Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Sanity check on hydronic system components & design

Hi all,

I’m about ready to order the boiler and related parts for my hydronic system. I think I’ve got it figured out (lots of research here and elsewhere) but would like some feedback if I’ve made any glaring errors on the design. First, the basics:
  • Large workshop with 19 heating loops on one zone with two manifolds
  • LoopCAD calculated a heat load of 47,730 BTU/hr. Total flow through the loops is 4.92 gal/min and head loss is 2.0 ft water.
  • Shop is on a private well. Water in this area is very high in iron and other minerals so I’m not going to let the system autofill from the well (even after the water softener).
  • On the DHW side, the boiler will supply a couple sinks and one shower. In the future there will likely be a second shower installed so I want to size the boiler to accommodate that.
A system drawing is attached. The layout generally matches the planned location of the items on the wall. The unused ports on the manifolds are spares for a future office area and will be blocked off for now.



  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,691
    How long are your loops?  Centers,  pex size?   Mad Dog 🐕 
  • OhioBarnBuild
    OhioBarnBuild Member Posts: 10
    The loops are 1/2" PEX and range in length from 272 to 322 feet. They are on 9-inch centers.
  • WMno57
    WMno57 Member Posts: 1,228
    edited November 2023
    Your water softener will replace the iron and minerals with sodium. Sodium is increasingly soluble in water in relation to temperature. Sodium will raise the electrical conductivity of your water and cause corrosion in your boiler.
    Calcium and magnesium are inversely soluble in water in relation to temperature. This is why they plate out to scale in coffee makers and boilers. That sounds bad, but if you have an old school cast iron boiler with large water passageways, it wont be a problem. Plating to scale gets the minerals out of solution which lowers electrical conductivity, so less corrosion.
    Another option is to buy a pallet of distilled water at Walmart and fill the system from a trash can with a pump.
    The sodium water from your water softener might be OK with the addition of some corrosion inhibitors. But CIs can also cause problems. Adding anything to water raises its electrical conductivity.
    I DIY.
  • clammy
    clammy Member Posts: 3,086
    Just throwing this out there 300 ft on 1/2 pex as I know is the limits on 1/2 pex unless you would like to buy a large pump and a large td on loops and issues balancing . General rule is more loops and keep the loop lengths at or with in 10 % of each other . Also be sure to buy quality manifold w decent flow indicators ,cheap on line manifolds are just that and replacing later is always more costly then spending once and getting it right . As a pet peeve be sure to include a manual hi limit on your radiant loop nothing worse then a bad mixing valve and a floor over heating and ruining say a hardwood floor who pays the bill ? I know it’s not seen much these days but ions ago they were usually included in a radiant system design and boiler diagrams but neither are rarely seen and when it does happen nobody takes any responsibility . Even on a mod con w mix temps I feel it’s wise to install in a last ditch effort to prevent an even worse issue from occurring and ending up in court . Just a clam pet peeve secondary back up or first line defense for damaging flooring or title on radiant jobs after you have witnessed it you always remember it and keep it in the bag of tricks . Ps I kinda prefer brass Manifolds over plastic and if zoning your radiant take a look at cross mainifolds the flow through them is decent for a radiant system and as for zoning if it’s all one temp it’s a no brainer . A learning curve on piping them and making it all look acceptable but the price point leave everybody else out ta bussiness . Great product for a job that fits the bill but hi gpm over 2.5 then ya gotta look else where for higher flow .
    Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • WMno57
    WMno57 Member Posts: 1,228
    Never mind. I read your post to0 quickly, just saw "water softener" and skipped over "not".
    I DIY.
  • hot_rod
    hot_rod Member Posts: 21,793
    .6 gpm in a 300' loop is workable, with 322' loops you should be at around 4' head.
    You start to loose heat at the end of long loops, but in a shop space it would probably not be an issue. 9" on center was a good call.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mattmia2
    mattmia2 Member Posts: 9,391
    The dhw depends on what the dhw feeds feed. If it is an indirect you can get virtually whatever capacity you need by picking the tank size. If you want to use just a hx 2 showers would be tough but might be possible at ~120000 BTU depending on your incoming water temp and how restrictive your shower heads are.
  • OhioBarnBuild
    OhioBarnBuild Member Posts: 10
    Thanks, everyone, for the feedback. Now on to the installation!
  • GroundUp
    GroundUp Member Posts: 1,862
    5700LF of tubing (300ft average loop) at 9" spacing makes a ~4275 sq ft building. Perhaps this heat loss calc should be revisited- 11 BTU/SF seems awful light for a shop space in Ohio, unless only being kept at 33* on a design day and has R60 insulation everywhere with no doors or windows. If anything, at least upsize the circ so you have the ability to move more BTU if/when required seeing as you have enough boiler to do so. I do these shop radiant systems almost exclusively and have several of them scattered throughout Ohio- there isn't a one under 16 BTU/SF with a 60* indoor temp, and that one has an R60 cellulose lid with R35 spray foam walls (only 9ft) and zero windows with only 1 walk door and 1 8x12 overhead door.