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Boiler Decisions For New Install

brichard917
brichard917 Member Posts: 10
edited December 2019 in THE MAIN WALL
Hi Guys -

I've been scouring this page for a while but I'm throwing in my hat, I'm way out of my league. Getting quotes for a new heating system, only two different setups have been suggested, but each contractor seems to bad mouth the system they are not recommending and my head is spinning. Looking for some unbiased insight, something a bit more tangible.

Current situation:
800sqft cape (1 story living space)
2 bds, 1 ba
Central MA
Old oil burner (96k BTU) which was converted to gas
Recently updated with blown insulation in attic and all exterior walls

Contractor Options:
1) Combi boiler (Lochnivar 199BTU) with DHW 4.8GPM
2) Condensing boiler (Lochnivar 110BTU) with a 40GAL indirect hot water heater (Superstor)

I've read a lot, maybe too much, and there are pros and cons of each that I can see. My biggest worries for the the combi boiler are getting enough hot water, the potentially expensive repairs, lime scaling, the boiler being required to run during the summer, and the potential for short cycling. My biggest worries about the indirect option, honestly, is the much higher upfront price and larger footprint in the basement.

Biggest hot water drawn would be 2-3 tubs per week, most simultaneous usage would probably be a sink or wash machine and the shower but it would be rare.

I appreciate any insight you are all willing to provide.

Comments

  • At least they agree on a manufacturer, who (hopefully) will have a stocking distributor in your area.
    If you have doubts about the water supply, you should be able to get an analysis from your water company.
    You may want to double check their heat loss calculations, by using the SlantFin app, which is straightforward to use.
    A combi boiler, by its very nature will be oversized for heating, because of the hot water load, and it may need yearly descaling, and maintenance, eating up the savings of lower fuel use. It may also be short cycling during the shoulder months.
    If you choose a heat only boiler with a separate tank, you could choose a more basic cast iron boiler which would be easier to service in the future, but will need to exhaust into the chimney, with a good source of combustion air from outside.
    The advantage of a mod-con boiler is the use of a direct connection to outside combustion air, therefore unaffected by interior exhaust fans interfering with the venting up a chimney. Also the modulation of the burner is a plus.—NBC
  • HVACNUT
    HVACNUT Member Posts: 5,803
    I'm not a fan of combi's in general unless there's limited space for the installation. I'd go with the indirect. Especially if you're filling bathtubs.

    Also, if there are radiators in the attic, then it needs to be added to the heat loss calculation, even if the space is not used.
    delta T
  • Icarus
    Icarus Member Posts: 143
    edited December 2019
    What I’m seeing is a much bigger boiler than you need. 800 sq ft, with up graded insulation? My guess is your current oil burner at 96k btu sounds like it will be way too big assuming marginal efficiency. I suggest doing a heat loss calc.

    As a side note, I have a house (1300 sq ft) in Maine that was oil forced air. When Nat. Gas became available, I called a local contractor (and being in a hurry, didn’t do my due diligence!) and had he replace the furnace with a similar sized Nat. Gas unit. The furnace was so over sized that it would run for 5 minutes, then shut off, then it would get chilly since the thermal mass wouldn’t get warm. I need up replacing it myself with a 2 stage 45 btu furnace. With moderate insulation upgrades, even this is too big and the duty cycle is too short.

    When in doubt, find a competent professional to really analyze your situation. I’m guessing a smaller mod con, either combi or with a demand gas fired water heater. The cited 4.6 gpm is plenty for tubs or 2 showers. In another house, we live with a mod con combi (Rinnai) that only puts out 2.5 gpm @ 70F rise. Works great, although tubs are slow

    Icarus

    PS for that sized house, I would seriously consider a heat pump, like a Sanden high temp coupled to your boiler loops. The HSPF is pretty high, and I’m guessing operating costs are possibly less than gas, even with MA high electricity costs. (Couple that with on site solar and you are golden...heating for free!). Problem is finding a good professional who understands the technology to do a proper install.
  • Jamie Hall
    Jamie Hall Member Posts: 23,159
    One of the dependencies on the main place I care for is a 600 square foot studio and art gallery. Cathedral ceilings (18 feet to the peak) On piers (air free to come and go underneath). No insulation -- I mean no insulation. It heats adequately (meaning it will hold 65 inside at 10 outside) with one 38,000 BTUh input (30,000 BTUh output) Rinnai wall furnace. It would take 40,000 BTUh output to hold 70 inside on a design day (0 F in this area).

    Bottom line. Both of those boilers are way too big (the Combi is insane). If those are your only two choices, I'd definitely go with the smaller Lochinvar with an indirect. You'll be happier with the hot water (like you'll have plenty of it) and the boiler won't cycle quite as badly.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Solid_Fuel_ManCanuckerrick in Alaska
  • DZoro
    DZoro Member Posts: 1,048
    Can't really go wrong with either system, when set up properly.
    The Noble combi 199 can be design set to max out its btu's as low as 19,000BTU. Don't get worked up that it is too big for the heating side of things. It will provide you with as much constant water as you need inside of 4.8gpm.
    D
  • KC_Jones
    KC_Jones Member Posts: 5,722
    @Jamie Hall is on the money. Think of those boiler sizes as clown shoes, they cover your feet, look good in some way, but do you want to wear them daily?

    For 800 sq ft you are looking for the smallest boiler you can find, and it's possible that will be too big.

    They are sizing for the hot water load which, for me, makes zero sense. The indirect can function perfectly fine with your loads, on a much smaller boiler. A typical stand alone water heater is 40k BTU. I have one and can easily do 5 back to back showers for my family of 5 and still have a little left over. Your contractor is essentially saying you need a 110k BTU water heater, I seriously doubt that.

    The combi, other than saving space I personally can't think of a single good thing to say about them.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Jellis
    Jellis Member Posts: 228
    If the contractor cant explain their product and methods well enough to make you feel at ease maybe try another contractor?
    Have you tried the find a contractor tool on this site?
    They should be able to confidently tell you what they calculated for BTU loss and why they are recommending the setup.
    Both options given sound dramatically over sized to me given you only have 800 sq ft and have had new insulation work.

    An over sized boiler will cause short cycling and will only add to service calls and repair costs in the future.
  • JUGHNE
    JUGHNE Member Posts: 11,042
    What type of emitters do you have cast iron or fin tube?

    I would go for a condensing boiler with an indirect DHW tank.

    It seems that some contractors over size boilers because they are also doing DHW.
    Most of these boilers have controls that will switch back and forth between space heating and DHW. So you do not add the two values together for sizing.
    I heat a 120 gallon tank and never know it is happening in the heating season. If DHW takes too long it will go back to heating to catch up and then back to the DHW job.

    BTY, my house is over 2000' with heated basement in northern NE. -5 design day. We have an 80,000 btuh boiler, probably could have gone smaller.
    Solid_Fuel_Man
  • hot_rod
    hot_rod Member Posts: 22,018
    I'm a Combi proponent, live with 3 of them.

    a Lochinvar Nobel 110 Combi for example could cover your DHW usage, 3 gpm or more.

    It can be ramp delayed or locked at it's lowest firing rate for heating use, that is 11,000 BTU/ hr at low fire.

    Assume 25 btu/ ft on design day x 800 = 20,000 BTU/hr load on design day possibly?

    I think some of the 50K mod cons fire down to 8,000 BTU/hr. But that in not enough for instant DHW production.

    I doubt you will find any fixed output conventional non con boilers in that range?

    I have a 16 year old Laars Mascot combi, never been descaled, it is connected to a softener.

    The small plate HX used in combis have pretty high flow (channel) velocity and seem to be less prone to scaling compared to tankless DHW units.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Solid_Fuel_ManDZoro
  • brichard917
    brichard917 Member Posts: 10
    The problem is I have trusted each contractor I have met with, they all seemed knowledgable and were willing to discuss any questions. I suppose bad mouthing was the wrong choice of wording, they've all just been passionate about the product they recommend. However, none if them did a heat loss test that I could see, they merely asked the square footage.

    The basis behind the 199btu boiler, as it was explained to me, is that was the only way I would get a decent GPM and the turndown (10:1) would compensate for the oversized boiler.

    Maybe I will have to look into the modcon boilers. Do those vent through the chimney? One of the reasons I have been drawn towards condensing boilers was due to my chimney deteriorating. I have a fully functioning gas fired water heater at the moment, but if I only replace the boiler or need to go through the chimney as well, i will be forced to reline the chimney at an extra cost rather than just capping it and forgetting about it.
  • Le John
    Le John Member Posts: 226
    hot_rod said:

    I'm a Combi proponent, live with 3 of them.

    a Lochinvar Nobel 110 Combi for example could cover your DHW usage, 3 gpm or more.

    It can be ramp delayed or locked at it's lowest firing rate for heating use, that is 11,000 BTU/ hr at low fire.

    Hi @Hotrod - I know how to lock it to its lowest firing rate but how do you set a ramp delay on the Noble Combi?

    hot_rod
  • brichard917
    brichard917 Member Posts: 10
    Not sure if this will help with decision making but with the current boiler at around 60% efficiency and 96k btu input (I think) the most I have used was 120 therms in a month and that happened once. Every other cold month for 2 years since insulation has been 100 therm max. Typical range 60-100 therms.
  • hot_rod
    hot_rod Member Posts: 22,018
    Le John said:

    hot_rod said:

    I'm a Combi proponent, live with 3 of them.

    a Lochinvar Nobel 110 Combi for example could cover your DHW usage, 3 gpm or more.

    It can be ramp delayed or locked at it's lowest firing rate for heating use, that is 11,000 BTU/ hr at low fire.

    Hi @Hotrod - I know how to lock it to its lowest firing rate but how do you set a ramp delay on the Noble Combi?

    Le John said:

    hot_rod said:

    I'm a Combi proponent, live with 3 of them.

    a Lochinvar Nobel 110 Combi for example could cover your DHW usage, 3 gpm or more.

    It can be ramp delayed or locked at it's lowest firing rate for heating use, that is 11,000 BTU/ hr at low fire.

    Hi @Hotrod - I know how to lock it to its lowest firing rate but how do you set a ramp delay on the Noble Combi?

    I have one of the first Nobels produced, I think the control has been undated or more parameters opened?

    On mine it only has Space Heat Rate Limiting, adjustable from 10- 100%, I locked mine at 30%.

    I might have misspoke on the ramp delay, it might only be on the Knight series?

    On the Nobel, mine has ODR and Heat Rate Limiting. Adjusted correctly it should dial the boiler heat function to your system needs very well.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Le John
    Le John Member Posts: 226
    hot_rod said:

    Le John said:

    hot_rod said:

    I'm a Combi proponent, live with 3 of them.

    a Lochinvar Nobel 110 Combi for example could cover your DHW usage, 3 gpm or more.

    It can be ramp delayed or locked at it's lowest firing rate for heating use, that is 11,000 BTU/ hr at low fire.

    Hi @Hotrod - I know how to lock it to its lowest firing rate but how do you set a ramp delay on the Noble Combi?

    Le John said:

    hot_rod said:

    I'm a Combi proponent, live with 3 of them.

    a Lochinvar Nobel 110 Combi for example could cover your DHW usage, 3 gpm or more.

    It can be ramp delayed or locked at it's lowest firing rate for heating use, that is 11,000 BTU/ hr at low fire.

    Hi @Hotrod - I know how to lock it to its lowest firing rate but how do you set a ramp delay on the Noble Combi?

    I have one of the first Nobels produced, I think the control has been undated or more parameters opened?

    On mine it only has Space Heat Rate Limiting, adjustable from 10- 100%, I locked mine at 30%.

    I might have misspoke on the ramp delay, it might only be on the Knight series?

    On the Nobel, mine has ODR and Heat Rate Limiting. Adjusted correctly it should dial the boiler heat function to your system needs very well.
    Thanks @hot_rod. I too have the space heat limiting set to 30%. I love that boiler. It would be nice if the control upon firing would limit it to 30% instead of ramping up near 100% then modulating down to 30%. Seems like an unnecessary step.
  • hot_rod
    hot_rod Member Posts: 22,018
    I think the challenge is flame stability and flame sensing at real low turndowns. Maybe they feel more secure lighting them off and proving flame at the higher firing rates.

    We are all waiting for that mod con that can turn down to a few thousand BTU/hr output.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    DZoro
  • mikeg2015
    mikeg2015 Member Posts: 1,194
    Go with a smallest boiler and 40 gallon indirect. I don’t like combi’s unless it’s high mass with lots of cast iron or infloor radiant in concrete. Otherwise, the space can cool off with longer hot water calls including changeover delay.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,713
    @brichard917 you said "Maybe I will have to look into the modcon boilers. Do those vent through the chimney? One of the reasons I have been drawn towards condensing boilers was due to my chimney deteriorating."

    ModCon is short for Modulating-Condensing boiler. This means the boiler is over 90% AFUE and can not use the chimney, unless you use it as a chase for the low-temperature vent pipe required for the new boiler... but it might be easier to vent out the sidewall. Modulating means the gas valve lets gas into the heater at a variable rate based on demand. The turndown ratio of 10 to 1 means the 110,000 BTUh will have a fire as low as 11,000 BTUh and ramp-up to the maximum if needed based on several inputs to the main control board. These inputs include outdoor temperature, supply water temperature and return water temperature room temperature and some other very technical algorithms that only Sheldon Cooper can explain.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    Absolutely the smallest boiler made will be too big for 800 square feet (see @Jamie Hall s post above).

    When you say 2-3 tub fills a week, are you talking about a standard size tub or something larger?

    If it's a standard tub, then consider a stand along water heater such as a heat pump water heater, the smallest ones I know of are 50 gallon. That should be ample for your needs and considerably less money than an indirect water heater.

    For another reference point, my home (3,200 heated square feet) in ME (-35F design temp) is heated with a 55,000 btu modulating condensing (mod-con) boiler.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • brichard917
    brichard917 Member Posts: 10
    @EdTheHeaterMan - okay, that makes sense. The way it was said I thought it was a different type than what I was calling condensing.

    @Solid_Fuel_Man - standard shower tub. I did start looking at heat pump water heaters but the cons I am seeing is that there is not a rebate for those through my state as with gas/indirect and that from what I read they take a significant time to reheat.

    Doing more thinking today and talking to a new HVAC company I reached out to, they suggested going with a smaller boiler than I had been previously quoted for and maybe going down to 90% efficiency which still offers a sizable $2k rebate. I'll be meeting with him tomorrow, seems like he is an older gentleman that is a fan of educating his clients before throwing numbers at them, which I appreciate.
  • Icarus
    Icarus Member Posts: 143
    You can buy a Rinnai mod con 60k btu with integral hot water, 96% AFUE for ~$2300. I installed the previous model (e50c) a few years ago, and the gas company paid me back $800 on the purchase. MIne works great, with an outdoor reset, it dials down to less than 20% of capacity, with outlet temps ranging from ~105-180f. If your state is going to pay you $2k it becomes a no brainer. The gpm of the hot water is a bit low, (slow tub fill) but you can always (especially for the price add either a circ tank or a Rinnai demand to increase the flow rate.

    https://www.supply.com/rinnai-m-series-boiler-m060cn-white/p1809138

    Icarus

  • brichard917
    brichard917 Member Posts: 10
    @Icarus you said "The gpm of the hot water is a bit low, (slow tub fill) but you can always (especially for the price add either a circ tank or a Rinnai demand to increase the flow rate"

    At the risk of sounding (more) uninformed, is a Rinnai demand a separate tankless water heater? What is a circ tank and how would that help?
  • Icarus
    Icarus Member Posts: 143
    The rinnai boiler cited has an on board (combi) demand water heater, check the spec but I believe that it delivers ~3 gpm at 70f rise. A circ tank would be a simple insulated holding tank to hold more hot water (connected to the boiler) to effectively increase the supply. You have to design it carefully so that the system doesn’t get “stuck” on hot water demand, and not switch to CH. typically the way the Rinnai combi’ s work is that the priority of the system is for DHW, and when there is no demand for DHW the boiler self switches over to CH demand via a three way valve. A perpetually leaking hot water faucet (or improperly designed circ loop) can allow it never to switch got CH.

    Icarus
  • brichard917
    brichard917 Member Posts: 10
    edited December 2019
    Had a new quote completed today. HTP Pioneer heating system (100btu) with an HTP 45g indirect water heater. [Pricing removed].

    More expensive than all the combi unit quotes I have received but it seems like a more reliable product that has a better warranty and less chance of expensive repairs and service requirements.
  • KC_Jones
    KC_Jones Member Posts: 5,722
    Still massively over sized, also we don't talk pricing on this site.

    Why won't these contractors size properly? Why won't they do their jobs? Boggles my mind, no matter how many times I see it.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    ethicalpaul
  • brichard917
    brichard917 Member Posts: 10
    @KC_Jones I removed the price, wasn't aware of that.

    It's funny, this contractor mentioned the oversizing of my other estimates but stated that this model was the lowest of what he installs that would modulate down to what I need.

    Should I be finding a contractor and specifically asking them for a smaller size? Would that be a considerable savings?

    I used the SlantFin app to the best of my ability, if anything under estimating the insulation and came up with a heat loss of 30,176. However, there was definitely a lot on the app I'm sure I did not fully grasp.
  • mattmia2
    mattmia2 Member Posts: 9,572
    Maybe I missed it, but what kind of heat emitters does the central heating system use? How is it zoned, are there one or 2 large zones or many small zones? The pioneer is sort of a boiler and buffer tank all in one which is meant to solve issues that a mod/con on its own doesn't handle very well so I wonder what problem they are trying to solve with the pioneer over a uft or an elite.
  • brichard917
    brichard917 Member Posts: 10
    @mattmia2 - hot water fin baseboards. Single zone. The Pioneer, according to the contractor, is just the only product he pushes because he has success with it and he actually doubles the manufacturer warranty length both labor and parts due to his confidence in it. Aka, warranty is 1 year he adds a second year which he covers personally should there be an issue.
  • KC_Jones
    KC_Jones Member Posts: 5,722
    The difficulty here is you need the smallest boiler and it's probably too big.

    The one he is proposing will modulate down to 35k BTU, which is above your load. So even at the very bottom of it's modulation range it's too big for your house on the coldest day of the year, which is only a few percent of the whole year.

    I think the lowest any of them go is 10:1 turn down on an 80k boiler so 8k BTU on the low end. If it was me I'd want to go that route. For these newer boilers it is my opinion you need to evaluate from the bottom end not the top.

    Your 30,176 is probably a bit high, but gives you an idea of what is going on here. You need 30,176 and he is proposing putting in 100,000, that is 3.3 times what you need.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • hot_rod
    hot_rod Member Posts: 22,018
    I think the Pioneer is a 50 gallon high mass boiler.

    With that high mass, or large water content, and turndown the oversizing is not as much an issue.

    A side arm flat plate HX would make a sweet DHW option. A high mass combi so to speak.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Icarus
    Icarus Member Posts: 143
    I am not a heating/HVAC contractor, but a retired custom home builder and now I consult with a limited number of clients on energy, energy conservation, solar installations etc, as well as having a sort of jack of all trades work on my own projects.

    It is incredibly frustrating to find tradespeople/venders suppliers who don’t/won’t/can’t think out of the box. I have been trying to track down a number of sort of esoteric ideas for myself and clients (some mentioned here) and too many of my local vendors/contractors have no experience in “modern” technology, and or are very suspicious of it. It is endemic in certain trades.

    A related story.., my sister in law was having trouble with her Combi hot water boiler, that had served her quite well (on L/P) keeping the house warm, and providing DHW under all conditions. The local guy she called, came out, told her the boiler was a POS and he would rip it out and replace it with oil. Against my (limited) advice she went ahead, and he installed a new oil boiler, along with tank etc, tossing the 10 year old combi, and guess what? He didn’t do any heat loss, didn’t look at the hot water base boards and do a heating load calc, he just installed a 85k boiler for a 1200 sq well insulated house. So, the boiler now short cycles, AND...she can’t stay warm! I haven’t tried to figure out why (I’m on the opposite side of the country) but clearly she got hosed by a “professional”.

    As I mentioned above...I am NOT an HVAC professional, just a moderately informed amateur, but even I know that at the very least, one ought to do a basic heat loss/heating load calc to try to come close to a reasonable design, and he should have figured out that she didn’t have enough emitters to actually keep the house warm. (What I don’t know is why the LP mod con was able to keep it warm, as I have washed my hands of this project!)

    So, back to the OP’s question...my advise, worth every penny you pay for it...Look for a different contractor, and find one who can adequately explain WHY he wants to do what, rather than simply justify it by saying, “I’ve done lots of these and they work great”. At this point, run each design by the learned folks here and get a consensus.

    Icarus

    PS. I am not trying to crucify folks in the trades. To the contrary, I am trying to promote those a that are truly professional and earn what they do.


  • mattmia2
    mattmia2 Member Posts: 9,572
    I like @hot_rod 's idea with the heat exchanger. Use a heat exchanger sized to have a close approach at the max dhw demand with an appropriate thermostatic valve. essentially the pioneer's tank acts like the dhw tank through the heat exchanger.

    The thing i didn't like about the pioneer was you would need a high temp in it to get decent output from the indirect but the central heating could probably be run at a much lower temp with outdoor reset much of the time. the high mass of the pioneer wouldn't make those adjustments very well so you would likely have to run it at the temp needed for the dhw where it would not be as efficient at extracting heat from the combustion.

    The other option is an indirect and a lower mass boiler.
  • brichard917
    brichard917 Member Posts: 10
    Right now I'm trying to look at it from an ROI perspective since I don't plan on being in this house any longer than 3-4 more years. All my estimates for low mass boilers paired with indirect are 1.5-3 grand more than the Pioneer so I think I'm more likely to get a quicker, larger ROI by the time I sell with the Pioneer.

    Maybe my thinking is off?
  • mattmia2
    mattmia2 Member Posts: 9,572
    The pros can comment better than I can, but i think the materials and labor for the pioneer + indirect are roughly the same as the low mass + indirect (although if you're buying the low mass that is twice the size of the one you need that will cost more)

    the pioneer + heat exchanger might be one of the least costly and most effective if the non-combi options if it is engineered properly.

    The combi is probably the most cost effective but it could not be able to keep up with a large volume dhw draw, unless it has a small tank, there will be some cold water while it fires, and it could require some expensive gas distribution modifications to get it the supply it needs. It also is likely to run relatively short cycles because it has to be oversized to handle the instant dhw demand. With a separate system you can raise the system or dhw tank temp if you don't have enough hot water, with the combi, if it isn't enough all you can do is reduce flow.
  • hot_rod
    hot_rod Member Posts: 22,018
    These DHW add on modules are fairly common in Europe, DHW from most any boiler source. This is the Viessmann brand. There were some Canadian manufacturers offering add on DHW modules.

    Probably a bit too far out of the mainstream for most contractors.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2
  • brichard917
    brichard917 Member Posts: 10
    This is a very small amount on gas usage especially when considering the current ~60% efficiency boiler, right?
  • ced48
    ced48 Member Posts: 469
    Been away from site for a while, so this might be a little late, but as far as boiler size, I have the same size house, with a 55k Lochinvar. The boiler never runs at more than 20%, unless we drop below 10. So, this is the largest boiler I would consider, smaller would be better.
    Solid_Fuel_Manrick in Alaska