rinnai i120sn piping

dough041

New to this but a DIYer for years.

I'm looking to replace my 23 yr old Utica hot water baseboard boiler.

Am interested in a Rinnai i120sn heat only.

My main question is do I basically plumb in the unit with new ( but the same fittings etc - re: fill valve, air seperator,expansion tank etc in the "same order"?

 It's a 3 Zone system controlled with 3 circulation pumps. I also use a taco zone controller and a tekmar outdoor reset...

Sorry if I'm not real clear in my question but would appreciate and feedback or suggestions.

I did assist in putting in the unit and the configuration in 1999. Served me very well but want to get ahead of it before any issues. Plan on doing it over the summer .

GroundUp

That Rinnai will likely require primary/secondary piping. The manual will have the proper piping diagram

dough041

Thank you

EdTheHeaterMan

The order of the equipment you mention (exp tnk, fill PRV, and air sep.) along with the primary pump location may affect the system's ability to expel air. Pumping away from the expansion tank is always preferred. As far as the boiler pump on a primary/secondary system, it should be installed on the return of the boiler. This will increase the boiler pressure by the amount of the pump head. You don't want it on. the supply, because that may cause the boiler to flash to steam by lowering the internal boiler pressure when the pump starts.

This illustration from the manual shows everything in the proper order, except the system pump. I have added the system pump in the best location for air removal.

dough041

Ed,
Thanks so much for your time.. seems easy to follow. My question is- I currently have a taco relay controlling 3 circ pumps for each zone via the thermostats. Should I substitute those 3 and keep the same setup or use as you have the one pump on the supply with zone valves?
Again thanks for your advice

EdTheHeaterMan

Here is the piping arrangement I would use for 3 pumps. The thing is, You need to have all the common piping large enough to handle the flow requirements for all three pumps operating simultaneously. Note the Red section as shared or common piping.
Also take note that each circulator must be equipped with an Internal Flow Check (IFC) or an external flow check valve to prevent reverse flow through unused zones. There are even some cases where it is advisable to have Flow Check valves on both the supply and the return.

dough041

Ed,
That really helps clear up the set up for me. Hopefully the last issue would be , my supply and return lines to/from my baseboard is 3/4”. Should I make the areas you shaded in red maybe 1 or 1 1/4” and reduce down into 3/4”? Again thanks for your help !