Radiant Design Feedback Requested

eheinkel

Hello experts!

I am looking for some feedback on a design I am working on for my radiant heating system. I have done many hours of research and I have attached what I have come up with so far. I have already taken the advice of many to NOT use a tankless water heater and use the correct tool for the job, so my current design utilizes a Rinnai combi-boiler. The Rinnai i090CN has an internal Grundfos UPS 15-78 pump for the primary loop and has integrated controls for 2 external zone circulating pumps.

Please see the attached pdf for specifics including heat load, zone specifics, and proposed design.

Some specific topics/questions at the top of my mind are:

Location of expansion tank and air eliminator- I see many variations and opinions on this. The Rinnai diagrams show the expansion tank and air eliminator on the supply(hot) side first thing after the manifold, that is what my current design reflects.

Manual fill setup- I have read since I am using 50% propylene glycol mix, even with a backflow preventor I should not connect the system to my potable water supply. I’m not sure how often I may need to add to the closed loop, but I was planning on plumbing a manual fill valve, backflow preventor and ball valve to a hose bib that I could hook a pump to if I need to add fluid.

Do I need a dirt trap for a closed system like this?

Do I need a condensate neutralizer? I am planning on plumbing condensate using pvc to floor drain with airgap that leads to holding tank.

Any recommendations on adding or removing isolation valves, hose bibs, and/or pressure/temp gauges anywhere?

Thank you all very much in advance! This has been a great learning experience so far and I can’t wait to implement it in the spring.

GroundUp

Any sort of feeder is about useless if you have a leak-free system, and diluting your glycol with water is a poor idea- if anything you'll want an actual glycol feeder or possibly a separate expansion tank which holds a higher pressure of glycol and feeds through a standard auto-feeder. 50% is much higher than any system will ever need in North America, including cold-start snowmelt. You'll need some sort of purge station somewhere, but a "dirt trap" (assuming you mean something like a filter?) is unnecessary with a clean new system. Doesn't hurt, but isn't needed. Regarding the condensate neutralizer, maybe. Your code may dictate that it's required but if this is simply a poly holding tank which gets pumped out periodically, it again will not serve any purpose. Isolation valves on each circulator and each return line, pressure gauge somewhere near the air eliminator, and you should be set.

eheinkel

GroundUp- thank you very much for the feedback. I think I will abandon any optional feeder plans as the system will be leak free. I could always add a solution if it became necessary. I am located in Northern Wisconsin, and my cabin will not be used in the winter. I found a chart somewhere that showed the freeze protection that each ratio of glycol provided, but it was confusing as it showed one set of numbers for freeze protection, and on set for "burst" protection i think, so i was going to play it safe. The "dirt trap" was a term right from the Rinnai installation manual lol- but again it sounds like I could skip this as the system will be new and clean. If i don't need to worry about the acidic condensate damaging my PVC DWV, then I will likely skip that as well- yes it is a plain old 2000 gallon concrete holding tank that gets pumped out about 2x/year. I kind of overlooked the purge station- see the attached screenshot from the Rinnai manual. Is the concept to be able to shut off flow on the return before it enters the boiler and allow air to escape via a hose bib? Thanks again!

Mad Dog_2

I haven't tried the Rinnai Combi, but I had great success with their Tankless Water heaters.  Please keep us posted.  Looks good   mad Dog 🐕