System keeps ruining circulator pumps

HeatingHelp

This discussion was created from comments split from: Help! My Hydronic heating system keeps destroying circulator pumps..

LeoB

It is November, 2023. I have had a similar problem with an Armstrong S-25 pump assembly with LR37479 motor. The old motor had worked for at least six years -- maybe a lot longer, since it came with the house. It began to squeak. I put a fan on it, and the squeaking stopped, but some months later came back. Putting a stronger fan didn't help. I suspect the lubricant had dried out. These Armstrong motors come pre-lubricated. The oil wick case is sealed. I see no reason for it to be sealed, but it is.

After watching some youtube videos, I took the motor apart, and sure enough, it looked like the lubricant had dried. I tried adding some 3-in-One oil. Unfortunately, I reassembled the motor incorrectly, and when it restarted, it broke a wire, and that was the end of it.

Fortunately, I had already bought another Armstrong motor. I installed it to the pump, and it worked fine for a few months, but then it began to squeak. I took it partially apart and reoiled the shaft at the back end, and that helped for a few hours, but then the squeaking started again.

But I had already bought yet a third Armstrong motor, which I installed, and unfortunately, it also started squeaking as soon as it heated up. I took it apart, and it appeared to be properly lubricated. I had run that motor earlier for several hours without a load, with no problems.

I decided to try another brand, so I bought a compatible Rotom motor, and tested it for several hours without a load, and had no problems. I installed it to the pump, and it initially ran well, with no squeak or vibration. However, after it heated up, the squeaking began. I put a fan on it -- a big, 18 inch square room fan, not just a little desktop fan -- and the squeaking stopped.

I am not a mechanical engineer, so I can't comment on bearing design or metallurgy. I won't comment on where these are being manufactured, nor on the level of quality control that goes into them, nor will I question whether they are tested under pump load conditions or just rotating freely. The old motor lasted many years. The new ones don't work properly for me. Draw your own conclusions.

I rigged my large fan on an extension cord, using a cheap digital thermostat switch box, with the temperature sensor taped to the motor. I set it to turn on the fan when the temperature reaches 28 degrees Centigrade (the box is so cheap that it doesn't even have a Fahrenheit setting) and turn off when it falls back to 26 degrees C. or below. That seems to be working. I am hoping it will last the winter, but have a bunch of cheap analog space heaters arrayed around the house in case it doesn't.

I have ordered from eBay an old Armstrong motor that is supposed to be compatible and has ball bearings. We'll see if it fits and works, after it arrives. The model number is partially worn off, but it's a long bunch of numbers and letters containing the strings KH39DN and 702BX. I called Armstrong tech support in Buffalo to inquire about the model, but they didn't answer the phone, so I left a voicemail message. After two days they haven't called back.

There are a lot of products that used to last 10 years or more, but the newer versions don't. It's too bad.

Let me give a shout out to Electric Motor Warehouse. A live person answers the phone. My Rotom CP-R1350 motor was delivered amazingly fast. They told me that in the first 30 days if it fails I can return it at their expense, and if it fails within a year I can return it at my expense. If it can just continue to operate in the current, fan-cooled mode, I'll keep the one I have, because I am not sure that any others would be much better.

I have learned more than I ever wanted to about motors. I was never able to find out which lubricant to use on the LR37479. There are oils and greases, and it seems that specific motors require specific lubricants. I still don't understand why the wick case is sealed on this motor. It is possible add lubricant by taking the motor apart, putting it upside down, and slowly feeding oil into the wick gate opening in the rear sleeve bearing, but that's a real chore, and maybe it should be greased and not oiled.

One solution is just to replace my whole pump system with something else. I have looked at the comments here about what to do, and it's interesting to see the various suggestions. All I know is that this system worked fine for years or decades just as it is, so it's a shame that replacing a part with a newer version doesn't work right.

By the way, the pump started to leak last year, and I replaced it with another Armstrong unit of the same model, so the problem shouldn't be coming from the pump, unless perhaps it is binding for some reason and overloading the motor. I have lubricated the pump according to Armstrong instructions using Armstrong oil, so it should be ok. It's been working fine for the past year.

We'll see what happens.

kcopp

Cross reference would be a Taco 0010.
Install that then you wont have to deal w/ oil any longer....

tim smith

1st off, B&G circulators, especially series 100 are quite forgiving. They don't create much velocity. They dont fail often. This is kind of odd. Dump the system through a strainer bag and really see what you get out. I think it will just be dirty water. Not metals etc. Just my guess but we as many here work on 100s if not 1000s of old gravity or pumps iron pipe systems with cast radiators. I never have problems like this with the old circs. Will be interested to see where this goes.
Tim

Jamie Hall

Are you quite sure it is the motor that is squeaking? Could be a failed seal or bearing on the pump itself overloading the motor and making it burn out. Or, if there is a chance to do that, a misalignment doing the same thing.

The number one cause of premature motor burnout is overheating from overloading.

Erin Holohan Haskell

@LeoB, welcome to Heating Help! I've created a new discussion for you here so that your post doesn't get buried in that older thread.

KC_Jones

Have you contemplated that the pump could be getting overloaded and that in turn is overloading the motor? For me, it seems obvious, there is something else at play here. This doesn't present as poor quality motor issue, it presents as some kind of system issue overloading the pump, especially when you say it's getting hot, which implies overheating.

Has the system been flushed recently? Any strainers or filters on the system that need cleaned?

Some pictures of your system would help the more seasoned people identify any issues.

LeoB

It is possible that the pump is overloading the motor, but the pump is only a year old, and has been properly lubricated according to Armstrong instructions. The previous pump lasted at least six years or longer. It came with the house. I would expect this Armstrong S-25 pump to still be good.

Water coming out of radiators from bleeding is clear, without debris. The water was drained and filled a year ago when the new pump was installed. No additives were used.

The spring coupling between the motor and the pump would seem to reduce the possibility of misalignment. Also, there is no rattling or clicking from the motor when it squeaks. Perhaps the bearing design or metallurgy in newer sleeve bearings is different than in old ones, in terms of heat expansion or lubrication.

The fan-cooled motor has been working since yesterday through several heating cycles without any issues. I'll let it continue. I haven't yet decided whether to put in the ball bearing motor, when it arrives.

The system is a single zone, four large radiators and two small ones. Height of the highest radiator in the two story house is about 20 feet or so above the basement boiler. Pressure is set to around 13 psi cold. There is a large expansion tank. Radiators are fully bled. The water temperature from the boiler is set at 160 degrees F. I read somewhere that temperatures lower than 140 degrees F. could result in condensation around the boiler and potential corrosion. The pump motor powers on at around 160 degrees F. and cuts out at around 150 degrees F. There is some water hammer in the nearest radiator above the pump on startup, but that has been going on for many years.

Robert_25

kcopp said:

Cross reference would be a Taco 0010. Install that then you wont have to deal w/ oil any longer..

A modern cartridge circulator would be my choice also.  0010 is direct cross to the Armstrong, but a 007 may work also depending on the piping size and configuration.  

mattmia2

LeoB said:

The old motor lasted many years. The new ones don't work properly for me. Draw your own conclusions.

My conclusion is that the motor and the pump are misaligned somehow, probably because of rotted out bushings but possibly something to do with not enough end play. Or the bearing in the pump was run dry at some point and is damaged.

Jamie Hall

mattmia2 said:

LeoB said:

The old motor lasted many years. The new ones don't work properly for me. Draw your own conclusions.

My conclusion is that the motor and the pump are misaligned somehow, probably because of rotted out bushings but possibly something to do with not enough end play. Or the bearing in the pump was run dry at some point and is damaged.

This comes under the heading of don't shoot the messenger. You are blaming the motor -- which is telling you that there are problems with what it is trying to drive (that's what running hot means).

pedmec

isn't the definition of insanity doing the same thing over and over again and expecting a different outcome! At some point you have to realize the problem is not the motor it's most likely the bearing assembly.

As far as having seal bearings its because most homeowners don't realize that a 3 piece circulator and bearing assembly need to be oiled. They have a sticker on the circulator telling you how many drops of oil and what interval. The motors used ball bearings and if not oiled wear out. So these motors basically never get oiled and fail. Bearing assembly dries out causing excessive load on the motor and then failure. it made sense then to seal the motors up and use sleeve bearings which don't require lubrication. The reasoning being that if the motors are not going to get oiled and fail sooner then you might as well seal them up and theoretically the sleeve bearings should last longer.

Now in my experience that theory i'm not sure in real life actually works as advertised. i feel that sometimes you tend to get water seeping into the shaft and killing the bearing.

LeoB

As mentioned, the pump (with bearing assembly), S-25, LR 4678, is only a year old. The previous pump lasted many years. This new pump bearings were always oiled according to Armstrong instructions, using Armstrong oil. If one looks at an exploded view diagram of the pump, the only places of rotational resistance that I can see are the bearing assembly and the seals. If the problem is not in the bearing assembly, it is possible that the seals are binding, but the water temperature at 160 degrees F. is well within spec for the pump. However, I am beginning to wonder whether the seals might indeed be the issue. If I take the motor out again, I will rotate the pump shaft by hand to see how much resistance I can feel.

The pump is connected to vertical piping. After the pump was installed, the system was filled with water. According to the following link, the S-25 pump has downward discharge.
https://www.nationalpumpsupply.com/content/pdf/armstrong-series-s&h-pump-installation-guide.pdf
I do not remember priming the pump. I am not sure how critical that was, since there was water above, at the intake, which should have filled the pump chamber, but perhaps the bearings or seals were damaged at startup and aren't turning as freely as they should. However, the pump has been working well so far, without any rattle or other noise.

It is a good point that water may have bypassed the seals and affected the bearing assembly, but I don't see any leaks. The system was drained six years ago when we got the house, and was filled and restarted without priming the existing pump. Everything worked fine for years afterwards.

In terms of misalignment, the spring coupling is a bit like a universal joint, with two separated parallel bars. The motor shaft goes into a hole in the middle of one of the bars, fixed with a set screw, and the pump shaft goes into a hole in the center of the other bar. The ends of the respective bars are attached together with small springs. With this setup, it would seem that a misalignment between the shafts would be mitigated by the springs and not transmitted as lateral strain on the motor shaft.

LeoB

I got a mechanics stethoscope and confirmed that the problem caused by the pump binding up. I got a new pump assembly from Wands Inc. with ball bearings instead of sleeve bearings, drained the system and installed it. I refilled the system, rotated the pump a few turns by hand, and then started up the boiler. No more squeaks. Water temperature is set to 150 degrees F. We'll see how it goes. I am disappointed that the previous Armstrong pump only lasted a year, because I oiled it properly. With a vertical pipe and downward flow, I don't think it could ever have been running while dry.

LeoB

So far, so good. Water temperature is set to 160 degrees F. The pump sounds smooth over a stethoscope. I am using a Bell and Gossett motor, which has oil cups for lubrication. It gives a slight thrum every 1/5 second or so, which I am not happy about. We'll see how it goes.