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Yet another boiler selection question TT with built in DHW or indirect?

LukeWarmLukeWarm Member Posts: 7
I am in the process of building a new home in northern Michigan. I have some questions regarding radiant heat source. I just read homeowner1’s thread and looks like I have the same questions with a slightly different set of conditions.

A bit of background:

• Total heated area is ~4000 ft. sq.

• Design temperature is -8°

• Well insulated and sealed: R38 walls and R60 ceiling

• Calculated heat loss is 43K Btu.

• There is a 24K BTU direct vent fireplace w thermostat control which is supposed to be ~70% efficient that could be used for backup / supplemental heat.

I had a contractor that suggested the TT 110 Excellence with integrated DHW, but I’m not sure if 76K BTU is overkill for this application. I should be able to use a TT Prestige Solo 60 but by the time you add an indirect DHW tank, and a couple extra circulators it will probably cost more. I compared the DHW capacity of the 2 units (using Dave Yates method) of the 2 units and it was dead tie using a 40 gal indirect with the TT60 (either would meet my needs)

I am a bit concerned about short cycling with the 110 as I will have several zones but it seems like there is not much safety factor at 47K BTUs with the TT 60. Looking for suggestions as to which one you would pick and why.



  • Paul48Paul48 Member Posts: 4,256
    Safety Factor

    There is considerable safety factor built into all heat loss calculations. If it were my choice, I'd go with the 60. I would run the house as a single zone, and let the boiler do its thing with outdoor reset. If I wanted my bedrooms cooler, I'd use TRVs for them. Trying to zone 43000 btus into several zones will cause problems with any mod/con. It is probably the number one problem that mod/con owners come here with.
  • unclejohnunclejohn Member Posts: 909
    I'd go with

    A smart 30 and the tt60. The exe. only has a 14 gal tank. The smart 40 may be just a little big for the tt60.
  • SWEISWEI Member Posts: 7,356
    To zone or not to zone

    When running outdoor reset, we do what could be called inverse zoning or off zones.  Any space which is subject to heating by other sources (most commonly solar gain or a woodstove) gets either a TRV or a stat and a zone valve.  Set the stat a couple degrees above the indoor design temp and it will prevent overheating.  You don't want to valve off more than about 30% of the load or there will be issues.
  • ChrisChris Member Posts: 3,056
    You Haven't Disclosed

    What your DHW demand is to give you the best answer. Based on what you have posted I agree with the others the PT60 is the right choice but as far as indirect size need to know the DHW demand.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • heatpro02920heatpro02920 Member Posts: 991
    edited February 2013
    Heatloss sounds a little low...

    must be very tight with short supply of windows... I haven't seen 4K sq ft with a sub 50K heat loss, {I have been doing manual j for a while}.... That is very good...

    What do you have for emitters, baseboard, hydro air, radiators, ect?

    How many bathrooms? {jacuzzi tubs, shower jets, ect?}

    What is your design temp? I am saying it sounds low for where I am , it is 9 outside rite now, lol I was in Northern Michigan 2 years ago in December, it was COLD, our guides were talking about tempss negative 20 in january, NO THANKS..

    I would go with the TT 60 and a Rinnai RU98 tankless for DHW...
  • ChrisChris Member Posts: 3,056
    Heat Loss

    House tight. Loss through the outside panels

    78/38 = 2.05 Btu/hr Sqft x 4,000 = 8,200 Btu/hr if we have 4,000 sqft of outside wall

    78/60 = 1.3 Btu/hr SqFt x 4,000 = 5,200 Btu/hr if we have 4,000 Sqft of outside ceiling

    13,400. Now we need glass and by the insulation in this place that loss might even be high because you could fart and heat this tight house..Don't see much infiltration..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • LukeWarmLukeWarm Member Posts: 7
    DHW Demand

    I used 80 gal @ 115° in 40 minutes. I am currently renting a house nearby and measured the shower flow @ 1.5 gpm which is entirely adequate for me. I can't imagine taking a shower longer than 20 minutes, followed by my wife doing the same. It is a retirement house for 2 so only occasional guest bath use and we can wash clothes anytime.

    There are lots of windows, approx 210 ft ^2. in the living/dining area alone which is about 600 ft ^2. They are triple pane windows with min R value > 7. Walls are 12" deep with spray foam insulation and basement is ICF. Originally designed as a passive house but my wife couldn't live w/o the regular dryer, fireplace and big range hood. :-)

    Am planning radiant heat. The main level is suspended floor, basement is slab on 4" insulation with walkout, and there is a shop and garage that I want to heat but not necessarily to 68°. Would be happy to keep the floor around 50° to thaw the car out. I did an area by area (open floor plan) heat loss and the entry level requires about 11.3 Btu/hr ft^2 while the bath/lav/laundry area is only 4.7 Btu/hr/.ft^2. The basement and garage/shop are around 8. Sounds like it would be quite a trick to get all those working with 1 or 2 zones but would like to hear how it can be done.
  • heatpro02920heatpro02920 Member Posts: 991
    edited February 2013
    Why mod/con at all?

    Honestly with that small load, just grab a Weil McLain CGi3 and an on demand tankless for your DHW, because with that heat loss I don't see a mod/con paying for itself over its lifespan compared to the small WM will probably last twice as long with very little if any service..

    Not to mention prices just for example, say a cast iron boiler costs $5000 and may last 30 years than a mod con will be 10000 and last 15, in 30 years you are paying $20000 for 30 years of modcon vs 5000 on the cast iron boiler... Numbers and lifespans are just examples and round numbers... you will have to come up with your own prices and ask what people think the lifespan of the equipment you get is {I was told TT max 15- 20 years, not sure how true it is and a lot of stuff can change these numbers like water quality and use}...

    The small standard boiler is going to get 85.+% and the mod con is going to get 95% {not all the time}.. {and you can install odr and idr's on the cast boilers too, the only thing it wont do is modulate and condense}.... I don't normally recommend mod cons unless the heatloss shows the units can at minimum pay for themselves over there lifetime...
  • ChrisChris Member Posts: 3,056
    edited February 2013
    No Way

    At this point it's time to define a budget and look at doing radiant in areas and panel rads in others. Get the needed design water temp as low as you can within your budget.

    You can still condense 85-90% of the season and if designed right 100%. There's a funny thing about efficiency. Everyone thinks return water temperature alone is the deciding factor and that is far from the truth. Rate of modulation plays just as important of a role.

    The other factor is stack loss from an idle boiler. That's energy you paid for wasting away in a traditional cast boiler and the same goes for jacket loss.

    Heat loss is not a deciding factor. A heat loss is the necessary amount of btu/hr you need. How you get it is what matters.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • SWEISWEI Member Posts: 7,356
    Why mod/con?

    The cons of poorly implemented condensing have unfortunately come to dominate the public discussion here in the US.  Modulation actually accounts for more of the thermodynamic, economic, and environmental coolness.
  • heatpro02920heatpro02920 Member Posts: 991
    Mod cons are nice, BUT...

    Is it worth it with such a small load? Ill admit I sell a ton of them, I actually just bought another brand new GMC utility truck that is setup solely for high efficiency gas installs.

    But the math doesn't lie, these units aren't going to last as long as a good cast iron boiler, and then of course you have the initial cost a tiny Weil McLain Gold like the CGi3 can be installed with an outdoor reset and delta t circulator for under $3000, I get them to run at almost 86%, they hardly ever break, stand by losses are minimal {no chimney vent}, and with a Rinnai tankless water heater the boiler will run half the year and last a VERY long time... With little to no maint... So if you factor all these things into your decision, you will see what the mod con costs you vs what the standard unit saves you.. Don't get me wrong I love mod cons, I just replaced my gb142 with a tt Solo 175, which is a very nice unit, but I don't have any illusions of that unit hanging there for 30 years, I know it wont happen... When I just installed 4 new small gas golds in one of my rental properties, I am expecting them to be there for 30+ years and that isnt going to be hard to do....

    On that note, mod cans are cool and look fancy but you can buy a lot of other cool fancy stuff with the money you save on the install and life span of a standard unit... Now if you had a 100K btu loss and heat was costing you 700 a month that mod con may make sense, but IMO its hard to justify it with a 40K btu loss {keep in mind that is 40 on the coldest day which can be under 5% of your season...

    I know guys love selling these things and they are fun to run, but money is money, "penny smart and dollar stupid" will catch up fast...
  • ChrisChris Member Posts: 3,056
    Then You May

    Want to look at Viessmann Vitodens. Designed for a 40 year life span with the exact same HX warranty as that cast iron boiler. One of the rules here is we do not talk price. Mainly becuase markets are different across the country. Labor cost could be higher or less dependent on the market. Please keep that in mind when throwing out pricing. Believe it or not that also goes for the product itself.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • heatpro02920heatpro02920 Member Posts: 991
    edited February 2013
    I had some bad luck with veissman...

    And Im not the type of person to come back for more. Believe me I tried to be a Veissman fan, there head US office is 5 minutes from on of my buildings, I actually have 3 customers that work for Veissman {2 of which have Veissman equipment}, BUT, I had some bad luck with the vito 100 and then the second 200 I installed had a bad gas valve after just over a year and that was the last straw, it took me way to long to get the part {luckily they told me it was going to be over a week rite upfront, so I installed a temporary boiler for the property}... I have installed over 30 Veissmans total {gas and oil} and I find them to complicate things just for the sake of complicating things with no real world gains vs the more simple options... {plus not to mention costs, but the veissmans are expensive, thats not a secret}

    I am not trying to argue, and I have only been here a short time, but I do find people are way to fast to suggest mod cons vs standard equipment, and I know about the no price talk rules, but its hard to compare something with out talking about price, when that is the reason they are comparing the items.... I apologize for mentioning my costs, and I understand the rule, that is why I gave round numbers, hopefully customers understand pricing changes throughout the country and that all installations are different and are going to cost more or less depending on the obstacles your property produces... Plus in the internet age, the secret is out, they can google the cost of any unit and find out what we {contractors} pay for said unit {of course never taking into consideration costs of all the other parts, insurance, trucks, tax matching, workmans comp, equipment, ect.. I just paid $48 for a 1-1/4c X 3/4f X 1-1/4c t and the job needed 2 of them}...

    Also before someone brings it up, I know there are people that have installed hundreds of Veissmans with no issues, just like I have installed more Buderus units than I can ever hope to count with very good luck.. The problem was that I only installed a few handfulls of Veissmans and had more problems than I cared for, that is where a good businessman looks to cut his losses and move on to a different product... I have toured the facilities I have been certified in everything they throw at us {as has my service manager}, I have talked about the products with reps and other contractors, look through them, install them, service them, and I no longer offer them for sale, if a customer asks for something specific, I will of course install it... But I always try to {normally with good luck} away from Veissman..

    I have to admit, I am new to the Triangle Tube Modcons {I never pushed them before the Trimax because I heard and seen problems with there old controls}, but now that I have installed a few {including one in my own home, I always try new equipment in one of my properties}, they are a very nice unit, I would go as far to say best I have seen, very Easy, not much to them, the efficiency tester shows real good numbers, quiet, aesthetically appealing, parts are actually on the shelves at a few supply houses, nice open cabinet, free flowing heat exchanger, superior stainless {on paper anyway, they are now using 439/444 when most other companies are using a low carbon 316 which is just a little better than the 304 grade stuff... So with them few points the TT is becoming my new go to over my old tried and true Buderus gb series... {I know they are getting outdated, but I have had extraordinary "LUCK" with them, I mean 100s of boilers with less than 10 service issues!!! They just WORK... But more and more customers are getting the SS bug, so I had to look elsewhere since the Buds are still aluminum... {not that I have seen any properly installed and maintained aluminum ones fail... I like SS too...

    And as far as heat loss not being a deciding factor on the question to modcon or not, I have to disagree... if you only travel 10 miles a day is it worth spending twice as much on a Hybrid car vs a regular car to save money on gas? regular car gets 25 mpg prius gets 50, regular car costs $15K prius costs 25K, you keep the car for 5 years at 3.50 per gallon over 5 years the prius saved you under $1300 you lost 8700 no matter how you look at it, plus the prius has more moving parts more batteries more things to fail ect.... {I know about resale value but then the math gets way out of hand so we will forget about that for now}

    Now if you travel 100 miles per day, it makes a lot more sense to drive a prius... Its the same thing with heating systems, I installed a $100K+ geothermal system in a 9800sq ft house last year, it makes sense because they are going to use it year round{heat/cool/dhw} and they have a huge home with driveway melt, pool heaters, ect, they will get that 100K back in less than 10 years {saving 13K a year, there energy bills were around $1500 per month before, and they had high efficiency equipment {propane}... Geo averages around $500 now!!!! But would it make sense to do that in a house with a heatloss 1/10th of that properties? NO because you will never get it back, even when you consider the system will only be $30K instead of 100K...

    I am just trying to give the OP something to think about, he most likely spent a ton of money insulating that property, so why not save which ever way he can and Im not talking month to month, I am talking in the long run, I always tell my customers how long does this have to work with out failing to pay for the difference in cost???
  • SWEISWEI Member Posts: 7,356
    edited February 2013

    Certainly have a bit of a checkered past here in the US.  Hard water, low pH, or chlorides were death to earlier heat exchanger designs.  The overwhelming majority of SS was indeed 316L, with a few 304L and some aluminum.  I'd just as soon forget all of those now that I've worked with the TT design, which is really the only one I can recommend with the hard water we have in the west.  Oh, and Viessmann uses 316Ti.

    Our current NG prices make for long ROI with smaller loads, and nobody makes a mod/con properly sized for a well-insulated little house.  I usually assume NG prices will double in the next few years.  A properly installed and maintained mod/con ought to provide 20+ years in my book.  40 sounds great on paper, and I have no doubt the Viessmann equipment will make it, but when I look at _any_ kind of high technology from the early 1970's I have to wonder.
  • LukeWarmLukeWarm Member Posts: 7
    edited February 2013
    Thanks everyone

    Thanks everyone – lots to think about here. Everything I have read says to insulate / seal as much as you can, but it seems like I’ve created another problem by doing exactly that. I get what you are saying in regards to a conventional boiler regarding payback, but don’t see how I can maintain 130 return temperature unless I just run a single staple up tube in each joist bay to boost the required supply temperature. That doesn’t make sense to me. From my initial calcs I only need 115 maximum supply temperature. Also I would need to cut a hole in my house to get combustion air to the mech room. Perhaps I’m missing something here – I have no experience with conventional boilers, spent all my time looking at modcons.

    I think I have my answer for the initial question. The Viessmann looks nice, but as far as I can tell it only modulates down to ~50% (28 MBH output on the smallest model). Maybe I am looking at the wrong one. Now I need to get to the second part, which is how to control and distribute the heat. Will have to look into TRVs, I did a search and it seemed like they were used with baseboard or radiators – didn’t see any reference to infloor radiant. I will wander over to the radiant heating forum and ask over there.

    edit: I am in the woods, so Propane is my only choice for fuel.
  • heatpro02920heatpro02920 Member Posts: 991
    316l vs ti

    This always confused me, the 316l and ti both have the same amount of titanium, and 316l is more resistant to corrosion so why would they use the ti, I am by no means a ss expert although I have a good background in welding, {actually just took delivery of my brand new dynasty 700 tig welder}, I couldnt wrap my mind around it, I remember asking this at a meet and eat and no one had any answers for me....

    But anyway NG prices are going to SOAR when they get a handle on the fracking BS, I was told by a good friend who has a 7 figure salary with the grid that they expect within 4 years 3 times the price, that is scary... My home has, propane{TT solo 175, rinnai ru98, 3 lenox gas fireplaces}, oil {buderus g115 direct vent}, wood {esse ironheart}, and coal {keystoker a 80}. I filter all the cleaning oil from my service trucks and use that in the oil boiler when my tank gets fullish, the coal is nice for real cold months, the propane is the main system, and wood has been used once when it was installed... I got the coal and wood units from customers that wanted to get rid of them... but they all have their place... We don't have NG available here, and probably never will since there are 4 houses within a couple miles and my house is a ways from the street, they would need a 8 foot main lol...
  • heatpro02920heatpro02920 Member Posts: 991
    edited February 2013
    in the woods?

    That is easy then...

    Water furnace series 5

    and a big indirect, you will never look back....
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