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Baseboard sizing and combi boiler

LoriP Member Posts: 6
edited November 2015 in Radiant Heating
Hello. I'm hoping to get some guidance on installing hot water baseboard and combi boiler/tankless domestic.

We are in a different climate than what we've been accustomed. We moved to Santa Fe New Mexico a little over a month ago and this isn't your normal house. Spent many years in a 100+ year old two story in Kansas running big old cast iron radiators with a conventional boiler. I will never abide forced air.

We did have a plumbing/HVAC company come and provide estimates but I felt pressure was being applied to go with a ductless mini split 4 zone heat pump/ ac option which was obviously the installers preferred system. Asked for the quote for the baseboard/combi option anyway. Wasn't surprised the quote for the mini split system came in at half the quote for the Navien NCB 240 plus 7 slant fins. (Didn't want the modern looking panels.) We aren't supposed to talk prices but I paid less for my Challenger than what was quoted for the baseboard system and that was surface running the supply and returns because the floors are a mix of flagstone and wood or Saltillo tile over slab. No sub floor or crawlspace to drop runs so we said surface run and we will build custom trim to hide the supply and return.

The quote didn't spec the slant fins size, but even assuming they'd all be 8 Ft (which they couldn't be in one of the rooms) I'm thinking either the boiler may be oversized or there isn't enough baseboard in order to run that system efficiently.

I tried to do a heat loss calc but this is not your average house and we've only been here a little over a month, but that has been long enough to experience some pretty good temperature swings and understand the thermal performance of the house
1) Hand built adobe with stucco exterior and plaster interior
2) Seems to be built with every passive solar feature they could manage. All southern exposures have some form of passive solar that keep the house comfortable during the day even when its 20* out and the north wind is blowing as long as the sun is shining. Trombe wall in the bathroom. That room is rarely in need of heat as long we don't have a couple of consecutive cloudy day. The only room that the heat doesn't penetrate during the day is of course the bedroom which has been consistently 60* sunny/cloudy/windy whatever.
3) The largest passive solar feature is probably the most inefficient right now. Solid glassed in entry consisting of 6 panes @ 48 x 76 (single pane, but have double panes waiting to go in which will help prevent losing that heat when the sun goes down so that loss will change.
4) Recently used half a case of silicone caulk sealing exterior door and window frames as well as repairing lose glazing

We've been unsuccessful in getting anyone else out, they either say they aren't licensed for propane and another that was recommended was into new construction, not retrofit... So

Roughly 2000 sq. Ft
Gas = Propane
Electric = Solar PV but do have municipal electric avail
Water = Well water. 1500 gallon holding tank filled by windmill at the top of a steep hill behind the house, so gravity flow, pressure depends on keeping the tank at least half full but the pressure is good

So... what I would like to do is source the parts, install everything I can, and eventually locate a plumber who will work with propane to remove the existing water heater, complete the install of the combi and make the final connections.

Maybe someone could tell me if I'm on the right track.

3 zone manifold with actuators and programmable thermostats to each zone based on usage
Zone 1- Bathroom all by itself , rarely needs heat but I can get 2-4 feet in there for occasions when that loop would need to be used.
Zone 2 - kitchen,15 Ft of baseboard and my office (work from home), 12 Ft of baseboard. These two are adjacent to each other and are also the most occupied rooms during the day so that zone would only call for heat early morning/late afternoon on sunny days or all day on cloudy days but really no need for evening heat
Zone 3 - living room 7 Ft of baseboard is all that I can fit in here, front room (lots of thermal mass holding days heat) 6 Ft of baseboard and lastly our bedroom, the coldest room that gets no solar gain and is on the north east side of the house which I intended to load with 34 Ft of baseboard (three whole walls). Reason is this is the last part of the loop before the return and also the coldest so load it up and assume I would be running lower temps for efficiency and need more radiator. This loop is the evening/night loop.

The slant fin 30 is 3/4 and from the studies I've done I believe I can use Pex-Al-Pex with shark bite connectors?
Proper size pex for the supply and returns?
I know I'll need a pressure tank, check valves , temp/pressure relief valves, air purger valve, three zone manifold, 2 wire actuators, thermostats. (suggestions as to specs)

Is that NCB 240 gonna do the job? I'm confident it'll do the domestic just fine, the utility closet is at the corner between the kitchen and the bath and laundry so a short run to each and everything is a low flow fixture with high efficiency washer.

What I planned to do was mount the baseboards, route and connect the supply and returns for each zones and get everything situated in the utility closet for a plumber to come install and dial everything in.

I'd just like for someone to point out any flaws in my thinking point out things I haven't thought of. I don't mind paying a professional to do the install of the combi, I just don't want to feel like I'm being held hostage for getting the system I want by what I feel was a quote slanted to encourage me to select the plumbers preferred system which 1) isn't what we want 2) we aren't going to want or need the AC option) We don't want the new Cadillac of the HVAC world, we just want simple good ole reliable, comfortable, radiant heat with simple traditional baseboard rads without destroying our floors and good efficiency because propane isn't cheap.... later plan to supplement with solar collectors and hot water storage but that's down the road and the bedroom needs heat NOW.

Thanks for reading and for any and all suggestions


  • SWEI
    SWEI Member Posts: 7,356
    That's a lot of info, but still nowhere near enough to make an informed decision.

    We're in Silver City and we do this. PM me.
  • LoriP
    LoriP Member Posts: 6
    PM Sent
  • LoriP
    LoriP Member Posts: 6
    well, we have 3 casitas on the premises but those don't have heat either. He'd be roughing it
  • hot_rod
    hot_rod Member Posts: 15,028
    no heat would further motivate him. It's nice to be able to see the job, it can open more ideas and options compared to an online consult with pics.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • BiggA
    BiggA Member Posts: 7
    Lurker here... This is really interesting. But you don't state explicitly what the house is designed to be, what heat it has now, and what the problem is. Is sounds like it was designed to be an entirely passive solar house, and has no heating system, or only electric baseboards/strip heat, or a fireplace or something, and electric for hot water? What is the problem? Does the house dip into the 50's for extended periods of time? Or lower?

    If this is the case, or if the heat load is relatively low, then you're trying to hit a finish nail with a sledgehammer. Here in New England, we have enough slant/fin 500 and 550 to go from here to the moon and back many times, but I wouldn't expect that because it works up here that it would make much sense in warmer or more southern climates where heat loads are much lower. Heat pumps are making inroads in places like Maine, but it looks like your climate is really well suited to some mini splits if there is actually load to heat or cool there. The installer sounds like he knows what he's talking about on the mini splits, and it may help that he's probably familiar with mini splits, and not with hot water baseboard, since I doubt you'd find it in New Mexico? That should be concerning using something that's not used in that part of the country, not only because it's ill-suited to the climate, but because no one around there is going to know how to work on that type of system. Up here, every Joe Plumber and oil company can work on hot water baseboard, some much better than others, but I digress.
  • LoriP
    LoriP Member Posts: 6
    No heat at all. Outside of three fireplaces and three Woodburners which we had inspected, only two are safe to use and don't supply heat to the areas needed. It may have been designed in its original form to be fully passive but we're pretty sure the house is larger than it once was and the northerly rooms stay cold. We've been coming here for years in all seasons and there certainly is radiant baseboard in the area. We don't want mini split heat pumps with ugly head units all over the house nor the instant chill that happens the minute the heat stops blowing. I've lived with air and I've lived with radiant and radiant wins hands down for me and always will. I'm not sure where it may have been implied I was trying to hit a finish nail with a sledgehammer. My rationale, at least in theory, had minimal amount of baseboard in rooms that needed the least heat both based on their solar performance as well as usage and more in the rooms that needed more heat due to no passive solar gain and being uncomfortably cold. I started out by asking if that boiler wasn't oversized for what we really needed so I don't understand where what part was considered overkill.

    That was sort of my point.. We weren't looking for a blast furnace to heat a concert hall and we didn't want to be sold more than what we wanted or needed. Just wanted a simple radiant system.
  • Gordy
    Gordy Member Posts: 9,514
    Kurt will take good care of your situation.
  • SWEI
    SWEI Member Posts: 7,356
    BiggA said:

    The installer sounds like he knows what he's talking about on the mini splits, and it may help that he's probably familiar with mini splits, and not with hot water baseboard, since I doubt you'd find it in New Mexico? That should be concerning using something that's not used in that part of the country, not only because it's ill-suited to the climate, but because no one around there is going to know how to work on that type of system.

    Northern NM is full of radiant systems -- enough to support several supply houses stocking parts -- including one that sells exclusively radiant. There are competent plumbers and (as usual) a few actual experts in the area. Much of the basic research passive quantifying solar design was done here by LANL and Sandia scientists in the 1970's and there is still a solid knowledge base as long as you know where to ask.
  • BiggA
    BiggA Member Posts: 7
    So maybe the house needs a little bit of heat if it's no longer fully passive. However, you haven't posted anything about what temps it gets to with no heat, which would be important. If it's only getting into the 50's, you're talking a very small amount of supplemental heat to get it back into the 60's. If that's the case, then a hot water baseboard system is total overkill, and is going to be an unbalanced, overheated mess, hence hitting a finish nail with a sledgehammer. They are OK where you have higher heat loads, but if it's a small heat load, you need something that can balance itself out, hence the minisplit system. I can't read the contractor's mind, but that may be why he was recommending heat pumps over baseboard. I would ask for his rationale, and understand what he's saying, not come in insisting on something that may not be appropriate for that building and climate, even if it would work fine in the typical house in New England or other northern climates. I have had both gas and oil baseboard, and I like it, but I'm under no illusion that it would work for all types of buildings in all climates.
  • BiggA
    BiggA Member Posts: 7
    You may want to get another estimate or two too, and ask each company what their rationale is for a particular type of system.
  • SWEI
    SWEI Member Posts: 7,356
    Lots of unknowns -- we'll get her straightened out.
  • LoriP
    LoriP Member Posts: 6
    A properly sized and zoned Radiant system can also be properly balanced and thanks to SWEI being gracious enough to assist, I'm confident things will be just fine.
  • Gordy
    Gordy Member Posts: 9,514
    Radiant is a very flexible emitter. Radiant cooling comes to mind in your region.
  • j a_2
    j a_2 Member Posts: 1,796
    I second SWEI, I have followed his posts, that guy knows what he is talking about..
  • Rich_49
    Rich_49 Member Posts: 2,610
    edited November 2015
    BiggA . You would probably be best off posting on A/C , heat pumps and refrigeration , sounds like you know a bit about those things but have not a clue about hydronic solutions . You are completely wrong about baseboard and seems you don't even know it gets down right cold in parts of NM .
    Don't know what your background is but we usually assist folks in finding solutions to problems that exist , not imaginary ones made up by folks who don't understand anything other than an agenda .
    You must know MH , DD from GBA .
    Or possibly you could ask us for assistance in understanding better the capabilities of the oldest heat transfer medium on EARTH . We'd be glad to help you .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • BiggA
    BiggA Member Posts: 7
    I have learned way more about hydronics than I ever have wanted to by living with baseboard heat. It works well in the right applications. Although the OP still hasn't provided complete information, it sounds like this application is ill-suited to baseboard, and well suited to heat pumps. I'm filling in the gaps in her story with some assumptions, but if I'm even vaguely correct in those assumptions, the original HVAC guy was right on the money, but the OP refused to listen. Can only lead the horse to water I guess.
  • BiggA
    BiggA Member Posts: 7
    Also, calling low-mass hot water baseboard "radiant" is really bizarre. It's mostly not radiant, it's a passive convective heating method. You're ultimately heating and moving air around, baseboard just does it passively. I loved having hot water baseboard when I had it, but I'm not so arrogant to think that what works for me here would be well suited for use outside of the upper Midwest or Northeast in the US.
  • LoriP
    LoriP Member Posts: 6
    Because the OP has managed listservs and online forums before and dealt with those who lurk until they feel there is prey to be pounced upon. I'm not that prey and won't be badgered. Not by a contractor who wants to force a system on me that I don't want and not by someone who feels they need to be combative. It's my home, my comfort, and my choice which will be accomplished with the assistance of someone who DOES know the climate and how to properly size and implement the system. You don't have to agree with it. I'm sorry if you can't get past your assumption that it doesn't get cold enough here to need heat, that passive solar heats the house when the sun isn't shining or that there's not a bowl of dog water outside right now that went from warm in the sun to frozen in about an hour and a half.. This isn't the deep south and it's not Florida. It's at altitude and arid, but speaking of that mini split, I didn't see you pointing out any flaws with a contractor trying to sell me the cooling option on that system instead of a swamp cooler in this climate, but *I * digress. I avoided your baiting until now, because I didn't want to contribute to bad forum behavior, but you feel a need to keep calling me out, even after I politely replied that I'd found someone to help. Please accept that and move on. Thanks
  • Paul48
    Paul48 Member Posts: 4,470
    BiggA........I posted that climate information, for you to have the opportunity to not embarrass yourself. If you had looked at it, you might have realized that her annual temperature is slightly less than Boston's.
  • BiggA
    BiggA Member Posts: 7
    The lows in NM aren't anything like the lows we see here. More moderate. And in this case, the heat load has more to do with the design of that house than with the climate.

    LoriP, the contractor tried to get you on the right track, but you obviously are bent on putting a square peg in a round hole, hitting a finish nail with a sledgehammer, whatever you want to call it. You still haven't posted any data that indicates what the level of heat actually required is. Have fun with a dysfunctional heating system and wasting money on propane doing what a mini split could have done with more comfort and at a fraction of the cost.
  • SWEI
    SWEI Member Posts: 7,356
    We regularly specify mini-splits and multi-splits. They often do represent the best solution -- but not always.

    Not all brands are created equal, especially with regard to low temperature heating performance. I've had to play the bad guy more than once on oversized, underperforming units and I really don't enjoy the role.