Boiler System Replacement

DSquared

I am in the process of acquiring bids for a boiler system and water heater replacement. The current system is on its last leg and our home is heated by gas via radiators.  I am contacting reputable licensed 'heating/plumbing' contractors and so far all of the reps have done a measurement of baseboards and home.  I have done some reading on forums and blogs (heatinghelp seems to be the best!).

I have bids on Utica, Burnham,  Presige (triangle tube) and Lochinvar.  I understand there is typically a high efficiency and mid efficiency boiler  to choose from...but it seems like it would take more than the life of the boiler to see the savings back. Plus I have seen a few complaints on higher end units malfunction or extra costs for repairs plus higher than average yearly service fees.

 Bottom line is, we would like to install a reliable, long lived boiler / water heater that are the best value for quality.  Our home is getting an insulation make over this fall yet even without that, the thermostat with radiant heat keeps us comfy at about 68*.

It is very difficult to assess all the differing info on the bids and the prices are comparable on similar units to within $1000.  I know a quality install is of utmost importance. So far only one contractor has done a full house measurement and checked crawl space and looked around at other insulating. (We need to beef it up)

I know the 90%+ efficiency units are going to be the wave of the future, but I am getting a gut check that the 84% will serve us extremely well (at a more reasonable price) until we need to replace it - when even 'today's high efficiency units will be out of date.

Across the board, it looks like the house will need an 80000btu unit.  Any comments on favorite brands and or combo boiler / water heater units?  (We currently have 40 gal free standing water heater with separate flame - and 'hard' well water - if that means anything.)  Sorry I'm so long winded. 

D2

SWEI

first things first

Measuring baseboard is only part of the story.  Has someone actually done a proper room by room heat loss calc?  You'll need to know the existing structure losses as well as projected numbers after your insulation upgrade.



Fuel savings from a properly installed mod/con usually end up more like 2-3x the nameplate efficiency difference when compared with a conventional non-modulating boiler.  There's also a difference in comfort that comes from properly controlled distribution temps using outdoor reset - you can get this from a conventional boiler, but it requires additional controls, labor, and piping that mostly negate any initial cost savings.

DSquared

Heat Loss Calc

I received one additional document from a contractor/rep, but I am not sure it is a heat loss calc.  It has a general footprint of our home with external doors and windows in place....I just don't understand the data. At the top is weather data followed by heating and cooling summary and equipment load sizing for heating and cooling equipement. (though no AC system)

An insulation company is coming to our home tomorrow, and I will explain our pursuit of a new boiler/water heater and ask for their insulation expertise. Is the heat loss calc something that both heating/plumbing and insulation experts do, or is it mainly the insulation folks? I will ask about current and projected numbers after upgrade.

Sorry, could you give me a simpletons example of  "mod/cons 2-3x the nameplate efficiency difference ".... I get the mod/con verses non modulating, just not sure what your sentence means. (Boiler green here).   Our current boiler is probably running at less than 65% efficiency and there is serious waste as our lower level is seldom used, and boiler is always on to heat upstairs.

Thanks kindly for posting

SWEI

that sounds like a start

Equipment load sizing is almost certainly a whole building heat loss.  This needs to be broken down room by room in order to properly size emitters - or to determine what fluid temp will satisfy the demand for a given emitter in a given room, and if any of those rooms have improperly sized emitters.



As to the savings potential, the difference between an 84% conventional boiler and a 95% mod/con will be much more than the 11% difference on the nameplates.  Unless the conventional boiler has a motorized mixing valve controlled by outdoor reset and sufficient water volume (in the boiler and possibly a buffer tank) to eliminate short-cycling during shoulder seasons, the net annual fuel savings from the properly installed mod/con could end up in the range of 22-33% in many cases.



If your boiler is 65% and the new insulation can get your fluid temp at design conditions down to something like 130F, you could see a much larger reduction in annual fuel usage.

DSquared

Boiler

Thanks SWEI...



http://www.webrepshvac.com/category.jhtm?cid=2994  Here is a link to the exact type of document I have, different numbers of course.

Thanks for translation on 2x3 point.

No doubt upgrading the 25 year old boiler will be huge a improvement.

The same contractor that did the whole house heat loss was also the one who checked current crawl space and suggested insulation overview.  He bid Lochinvar Knight, but I read a spooky thread on the same unit on this site just earlier today, hence my logging in with questions. (I know many variables must go into consideration...but this same bidder said he has seen more issues with Loch high efficiency (?). He mentioned something to the tune that the radiant heat we have needs 180* temp and that the 96-98% high effiency unit would probably only net us 92-94%.  Still given your 2x3 that does add up.... just not sure on overall cost of h.e. unit compared to monthly savings.

Is it possible that radiators would require less temp output with better insulation - is that what your last statement means?  I guess I understood that the radiators would run at 180* regardless and therefore require more constant furnace work 'from h.e. unit' vs the 84% unit that (if I understand) is designed to run at higher 180* all around.  (Remember boiler green)

SWEI

getting closer

Insulation is your best investment - ROI can be 25% or better in many cases.  Once you insulate, the temperature required for design day heating will be lower than it was before.  This plus an outdoor reset curve should allow the mod/con to condense much of the time while offering superior comfort.  Any mathematical comparison would require a lot more info and would still involve some guessing.  You can probably count on at least 25% if there's no mixing valve-based ODR or buffer tank on the conventional boiler.



I'm not a big fan of their earlier mod/cons, but the Lochinvar WHN is a fantastic boiler.  It (or a similar fire-tube design) can be direct pumped, which will simplify the system piping and reduce both first cost and operational expenses for pumping.

DSquared

post lost

Lost last typed post yesterday due to power outage...I was seconds from hitting submit post. arg



Insulation Co. came today and with additional blow in rafter insulation and crawl space block wall foam treatment, 'guestimation' of energy savings would be 25 - 30% overall summer and winter.

I had another heating / cooling estimator today and (now) have third Lochinvar Knight brochure.  Are they that good, or is the marketing and contractor deal that good?

Out of curiosity I visited the Weil McLain site to see what they offered in 80-90+% gas boilers (as our current low maintenance is 30 years old) and found they had a dual (cast iron / high efficiency unit) GV90. I have called a few of the 'bidders' back to ask about this unit, and they know very little about it.

I go back to being concerned with overall longevity, higher price compared to 84% units and maintenace needs (including digital board types).

SWEI

Lochinvar and more

Lochinvar is big -- very big.  Immense would probably be more appropriate at this point.  They have a long history (for an American company) with condensing boilers across a wide range of sizes.  Until quite recently, they (like many other brands you might recognize) built their mod/con boilers around a heat exchanger manufactured by a French company called Giannoni.  As long as these were properly installed and maintained, they provided impressive efficiency.  The design was what we call a water-tube: Passages in the stainless steel carried water and the gas burner operated in an open chamber at the middle of the spiral.  These passages were rather narrow, and did not like hard water.  Most of the western US continent has hard water.



Another company called Triangle Tube (which is part of the Belgian ACV group) introduced a condensing boiler a few years back based on a new fire-tube heat exchanger.  In this design, the 'tubes' in the heat exchanger carry combustion heat through a vessel which contains water.  The design is far more tolerant of hard water, has significantly less restriction on the water side of the HX, is impacted less by the byproducts of natural gas combustion, and has less risk of flash boiling.  They also used a different stainless alloy (439) which proved more resistant to natural gas condensate and chlorides than the typical 316L alloys used by most other manufacturers.  The combination of these features took Triangle Tube from relative obscurity to a significant percentage of the North American condensing boiler market in just a few years.



Thanks to a series of events which are not particularly relevant here, that heat exchanger is now being used in several manufacturers' boilers which formerly used Giannoni or other (sometimes aluminum) heat exchangers.  There's a reason they all jumped on this the moment it became available.



Lochinvar is one of those manufacturers.  The WHN models are in a different league than the earlier Giannoni-based designs.  Lochinvar's controls are excellent, and when paired with the superior fire-tube heat exchanger design, they make something I can comfortably recommend.  If the boiler proposed is not a WHN, please ask your contractor to bid a WHN-based system.  The low head loss of their fire-tube heat exchanger allows the vast majority of residential systems to be direct pumped.  This saves money up front (one less circulator to buy plus lower materials and labor costs for your near-boiler piping) and additionally lowers operational expenses (only one pump to power.)



Triangle Tube now has an improved version of the fire-tube heat exchanger and some spiffy new controls to go with it.  They're a pretty smart company and I suspect they might have another home run on their hands.  Time will tell.  Meanwhile, the old (proven) heat exchanger is available in a whole lot more boilers and seems to be taking over the market quite nicely.



Most of the bad press on condensing boilers is attributable to either bad designs (especially early aluminum heat exchangers), poor installation, or lack of maintenance (water-tube heat exchangers require regular maintenance which few actually get.)  Like all boilers, whatever their construction, the fire-tube heat exchangers should have an annual inspection and cleaning.  Similarly to cast iron boilers, the fire-tube designs are fairly tolerant of knuckleheads:  if you ignore them for a decade, more than half will probably survive.  The same can not be said for most water-tube designs.

McMaster

Good boiler explanations

The above overview was well articulated. I second the Triangle Tube boiler recommendation. I've seen a few boilers using the Gioninni style heat exchanger get plugged up with lime due to neglect. This style of HEX uses a round coiled tube. They are extremely difficult to completely clean because the passages are so narrow. If the water treatment is good, you shouldn't have to mess with them, but like was pointed out above, neglect and hard water lead to trouble. Also, these boilers only flow so much. You might need a tank because the flow may not match your system.



The Triangle Tube boiler design OTOH is actually a very close miniature copy of a HEX design used on commercial boilers by Thermal Solutions that came out not that many years ago. We've installed several of these boilers in commercial settings that have performed great. One other benefit of a Triangle tube boiler is they have higher water flow. You likely will need higher water flow for your radiators. Plus, I believe they have the outdoor reset included in their controls package. You want that.



Another boiler I haven't heard you mention is Viessman. Viessman is a German company that makes a boiler with a coiled heat exchanger, but unlike the Gioninni HEX, the Viessman uses their own design that consists of a much larger diameter tube. It is about 4-5x larger in diameter. So, they flow more water. The thickness of the tube material is at least twice the thickness of a standard Gxx heat exchanger. Furthermore, they use a 316 Ti (titanium alloy) that nobody else uses due to the increased cost and difficulty to work with. Their boilers contain a better burner design too. They come with sensors that make them self-correcting to find the most efficient flame levels. They modulate so you don't have to have the 'exact' BTU rating of your house. Certain models have an input for a hot water tank so you can make hot water for your domestic HW needs. Other boilers also have such an input too, it's not exclusive to Viessman. Viessman is one of the largest boiler mfgrs in Europe. They have an impeccable reliability rating. It's a private company therefore they don't have to cheapen up their design to satisfy investors. For instance, in europe they have higher standards for their gas valve capabilities, therefore the Viessman's is rated to survive for twice that of what is required in the US (300,000 cycles I believe). The boilers are about as quiet as a refrigerator when operating.



I don't sell Viessman or represent them, I've just done a bunch of homework on boilers and I was invited to a Viessman training session that was earlier this week. I do sell and install commercial boilers, but they are usually about 1 million BTU and up. I did, however, buy a Viessman boiler from the Viessman rep last year for my home but I haven't installed it yet, hope to soon.  



The boiler installer outfit that suggested your system is designed to operate at180*F water to get the rated amount of heat out of it, makes a very good point. Therefore if you add more insulation, you will be doing yourself a big favor by not needing as much BTU out of your radiators. We run into this at schools all the time. You find a school that has a perimeter radiant loop and it is no good to recommend them to pay the extra for a high efficiency boiler that they will never turn down below 140*. Boilers only operate in the condensing mode when the return water is 140* and below. The lower the water temperature you can operate a boiler at, the higher efficiency it will operate at. But a boiler that is operating 180* for instance will never get into the condensing mode and the most it will operate at is about 80% efficiency at that mode and you can usually get 84-86% if you can turn the water temp down to 140-150 in the spring/fall. For this reason, we usually recommend a 'near-condensing' boiler to a school that is high efficiency, but non-condensing.  



And in case you don't understand condensing vs non-condensing, just know that there is moisture in natural gas and propane. A condensing boiler (or home furnace too) has a longer heat exchanger path to capture as much heat as possible before the heat goes out the exhaust vent. If it is cool enough, the moisture contained in the flu gases condenses (turnes from water vapor back into a liquid). It gives off additional heat during this phase-change (remember your High School physics?). The byproduct is water which has some acidity, about the acidity of lemon juice. This acidic nature of the condensate along with combustion would corrode your cast iron boiler if it were allowed to operate cool enough to condense. Therefore the condensing boilers (and furnaces) switched to some form of stainless steel construction.



Another point to make is to consider using your new boiler to make domestic hot water via an indirect hot water heater (basically an insulated tank with a HW coil in it). You could produce hot water much more efficiently than you can with your standard hot water heater, which aren't very efficient, unless you are one of the few that has an ultra-efficienty HW heater. You can get by with a smaller tank, plus, they recover faster.

Good luck! 

DSquared

boiler education

Thanks for your most recent explanation of boiler functioning...the only thing I was lost on was the acronym WHN.....

After all of my reading and asking questions, the strictly high efficiency boiler may not be worth the extra upfront expense of the unit, higher maintenance costs, unit warranty/longevity and overall savings in heating bills since we have radiant heat with 180* temps (not meeting the 120* temp return - where the efficiency nets highest returns).

Over three years, our total heat costs for six months are:

$750 2011,    $872 2010,    $825 2009  (combined Oct thru March) (Some of this time, the house is unoccupied at 55*)

Other factors are:

We will be adding insulation first for overall energy savings of 25-30%

We are on 'hard' iron heavy well water

We have a water softener for whole house, but I am not sure if the boiler is picking up water pre softener or not (it doesn't look like it is piped through softener)

Water numbers from tap before softener replacement:

TDS 273,   Hardness 15,   Ph 7.3,    Iron 1.4

I believe we have an open loop water system to boiler....we have a boiler and a separate water heater (again original Weil McLain is 1978-80).

Winter temperatures reach 20's on occasion

We want to move into indirect water heating system with the new boiler.

We have 100's of feet of fin style radiant heat with two zones upper level and one zone for lower level.

From what I can gather on numbers from heat loss calculation- we are (before insulation fix) just under 60,000 btu (adding more roof venting and spray in insulation from 36 R to 50 R Value, with spray foam for crawl space  from 0 insulation to 13 R Value)

Favorite brands so far

Weil McLain GV 90+ (though I am making some calls Monday to see if these are well used in our area - and if service is easily accessible) (partial to WM since our last was simple to maintain and overall hastle free - one of our goals besides comfort and cost)

Triangle Tube Prestige 95%

Lochinvar (kinght modulating - solutions  two stage)

Buderus

Utica

The install will be a story of 'the beauty and the beast'... currently have a retrofit to a probable retrofit with excessive copper piping in a labyrinth design.



Q: Would you recommend cutting all existing pipeworks at ceiling and starting fresh? A couple of bids came in using 'existing' with design upgrade.

Any last thoughts are appreciated. This is so guy stuff, my girly head is about to blow. Thanks again SWEI for all the feedback.

D2

DSquared

last Q on radiant temps

I haven't quite grasped the concept of running radiant heat at lower temps....

I don't think lower overall temps of 140-150* have to do with the temp setting on my thermostat,but the setting on the boiler?

Will adding insulation to home enable a lower boiler unit temp in order to take advantage of high efficiency mod/cons?

I saw on this forum that Viesmann is also highly popular, but in all of my investigating, I haven't heard one iota from locals about that being a brand used (therefore serviced) here in Northern MI>  I also want to support 'made in America' businesses - which there are a few good options

We are for certain going to go the indirect water heater route and again, finding the brand with reliable 'boiler, indirect WH' partner is the goal. 

I posted above to swei with last few comments and numbers - any last comments are appreciated and thanks for additional info.  I particularly liked the school example. Based on your comments, if I can't get my radiant head to return under 140* the strictly high efficiency boiler won't do me much good - for overall higher cost.

Is the Triangle Tube the 'tweener' that offers high efficiency without being 'condensing'?  Any others>? Do you have any opinion on the WMcL GV90+

Thanks McMaster

D2

SWEI

temps, boilers, etc.

WHN = Wall Hung.  These are the new fire-tube designs.  The older Knight is a Giannoni based design.



From your list, I'd pick either the TT Prestige or the Lochinvar (if it's a WHN.)



In a properly tuned ODR system, the thermostat serves basically as a high limit controller - set it a few degrees over your desired space temp and it will prevent the boiler from continuing to heat if the room gets warm due to solar gain, cooking, or a bunch of dancing partygoers.



Proportionally controlling the fluid temperature according to (and anticipating) demand will provide superior comfort and save fuel.  As the temperature of the returning fluid drops, a condensing boiler becomes more efficient.  In shoulder seasons with a highly efficient emitter system, return temps can drop as low as 70F for an occupied space, which can produce boiler efficiencies upwards of 98%.  So the lower the water temperature you can run, the less your boiler and pumps cycle on and off and the more fuel you save.

McMaster

Weil-McLain

I've seen that boiler, and was given demonstrations at HVAC shows. No personal experience but W/M has a good reputation for boilers, esp. cast iron boilers. It's a little different system how they achieve the condensing feature of their boiler, but it seems like it essentially achieves the same thing while giving the ruggedness and full flow of a cast iron sectional boiler. A lot of commercial boiler companies have a non-condensing and a condensing line and sometimes it's just the 'afterburner' section that is attached onto the standard non-condensing boiler to achieve a higher efficiency. That's basically what Burnham is doing here. It's sort of an after thought vs a whole boiler re-design which the Triangle Tube company has done, but nonetheless you will probably get the best of both worlds with this boiler: Flow, longevity, simplicity ...and efficiency. I guess that's more than two worlds.



As for the boiler loop temperature, your system will run with whatever water temperature you give it, you just won't get much heat out of the radiators at 100* water. And, I did the calcs a couple times over the years and those few days you do run it at low water temperature when it might be, say, 55-60* outside, the boiler isn't using a heck of a lot of fuel so you aren't really saving a bundle. To get the necessary heat out of your radiators to warm your rooms as they were sized to do, you'll need warmer water, probaby between 140 and 160 (or more) when it gets REALLY cold outside. You can (and should) have the company install a outdoor temperature reset system up so your boiler loop temperature will be reset (raised or lowered) to track with the outdoor temperature. That is a good energy savings feature.  



More insulation on your home walls, ceiling, etc and tightening up your house to prevent drafts and any other outside air intrusion would make the difference between needing to run your loop at 180*F day and night in the cold dark days of the winter vs being able to do the same amount of heating with, say, 160* water.



Hope this helps. I think you are on the right track. 

McMaster

More boiler thoughts

I just wanted to add one drawback of cast iron boilers, especially for indirect HW use is something that called Radiation Convection Loss (RCL). When considering boiler efficiency, a hidden component of efficiency, or inefficiency in this case  that usually goes uncalculated is RCL. What this means is that a certain amount of energy is required to heat the cast iron heat exchanger (and water within it) up to the required temperature. All boilers cycle on/off to some degree and when they cycle off because your house temperature is satisfied, guess what happens to the heat in your boiler? Well, some of it is going to go up the stack. If the boiler were to cycle off, then in a few minutes cycle back on and stay on for a long period of time, then a lot of that heat will be used in your system.



But if your boiler were to cycle on, run for a period, then cycle off again and not run again for an extended period of time (like in the spring/fall, or during making domestic H/W), then most or all of the energy it took to initially heat up your boiler will go right up the stack. That's energy that you used to heat up your loop, but aren't using to heat your house. Over time, this sort of cycling adds up. This is where the new style condensing boilers with the coil-type heat exchangers gain so much, including the triangle tube type boilers. They use much less water in their heat exchangers, AND, they have small passages and less mass to heat up. Plus, they modulate down to low levels allowing the boiler to operate as much as possible with less heat loss up the stack. Therefore they can be more efficient in real-life use that goes beyond the published specs.



Another factor is that if you have much radiant loss in the summer, that heat will flow into your building envelope (the house) and you will spend a little extra to cool it down. If it's in the basement, then it probably won't matter anyway, plus the fact that it'll be more efficient and recover faster than a standard water heater (and contain less water mostlikely) will probably cancel out RCL loss.



I still think the W/M might be a great choice for you. You just want to be sure it's not oversized to the point where it cycles more than is necessary, and you have to consider at other factors too, like reliability, local service, long-term cost of ownership and things like that.



Anyway, just wanted to add this to my above comments.

SWEI

system temps and ODR

No experience with the GV90+, but adding a recuperator onto a conventional CI boiler seems like a hard way to get to the destination.  Two heat exchangers to clean plus additional flue piping connections would be my concern.



"those few days you do run it at low water temperature when it might be, say, 55-60* outside" does not match my experience.  Especially as he is adding insulation, I'd strongly suggest a review of these:



http://www.heatinghelp.com/files/posts/12471/AshraeCondensingtechnology.pdf

http://www.bnl.gov/isd/documents/28709.pdf