Hydronic heating system Denver Colorado

tlorenzi

Two questions. Can the pumps go on either the supply or return line? I currently have them on the supply side with  a Rinnai manifold. 2. Why do you need to prime the exhaust before you start up the Rinnai duo tankless.  Any help would be greatly appreciated.

Alan (California Radiant) Forbes

It looks like you've got it right, i.e. pumping away from the expansion tank.

When you pour a cup or so of water down the exhaust, it fills the condensate trap so that flue gases don't fill the room.

EdTheHeaterMan

The pump acn go on the supply of the return. For years the old dimers installed pumps on the return side of the system. However for years there have been all kinds of problems with getting air in the system, overloaded expansion tanks and poor operation in general. If you get a chance to read @DanHolohan book called Pumping Away, there is a detailed explanation of the benefits of placing the pump on the supply side of the system and pumping away from the expansion tank. It has a lot to do with the physics of water including Boyle's Law and Henry's Law on the absorption of gasses in liquids based on pressure and temperature changes.

Or you could just take our word for it and place the pumps on the supply side with the expansion tank between the pump and the boiler with a way to eliminate air at that point.

mattmia2

There is an article on this web site too:
https://heatinghelp.com/systems-help-center/pumping-away-piping/

Mad Dog_2

TLorenzi ...is this your first Rinnai Unit for heating? Are you happy with them?  I've installed many of the Domestic water 💧 heaters with zero issues, just never used for Hydronic Space heating yet. I'd like to revisit them.  Thanks for the input.  Mad Dog 🐕 

HVACNUT

The secondary manifold looks like it's reduced in size from the primary manifold. Is that what the manual says to do? 

Nice neat job though. 
Gonna run copper to the ceiling before the pex connections are made to keep it neat?

tlorenzi

Thanks for all the input great information. Not sure how to answer individual comments, but this my first Rinnai duo. I have used for DHW in the past with great success

tlorenzi

This is what I have been modeling my install after. Probably a little over kill

Derheatmeister

Why so many circulating pumps ?
Do you have 40.000 sqft.

dko

I've changed teams recently in favor of zoning with zone valves in most residential builds, though it does hurt the bottom line a little not selling more pumps.

hot_rod

Derheatmeister said:

Why so many circulating pumps ? Do you have 40.000 sqft.

About 800W worth, no need to fire the boiler on mild heating days😗

Each one running about 20- 25% wire to water efficiency?

HomerJSmith

So, you are going to have 5 thermostats? I think your supply piping should be 1-1/4" In Denver in the dead of winter all your circuits will most likely be running. The returns are 3/4" ? Since you are zoning with circulators, how do you know what the flow rates in gpm in each circuit? I use balancing valves on the return to set the gpm. You also need check valves to prevent ghost flows. Also it is good to have shut off valves with a hose bibb to isolate circuits and make filling the sys easier. I guess you are going to use a relay panel to manage the thermostats and pumps. I would put a Webstone valve with hose bibb at the top of the X-Tank. There is going to be air trapped there.

tlorenzi

Thanks for all your comments. Very much appreciated

exqheat

With that much demand, one would want the largest possible manifold to allow for flow when many pumps are on.

hot_rod

The header size depends on how many gpm you need to supply all the zones. Its possible that 1" is adequate.

exqheat

Why not use what is available? To run on lower temps, circulation will be high.

tlorenzi

Finally have the entire hydronic heating system complete at my daughter's house in Denver but am intimidated by the startup procedure for the Rinnai Duo. Seems like a lot of steps to get it started.

Any suggestions?

Jamie Hall

First thing, which may not be in the manual, make sure that you all the air purged out of the system and that the cold fill pressure is correct.

From there I'd say to follow the manual...

tlorenzi

Thanks.

psb75

Rinnai boilers have an initial de-aeration cycle in the start-up/commissioning stage. It starts as soon as you power-up the boiler and be aware it happens each time you power-up. You can override that function
with a special code (provided). The manual has a proscribed commissioning proceedure.