boiler choice for radiant

keyote

Renovating a 5 level, 5000 sf, 100 year old town house from the top down the top floor is about done, and its time to buy a boiler. Plan is to add each completed floor to the new system as i get them renovated. so unfortunately ill have the old dragon in the cellar feeding the cast irons going at the same time for a while. Anyway its 4 floors with 1100 sf typically 4 loops/ zones of 1/2" pex. 175'- 225' length of loops. I'm sort of between radiant designers [guy was an idiot] and may just design it myself in the end [its not as bad as it sounds; though im not a plumber im a tinknocker but I've personally built half a dozen houses from ground up as well as all sorts of other things] i am going to have 2-3 manifolds close to the loop ends serving the a floor or two they are going between joists in center of floors and stacked near a riser shaft , the boiler will be on the second floor under a stair also against this riser shaft so all piping runs are short as possible. total14 loops/ zones, thinking delta t15 s/r as a compromise but i think i can hit 10 with this setup. the fifth floor is a PH of only 600 sf and might add a snow melt zone. Putting actuators on every loop and ill hve the control boxes with the manifolds they serve they located for easy service as well. its been a couple years since i last studied up on the radiant but primary secondary piping seemed the way to go i think. I like control LOL. Itook it down to the brick and had 2 1/2" of closed cell spray foam put in so its nice and tight also triple pane windows, i made my own warm boards with aluminum flashing and plywood with 3/4 oak over the tubes and of course the underside of subfloor is spray foamed for the noise and radiant.. This top floor will be two 1 bedroom rentals each has its own tankless DHW in the bath / kitch drop ceiling again zero pipe runs. I have another tankless for the rear of my triplex.
So been thinking the triangle tubefor a few years while working on the house and was kind of leaning toward their challenger "combi" to delete the need for another tankless for the front of my triplex. i just saw the cc125 for $2400 at my local supply house today. But all the different models of "triangle tube" get me a bit confused if they are really comparable internally ,especially when trying to sort out which models pros are recommending, and what they are recommending them for. as i said this is a radiant job and will likely be over controlled so their outside temp and other control features appeal. But it seems some of these have AL HX others SS HX I dont think they really have a "triangle tube" in them at all anymore. So i guess im asking are guys still liking the triangle tubes, and are their only certain models recommended generally, or recommended for my paricular application. BTW heat loss calc , I know you guys are all about that, and being a hvac guy i get that but well i havnt found any that can calculate 100 year old brick town houses that have spay foam insulation and triple panes flat roofs etc i played around and my best calculation as a tinknocker is 110 btu , ill be upping the insulation thickness from 2-1/2" to 3-1/2" once i get some rent money coming in and start the next floor down hopefully next month. If any of you want to chime in on heat calc guesses i will add the info that and one level is 2/3 below grade and im fully detached but decent solarization south east and north sides. ill be using about 3 inverter type mini split heat pumps for cental ac which could supplement on design day [ well at least Mitsubishi claims they can put out heat on coldest days] but id rather get this right with boiler only, so i will be getting to the bottom of the heat loss calc before purchase and it could be 125 btu. but somewhere between 100 125 im sure. Correct me if im wrong but isn't the point of the mod cons that its not so critical sizing kind of like the inveterate technology on the heat pumps. I wonder because if it doesnt cost efficiency i would even like to oversize a bit cause the only climate change i believe in is caused by solar cycles and we are due for a much colder period starting now. so say the final calc is 110 is it stupid to put in a 125? thanks in advance

Harvey Ramer

I can tell by reading through your post, that you would be best served if you hire a pro to do this work for you. At the very least, someone to do consulting and system design work.

Nothing but good intentions here. Don't take it the wrong way.

hot_rod

Do your homework on Combi boilers. They can be oversized for the heating load, and at the same time undersized for DHW.

Tankless DHW experts tell me at least 180,000 input on a tankless for adequate DHW.
Very important if you wintertime water temperatures drop into the 30's

I have a 120 Combi and it fall behind on DHW capacity when the supply water drops below 50°F. In a household of two, by the way.

keyote

@ harvey
its true i am not up to speed on this yet and i realize my post was way off the cuff. though i have previously done a couple small radiant jobs on additions i built for others as side jobs. what i envision in my house is state of art. I had a designer who had pretty drawings in his resume but when he recommend a tankless water heater i knew he was that 70s guy. what i really want is someone who really knows radiant to talk with me about options. or some really good books but i have not found any that are up to date. no offense taken but youre wrong about my skills i really have built with my own hands and designs half a dozen very sophisticated houses as well as boats airplanes alternative energy systems tractors computers and have been an hvac forman doing major institutional systems for thirty years. but no matter what it is you build the new thing you have to learn from the beginning but i always figure it out.
let me know if you have any books etc to recomend

keyote

@ hot rod
yes I was worrying about that 2.5 - 3 gpm dhw im thinking of building heat exchangers from the the shower drains to boost the watertemp into the tankless units, I figure its while a shower is pouring 70 degree water down the drain they are most stressed. Im in brooklyn NY its really not that extreme here.
I have never used rankless before before and researched a lot including the fine print about under what conditions they would deliver the big print GPM. as for reveiws, its hard to tell whats hype whats poor install whats unrealistic expectations or undersized. The triangle would serve only the master bath and powder room but i might put a big tub in there.seems one of the TT has instead of a tankless loop has a 14 gal tank in tank which if i understand is kind of a tankless with buffer and i think they are suggesting a system where you have something like a solar tank indirectly heated by a second zone of the boiler. it would be nice to get that last hot water system solved with the boiler but the priority is the radiant. thanks

Rich_49

Keyote ,

I have 2 consult / design jobs in Brooklyn right now . I am in Jersey . There really is not that large an obstacle in modeling a home like this correctly . One must just know assemblies . Both homes being done presently are double wythe brick , one is having the 2 lower floors foamed , the 2 upper floors will remain untouched .

Tankless is not gonna be conducive , I would increase tank size and storage temp and mix down .

Maybe there is a lack of the proper knowledge of heat loss and building science in NYC .

hot_rod

The math for DHW, even tankless is super simple, shown below.

I like the grey water HX concept, I understand they have some horizontal mount versions now. fairly good ROI for a non mechanical device.

Many good options for DHW in this issue of Idronics.

If you end up with a boiler that needs, or can benefit from a buffer, I have learned to really embrace the external FPHX method of DHW generation. Somewhere between a tank and tankless, I suppose.



http://dandavissales.webs.com/Lit - Caleffi Idronics 11 Domestic Water Heating.pdf

keyote

@ rich I know its not impossible just the free heat calculators have built in building assembly's and mine are not common so i have been guestimating conservatively. Im 3 wye metal studs 2 1/2"closed cell and 5/8 rock. fully detached partially shaded maybe i shouldnt have mentioned the heat loss is not solid because though i intend to get to the bottom im fairly confident im really close.
Im not sure what your were referring to about tankless and tank size dont have a tank at all, I know I dont write very carefully. I was simply saying that i already have installed three tankless DHW one each for the two apts and another for the rear of my triplex, but will need another for the fron of my triplex unless i use some type of system from the boiler.
I was really posting about the different triangle models. They have the challenger 125 combi 3 gpm domestic $2400, and the 110 prestige with a 14 gal internal tank $4000. from the DHW perspective I dont see the advantage to the prestige once it empties its 14 gals its a 110 vs a 125 if i understand correctly. from the radiant heat perspective i wouldnt mind a slightly oversized unit and a lot cheaper and smaller too, but I dont know if there are other considerations between the two; internal construction?, control parameters?, since mine will be a fairly sophisticated system i included that info to advise on boiler choice.
I wish i could afford to just hire an engineer but i really cant the only labor i have hired on this entire project is some demo guys to load dumpsters and offload sheetrock the rest has been my brain and brawn. so far details like balancing the loads on the three phase electrical system to trap primers on the condensate and pressure reliefs dumps are turning out the way the lads and I build hospitals etc union in NYC. well i did cheat on the sprinkler system using pex not black.

keyote

@ hotrod Thanks for the intro to Idronics im sure its going to give me a lot of info. The picture of the woodstove with a coil is something like i did in my idaho cabin but i did it with a propane DHW heater as the tank so if the stove goes out while im away the tank kicks on, also i tied in solar water panels so when its too warm for woodstove DHW still is only on pilot. Everythings convection so no pumps. I built a hydro electric system for this cabin and am in the process of converting the the hear sink [too much electric] into a hydrogen electrolyzer that will make me hydrogen gas to replace the propane. also built a still to make alcohol ftom jerusalem artichoke to run the rigs.
oh the HX under from the shower drain i was just going to solder up a pipe in pipe deal about 60" some clever guys on the web have worked out the details and run tests copper to copper is best but i understand the bigger out pipe could be insulated PVC to save money. honestly when i looked into it it seemed it should be standard practice if you have a tankless near a shower which in my opinion is the only place to put a tankless bath ceiling my hot water runs are under ten feeet with 2" insulation. But i got to design the bath kitch laundry locations to centralize piping.

SWEI

Step back and look at the big picture for a bit on this. You have described a semi-complex system serving multiple tenants which you presumably intend to own for some time. It's going to take some time to understand before we can reasonably expect to offer you the best advice. What did the heat loss calculation show for each floor/unit? What are your gas and electric rates like there? How many gallons is the soaker tub? Are there any other large DHW demands?

keyote

@SWEI Thanks for responding. conservatively about 30k ea on the on the three typical 1100' floors the 600' ph and 1100" basement were about that combined.
NYC nanny state electricity is second highest in Nation, i imagine nat gas is not much better so im building efficiently [i would anyway because its a challenge i got into while building my alternative energy homestead]. I'm putting electric solar panels on roof since nanny state is subsidizing that.
As for DHW its all taken care of except for the front of my triplex which will have a master bath and a powder room or guest bath. A big tub would probably be seldom used so i have thought if that were the issue i could add a little something to assist just the tub. But the TT s give 3gpm DHW so even the tub should be ok.
What im wondering is has the opinion on triangle tube changed in the three years since i started the reno? and with the price difference between the prestige and challenger am i missing something, because the challenger seems a better deal. like i said i dont want to drive the choice of boiler because of the 1 1/2 bathrooms, the radiant system is primary focus but if its all the same then it would make life easier.
As far as the entire radiant system; the house has typical floors and ill continue using 1/2' pex . The 6 loop manifold installed at the top floor has four aprox 200' loop/zones two ea for the apts and two futures for the PH [each apt will become a duplex and get a 300' 2nd bed/bath and roof deck eventually].My floors will likely get thee 250'-275'loops each,instead of four loops. i haven't decided how to manifold them yet but I think Ill put them all on a 9 loop manifold at the second level under the stair so three only travel up ten feet, three down 10'and three have zero lead. that would put that manifold almost directly over the boiler in the basement below. The basement is the only floor thats not a homemade warmboard under hardwood its a slab 5' below grade. or possibly radiant walls instead of floors. chopping it up for insulation under the tubes doesnt appeal but if i dig it out anyway to get a bit more headroom its no more work.

keyote

@ harvey etal
look I know its frustrating to listen to someone minimize your 20-40 years of experience. Thing is I have worked 33 years off of **** mechanicals and shops as a foreman i constantly find engineering architectural **** and sub optimals, i have disdain for the you cant go wrong following the print mentality. So no matter what, any design i would commission I would would never install in my house until i thoroughly understood not simply how it functions but why this design over all other possibilities. once i can do that im going to wonder why i paid someone to design it especially because im sure to decide to modify it. That still doesnt make me a master plumber and i am only going to learn this by pestering dozens of plumbers and engineers. now i have on my shelf a dozen books including dan holorans 3-4 years ago when designing my house i bought them and read them i actually found pumping away and primary secondaty thrilling reading yeah im a nerd. but its been 4 years i learned enough then to design the loops and keep in the back of my mind the decision points id have to cross as construction progressed. Ive logged my 100 mountain acres Ive built several 70' bridges that withstood the legal onslaughts of usg i figure stuff out.its not a knock on your skills i sit at construction meetings with 30 50 year old forman that im sure we could put a man on the moon in a decade id we set our minds to it. but you have to start with the dumb questions.

Gordy

You always need a plan on paper. Plans can be modified.

There are certain initial steps you need to take.

Envelope where are you going with it? What improvements are you willing to make, and what is in your budget.

Heat loss nailed down. This is the beginning of any design.

SWEI

Stay away from those 275 foot loops of half inch if at all possible. Look at the flow/head numbers (Uponor CDAM has great ones, and they apply to any ASTM-compliant SDR9 PEX.)

The newer TT Prestige stuff is excellent. No experience here with the Challenger -- none of their wholesalers here bought into the line.

Remember that GPM is purely a function of heat rise, so read the fine print. If this were my project, I would seriously consider a small (think one or two collectors) solar thermal system. Look at it as a preheater that will double or triple the recovery rate of your water heater.

For the soaker tub, a separate, dedicated tankless water heater may make sense.

keyote

@ SWEI
yeah im thinking ill add solar water when i get the solar electric installed, i cant install the solar electric myself if i want the nanny loan etc so i have to wait.
yeah i reallly really get the heat calc but as ive said over and over i cant find any info that has numbers for how i built my house its all for suburban and commercial assemblies. fror instance i looked at the uponor you recomended probably looked at it years ago as well in fact a supply house once gave me the design dvd when i installed a small radiant for an addirion i builrt someone but i cant find it. anyway when you get to the supply water temp the closest they have to me is quick trac 8" OC which as far as i know is not for 1/2" pex but 5/16 hpex. its the same for the walls and the windows.
so if you guys can point me to the numbers for my type of construction i could give a more confident heat loss etc. again i have 3 wye brick with metal studs and 2 1/2' of closed cell spray foam 5/8 rock. the floors are 3/4" osb sub floor panels then i ripped 3/4 ply into 12'' rips for sleepers which i spaced 3/4 to make tube channels at the perimeters and where needed i rounded thge rips male and made female end pcs. I favored the exterior walls both by coming in to the rooms along them and exiting along them and tightening the spacing on the first loop as well. i used aluminum flashing below the tubes and above the tubes to spread the heat a bit so basically the tube has only some flashing and 3/4" oak above it. underneath the subfloor will be spray foamed probably 4" open cell what evers best for radiant and noise. the windows are vinyl triple pane uponor lists none of these systems in that work book. On top of that ill bet its all based on a suburban home sitting on a half acre i have four stories above ground with a 5' alley on 65" long west side with a building taller than mine but no windows and a 10' drive on the east side with a building the same height the south side is 20' long and open except for a tree the north has a taller building about 40' away so this is not typical, see my problem. now some of the free software will give you a ball park of say 140k for an old 5000 sf and a 110 k for a new construction but i bet neither are anything like i have. I hired a designer on line who was reasonable he certainly had a lot of knowledge and experience [ im in the hvac bus i know when someone has a fair amount of knowledge] but i started to get the feeling he was a bit behind the times and tilted to rural applications and was biased against more expensive complex options, im frugal but not penny foolish he talked me out of pex a for the top floor which i kind of regret a little, mainly because of kink risk with my tight manifold locations. and 12" OC which i think is ok but with the wood floors i could have maybe lowered temp with closer spacing. then when he tried to talk me into a hot water heater instead of boiler i knew from the 80s this hadnt worked well and am not sure why todays tankless which are made for short cycles wouldnt work but since he could really explain it easily and he got ill so we havnt spoken in a couple years i never got the plan but only gave a small deposit we are good.Im perfectly capable of being talked to in tech speak and simply google a term i dont know but being a tinknocker working large plants hospitals etc im passing familiar with all the mechanical jargon and systems but radiant is not really used much its more cooling towers and chill beams heat pumps etc, but like ive said ive built enough things to have a bank of peripheral knowledge that will give me a sense of what my unknown unknowns are might be. I really wasnt going to get this far into this with this post i know how guys are and i meant to go back to all the notes and research from three years ago ago then ask specific questions but over the past couple days some of it has come back and yeah the biggest headache is the heat calc reliability. Im going to have try and get some professional software i guess where i can plug in the exact assemblies i have made.