Taco RMB

BenWoj

We just recently had a geo system installed in our house. Previously I had a boiler and used a taco rmb with outdoor reset to control my temps. Is there a way to convert this to being used with my geo system?

Ex: my current set up will always call for my boiler to fire up, even though it's no longer in use. If usable, is there a preference on how it's to be used?

Harvey Ramer

A little better description of the configuration of your system is needed for proper assessment.

Is the Geo system water to water I assume?

Typically, a water to water system requires the use of a buffer tank. The buffer tank temp is controlled by a standard ODR controller such as this http://tekmarcontrols.com/products/hvac-systems/256.html That control will turn the Geo system on and off as needed to maintain proper temp in the tank. The heating system will then pull off the tank as needed for central heating. The boiler may also be tied into the tank as a second stage if the geo system cannot keep up. With this setup it is imperative that the maximum required water temp does not exceed the output of the maximum water temp the geo is able to supply.

If the required water temp is higher than the geo supplies, you can run ODR on the tank till such a time when the geo is maxed out on water temp. At that point, switch over to the boiler with the RMB to continue the higher water temps to the system. This requires a bit more of an elaborate control.

Tekmar, should have the control you need.

I am not sure why your boiler is fireing every time there is a call for heat? Shouldn't be that way.

BenWoj

Sorry Harvey, I sometimes forget people can't read my mind. Yes, this is a water to water system. The boiler is connected with the geo system like you mentioned In case my geo system can't keep up. I don't have any plans to use my boiler anymore and have secondary heat already taken care of.

My buffer tank has an ranco etc which monitors my water temp for the geo. When my thermostat calls for heat My taco rmb would only mix at 85 deg even when it was calling to maintain a 100 deg mix. I switched the rmb to manual and it's now finally mixing at 100 deg( buffer tank temp).

Should I just remove my rmb and replace it with another outside control and circulating pump?

Harvey Ramer

Yes, I believe so. See the RMB has a hx built in it and varies the speed of the supply circ in order to achieve an ODR mixed temp output. Now any hx requires a temp difference between fluids in order for heat transfer to occur. Likely the tank temp isn't high enough for the hx to transfer adequate supply temp to the system.

So you don't need the boiler anymore? Good, that makes things very simple. Do away with the RMB and the Ranco that controls the tank temp. Install an ODR control such as this http://tekmarcontrols.com/products/hvac-systems/256.html to control the tank temp. Then you can pump straight out of the tank to the system.

Noteworthy; The ODR control on the tank is going to significantly increase the efficiency of the Geothermal unit.

What is the max required water temp for the system at design day?

Rich_49

Only the XBlock has a heat exchanger Harvey . The RMB is an injection mixing device .

Harvey Ramer

Of course! I got my wires crossed. Sorry about that gentlemen.