Taco RMB1 only works in manual mode

lobsterlogger

Hey everyone, I have searched the web for people with my same problem and have found a few...

Living in very remote Maine in trying to diagnose and fix myself. As the description says everything was fine for years then yesterday no heat to the floors. Went into the crawl space and started to see that the supply temp was only 70 when it's is set at 125. Read a little and saw that I can make it work in manual mode to see if it's the pumps or something else. Well the pumps ran perfect in manual mode. Next I saw that the air vent may be the issue. Took that off and blew through it and cleaned everything up. All good so if any air got in somehow it can certainly get out. That didn't fix anything either. Could the controller just be shot? It has a date on it if 2015. Any help or guidance would be appreciated.

SteveSan

@lobsterlogger Any error codes on the screen? Could be a sensor or setting issue.

Please give Taco Technical Services a call during normal business hours Mon-Fri 8am-5pm EST 401-942-8000 and just ask for Technical Services.

Dave H_2

There are many wide open answers to give there. Are you able to take a pic of the screen and post here?

Many times it could be a simple as one of the sensors not reading properly since it has been heating properly all these years.

lobsterlogger

Sorry for lack.of details. No codes are showing. Also when I put it in manual mode the screen does not show the little graphs showing pumps at 100%. That seems odd. The sensor showing the mix temp certainly is working. It will slowly rise to 227 or more if I don't turn off manual mode. Then it quickly goes back down when I switch the controller back to auto mode.. Should my next steps be to try the ohm test on sensors? Seems like the 1 sensor that would tell the 2 injection pumps to turn on is working but I am no expert. Late tomorrow I will give Taco a call. Of course we're looking at single digits this weekend.

Greatly appreciated the the help though fellas.

SteveSan

There is an ohms chart on page 13 to check to see if the sensors are reading correctly. Please see the IOM below.

Radiant-Mixing-Block-Instructions_102-151.pdf

109A_5

Hello lobsterlogger,

With your symptoms this sounds interesting. From the manual SteveSan posted.

lobsterlogger

Okay some updates and more head scratching. I thought the fuse on the backside of the rmb controller was gonna be the answer but nope. Great idea though.

So I have taken off the air vent and cleaned. And my boiler shows about 12 lbs. I think that rules out air or water being the issue.

I checked the little tiny round fuse and swapped it out for a new one. No change in how it is acting and still no codes whatsoever.

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Changed out all 3 sensors even though the others were reading properly. 1 Mix supply temp. 2 Boiler water temp. 3 Outdoor temp. Changed all 3 sensors and the variable speed pump and constant speed pump still only run in manual mode. Could it be something with Taco 6 zone switching panel? Could something have burned out in there and that is why it's not sending a heat demand signal to turn on those 2 pumps.

There is one thermostat wire going from the 6 zone panel to the rmb unit. It is labeled "heat demand rco". Only 1 of those 2 wires is hooked to anything in the 6 zone panel. I have not touched that however. It seems like 1 wire is all that has ever been hooked up in there. That seems a little strange to me but 1 wire is hanging and the other goes to the block labeled "X Isolated end switch". It is right under the "120 VAC relay". The red wire is hooked into that X and the white wire is just hanging in there.

All thermostats work. I turn them on and the click occurs and the red light comes on the 6 zone relay panel. Then the individual circulator pumps kick on just like normal.

Seems so strange that those 2 pumps in rmb just decided to not work in auto mode. Noone touches anything down here in the basement Actually hate coming down here. I have found one online for $1600. That may be the next stop. Just replacing it. If that doesn't fix it I have a spare I suppose and it will at least let me know if those pumps or that controller are what is causing my problems. It's gonna be a expensive experiment but again I will have a spare in case I need one or a buddy does

109A_5

I would think that white wire should be connected where the other X-X white wire is connected if that wire pair goes to the heat demand terminals of the RMC. Could it have just popped out if it was not secured properly ?

Otherwise how does the RMB1 know when to energize the pump(s), if it can't sense demand.

Dave H_2

If you can, take a pic of the screen of the RMB. There is alot of information on the screen to tell what happening. Scroll thru the View menu, it should tell you a target temp as well as the actual temp among other things.