Hydronic heating water temps (1 Viewer)

[AJP]

Seems to be many opinions on the internet on what the maximum feed temperatures should be for various heating situations.

Would appreciate thoughts and experience on this. I have 3 zones I am feeding from an electric boiler - each zone has its own Taco circulator controlled by its own thermostat; not sure what the maximum temperature each zone should be fed (eg can handle/is normal)

first zone is basement concrete slab with 4 loops
second zone is the main floor with suspended PEX; two lines between each floor joist
third zone is cast iron radiators (reclaimed)

any thoughts on mixing valve(s) as well also appreciated.

 

[titanpat57]

Id put an aqua-stat on it...maybe start at about 100-120 or so, and work up from there.

They're some variables missing though, such as wall/ceiling insulation and construction type....winter severity, your location, etc.


p.s....when you say an electric boiler...you mean like a radiant heat type boiler?..if so ..what size?

 

[AJP]

Thanks .. boiler is Slantfin Monitron eh 12-135-S

temperatures consistent with UP Michigan ... my walls are 2x10 (actually unfinished and closer to 2 1/4 +/-) and full of pink so approximately R30, the ceiling is engineered cathedral and I think we were at R50 (code here is r40). Windows are Inline Fiberglass and pretty fair but I would have to check the order forms for the spec. Basement is ICF and the slab went on similar foam ...


the boiler has an aquastat ... but that controls the common output .... are you suggesting that I feed the same temp (100-120) to all zones? That would be a straight forward solution.... I can prioritize the heat call with the TACO's on board logic.

I am still trying to understand how I deal with the different loop deltas

appreciate your guidance..thanks

 

[Toyo FJ40]

Radiators work best at around 160-180
Radiant in slab I wouldn't go over 120.
Radiant suspended under the subfloor will need 130 to 140.

You need mixing valves for both radiant zones, the radiators can run at the boiler temp which should be set at 180.

I like the Taco I series mixing valves that adjust by outside temp but they are kinda pricey. Taco I series mixing valve

You can use a standard mixing valve like Watts or Honeywell in the temp range you need.

 

[AJP]

Thanks!!! .. reading up on them right now!!

(Is 130 - 140 considered ok for the suspended pex between the engineered joists ... the conflicting stories I have had come from anecdotal comments that too high a temp will degrade the structural strength etc - ... also I havent put any reflecting barrier in yet as I was waiting to ensure those loops were leak free .. any recommendations on the best barrier/reflecting foil?)

 

[Toyo FJ40]

Trouble with suspended pex is you need to put more heat to warm the subfloor and drive the heat through to the finished floor. Under staple or reflector hangers will help because the tubing will be in contact with the subfloor. Last suspended job I did I ended up at 135 to get the heat through the subfloor and hardwood floor. The nice thing with the Taco I Series is if the max temp is set at 140 it will only hit it when the outside temp hits the design temp (0- 10 F) the rest of the time it will be cooler.

You can cut foil backed insulation board to fit between the joists and push it up till the tubes touch the floor and hold them in place with wood strips.

 

[AJP]

You can cut foil backed insulation board to fit between the joists and push it up till the tubes touch the floor and hold them in place with wood strips.

I will do that ... the reason the pex was suspended and not against the floor with plates (as originally intended) was the protruding screws/nails used on the underlayment that was laid on the subfloor

 

[haystax]

Sounds like you're on the right track. Good post by Toyo on temps. I've learned a lot from folks on www.heatinghelp.com. Good luck

 

[AJP]

Thanks .. good site!


There seems to be a catch 22 with "staple up" ... all advice suggests that porcelain is the best flooring material (certainly compared to wood or even heat rated engineered flooring) for heat transfer and as thermal storage ... unfortunately to ensure the underfloor is stable and secure for the tile invariably means "lots and lots" of screws holding the underlayment ... which means suspended pex... ... I wasn't thinking when the patio and other doors went in that I should have made about a 2 1/2 inch allowance to allow for pex to be installed above the subfloor...
although at that point I was seriously considering rads as I installed on the upper floor....I got lucky in finding some older cast iron units for upstairs and they got refinished nicely... really too bad that folks have been ripping these out and scrapping them ... when refinished they do a great job oh heating!! But a bxxch moving them around !!!

 

[Toyo FJ40]

Thanks .. good site!


There seems to be a catch 22 with "staple up" ... all advice suggests that porcelain is the best flooring material (certainly compared to wood or even heat rated engineered flooring) for heat transfer and as thermal storage ... unfortunately to ensure the underfloor is stable and secure for the tile invariably means "lots and lots" of screws holding the underlayment ... which means suspended pex... ... I wasn't thinking when the patio and other doors went in that I should have made about a 2 1/2 inch allowance to allow for pex to be installed above the subfloor...
although at that point I was seriously considering rads as I installed on the upper floor....I got lucky in finding some older cast iron units for upstairs and they got refinished nicely... really too bad that folks have been ripping these out and scrapping them ... when refinished they do a great job oh heating!! But a bxxch moving them around !!!

If I'm stapling up heat under tile I wait till the backer board or wire is down so I can weave around the nails or screws when I attach the pex.

 

[AJP]

As Toyo suggested.. bought these two iSeries Taco's ... not the outdoor reset type but they have the remote sensors to control the tempered output. Hope to get around to installing these next week.