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New Heating System – Boiler Selection, Controls & Solar

Mark_129 Member Posts: 17
I’m a homeowner hosting potential installers for replacing our heating system (Boston metro west). I’ve been part of the industry in the past (the group I was in developed the Vertex for A.O. Smith and other products), and am quite interested in the details of some of these new systems. Apologies in advance for the long length.

I have most of the info the installer needs for my house (forced hot water baseboard lengths, dimensions), as well as future expansion plans that will at some point integrate radiant floor heating (at least for the first floor) and some solar for DHW. I know the heat loading exactly due to the programmable thermostat we’ve been using for years. I’ve spelled out future improvements in the home (radiant heating, etc.) All of this is in a spec for the installers to make their life a little easier.

I have 2 groups of candidates (all are modcon). The first group is comprised of Triangle Tube Solo 60 or Excellence 110 and Viessmann Vitodens 200-W. The second group would be Burnham (discounted via the utility), Lochinvar, Weil McLean, Eternal, and a few others. I haven’t done enough homework on the second group to rank within them. I’ve eliminated Buderus due to the aluminum HX.

In short, I’m looking for value. The metrics I’m using to evaluate units (with weightings x, 2x, etc.) are below. Some of this is qualitative, some quantitative. It helps to get it all on paper so that I can ask good questions of the installers when they show up to quote.

(1) Operation/Servicing cost (2x): high efficiency, minimal servicing, high reliability - will have the installer quote their current servicing/maintenance package

(2) Controls Capability (2x): for comfort I want the unit running all day at part load (via outdoor reset) to make the house feel warmer, and I want to be able to adjust the controls if needed to dial it in exactly.

(3) Installation cost (3x): Up-front installation cost

(4) Expected lifetime (1x): I’m willing to pay more up-front for something that will last longer

(5) Flexibility/expandability (1x): For radiant floor heating, accepting solar input

(6) Field convertible to Propane (1x):

They all appear to offer direct vent, so that won’t affect my decision.


I have a single zone system now that will eventually expand into 2-4 zones with at least 1 radiant loop, and maybe even one snow melt loop for when I’m on travel. Is there an advantage of one system over another for multiple zones? Should I plumb for additional zones now, or just have the installer leave space for it since plans can and always do change? For example, one advantage of the Triangle Tube seems to be its low pressure drop HX, reducing the pumping and simplifying things for the one zone that I have now.

The Excellence is an interesting product since it would avoid having to plumb in a separate indirect tank, saving cost and space in my basement. Are there similar products out there like that? The Eternal is one, but it’s too new for me to explore right now. How would I integrate solar with the Excellence – would the cold water inlet to the Excellence simply be run through a solar heated "pre-heat" tank first?

One disadvantage of the Excellence 110 is that it only modulates to 30kBtu/hr, and my peak heating load is only 40kBtu/hr, so there would be more cycling in the fall/spring.

Other posts here comment on the Vitodens reset curve adjustment that is available to the user. That seems pretty useful. Is the Triangle Tube curve resettable by the homeowner – and how complicated is it to do that?

Are there other controls benefits to using the Vitodens? For example, the ability to include a mixing valve with radiant heating seems like a nice feature. The integration with solar appears nice, but I’m not sure I can afford to go all Viessmann.

Do any systems offer a setback for the DHW setpoint? For example, our home’s hot water use is well defined and limited to mornings. I would like to do a 140F “kill” cycle early in the morning, and then let the water temp fall to 110 or 120 during the rest of the day when hot water is rarely used.

The stainless steel indirect tanks offer “lifetime” warranty – what does this mean? Are there advantages or disadvantages to the Triangle Tube stainless tank, the Viessmann tank – I’m assuming the Heat Transfer Products Superstor is a fine product as well.

How is the servicing of the Triangle Tube vs the Viessmann. I’ve heard that both are quite serviceable and internal components are accessible, but I haven’t seen them up close.

Realistically, how long do the mod-con systems last (assume yearly servicing and a correct installation). For the price I’m expecting to pay for these systems I would hope that they would last 10-20 years. How long has the Triangle Tube product been around?

On a side note - the new A.O. Smith solar product line looks very cost effective compared to some of the others that I’ve seen. Can anyone comment on the effectiveness of these units?

Thanks in advance for any advice that you have.


  • tim smith
    tim smith Member Posts: 2,770
    RE: boiler selection etc

    Some responses to ?? First off, did you work with Howard from AO Smith? in engineering.

     Now to responses. The modcon lifespans for the Triangle or Viessmann I would venture to say is 15-20  + I would hope but no gaurantees. I would not give most of the other modcons that rating although.

     Both Triangle and Viessmann are a solid design. I happen to really like the Triangle as it has been pretty much bullet proof. We have been installing them for close to 5 yrs. Heat exchangers don't get much build up in them over a couple years like other designs due to vertical firetube design. Computer and components have been really solid.

     Maintenance, I feel the Viessmann may have a little more maintenance cleaning that the TT boiler as it is a horizontal spiral heat x that allows for debris to collect in bottom of the heat spiral, the TT does not. All of the stainless modcons to get build up in condensate trap so they should be checked once a year along with general combustion/safety tests and some other minor maintenance items on boilers in general.

    Re: indirect water heaters, we use the HTP superstor, it has been a good performer for us. The triangle is good also. The viessmann indirect is the top of the line I would say but you really pay for it.

     Re: the Excellence, good idea but I  am still a little leary about its production rate for any sort of quantity of hot water. I would be more inclined to go with the TT prestige 60 in your application and maybe a SSU 60 superstore. There per hr heat loss is very good although you are storing HW which we all know is not the most efficient way of doing things but I think a good compromise.

    All the rest of your questions are pretty much not appicable as the cost is the cost and modcon cost more but are more efficient. TT boiler is field convertible. The reset curve is adjustable, you would have to be instructed. Either TT or viessmann will be a good pick, I just prefer the TT prestige. Good luck.
  • TonyS
    TonyS Member Posts: 849
    Like Tim said

    We have been installing the Triangle Tube also. We have no complaints.

    We also have been installing Navien tankless water heaters and they too have been excellent machines. They now have a combi unit which I have recently seen at a show and have been trying to sell one. The unit is 200,000 in but is only 60000 on the heating side but with a turndown to 17000 They are half the cost of the other units with the same warranty. This may be what your looking for.

  • Mark_129
    Mark_129 Member Posts: 17
    Thanks, Tim

    I will look into the Excellence more carefully based on your comments. While I like the simplicity of the combi approach, not having enough hot water would get me in trouble :) Good to hear that the TT reset curve is adjustable - I would be glad to be instructed on how to tweak it - I like knowing the details of how things work in my house - I just hope it wouldn't void warranties or anything like that.
  • Mark_129
    Mark_129 Member Posts: 17
    Thanks, TonyS. Navien looks interesting

    I had heard of them before but did not look into them. I will spend some time tonight looking at their website. Based on your comments, it sounds like they've integrated a tankless for DHW and then have a separate burner(?) and loop for heating the home? My only concern would be their reliability and expected life, but your comments suggest they are well made. I'll see if I can track down any installers in the Boston area.
  • Mark_129
    Mark_129 Member Posts: 17

    My preliminary research sees alot of problems showing up with early releases of the product. It seems to have improved in the last year but it seems too risky for me right now. Anyone else have Navien experience?
  • Nick Ciasullo
    Nick Ciasullo Member Posts: 44
    Vitodens answers

    Mark, let me start off by stating I am a Rep for Viessmann.  I can not comment on questions about the Triangle Tube unit.  You should contact their Rep for details on their product.

    Operation / Servicing cost: As a Rep since 2004, I have had 1 warranty replacement of the pump controller, and 1 blower motor.  I am not aware of any replacement parts being sold beyond the warranty.  We signed on with them because we understood them to be the "Holy Grail of Boilers" and so far, I am still of that opinion .

    Controls Capability: You can preprogram several different house temps at different times of day, not just night time setback.  The purchase of the optional Vitotrol 200 or 300 stat will allow your boiler to sense the temp inside the house, and fine tune the adjustment to your needs.

    Installation Cost: I would assume this to be similar to any other modcon.  I suggest the use of a Low Loss Header to reduce the potential for debree from the system entering your boiler, reducing its efficiency.

    Life Expectancy: Viessmann uses 316Ti Stainless (stainless and titanium blend) for longer life of the heat exchanger.  No one else does.  The addition of Titanium adds resistance to corrosion issues from the condensate.  Do a search for AL29-4C for a corrosion comparrison of stainless and titanium.  You should find the Vitodens 200 is similar in cost to the others you are considering.

    Flexibility: You answered your own question

    Propane Conversion: No kit is required for the Vitodens 200.  There are two field adjustments.  There is a quarter turn screw on the gas valve, and a software adjustment during setup.  These are not required for proper operation with propane, but recommended.  Because the boiler uses Lambda Pro technology, the boiler will recalibrate each time it fires.  This is especially helpful when the gas quality changes with each delivery.

    Other questions: The Vitodens 200 can control a motorized mix valve.  That is where you will start to see Viessmann's cost stray from what you would accept as normal, but in my opinion, it isn't out of reach compared to other avenues.

    As the Vitodens 200 allows for multiple set points for heating during the day, it also does this for the indirect.  You could set the program to "spike" the water temp in the morning, then set back to your "normal" temp during the day.

    The Vitocell 300 has a lifetime, non-prorated warranty.  As long as you own it, you get a full replacement should it fail.  It is made of the same 316Ti stainless mentioned earlier, and is seemless weld construction.  So far, I have had a single failure of this tank, due to a poor weld at the foot.  This tank will be double the cost of whatever other tank you may consider, including the Vitocell 100, which has an 8 year warranty.

    I have surfed some of the blogs in England to see what people are saying about modcons life expectancy, and the rule of thumb that was thrown around the most was "10-15" years.  I could not find independant information on Viessmann.  It has been suggested to me that Vitodens should be 15+.  They have had commercial equipment using the same stainless in existance for 28 years.  Vitodens is not that old so I can't offer anything beyond that.

    IMO, I think you should set up the boiler as primary / secondary with the Low Loss Header, and after your initial zone, leave a stub out for the addition of new zones later.  This will make adding them relatively painless.  Use isolation ball valves.

    Viessmann has 4 different solar products to choose from, two flat panel and two vacuum tube.  You will find them to be competitive.  I tried not to get too "sales pitchy" but again, I am a Rep for Viessmann.

  • Robert O'Brien
    Robert O'Brien Member Posts: 3,542
    I agree with Nick

    I'm not a Viessmann rep, but the 200 is tough to beat,the HX is in a class by itself,great control,Lamba Pro etc.  The Triangle Tube is my next choice and in some cases first,primarily the ability to pump through it,eliminating the LLH and the cost/space constraints involved. I don't havr NG available at my home but if I did a Vitodens 200 would be my first choice,followed by the Prestige/Vitodens 100
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Mark_129
    Mark_129 Member Posts: 17
    Thanks, Nick


    Thank you for your detailed answers to my questions. I don't know if I stated it in my original post, but I'm a  mechanical engineer by training, and so I appreciate the information. The corrosion info is helpful, and the ability to run on propane or nat gas with those minimal changes that you mentioned is very impressive. I'm also glad that it could "spike" the indirect temp as you stated - while others may have this capability I have not seen it explicitly stated anywhere.

    So far I have interacted with Viessmann and Triangle Tube reps and have been impressed with the speed of response and information provided.

    The installer visits for quotes also suggested that Lochinvar is a top product. If anyone else out there can speak to its capabilities vs these 2 boilers that would be helpful. I'll also search the archives here.
  • TonyS
    TonyS Member Posts: 849
    As with any product

    Navien had a few troubles when first introduced, I have had little trouble with them and have seen many of them poorly installed. However I thought I would mention it because of its lower cost and excellent warranty.

    Getting back to the Triangle tube, The exchanger on the Prestige is the finest made. The 316 ti you hear about serves it purpose well, it is an off the shelf austenitic stainless that lends itself well to bending and stamping, very common. What it doesnt lend itself well to is welding, but thats ok because most of the cheaper exchangers are not welded, that takes money and technology.

    Triangle tubes real claim to fame is their parent companys ability to roboticly weld. It is truly an art form that can not be easily acomplished by just anyone. This is why the Prestige exchanger is self cleaning...because it was designed that way. The designers werent limited by what could be bent or stamped. This is why the Prestige uses a ferritic 439 stainless(it also contains titanium) both types of stainless are very good corrosion wise but ferritics lend themselves much better to welding and expansion stress. As a mechanical engineer you will be able to easily verify these statements. I just wanted to clear this up, titanium is not the holy grail of metals and is relatively cheap when used in the amounts alloyed in these stainless steels, it is by no means really special.
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