They tell me the last time they put it on line it { in thier words } sreamed and made such horrible noises they shut it off. Now I have been enlisted to reinstall a new pump fresh out of the box -- you quessed it the same pumpp only brand new. I say [ no one will listen } this is not the way to happiness. I feel that this is just plain --- well dumb. What is happening to this poor secondary pump?? I have my own ideas but this is something I have not run into before so theory is wonderful but: experince is the real teacher. Any ideas -- I mean really tradesman / engineering theory ideaa I need some intelligent help.
Thanks I am really hopeful I will know what is going on soon Jack Ennis Martin

Brad White_27 · February 2006

Jack,

Some more information, please.

The Honeywell 3-way valves: piped as bypass to return before the coils? And if so, are there balancing valves in the bypass port? Please describe a typical FCU hook-up.

What is the primary pump GPM? You say 20 psig but not sure if you mean that is the GPM. Flow and head is...?

P/S interface- closely spaced tees? Injection? What does that interface look like?

On the primary, you say two pumps, I assume 100% standby? Or do both run together?

You are right about the approach: Doing the same thing over and over expecting different results is, well, dumb. Solving the problem first as you are doing -Smart.

Weezbo · February 2006

Maybe they no like air ...

Brad White_27 · February 2006

It could be

that simple, Weezbo. In the end you probably will be correct, especially if water-lubricated and not vented. I just like to lay out all the cards and play with them a bit. The engineer in me, ya know!

Stay warm-
Brad

Rich Corcoran_32 · February 2006

Screaming

genreally indicates air in the pump. The pumps you describe is a 1 HP wet rotor pump. The pumps have a fitting at the end of the rotor can to vent air from the rotor can. The venting of the rotor can is part of the start-up procedure for the pump.

If the pump was selected based upon a direct crossover from a previously installed pump, you may consider changing the speed. There's a speed plug in the terminal box that enables you to quickly change the pump's performance.

Contact applications engineering at 800-333-1366 if you need any further assistance.

Good luck,

Rich Corcoran
OEM Sales Manager
Grundfos Pumps.

Pumps

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