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DHW now, Radiant later?

doughpat
doughpat Member Posts: 36
edited April 2020 in Radiant Heating
When I installed the PEX tubing in the slab of our new home (which may end up being a high rental and not actually our home), I told myself (and my more financially responsible wife!) that I "just wanted to get the tubing in -- you can't put it in afterwards!". That approach somehow morphed into, "we have to hook it all up now", mostly because of a mistaken idea I had that the gas company would only provide a new service line if I did both room heat and DHW. It turns out I was mistaken -- just one "gas appliance" was apparently enough to get them to cut the street, lay the pipe, etc.

So. We are way, way over-budget on this project, which is a function almost solely of me acting as general contractor (as well as some snags in getting the sewer and water lines hooked up...long story).

The point is, I currently have reasonably well-installed PEX lines throughout the home, but we are having a hard time dropping the kind of cash it takes to "do it right". Every well-thought-out system seems to be a minimum of $ (plus major labor costs). I definitely do not like the idea of doing this cut-rate and ending up with an inefficient or unreliable system.

Is there an approach where I can install only the DHW side of the system now, and add the radiant side later? Once we recover from the budget overshoot (and maybe get a better sense of how the house will be used), I feel like we'll be able to put together a proper system.

I realize this might incur some unnecessary expense, and I'm ok with a small amount of 'waste', if it means I can not spend thousands of extra dollars now.

Some info:
-1 bed/1 bath home (bath-shower)
-Relatively cold groundwater (I've been told to look for 70F temp rise)
-Approx 31K total radiant heat load (with 11K the smallest zone, which very well may be the only zone that operates often).

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    Well, since running both your domestic hot water and your radiant off the same appliance rarely works well, seems to me that you won't be out if you were to install whatever you need -- such as a nice tankless wall hung -- for your domestic hot water now, and later on when you are ready install a nice small mod/con boiler for you radiant. That will work well now, and work well in the future.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 18,190
    Radiant Ready is the term we use for jobs where the tubing only is installed Some installers would install the manifolds and leave the pressure test on, until the system is connected and finished

    At the very least cap or tape the loop ends to keep bugs out😉
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • doughpat
    doughpat Member Posts: 36

    Well, since running both your domestic hot water and your radiant off the same appliance rarely works well, seems to me that you won't be out if you were to install whatever you need -- such as a nice tankless wall hung -- for your domestic hot water now, and later on when you are ready install a nice small mod/con boiler for you radiant. That will work well now, and work well in the future.

    @Jamie Hall Thank you for your reply. I suppose what I should do now is think carefully about placement of the DHW equipment so that I don't end up running out of room for future radiant gear.

    I have this reluctance to use tankless DHW because I've been irritated with cold-water sandwich effect, but from what I've heard that has been improved (and may have been a function of inadequate gas pipe sizing -- we have a large gas line). They also just seem needlessly complex and high energy....I like the "low and slow" idea of a tanked heater. It sort of seems crazy to me to fire up one of these beastly tankless heaters just to wash your hands.

    But maybe I'm just being old-fashioned or paranoid. I suppose there is a reason so many people are using them now. Plus, the concept of a future radiant setup in a relatively small area probably is another reason to go tankless....just the space savings alone.

    Do you happen to have any recommendations on a "nice tankless wallhung" for my situation? 1 bed 1 bath, 70F temp rise, and if I understand correctly, many people around here use 150-199K heaters (my plumber is recommending the Navien npe-240s). I believe he said I could also use a 180K heater but recommended the larger one for better performance.
  • GroundUp
    GroundUp Member Posts: 1,495
    If the budget is the main concern at this point in time and the radiant is a "down the road" thing, for simplicity's sake I'd probably just go with a regular old powervent water heater tank and deal with the rest later when finances allow. Just make sure to rough in an intake pipe through the wall or ceiling to serve the boiler when that day comes. Even a combi-cor tank like we'd discussed in the other thread is going to be within the price range you mentioned above so if $3k in parts is irrational, you don't really have much of an option at this point besides a tank or tankless WH only. A good condensing boiler and indirect tank is going to be well above your noted budget for parts alone.