Taco RMB-1 cartridge question

Flaps

I removed a cartridge(008-045RP) because it was not circulating the water in my system. I noticed that there was brown rusty water coming from within the cartridge itself. I don't think there should be water in the cartridge. Can anyone confirm this? I will be replacing it regardless just wondering.
I ran the circ motor with the cartridge installed ( motor not in system)and you can tell that the bearings are no good. I think the bearing seal went and allowed water into the cartridge and it rusted out the bearings while the system was idle over the summer.
Photos are just for reference



Thanks

hot_rod

yes there will be water in the cartridge, it is a wet rotor design.

Does the black impeller spin easily? It should also spin when re-installed and powered on before you bolt it back in to the body.

Flaps

Yes it does spin and really was not seized as I have read in other posts. I did power it up out of the circuit and it did spin but it was a bit rough. I could hear what sounded like a bearing squeal a bit. This is the variable pump cartridge and I am wondering when the system slows the pump down it just stops. I have to still measure the current draw when it is in the body of the unit. I could swap the 2 cartridges but I don’t want to end up with 2 bad cartridges.

When I first thought there was an issue, the pump housing was significantly hotter than the water going into the system (thinking that the motor was locked) and I was not getting any heat through the heat exchanger on the back of the unit. The pump that does the radiant floor was cycling the water because I could see it in the flow meter in that side of the system

Does this make sense to you? I didn’t realize that it was a wet rotor but if I was getting brown rusty water out of it you would think that there is something rusty inside. Couldn’t this bad water get back into the domestic hot water system, although it would be just the smallest amount?

Thanks

Flaps

Wouldn’t the water inside the cartridge be more of a resistance to the rotor itself? I would like to see a cut away of one.

hot_rod

The fluid both cools the motor and Lubricates the bearing
Most have ceramic bushings not ball bearings
Not so easy to cut open, I think you’d be disappointed when you got inside😳 a shaft and and sleeve

Yes it does take some energy to sling a shaft in fluid, 3 piece dry rotor pumps are an option, but then you need an air cooled motor with a cooling fins or a fan wheel. A trade off, dry rotor are better in crappy water

Usually the circulator runs about the temperature of the fluid passing thru. If it is hot, hot it is probably airlocked if flow is blocked.

Flaps

Thanks for that info. My circulator pump runs no problem (I think, looking at my flow gauges) and is about the temp of the water running through it approx 90 degrees. The variable speed pump (the one I think is my issue) was stupid hot when I found it (wish I hand my thermal gun). Water going into this variable pump comes from the hot water tank and is around 130-140. This thing was just radiating heat and the return line going back to the hot water tank was much colder that the line going in (pump not circulating).

When I did remove and replace this cartridge I fired up the system and the return line was the same temp as the supply line. The motor was running at 100% but when the system got up to temp the controller slowed the pump down then I noticed that the cartridge got really hot again but the return line temp got cold again.

I think the cartridge is shot. Just trying to figure how this system functions. A1-A2 is the variable speed pump from the hot water tank B1-B2 is the circulation pump for the radiant heat.

hot_rod

How long has it been installed? Is it possible the potable side of the HX is plugged or scaled badly?

Joe Mattiello

Hi Flaps
you made it to heating help! great resource for troubleshooting. if the radiant mixing block is not moving water on demand, one of the easiest diagnostic tools is the manual switch located on the back of the black control module. there is one screw in the middle of control that needs to be backed out, grab the module with your fingers and easily flip it over until you have access to manual switch. go ahead and put that in manual to see if the cartridges are working. Manual switch will allow system pump, and injection pump to operate at full compliment. see if heats getting to system?? if it is, it's not a failed cartridge or pump for that matter, it's a control issue. perhaps boiler protection energized, or one of the sensors failed. if you can not figure it out over the weekend, Monday call Taco tech support 401-942-8000 for help. If you need heat, don't be afraid to operate in manual, but be sure you're able to manually shut it down because it will not be regulated by control or thermostat. Please reach out to me if you have any problems

Flaps

System was installed in 2011.
Everything is original. The lines from the hot water tank to the system are PEX. There were no signs of scale at all when I had the pump out So I think the lines are all clear.

I did put the system into manual mode and was getting 120v at each of the motor outputs on the board. I then plugged the motors in one at a time and they did turn on and I could feel the temp change in the output pipes so they are moving water.

I still think there is an issue with the cartridge when the system slows the pump down on the A side of the system. If there is a bearing gone or going it just may be binding enough to not spin at the supplied voltage that the system is trying to run at and just locks up and heats up really hot. like I said the water in the cartridge was very rusty and that would lead me to believe there is particulates in there somewhere.

I will be calling Taco on Monday to see what they think about my situation.

Thanks for all the info, glad there are people willing to help others in a time of need. I’ll post back any info that Taco gives me so that it may help the next person.
Jay

hot_rod

Certainly no harm in replacing the cartridge if you don't trust it. It is an easy replacement as you can see.
I'm not sure how easy the replacement cartridges are to source.
It may be less $$ to buy a complete pump, swap the cartridge and keep then motor for a spare. Shop around for pricing.

As for hard water scale, it rarely builds up in pex tube, it would be in the small passages of the plates that it plugs.

I installed some of those years ago, one homeowner de-scales the A side of his yearly due to the hard water conditions around here.

When his radiant no longer maintains temperature he knows the HX is fouled.

Flaps

Didn’t even think about the plates in the back. Our water is very soft but anything can happen. Just other thing to ask Taco.

Flaps

This is a picture of my setup and a color photo of the heat exchanger. The variable pump is the upper one and the floor pump is the lower. Doubt it would help but it might make things a bit clearer for anyone reading the comments

Joe Mattiello

Following up on this. If the manual mode enables pumps, the problem is in settings. It could be in boiler protection mode.
Also noticed you have pex, can’t put sensor on pex which is an insulater.
Let us know how you make out

Flaps

Sensors for the system are all on copper pipes. The cartridge would run in manual but when the system slows the pump (chopping the A/C wave) the cartridge would stop spinning. The brown color water in the cartridge is the bronze from the bushing. I think the bushing was no good.

I have replaced the cartridge and the system is back and running again.

Thanks for the follow up response. Hopefully this info may help someone else. I am now a Taco expert......lol.