Single zone boiler plumbing *UPDATE* with install pics.

cfar

First time poster,  long time lurker.

I'm installing an I series Rinnai combi boiler and have a few questions.

My first question is feed line to the boiler half of the system. Rinnai has a diagram in there install manual that I'm using as a basis for the layout of my system. I'm curious if the teal markings (DCW) are plumbed correctly. Simply a tee fitting from the DCW to the supply line for the boiler. I have been looking at several pictures and they all differ some. Next is the location of the single pump being located after the air separator.  Not really a question as it's more of a verification.

Missing from the diagram is the condensate line with a neutralizer.

Any questions and concerns are welcome.

I'm sure Ill have many more questions once the boiler arrives and install begins.

cfar

Next question.

Can I still use the water heater portion of the combi boiler while I plumb the boiler system if I close the system after the expansion tank?

Alan (California Radiant) Forbes

OK, the teal line is correct. Just install a ball valve on the branch to the DCW inlet. 

The boiler needs to be filled with both the heating water and domestic water in order to work properly. With all air pockets removed. 

EBEBRATT-Ed

where is your circulator for the main loop? it should be located a the red mark where it says "system supply"

cfar

EBEBRATT-Ed said:

where is your circulator for the main loop? it should be located a the red mark where it says "system supply"

My mistake. Red is circulation pump.

cfar

Alan (California Radiant) Forbes said:

OK, the teal line is correct. Just install a ball valve on the branch to the DCW inlet. 

The boiler needs to be filled with both the heating water and domestic water in order to work properly. With all air pockets removed. 

Ok. So if I understand correctly, I CAN NOT use the water heater portion of the unit while I take my time to plumb in the boiler's supply and return lines?

Thank you two for your help.

Alan (California Radiant) Forbes

I would wait until you have your heating piping up and running, purged of all air. When there is a call for DHW, the internal pump in the Rinnai boiler will pump water to and from the heat exchanger to heat the DHW. If the boiler is not properly filled or not free of all air, it could fry the pump.

hot_rod

If it is a combi there is a circ inside the boiler
In the piping schematic you show, a valve on either end of that straight horizontal pipe, and you could fill and run the boiler.

On the left side put a pump iso valve/ flange, where the red blot is on the pic. On the right side a webstone purge ball valve. Now you have two useful valves and could pressurize and run the boiler.

cfar

Thanks for the info. I'll do just that!

Is there anywhere else you think I should place more valves, unions, etc.? 

I will be uploading my build process once I start making some real progress which should be this weekend.

hot_rod

I'm not a huge fan of unions that will never get used. The circ by default are unions, that is the most common replacement item.

cfar

I need help connecting the pump wires to the PC board. The Grundfos pump has a "line", "neutral" and "ground" wire connections, but the Rinnai install manual does not differentiate which wire goes where on #2.

ETA: the manual also does not differentiate where each of the thermostat wires go on #4.

I did call Rinnai's customer service but because I'm Joe Smoe the homeowner they will not tell me the wire orientation.

The install is 99% complete. I still have some finish work to do but here it is mid-install.

What I started with.

cfar

One thing I think I would change is the autofill bypass valve orientation.  It sticks out and can easily be bumped while walking past it. I'll probably remove the handle to prevent that from happening.

I'll post some more pics once I finish the wiring.

pedmec

Couple of things

Your union and gas cock need to be swapped. Gas cock needs to be before the union so you can break the union to repair any gas components.

What size is this boiler and how long is that gas line 1/2". What is on the gas line. Model # of the boiler will help.

Where is your expansion tank?

cfar

Ill swap the union and the cock. Makes sense.

120,000btu. The gas line is what you see plus 3 ft. Propane with intentions to swap to NG in the near future.

The pic was taken mid install. In the pic I'm missing the expansion tank along with the exhaust/vent and hot water supply just name a few things.

cfar

I have my auto fill set at 22psi which is in the middle of the recommended range (17-26psi) for the boiler. Should my expansion tank also be set at 22 psi empty?

cfar

hot_rod

15 psi would be plenty if you are 3 stories or less? Yes the tank needs to be pre-charged before installing.

cfar

Single story with a basement. The expansion tank at 15psi for a 2 story is what I read during my research so I never gave this any thought.

I left the expansion tank at the factory 12psi at install, but the boiler will throw a code if I don't fill the system to a minimum of 13psi. I currently have it at 22psi to avoid the code and fall in the middle of the recommended pressures..

I guess what I'm asking or at the least curious about is the 2 pressures and do they need to match?

hot_rod

Some hydronic pros like to keep the tank pre-charge a few lbs lower than the pressure you fill the system to.

If you have a min. of 13 for the boiler pressure switch, maybe 15psi pre-charge in the tank, 17 fill into the system.

Assuming you fill with cold water, as the psi would go down it the water was hot, when it cools.

With a critical pressure, be sure you have a working fill valve left open. At least for a few heating cycles as air comes out, you need water to go in. That small capacity forced in the under-pressurized tank will help assure you don't drop after small air removal also.