Taco Radiant Mixing Block (RMB-1) Pump Diagnosis

Glenn Harrison_2

Anyone in here ever diagnose a pump problem with a

Taco Radiant Mixing Block. I have one where the system pump is not

pumping and not drawing any amps. The only thing I don't know, and is

not in the RMB instructions, is which wires should be getting power, so I

can make sure it is the pump and not the controller.

heatboy

Check motor wires?

Glen, 



Have you check the wires connecting to the motor itself?  I love the RMB, but their achilles heel is the wiring to the motor terminal is pretty fragile.  I have had calls on RMBs installed by others where the wire was pulled from the terminal in the motor.



Does the motor spin when you set it to "manual" with the switch?



hb

Joe Mattiello

RMB

Try using the manual toggle switch on the back of the control. if you switch to manual, both pumps should run at full speed, circumventing the control... this is a good way of validating the pumps.  if the pumps run you can looks at the sensors, and validate them using the temperature/Ohms correspondence matrix found in the RMB instruction sheet. If you want to discuss further, try calling me at 401-942-8000

Glenn Harrison_2

Joe,

I guess I should have been more detailed. I had the RMB-1 in test mode, so both pumps were engaged full power, and both pump symbols were lit. The variable pump was drawing amps, the fixed capacity pump was drawing 0 amps.



My question is, what are the voltage readings supposed to be between red and yellow, red and black, and yellow and black. I have already ordered a new motor and cartridge, as based on the knowledge I have, and the fact that I ohmed the motor out, and only had continuity between to wires, and it was a high (k-ohms) reading. However it would be nice to have these numbers for future reference. I am very busy working right now, so if you could post these readings either here or e-mail them to me I would greatly appreciate it.



Also might I suggest that these voltage readings, and maybe the correct ohm readings for the pump motor(s) be written into the diagnostics page or the RMB installation manual. Seems to me that it is basic and necessary information to have for everyone to perform proper diagnosis, and prevent parts changing or multiple service calls from guessing.

Mark Adams

System Pump Issues After Vent Repair

Hi Gang,



I too am in the same boat I think. On my RBM-1, the vent had been leaking since middle of last heating season. Just last week I replaced it. All was good till I tried to fire up the system. The RMB-1 would not supply any hot water to the two underfloor zones. The zone valves were opening OK. The odd thing is that while the boiler was supplying hot water, my Radiant Return line at the RMB was getting very warm while the Radiant Supply line was dead cold. The RMB display show the mixing pump at high speed and no icon for the system pump. When I go to manual mode with the switch, it seems like the system pump is running, but the pump gets VERY hot! Much hotter than the mixing pump. Both pump icons show operation.



Maybe I pulled a lead off the windings when I took the RMB cover off? Maybe the cartridge needs to be replaced? Maybe the whole pump is horked? Mabye the pump is full of muck and will not turn?



The Taco rep at their customer service site was adamant about getting the pump properly vented and I believe that I've done that.



So if anyone knows the proper ohm checks on the system motor, could you pass them along?



Thanks,

Mark Adams

Clarence, NY

Mark Adams

Pump is Horked!

So I took the system pump, an 008 out for a look. I could not spin the impeller unless I grabbed it with a rag. Super tight. The cartridge was basically rusted in place and when apart It had a burned electrical odor.



The cuase of this appears to be the vent. When it was leaking, the water dripped right into the pump casing. Not the best mechanical design IMHO.



My supply house had no idea what part to order so hopefully the Taco crew will.



Thanks for reading my rant,

Mark

Mark Adams

Taco Steps Up: Thanks Joe!

After discovering the Taco system pump was not working, and not being able to easily find the exact part number for replacement, I called Taco. Joe Matiello responded with the offer of a new cartridge which I gladly accepted. He was also very open to listening to a design grievance I had with the RBB-1.



IMH (Engineering)O, a potential problem with the RMB is that the vent assembly is directly above the pumps and the pumps have their wiring running through an opening in the pump case that will allow water penetration. If you don't catch the leak right away, a significant amount of water can get into the pump housing. In my case, it was obvious that water leaked in over time. It was also obvious that it had no affect on the failure of the pump cartridge.



With that fixed and put back together, everything worked fine, but not without more head scratching. I discovered that the installer mixed up the wiring for the boiler supply and radiant supply sensors. Now, I've had good underfloor heat for the past 5 years but many times thought something was "funky" and now know why.



One other thing I've discovered is that the Target Supply temperature is frequently overshot by a quite a bit. If the boiler has just finished a DHW call at 180F or a space heating call at a high temperature followed by a call for the RMB to supply, say 116F, the actual supply may be 140F. The RMB mixing pump will stay off until the Radiant Supply is down to 110F or so, at which point it runs, pulls heat from the secondary piping and enables the boiler as necessary. Is this overshoot normal?



Anyway, great customer service from Taco!!



Best regards,

Mark

dano415

This is to Taco Engineering

1. Nice product!

2. It would be nice if you included the normal resistance(OHM's) on your pump product sheets.

3. I can figure out what factory specs should be using volts=amps x resistance, but

a range of "acceptable" resistance readings would be helpful.

4. As another poster pointed out; readily accessible data would prevent ordering mistakes, and save time.

5. Right now I have a 007 pump that is reading 40 OHM's. I believe that reading is acceptable, but would like to be able to look it up on your site.

6. Yes, I will connect the pump to 120 volts and guesstimate.

7. If I missed the acceptable resistance values--sorry, and disregard this post. Again I

like your product.

Weezbo

when the rimbee came out

i took a small clear hose ran it from the air relief down along side the back of the pipe

spun a 3/8 rigid single hole pipe clamp to the diamond plate and called it good .



what the answer is for resistance i havent off the top of my head , i too use the click manual button .



the stethoscope works too *~// ; )

LukeBJ

Hey Guys! 

I had the same issue here with the vent leaking but it looks like it grilled my PcB plus my 008 doesn’t seem to move anymore!

anything can be done? 

Erin Holohan Haskell

Welcome to Heating Help, @LukeBJ. I recommend you start a new post so your discussion doesn't get buried at the bottom of this older post. Thanks.

SteveSan

Hi Luke, I believe you sent an email to Joe Mattiello about an issue you were having with an RMB. He asked me to contact you about the part # you need. The replacement control board is 193-004RP. Please feel free to contact Taco anytime Mon-Fri 8am to 5pm EST. Hope this helps.