New Construction, Need Hydronic Piping Advice.

OldDude

Need to build Hydronic In Floor Control Panel for New Building [Shop & Apt].
Would like to know if this system will work, need advice or suggestions.
Complete piping diagram & parts code here:

hot_rod

A common P/S piping, looks fine. Is that Rinnai a water heater or boiler? If it is a condensing model, why the thermostatic mix valves/ seems you could just fire the boiler to the required SWT?

OldDude

The Rinnai is a Tankless Water Heater only, Non condensing, LP Gas 150000 BTU.

EdTheHeaterMan

You have specified a water heater for a space heating project. you should use the Q85SN for space heating only. They also have combination models for both Domestic Hot Water and space heating. But do not make the mistake of trying to do space heating with a DHW unit. There are many "How do I fix this?" problems here and on other similar websites that can be avoided by selecting the proper product in the first place.

Here is an amended diagram for your piping,

but there are better diagrams in the instruction manual for the proper heater

Respectfully submitted,
Mr.Ed

geno907

is rinnai q series a pump into instead of a pump away boiler?

EdTheHeaterMan

Most of the boilers are pump on the return. The expansion tank should be on the system loop, making that the primary loop. (according to Dan H. the primary loop is the one with the expansion tank). The boiler loop is now the secondary loop and the boiler pump should ADD pressure to the boiler heat exchanger to increase the pressure in the boiler. higher pressure in the heat exchanger will allow higher temperature before boiling the water. If you put the pump on the boiler outlet the pressure in the heat exchanger will drop, lowering the boiling point.

I find that the manufacturer's instructions are usually pretty good as to where to put the pump(s) on these systems. Most of them have tested all the options and have put the parts in the best place for the best outcome.

Yours, truly,
Mr.Ed