Check please!!!

Discussion in 'Boiler Forum' started by Crooz1n, Sep 10, 2013.

  1. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Hello I am looking for some verification/ devils advocate on my selection of boiler before I commit fully.
    My house was built in 1926 it’s a brick veneer foursquare of 1612 sq feet. We installed double pane low e argon filled replacement windows when we first moved in 2006, The walls have blown in cellulose insulation. The basement is above ground on 2.5 sides (~12 inch thick poured concrete) with a walk out door and 4 old single pane windows with storms. The ceiling of the basement is insulated some with 3 inch fiberglass.
    The attic is a walk up with a storage platform of around 12 x 30. It is all insulated with rock wool bats of 3 inches then loose blow in up to height of joists.(8 inch) I am in the process of air sealing and am going to further insulate with blow in up to 12 inches or so. The storage area floor is insulated underneath in the same manner with rock wool and blow in. There is a single dormer with replacement window here.
    I am currently heating with a 20 Kw /68000 BTU electric boiler. 4 elements – 2 come on when called for heat then 30 seconds later the other 2 come on until heat need met. Single zone 1circulation pump. Needless to say the electric bill is killing us.
    Heat loss calculations range from 29000 t0 55000 depending on who did it and which calculator you use. I have used around 10 methods as well as contractor done. I used 16 degrees as well as 0 degrees just to make sure I was covered. Average around 47700.
    I have standing cast Iron radiators 580 Sq. feet worth and a single toe kick heater under the kitchen cabinet that I installed when we remodeled the kitchen and had to take out the cast iron monster under the sink.
    I have an unlined brick open chimney (30 feet from flue opening to top of chimney).
    I have contacted some contractors who mostly wanted to install their brand of boiler Bryant, Lennox in particular but they also quoted, Weil Mclain and Newyorker. A couple wanted to use way to large a boiler ( 105 Ultra and Bryant 75E)
    After some consideration I decided to have all of them quote a Weil Mclain GV90+3 for my house. That way I can get a feel for the install cost alone as I know I can get the boiler for ~2500.00
    The GV90+ can be run thru my chimney with only PVC. The others that I was quoted require AL29-4C liner at a cost of 600-900 dollars.The GV90+ is a cast iron boiler with external heat recuperator.
    All have quoted Weil Mclain so I suspect it has the biggest base of trained technicians and with it being basically a cast iron unit there should be less hassle with any servicing issues.I could have went with a slant fin Victory VSPH- 45K but by the time you price in the liner you are at the cost of the GV90+. I asked about the Slant fins and did not get a good response here.
    I originally thought I’d like a Burnham PVG3 or New Yorker PVCGA. I was told the local distributor doesn’t carry them.( R.E. Michaels) So I’m kind of limited as to what will be able to be readily serviced. As to higher efficiency units I don’t think the ROI is good. Am I on target here or missing the mark for a better solution?
    Last edited: Sep 10, 2013
  2. Dana

    Dana In the trades

    Messages:
    2,790
    Location:
    01609
    The GV90+3 is about 2x the boiler you actually need.

    IIRC the PVG3 is no longer made replaced by the ESC-3 (power vented sealed combustion, which can be side-vented to save the cost of the chimney liner) and ES2-3 (atmospheric- but can be B-vented) which are also 2x the boiler you really need.

    The 99% outside design temp for Roanoake is +17F, and designing for 0F would be silly, and would oversize the system by more than 25%. Even if you designed EXACTLY to the 99% design conditions using a Manual-J methods you'd still no be cold on those rare nights when it hit zero F. But the boilers you're looking at are all 2x oversized for your likely true heat load.

    If I were to believe any of the heat load numbers cited it would be the 29,000BTU/hr, but even that's on the high-side for a 1600' four-square that has better windows and at least some insulation. If you had a mid-winter's power bill with the exact meter reading dates we could use that to MEASURE the heat load of the house or at least put a firm upper bound on it by looking up the heating degree-days that occurred between the reading dates on degreedays.net, and converting kwh/HDD to BTU/degree-hr.

    If you've played around with heat load calculation tools at all you'll notice that the uninsulated basement is a significant fraction of the total load. Air sealing and insulating the band joist & foundation sill is important, but insulating the walls to at least a couple feet below grade is too. Read up on it before diving in though- there are plenty of ways to screw it up and create a mold-farm. (I've covered that territory often on the remodel forum on this site, if you want to search it out.)

    It might make better economic sense to design the heating system around a condensing hot water heater like the Vertex or Polaris, since you probably have sufficient radiation to deliver the heat at 130F or cooler water, once you've finished your air-sealing & insulation upgrades. With those you get the benefit of cheap PVC venting and 95% thermal efficiency, probably at a comparable or lower installed cost to what you're looking at. You'll need to isolate the potable from the heating loop with a plate heat exchanger, and use a bronze pump on the potable side loop, but these water heaters are designed for combi-applications, and come with the plumbing ports for space heating built in.
  3. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Wait a minute.... A water heater for home heating.... Thats just crazy talk.... Tell me more.
    Oh and as far as electric usage.
    12/10 12 to 1/11/13 4774 KW,
    11/7/12-12/10/12 4973 KW
    10/9/12-11/7/12 3389 KW

    Now that's total electric usage. My base is around 1900 Kw /month in spring and fall.

    Thanks for the info Dana.
    Should I call a plumber then instead of HVAC businesses?

    How would one go about sizing a water heater for space heating?
    Wow and I thought I had it figured out. At least I didnt let them sell me an Ultra 110. :)
  4. Dana

    Dana In the trades

    Messages:
    2,790
    Location:
    01609
    At 1900 kwh/ month background that doesn't include heating OR cooling you'd be in the top 2 percentile of power (ab)users in the US- possible, but not too likely. The use median is half that, and 300kwh/month background you'd be in the bottom 2%.

    To be conservative I'll assume 500kwh/month background, 800kwh/month if heating your domestic hot water with electricity, but it could be higher if you have a bunch of kids, with high hot water use & electric clothes dryer use.

    OK, using data from the Roanoke airport weather station and assuming 500kwh/month went to other uses:

    12/11/ 12 to 1/11/13: 767 HDD using 4774 kwh, less 500kwh is 4274 kwh/767 HDD = 5.57kwh/ HDD

    11/8/12-12/10/12: 591 HDD at 4973 kwh , less 500 kwh is 4473 kwh/ 591 HDD= 7.57 kwh/HDD

    10/9/12-11/7/12: 381 HDD at 3389 kwh, less 500kwh is 2889 kwh/ 381 HDD= 7.58 kwh/ HDD

    Taking the worst case 7.58 kwh/HDD, at 3412 BTU/kwh thats 25,863 BTU/HDD

    At 24 hours in a day that's 25, 863 BTU/24 degree-hours is 1078 BTU/degree hour.

    Since the HDD is based on a presumed balance point of 65F between heating/cooling (which close enough- in most homes it'll be with a couple of degrees of that depending on how warm you keep the place), and an 99% outside design temp of +17F that's 65F-17F= 48 heating degrees.

    At 48F x 1078 BTU/F-hour gives you 51,744 BTU/hr. And that's with a large margin- most homes have other power use of over 500kwh/hr, and if you're heating your potable hot water with electricity (probably are) most homes would be using 300-450kwh/month on hot water heating alone. Taking the December-January number of 5.57, assuming you weren't away for the holidays, that would put the heat load at about (51,744 x 5.57/7.78 =) 37,455 BTU/hr, which is probably closer to reality, and still an overestimate.

    If one assumed another 300 kwh/month for hot water (800kwh/month background) that Dec-Jan number drops to 3974/767= 5.18 kwh/HDD, implying a heat load of (51,744 x 5.18/7.78=) 34,452 BTU/hr.

    Best guesstimate without more data on your non-heating non-cooling electricity use is you're probably in the mid-30s but certainly not over 52K for a heat load. (A wide range I know, but without a more careful analysis and better data that's it.)

    The 76KBTU/hr burner Vertex HW heater delivers over 72,000 BTU/hr, which is considerably more than what your heat load would be even if you had assumed ALL of the electricity use went to the electric boiler, and twice what your more likely numbers are. Subtracting out a hefty 45K for the space heating means you'd still have more "spare" burner capacity for the domestic hot water than a typical 40 gallon standalone tank heater.

    This is something you can't just hand to a plumber- it's a real hydronic design problem any way you cut it. The designer/installer has to know the total amount of radiation and water temperature requirements to be able to deliver the heat at the design heat load, be able to specify the heat exchanger & pumps etc. The flow & delta-T on the heating loop & HX needs to be set up to deliver the heat, but not the full 72K output of the burner or with high mass radiation you could find yourself in a tepid-water-only condition on a cold-start of the heating system. Bumping up to the 100K burner version of the Vertex or the smallest Polaris would give more margin, making that condition less likely. (A good designer could make it work with the smaller Vertex though.)

    The Vertex is glass lined, and you'd expect to get a good 12-15 years out of it, but the Polaris is stainless, good for 20+ years, which is why it's a more expensive option, but may be worth it.

    From a system design point of view it would be simpler to drop in the ESC-3 and an indirect water heater zoned "priority", and with the system properly tweaked it would really deliver close to it's ~85% AFUE number, since it has some on board smarts to manage the thermal mass (and an "outdoor reset" option), and is capable of low-temperature operation with 110F return water without damage.

    After all that is on the table, it's worth looking at ductless air source heat pumps (mini-splits) as the primary heating/cooling source, and using the existing electric boiler/hydronic system only as the backup. Better ductless systems will deliver a seasonal COP of about 3.3-3.5 in your climate, reducing power use for heating by more than 2/3, even if you set up the hydronic system as the "Hail Mary" backup. With a 99% design temp of 30-35K you'd do pretty well with ~2-tons of well-placed ductless, with an operating cost comparable to heating with gas, and you can get INSANE air conditioning efficiencies out of them to boot. The upfront cost for better-grade mini-splits is about $3.5K per ton in my neighborhood, sometimes less. On a two-story you'd want to have one ductless head per floor (or more), and being point-source heaters, doored off rooms remote from the head could run into comfort issues at the temperature extremes, but in general comfort levels are pretty high- much higher than most ducted-air heating & cooling systems. They are also significantly quieter than window AC units, even quieter than most single-speed ducted air systems.
  5. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Dana
    WOW,
    Thank you so much for the information you supplied. It makes my head spin. Unfortunately I seriously doubt there is anyone within 100 miles that could design and install such a system. I have been having trouble getting boiler quotes that are not 2-5 times more than I need. Seems like everyone wants to do forced air. I have considered a mini split for the 1st floor as I am cooling it with a window unit now but the quotes I have been offered are more expensive than a traditional heat pump with ductwork setup whats up with that?
    .There is central air on 2nd floor with air handler in attic. As for now I know I need to get away from the electric boiler so I'd like to do something before the heating season here. Again It seems I'm limited to local technical "expertise" to make sure servicing and warranty work can be done.

    Its only my wife and I although she is home all the time. I have an extra freezer downstairs, a small dorm Beer fridge, water heater but its like 1-2 showers a day 4 loads in the dishwasher a week and about 4 loads of clothes all washed in cold.
    We do have a hot tub but I've only had it since May 2012. It looks like it may have added about $40.00 a month. I have since throttled it back to minimal temp and filtration.

    Again Dana thank you so much for your time.

    I have learned a bunch in the last month probably more than many of the contractors I have talked to.

    Can you explain why you would choose the ESC-3 Vs the GV90+?

    Power usage last 3 yrs
    Date Your Usage (KWH)
    8/8/2013 2,062
    7/11/2013 2,329
    6/11/2013 2,046
    5/10/2013 1,867
    4/10/2013 4,639
    3/12/2013 6,394
    2/8/2013 5,857
    1/11/2013 6,179
    12/10/2012 4,973
    11/7/2012 3,389
    10/9/2012 1,734
    9/10/2012 2,521
    8/8/2012 2,237
    7/11/2012 2,643
    6/8/2012 1,789
    5/9/2012 1,848
    4/11/2012 2,026
    3/9/2012 4,315
    2/10/2012 5,174
    1/11/2012 5,512
    12/9/2011 3,797
    11/8/2011 2,831
    10/10/2011 2,042
    9/8/2011 2,185
    8/9/2011 2,187
    7/12/2011 2,029
    6/10/2011 1,558
    5/11/2011 1,580
    4/11/2011 3,489
    3/11/2011 4,489
    2/10/2011 6,355
    1/12/2011 8,434
    12/9/2010 5,760
    11/5/2010 1,929
    10/11/2010 1,887
    9/9/2010 1,651
  6. Dana

    Dana In the trades

    Messages:
    2,790
    Location:
    01609
    I'm not sure the GV90-3 is necessarily a bad idea compared to the ESC3- the fact that the condensing HX on it is stainless makes it less sensitive to the water chemistry than W-M's aluminum HX mod-cons. The controls on the ESC-3 are smarter, making the system potentially easier to tweak in for optimal performance (or not), but side vented it would be cheaper to install.

    A Polaris would give you higher net efficiency at a comparableinstalled price. You'd be trading the cost of an indirect HW heater & pump that you'd need with the GV90 for the cost of the heat exchanger and pump for a Polaris based system, but you'd have 95% efficiency.

    A Vertex would be about $1,000 less money for the equipment at the same efficiency as the GV90, with the caveat that it won't last as long.

    You may want to ping BadgerBoilerMN, who has quite a bit of experience designing around the Polaris. I'm sure he could be hired to spec a system that could be plumbed in by a competent plumber or DIYer.

    The hot tub is a real power load, which probably adds another 300kwh/month during the summer and a bit more in winter.

    A 1-ton mini-split that does both heating & cooling would normally be under but around $4K in my neighborhood, even for a decent Mitsubishi or Fujitsu. With Daikin you'd pay a few hundred premium, but for many of the others you'd be a $3.5K or less. It's not rocket science to do the 95% of the installation yourself and only hire the tech with the necessary tools & experience at the point that the system is ready to be pumped down, charged, and tested, which shouldn't be more than an hour or two of tech time. The hardware is pretty cheap. With the extranous mounting hardware and electrical work you might get the hardware costs up to nearly 2 grand, but not more. If the techs cost $150/hour you'd still be around $2500 or less out of pocket for a fully warranteed system. Read up on it before embarking on the DIY path- there are plenty of ways to screw it up, but it's well within the range of people who do their own electrical work & home maintenance/repair. Whether DIY or professionally installed, the upcharge for a heating + cooling version vs. a cooling only is a couple hundred or so, and generally worth it. During the shoulder seasons when it's 45F or higher the efficiencies on these suckers SOAR, beating the cost of heating with condensing gas with significant margin in most markets.

    I'm not sure how you're ending up using over 1500kwh/month in non-heating non-cooling months. In my own home in MA the hot water is gas, but the dryer is electric, and we also have central air (doesn't run much, but some), but I can't recall any month over the past 100 that have seen even 1000kwh. Our electricity is 30% more expensive than the nat'l average, and we've long since gone over to only high-efficiency lighting, but even then 1500kwh/month seems high to VERY high for a family of two, even if you're the types that thrive under the hot glow of 150W halogens. The national average power use per household (all uses) is 940kwh/month according to EIA data, and the highest state-average (Lousiana) is 1348 kwh/month (skewed by extreme air conditioning loads no doubt.)

    The central air with the air handler in the attic approach is cheap to install, but about the least efficient configuration going (at ANY nameplate SEER efficiency), since at peak conditions the air handler and ducts are in an environment several 10s of degrees warmer than the outdoor air, and the penetrations into the attic all leak air 24/365 from stack effect forces, and ducted systems create pressure differences between rooms that drive infiltration rates from other leakage points. You can usually downsize significantly in total nameplate cooling BTU when going from one of those to ductless systems. I'll bet it's something like 3-4 tons(?) of compressor, but about 1 ton of that is to make up for the direct gains from the attic sited ducts & air handler and air-handler driven infiltration. Depending on the depth of the cellulose in the attic and square footage of west-facing windows the peak load for the second-floor-only are likely no more than about 1-ton, now that you have the lower gain of low-E windows, but it probably takes about 2 tons of compressor to actually cool it with an ducted attic air handler configuration.
    Last edited by a moderator: Jun 9, 2014
  7. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Again Thank you . Lots of information. I have contacted an energy audit company in Blacksburg and asked if they could help me with a water heater system. I'll see what the cost will be for the design consult and maybe have a blower door done as well. I just hate to shell out 450.00 for advice. I guess though its worth what you pay for it. Unlike your priceless advice which you give so freely and is so valuable.
  8. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Dana I just got a good quote for installing a PF80. It will modulate down to 26K and max at 80 K(63). I think I would be good with a PF50 though. It has a low of 16K and an upper of 50K (40). I just wondered what your thoughts are concerning the size and if you have any comments on the PF line vs. the GV90+
    Peerless.jpg
  9. Dana

    Dana In the trades

    Messages:
    2,790
    Location:
    01609
    The Peerless Purefire series are modulating boilers, and on a comfort basis alone would be worth the upcharge over the GV90.

    The PF50 is the right one for your application- smaller is (almost) ALWAYS better, as long as it has sufficient output on the high end to meet your design day load. The PF50 covers your peak load with margin. If you go with the PF50 and tweak the outdoor reset curves right the thing will modulate, tracking the load for much of the winter, since it's minimum fire output is below your average winter load. When looking at the heat ratings of boilers, since the boiler is inside of conditioned space, not in an unheated shed or garage, use the D.O.E. output number. The I=B=R number only applies if the standby and distribution losses from the boiler are going somewhere outside of the house.

    If you go with the PF 80 it would run at least twice and maybe even 4-5 times as many burn cycles no matter how finely you tweak the setup, since it's min-fire output is greater than your average mid-winter load. There is no up side to having a modulating boiler that rarely (if ever) modulates. With your high-mass radiation it won't cycle so often that you burn it up, but room temps won't be as steady as with the smaller boiler with the outdoor reset dialed in. (In some high-mass radiation situations it's sometimes possible to dispense with the thermostat, and let it run continuously using the outdoor reset adjustment, but I don't think this will be one of those.)

    Put it this way, doing the napkin math:

    If as we've estimated from power use your load at 35,000BTU /hr @ +17F and 0BTU/hr @ 65F, your load only varies byt 35,000/(65-17)= ~730 BTU/hr per degree below 65F. With 16K input at 95% you get 15,200BTU/hr of output, which can cover the whole load at 15,200/730= 21F degrees below 65F, which is 44F. Any time the outdoor temp is below 44F it will modulate up with load.

    With 26K of input at 95% you get 24,700BTU/hr of output, which only starts to modulate at outdoor temps 24,700/730= 34F below 65F, or 31F.

    The average mid-winter temp in Roanoke is about +37F. The average high temperature in January is about 45F, the average January low is about 29F.

    The ability to modulate in the 31F-44F outdoor temp range is what you get with PF50, which accounts for the majority of hours during the 3 months of winter. If you were to go with the PF80 it would be modulating fewer than 10% of winter hours.

    And that is why you would want to go with a PF50, and NOT a PF80.

    But you'd be surprised at how many PF80 size or larger boilers are installed in houses with heat loads even smaller than yours. The PF80 could still heat your house as-is but moved to the coldest parts of North Dakota or Minnesota, and is a ridiculous choice for most houses in Virginia. But people up-size out of an ill-considered irrational anxiety about being cold, and contractors who don't want to bother calculating heat loads are perfectly comfortable with going along with that, since it's often hard to make people believe that their heat loads are as low as they really are.
  10. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Thanks again Dana. You have confirmed my thought process.

    Ok It looks like I'm getting the PF50. I hope it's right...
    Last edited: Sep 23, 2013
  11. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    Ok so they finally got my boiler installed and so far it seems good although its only been in for a week.
    They incorrectly installed the pump vertically instead of horizontally but are coming back tomorrow to change that.( B & G NRF-22) I was concerned that they piped it direct rather than primary/secondary but contacted Peerless and they said it was OK as long as the correct pump was spec'd as I only have one 2 pipe zone.
    I've been trying to see how long the boiler runs are but its been hard to catch as it seems to run only 2 or 3 times a day. ( temps at night have been falling to upper 30's and 40's during a few days) I'm still trying to get a handle on the reset curve settings but I think its going to be OK. I have it set to 140 @+16F the top right now but I think I might try it at 120.

    Dana I want to thank you for all the advice in this as well as the other posts you have so graciously taken the time to make.

    IMAG1065.jpg
  12. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,075
    Location:
    Maine
    PHP:
    Where do the vent pipe and combustion air inlet go? It looks like they ran them into the chimney. Did you have an inspector come out and look at the installation? I ask because I see several code violations there.
  13. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    They went into chimney per my request and go all the way thru the chimney out the top of the chimney.( chimney is just a chase) I didn't want the pipes sticking out the side of the house.These are the only thing in the chimney. Inspections are complete with exception of dripping relief valve atop expansion tank.
    Last edited: Nov 11, 2013
  14. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,075
    Location:
    Maine
    So the mechanical inspector passed the venting, wiring and the gas supply?. Was the installer licensed?
    Last edited: Nov 12, 2013
  15. Crooz1n

    Crooz1n New Member

    Messages:
    26
    Location:
    Roanoke VA
    yes Tom he is licensed. Just tell me what you are seeing and I can ask inspector about it.
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