Primary Taco pump keeps seizing

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Old 03-15-04, 06:10 AM
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Primary Taco pump keeps seizing

My house was built in 2001. We moved in in 3/01. We have a gas-fired Lochinvar boiler (300KBtu) with Hydro-Air.
The circuit has a Primary circulating pump, and then 4 other pumps (1 for the 1st floor Hydro-air, 1 for the 2nd floor Hydro-air, 1 for the indirect hot water heater, and 1 for the radiant floor in the master bath).
Since the floor in the master bath runs 24 hrs/day, the primary circulating pump runs the same amount of time.
We just had someone to the house because we have no heat/hot water. The main (primary) pump is burned out. this is the 3rd time this has happened. It burns out about once a year. Has anyone heard of this? This seems ridiculous to me.
 
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Old 03-16-04, 06:05 AM
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Something is wrong there. Those pumps will last a long time. What is the brand and model of the pump that is failing? Is there ever a time when it can be running and not allowed to move water? Like if all zone valves were closed or something in that loop that would stop the flow? A few pictures could help but can be tricky to make available to us. Lets get this figured out before the next pump gets ruined.
 
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Old 03-16-04, 06:52 AM
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Im with KField here more info would help. Dont know if you have one. But if you could put a amprobe on the pump motor and see if the Amp draw is the same as it said on the motor there on the pump. ED
 
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Old 03-16-04, 08:49 AM
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On the primary circuit is a Taco 0012-F4 circulating pump with 2" cast iron pipe. The total head is about 5 feet per the service person.
This pump is overamping (amperage is 1.5 amps when operating, but 1.3 is max specified)and seizing once per year. I was told by the service person that it is too large for the current setup. He showed me by almost completely closing the valve in the main cicuit and the amperage dropped to 1.33. However, the valve was closed so much that the flow sensor that makes sure there is water flow kept shutting the boiler off.
There are also 5 other zones (secondary circuits) with Taco 007 pumps on them and 3/4" copper piping.
From what I can tell from Lochinvar's specs, the boiler pressure drop and pump head are minimal.We originally had a problem with flashing in this boiler system and noise which is why the original installer put in the larger pump.
in the Lochinvar specs, it also recommends a bypass in the primary circuit, which seems to be to prevent low flow stses/overheating the water.
We do not have a bypass in the primary circuit, but we seem to have the opposite problem, with too much flow.
I would be happy to email someone a digital picture if this would help.
 
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Old 03-16-04, 09:51 AM
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Without doing the math I am only speculating but I think the 007 would come close to doing the job for you on the primary loop. If not, the 0010 would surely do it. You may have to adjust the flow switch for more sensitivity but I would suggest replacing the 0012 with the 0010 instead of repairing the 0012 again. I'm not sure what the effect of the primary pump would be on the flashing problem you were having. It sounds like a problem was created there instead of a solution.

Ken
 
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Old 03-16-04, 09:51 AM
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Without doing the math I am only speculating but I think the 007 would come close to doing the job for you on the primary loop. If not, the 0010 would surely do it. You may have to adjust the flow switch for more sensitivity but I would suggest replacing the 0012 with the 0010 instead of repairing the 0012 again. I'm not sure what the effect of the primary pump would be on the flashing problem you were having. It sounds like a problem was created there instead of a solution.

Taco pump curves link

http://www.taco-hvac.com/uploads/Product_Chart/1.jpg

Ken
 
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Old 03-16-04, 10:22 AM
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Thanks. That seems to make more sense. I'm just wondering about this recommendation for a bypass circuit, which my boiler does not have. It's shown on page 35 of the following link.

www.lochinvar.com/pdf/EB-EW-I&S.pdf

Do you think that the reason for the pump failure is because it's too large? In other words, what other things could be causing the pump to overamp? It would make me think that it has to be the super high flow since the only time the amps go down to near the acceptable range is when the inline valve in the primary circuit is almost closed.
I just want to be sure since this will be not an insignificant expense in putting in a new pump and repiping to fit it. The original configuration that caused the flashing problem had smaller diameter piping, but i remember the installer putting in the larger pump to move more water. Now, our piping is 2" black steel.
I just don't want to go back to having the problem with overheating again.
 

Last edited by Dave4242; 03-16-04 at 10:58 AM.
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Old 03-17-04, 06:29 AM
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I think you are right on your thoughts about pump size. If you had put the 0012 into the pre-existing pipe sixw, you probably wouldn't have had a problem. Or if you increased the pipe size with the old pump, you might have gotten away with it. With the new pump and no (or very low) head, the pump is running away. If you could throttle the pump discharge and adjust the flow switch or use a larger paddle, you might be OK.

There is a 1 7/8" difference between the 0010 and the 0012. Hopefully if you plan to use the 0010 you can just replace one nipple on one side of the pump to change the opening.

There could be other issues here too, but I think you would be on the right track to go with a smaller pump the next time you have trouble.

Ken
 
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Old 03-17-04, 08:26 AM
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Do you think this is something that I could do myself? First of all, the piping is 2", and Taco does not make 2" flanges for the 0010. Therefore, I would have to step the pipe down to 1 1/2". Could I just reuse the flanges from the 0012?
Also, there are shutoff valves in the primary circuit. However, they are not particularly close to the pump. I assume I would shut off the secondary circuits so no water drains from the rest of the house, then drain the primary loop and refill it after the pump is changed over. I know there is an inline fill valve near the expansion tank.
Would you possibly be able to give me a play-by-play for the most common situation?
 
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Old 03-17-04, 11:16 AM
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You are correct about the valving during the repairs. A play-by-play is no problem and a picture of the pump and nearby piping could be invaluable for that. I think the flanges are the same for bolt-up purposes so you could keep the same ones.

Ken
 
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Old 08-14-04, 09:20 PM
Homer Simpson
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Dave, Dave, Dave,
I'm late in the game But...
The person that installed your boiler, please, don't tell me it was your builder,
put in too big of a boiler. 300,000 BTU/H Imput nat gas, what are you heating
North Dakota? You size the boiler to the BTU/H loss for the house + 10% +
a small margin for the indirect water heater. Usually the indirect w/h has
priority over space heating and is settable for the priority function. I like
1/2 hr. You have a new house so it should be tight 2-5 air changes a day,
well insulated to todays standards. Your builder probably had to provide the
building dept with heat calcs so they are on your plans. I bet your heat loss in BTU/H is about 80,000 and that is at 0 deg in winter and 65 deg inside.
What are you doing with a 300K boiler besides spending the kid's inheritance on gas.

Ah! the Lochinvar Boiler. It is a mini-tube type boiler, I believe, as opposed to
a reservoir type boiler. That means a small amount of water is in the boiler.
So, at 300K heating the water, water had better move pretty fast through it or the water boils and creates steam pockets with subsequent implosion pushing water in both directions. THAT'S WHY FLOW AND HEAD ARE EXTREMELY IMPORTANT. YOU CAN'T SIZE A PUMP WITHOUT KNOWING THAT. Lochinvar will tell you what the flow through their boiler is in gal/min and also the Head in feet of water column or psi (1 psi = 2.31 feet of Head). That is just for the boiler, but you have primary loop and the pump is pushing through the primary loop, too. You need the Head and the gal/min through that too. Lo & behold you add them together and you can size your pump. How do you size a pump? By looking at the pump performance curves, which are in Feet of Head and Gal/min.
1. Choose a flat curve if possible.
2. Only use the middle 1/3 of the curve.
3. Find the Head that you need + 5-10% and follow the curve to the gal/min
that you need
The TACO 00 series pumps are a cartridge type pump. When you say seized or burned out, I don't know what you mean. Did the impeller seize (can't rotate it by hand? Did the winding fry and smell so that the electricity wouldn't go through the windings? If the cartridge seized just replace the
cartridge. If the windings burned, save the volute and cartridge, and replace the pump. But why, your asking. If the cartridge seized cut it open and see
why. If it's burned check the line voltage, 110-120V ac. Put a computer surge protector on it, lighting, surges, etc. .
I think that your heating design is a guesstimate. It maybe more economical to get a smaller boiler, one that fits the house design calcs.
But there are balancing valves, bypass loops, ganged circulators, differential
pressure valves. But...That's another story. Say goodby Homer, Goodby
 
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Old 08-15-04, 10:44 AM
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Homer,
The boiler was installed by the licensed heating contractor (not the builder). He said it was needed as the total finished space in the house (on 3 floors is about 6000 sf.
The cartridges are the parts that keep burning out.
Currently the Lochinvar rep has been out with the heating contractor and a new plumber and is redesigning the piping, etc with a new pump in the primary circuit.
The heating contractor is picking up the tab on this one.
 
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Old 08-15-04, 11:38 AM
Homer Simpson
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Dave,

I looked at your PDF on the Lochinvar and it was nice of Kfield to provide
the pump curves for Taco 00 series pumps.

The Lochinvar manual tell it all. The mimium flow through the boiler is 12 gal/min. The head is about 1.25' HD. Less is better. But the heat load for water without glyol is 10,000 BTU/gal/min. So I would expect about 30 gal/min flow through the boiler. But the heat load of the radient floor and
air handlers? or baseboard? is a lot less that 300K BTU/H. So the boiler should meet the building heat load requirements. An over sized boiler is just a waste, more costly to operate and less effiecient.

Bypass circuit. The bypass is for two main purposes. If the primary loop and the secondary loops suck the btu s out so that the return water temperature to the boiler is less than 135 degs that is bad. A bypass allows some of the
just heated water to flow back to the return to heat the return water above
135 degs. Secondly, the bypass allows a smaller pump to push the minimum
flow in gal/min (12 gal/min) through the boiler to prevent flashing. This is just
a fix and is inefficient.

You should have a seperate pump to push water throught the indirect water
heater matched in gal/min and feet of head for the W/H system to lessen the
pumping load on the primary system.

The boiler pump should be on the return line to the boiler to minimize cavitation.

The supply water temperature should be about 180 degs.

Dave, it all boils down to how much heat do you need on the coldest day in
winter to keep your house comfortable. Anything more than that is a waste
and inefficient. That is what proper design does. Boiler design is complicated
and you have to have a lot of information to do it right. The old days of putting in a larger boiler to be on the safe side are over. You really have got to need that larger boiler.

I don't think that I would worry to much about the current demand of the
pump. I have never measured current and probably never will. I do measure
voltage and continuity or resistance when needed. Taco Technical personnel
will gladly talk to you about your problem, but inspect the pump so that you
can convey the information about it intelligently.

I know this is just about a pump repeatedly seizing so I'll pass this on.

I was called out to service a Lochinvar boiler 140K BTU/H that stopped producing heat. It had a Taco 0010 on the primary loop. The house had radient floor heat (3 stories). The primary loop connected to INFLOOR injection units on each floor. A long primary loop. The Taco pump rotor
would't turn. I cut the cartridge open and it was filled with what looked like
black sand. I flushed the system 4 times installed a new pump that fit
the system design better. What caused the problem I think was that the
installing contractor set the boiler supply temperature at 125 degs. The
return temp being lower. Thermal shock in the heat exchanger caused this
black sand like substance to flake off and circulate in the water and getting into the pump cartridge causing it to seize. Needless to say, I set the supply temp to 165 degs. Say goodby, Homer. Goodby
 
  #14  
Old 08-16-04, 11:29 AM
Homer Simpson
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Dave,

Wow! Big house. I know that from Montana to Minn. the Siberian Express
comes through every winter with -temps. But I still would expect about
150K BTU/H loss max in 6000 sq ft. I would size the boiler to the house heat load + indirect w/h + snow and ice melt.

Cut the cartridge open and look inside. Your experience may be the same
as mine. I don't know what your return temp is but it must be over 135 degs.
The higher the supply temp the more air comes out of the water. Air in a
system is not good.

Modulating boilers are a great money saver. (if you decide to replace the
boiler). If you find out the problem, post it. I am interested in the outcome.
say goodbye , Homer. Goodbye
 
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