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Boiler Suggestions for confused home owner
MikeAR
Member Posts: 15
I am getting mixed opinions from the different sites I've looked at, so hopefully someone can straighten this out. I need to replace the boiler in my 100 yr old 2 story home. The current boiler (approx. 25yrs old) is rated at 165,000 btu output and it is a converted gravity system with a circulator. The one HVAC guy I had come out estimated the new boiler would need to be 90K, and from the info on radiators I have found on your site, 90-100k would be about right. What I am wondering is this: Would I be better off going with a more conventional type boiler like the Burnham revolution, or something like the Monitor MZ series, or even the Takagi T-KD20, which Takagi says can be used as a boiler. Also, is it true that in an old system like mine with large pipes (2-3")and lots of water volume, you will never achieve more than about 85% efficiency? Any help would be greatly appreciated. I live in a very rural area, so finding someone that knows these old systems, plus has any knowledge of the new technology in boilers, is pretty hard to find.
Also, I forgot to mention that whatever I go with, it needs to vent through the sidewall, since my old chimney is starting to fall apart. I figured this would be a good time to update the boiler and just tear the chimney down.
Also, I forgot to mention that whatever I go with, it needs to vent through the sidewall, since my old chimney is starting to fall apart. I figured this would be a good time to update the boiler and just tear the chimney down.
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Comments
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Mike, I like the guy who
seemed to know about the BTU's you actually need - as opposed to those guys who (I assume) just looked at the 25-year old clunker, read the plate, and decided to use THAT data instead of a radiator count, or "true" heat load calculation.
I didn't see where you mentioned how he arrived at the correct size boiler, but assuming he did NOT use the existing data plate on the existing one, is one feather in his cap.
However, measuring the standing radiation in a gravity system is not the correct way either!
Dan offers a free heat load calculator from Slant/Fin on the index plate on the top left of this website (5th from the bottom). Play with it and see what YOU come up with!
That calculation would confirm the correct replacement boiler sizing.
With natural gas prices (and oil) spiraling upwards at alarming rates, the MZ would be an awesome choice. The use of an indirect water heater would save you a fortune in year round domestic hot water generation fuel costs as well.
Sounds like you already have a handle on your situation.
Let us know how you make out.
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Good News - There is savings on your horizon!!
Judging by the age of your home, the standing radiation is most assuredly oversized. They oversized by practice and if you have had shell work done(windows,insulation,doors,air sealing) they are even more oversized. A condensing,modulating boiler with outdoor reset will literally wring the dollars out. Since the rads are oversized you can run lower temp water through them. There are good otions available to you. An indirect water heater is also a great idea. Abundance of hot water combined with low cost of production. The efficiency of a indirect is directly related to the efficiency of the boiler. The more efficient the boiler, the more efficient the indirect. Happy boiler hunting.0 -
Mike
Where are you located.
Mike Norgan
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Efficiency of Gravity Conversions
You have to think of the efficiency of the boiler as separate from the ability of the rest of the system to deliver heat to the living space.
Gravity conversions have some good points and bad points when it comes to delivering heat.
Bad: Pipes are large, thus they have a large surface area and loose more heat. Volume is high and it can be very easy to either over- or under-shoot the desired room temperature reducing comfort.
Good: Pipes are large, thus there is little restriction to flow and it takes little energy to circulate the water. Volume is high and it can be very easy to modulate room temperature increasing comfort.
Reduce the bad and enhance the good.
If there is crawlspace or the basement is already warmer than you think it should be insulate the piping well. Do your best to seal the gaps between foundation and sill--in old houses this is generally VERY leaky. If your basement is substantially above grade, you really do need some heat down there to keep the floor above from being too cold. Beware of insulating the floor above in old houses in warm, humid climates.
To use the high volume of the system to best advantage, use it as a flywheel instead of an accelerator and a brake. At a minimum, use outdoor reset. To go farther, install thermostatic valves on the radiators and get rid of the conventional wall thermostat for anything but whole-house setback.
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Gravity conversions do, IMHO drag at the efficiency of conventional boilers. Not so much because of their high water volume, but because of their ability to rapidly absorb heat combined with a low temperature requirement. "Fixing" that problem is difficult as you essentially need a reservoir (buffer) of water much hotter than required by the system. This will help the boiler work more efficiently, but it creates new losses and adds to cost/complexity.
Gravity conversions do, IMHO allow condensing (and especially condensing/modulating) boilers to operate at peak efficiency. Such thrive on the low temperatures and the more proportional you make the system the better it will be both comfort- and fuel-wise.
Considering your remote locations, your choices are going to be limited. Considering your desire to eliminate the chimney, your choices are further limited.
A properly sized power-vented conventional boiler will seem to be your least expensive option in first cost, but will be the most expensive when it comes to fuel used. Also, make certain that the installer takes protection from low return temperatures seriously--such a boiler won't be as tolerant as the old, oversized current unit.
If budget at all allows, consider the MZ or Vitodens. Both are highly reliable and require little maintenance. If installers balk about working with the "fancy new stuff" it's probably because they're unfamiliar and unwilling to study. Keep looking.
Properly installed in the system you describe, fuel consumption should drop by around 50%--I know it sounds incredible, but there are many comparables. Note however, that you're likely to see some drop in fuel use with a properly installed and properly sized conventional boiler--just not close to this degree.
If you want to utterly maximize efficiency and comfort by adding TRVs, I'd suggest the Vitodens. If you plan on staying with a conventional wall thermostat (and reset of course), the MZ would be my choice.
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location
I am in central Illinois, just North of Bloomington / Normal.0 -
Out of that list
I would give high marks to the MZ. This could be outdoor reset controlled for further efficiency. Plenty of guys here have used condensing boilers on old radiator systems like that.
I have a MZ in my shop and it has performed above and beyond my expectations. Very, very dependable, for a condensing appliance.
hot rod
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Check out...
the Weil Mclain Ultra boiler, modulating, condensing, outdoor reset, and if hooked up right, can work wonderfully on a gravity system and give you eff. well into the 90% range.
The hooked up right is the key to ANY boiler working well on your system!!!!! The INSTALL practices will make all the difference in the world as far as the eff. and comfort of your system after the change out.
Make SURE you find someone that is comfortable with the high eff. boilers and has the knowledge to pipe everything correctly.
Good Luck!!
Floyd0 -
BOILER ISSUES
i would keep it simple. being in a rural area #1-reliable equipment #2-ease of service. these would be my objectives,BURNHAM SERIES 2 OR THE INDEPENDENCE SERIES IS AN EXCELLENT WATER BOILER FROM A USA CO. FOR OVER 125 YEARS. TELL ME HOW EFFICIENT THE BOILER IS WHEN THE DRAFT-INDUCER GETS REPLACED ?0 -
converted gravity system
As others have said, you can't use radiators to detemine how large a boiler you need. It is better to use heat-loss calculations, but not much better, because they are based on assumptions that might not apply to your house, and allow quite a bit of cushion. If you know the therms/degree-day gas consumption in your house, and are handy with a calculator, you can determine what your current boiler consumes on a design day (typical coldest day--well, not quite, but something like that). Your new more efficient boiler should be somewhat smaller than that.
As others have also said, but worth repeating, having excess radiators means you can use lower-temperature water and thus get the increased efficiency of a condensing boiler. An MZ is good, as are Munchkin, Vitodens etc.
Gravity systems don't have intrinsically poor efficiency, but most conversions are not done right. You need to wring out all the energy you have put into the water, and start/stop circulators don't let you do that. You need to have your circulator wired so it runs ALL the time except in summer. Not even the thermostat should stop the circulator; the thermostat should stop only the boiler. This will also give you more even heat with much less noise from the pipes (because the system doesn't have a yo-yo temperature).
If you get a condensing boiler like the ones mentioned, the water can circulate all the time without any of the issues you would have with a cast-iron boiler. A running circulator consumes only about as much energy as a (relatively bright) light bulb.0 -
You want to contact Boiler Professionals out of Amboy, if they don't work in your area specifically- he can suggest someone with this level of expertise. I, too have an MZ monitor in an old system... and have achieved astounding results in lowering the gas bill. How about 15% of the gas consumption after conversion? Largest gas bill below $200 for a month. Good luck,
Luke Lefever
Lefever Plumbing & Heating, Inc.
Elkhart, Indiana0 -
CONDENSING
radiators dont' deliver many btu'h under 180 water-no boiler will condense at 180 supply.0 -
you ain't got a clue......
radiators is gonna put out heat as long as they are warmer than the air around them, even a dummy nose that.....
Also wish I knew who your boss was... your really screwing up his bottom line.... you could be making him a TON more money if you would just get your head outta the......
dark ages!!!!0 -
dumber
is their 90%+ efficient boiler for space htg ? i would like to see it. published afue ratings are based on 140f supply water temp. combustion process a percentage of heat must go up the stack. the recognized max. efficiency for atmospheric boilers is 85% this would represent 7.5% co2 reading and stack temp of 175. the 7.5 CO2 IS REASONABLE but 175 stack temp is not. the dew point for nat. gas with 50% excess air is 127f. to have 127f surface in the boiler,you would be limited to boiler water temp that are not often seen with ANYTHING but floor htg. AGAIN IF IT WAS ME AND LIVING IN A RURAL AREA #1-RELIABLITY0 -
I'm only a homeowner...
> radiators dont' deliver many btu'h under 180
> water-no boiler will condense at 180 supply.
...and even I know better than that. (I set my aquastat at 140 and it stayed there all winter.)
I sure wish more people in the business were better trained. The guys who count radiators in order to size hot water boilers, for example.0 -
What boiler's does McCoy sales represent? Whatever that is- I don't think they are being represented well. There are fully condensing boilers available- that are extremely reliable, and are applied to space heating every day of the year. The days of cast iron and a maximum efficiency of 83-85% are competely over. With the price of fuel oil going up, natural gas and LP through the roof, anyone who doesn't offer a fully condensing option to their customers is just behind the times. Certainly some customers, for their own reasons, will not select the most efficient product we have to offer, but to not offer it is almost a crime. Just my $.02.
Luke Lefever0 -
Thank Goodness
for involuntary bodily functions because without them alot of people would not be around.0 -
he may be a real guy
If that e-mail is right, this is a real person in the heating business!
http://mccoysales.com/contacts_frame.htm
Go down to 'Heating and Plumbing'---Bill Garnett
God help us all.0 -
180???
I would say my old coal boiler converted to gas never heated my water much more than 125 to 130. I got a new outdoor boiler and had to turn the temp way back from the recommended 180 because my huge radiators were running me out of the house...I had great heating even at 150.0 -
Consider the Munchkin w/Vision 1
Heat Transfer Products Munchkin w/Vision 1 may provide a more reasonably priced condensing boiler than the Viessman or W/M Ultra and may hold up better with the funky Central Illinois water.
You should spec that the boiler is installed with Primary/Secondary piping exactly as the manual(s) state. Since you are taking out the chimney, an indirect water heater piped off the boiler might be necessary and your best means for hot water.
The important feature is to have a modulating condensing boiler based on outdoor reset which means the boiler runs almost all the time, but varies the flame to burn just enough gas to keep the water at the temperature needed to warm the space based on how cold it is outdoors.
Look at your gas bills and do the math to figure out the btus/hr needed at design condition. Do a search on The Wall for "Therms per degree-day" to find out how.
Have you considered geothermal now that they have it for hot-water heat too?
You might contact Kupferschmid, Inc. in Forrest 815-657-8147.
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Thanks Luke
I plan on getting in Find A contractor, Just haven't gotten a round "toit". Bloomington/Normal is a bit of a hike, but I do consult. I've had other folks in similiar situations.....contractors telling them completely opposite things. I can imagine the frustration!
Boilerpro
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What about the Takagi?
First of all, thanks for all the input. I do have another question. The info on Takagi's site shows the T-KD20 being used as a boiler. And not being an expert at any of this, I can't see what the big difference is between the Takagi and the MZ Monitor. I know the Takagi would have to have an external circulator and probably some extra controls, but mechanically they seem very similar. Can someone please explain why I should or shouldn't consider this as an option? Thanks
Mike
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Very Useful Post
Just as some individuals garner a lot of respect as a result of thoughtful, well-informed postings here, as far as I am concerned Bill Garnett did the opposite just as quickly. Having said that, it is awfully easy to fake someones identity here... so it may not have been Bill who posted the above.
However, the rant is all the more amusing considering that McCoy represents and presumably sells HTP Munchkin units. Granted, radiant systems are the ones that will benefit the most from a modulating, condensing gas boiler but from the little I know as a mere homeowner, condensing gas systems are the way to go unless you're trying to run steam.
On the oil side, the above makes a bit more sense. Condensing oil boilers are not common in residential applications in the US. And, until the sulfur levels in US fuel oil drop, it will most likely remain that way. However, there is a good chance that modulating oil systems are coming our way within a few years - the technology is already available in the EU, now we just have to wait for a courageous US company to license or develop the stuff. Thank Alan Mercurio and his colleagues for their development help!
Coming back to the rant, the reason we apparently use 5% design conditions for heat loss is because they only occur 5% of the time. Those are the days that the efficieny may drop in a hot baseboard system. Otherwise, a continually circulating and modulating system will run much lower water temperatures, even with baseboard, unless it's been horribly undersized.
Never mind older hydronic systems that have huge radiators just dying for a control system that replaces heat loss over the course of the entire day instead of the old "on-off" control strategy. Furthermore, I cannot think of a better way to keep a boiler happy than to modulate it all day instead of subjecting it to far more extreme temperature cycling via cold-starts.0 -
conversions
the reason that a wall hung boiler or water heater might not work in a conversion application is there is not enough thermal mass involved i looked at a situation last fall a wall hung boiler in a house with big massive rads 3in pipes house never gets warm not enough thermal mass at the wall hung boiler
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Mike, I have installed Vitodens in this application
in a few jobs. How did we size the boiler? We look at the gas bills over 3 yrs [if you have natural gas] then look for the month that had the most therms used in thoughs 3 yrs. Some gas companys will give you the read out with alot of information on them. This is how we did 1 of the houses,
the read out had avg/therms/perday in the 29 day reading, we took the highest number in thoughs 3 yrs then multiply that by 100,000 [btu/per/therm]then divide by 24 hrs and that gives you an average load for that time period. Then we looked at the average outdoor temp for that same time period. Then look at the average Delta T from inside temp.[70F] to average out door [in this example it was 7F,= 63F dt] and then the delta T on a design day [70F in, to -20F out,= 90F dT]now you have 3 parts of the equation so now you would cross multiply and divide to get the load for design conditions.
For example in the house we did, it had a 460,000 btu boiler. the average was only 135,000 x 90F divide by 63F = only 192,857 so we put in a Viessmann Vitodens 200 15-60 it is 230,000 input and an AFUE rating of 94%. We also run the system on constant circulation no T-stats any where or TRV,s the reset on the contol is set at .7 that means only about 122F water temp on design!!!! This is showing a 50% fuel savings!!!! Look into Viessmann, you won't regret it!
Ted0 -
Mike the Takagi
is not a boiler!!! ASME boilers have to stand up to more safty tests and other requirements then water heaters because a boiler is in constant use over the heating season and a water heater is intermitant use not ment to be used as a boiler!!!!
Ted0 -
We've had great success with low mass boilers with high mass systems. I have an MZ 25C running a former steam system that holds better than 200 gallons of water, 4" pipes in the basement. If your're makin' heat- it has to go somewhere. Sure, it takes a while to warm up the huge amount of water in the system, but the heat your making doesn't just disappear. In my mind, stay away from anything without the ASME approval. GO fully condensing and laugh all the way to the bank every month. Best of luck, Luke0 -
I think it must have other issues
like incorrect circulator selection or placement, or way undersized boiler. Was it two pipe single pipe?0 -
It's a cheap solution
and probably only last a few years, but hey, you get what you pay for. Also no way to do outdoor reset, unless you go downstairs and start lowering the manual temp setting.
Remember a wall hung may only have 3/4" or 1" at most for supply and return. A cheap non-condensing wall hung might give you 85% if you're lucky. Trying to pump that much water through the unit for very long cycles will probably wear it out in a few years. Maybe buy two! Keep one as a spare.0 -
you've got to be kidding!
> the reason that a wall hung boiler or water
> heater might not work in a conversion application
> is there is not enough thermal mass involved i
> looked at a situation last fall a wall hung
> boiler in a house with big massive rads 3in pipes
> house never gets warm not enough thermal mass at
> the wall hung boiler
I'm sorry, but this makes no sense. If a boiler puts out x BTUs per hour, it puts out x BTUs per hour. Whether it is a low mass boiler makes NO DIFFERENCE to how fast it will heat the entire system. Water is flowing through the boiler, it is not just sitting in it like a tea kettle!
Low thermal mass does mean that the first hot water comes out faster after a cold start. This provides no great advantage for converted gravity systems without DHW, but it is not a disadvantage either (actually it increases the efficiency slightly). If house is not heating up, the boiler BTUs are too low or there is some other problem.
MZ, Baxi, Vitodens, Trinity are all wall-hung boilers, and both the wall-hung and floor model Munchkins are low mass.
It is amazing how much misinformation is dished out, and not just by bgarnett. You're a listed professional?0 -
Let's Play Nice Boys
I believe the point that Bill is trying to drive home is that there are many applications where you are NOT going to get the maximum effeciency that a condensing boiler offers. Any system at 140°F will only put out half of what it would at 180°F. Unless you are operating below that 140°F range all the time, then the boiler may not be in condensing mode, relative to return water temperature. Although it would seem to appear different on this site, the vast majority of boilers installed are not condensing. On that premise, there is nothing wrong with Bill's opinion.
As discussed above, the proper way to determine what you need for a boiler is to do a heat loss of the building the way it is today, compare the connected load and then determine the water temperature needed to satisfy that heat loss on design temperature days. The closer the connected load is to the requirement, the higher the water temperature and vice versa.
A product like the Revolution can handle return water temperatures as low as 55°F without condensing in the heat exchanger due to its variable speed injection-bypass setup and will provide efficiencies as high as 88% at these temperatures. It is also a fraction of the cost of a condensing boiler and carries a limited lifetime warranty on the cast iron section assembly. The Series 2 is also a fine product and as Bill stated, simple. It however will need some sort of protection against cooler return water such as a bypass, boiler loop, primary-secondary or variable speed primary-secondary injection. The Revolution gives you this right out of the box.
Many of us here have grown up in the old school and remember a wave of highly efficient and compact "boilers" that hit the market during the 70's and 80's. The question is......where are they now? This may be the basis for Bill's comments of possibly keeping things simple. Boilers installed in the remote areas served by Bill's company may also suffer the consequences of parts not being available during the coldest times. I think we have all encountered this scenario. So let's be nice here and respect the opinions of everyone based on their own experiences of the past and present. The choice of what you want to install is yours and the choices are many. I like to keep the following things in mind when purchasing any major appliance:
1.) Strength of the manufacturer in the industry
2.) Overall dependability of their products
3.) Support when things don't operate as intended, both in the field and over the phone.
4.) Availability of repair components and ease of service.
5.) Long term overall track record.
6.) Affordability and long term value for investment.
Hope this helps!
Glenn Stanton
Burnham Hydronics0 -
pitch?
> Any system at 140°F will only put out
> half of what it would at 180°F.
Radiator output is pretty close to linear, going to zero at 70F. So at 140F, it puts out (140-70)/(180-70) = nearly two-thirds of what it puts out at 180.
And I wonder if your opinions are in any way influenced by the fact that Burnham doesn't make any condensing boilers? Just asking.
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Not a pitch at all !
Just fact. The chart below spells out very well the BTU per Square Foot outout of radiation at various water temperatures. The output of radiation at 180°F water temperature is nearly double that of radiation at 140°F water temperature. We have been making condensing boilers for commercial applications for years. Take a look at our Thermal Solutions boilers. As far as the residential market goes, we will be releasing products for this application when we are 100% sure that it will last for a good long time, utilize staple controls and that we will have the ability to produce our own heat exchangers in house to ensure the best overall quality control and dependability. Hope this helps.
Glenn Stanton
Manager of Training
Burnham Hydronics0 -
you could
VERY easily and succinctly state your case without personal jabs at someone you do not know. Especially since you post an apparently bogus e-mail address and no name. I'm sure there's something you could get chastised for. If you post enough, someone will find your "heel". Or is that your a heel ?
C'mon, be nice. 0 -
CAST IRON FINISHED ?
> What boiler's does McCoy sales represent?
> Whatever that is- I don't think they are being
> represented well. There are fully condensing
> boilers available- that are extremely reliable,
> and are applied to space heating every day of the
> year. The days of cast iron and a maximum
> efficiency of 83-85% are competely over. With
> the price of fuel oil going up, natural gas and
> LP through the roof, anyone who doesn't offer a
> fully condensing option to their customers is
> just behind the times. Certainly some customers,
> for their own reasons, will not select the most
> efficient product we have to offer, but to not
> offer it is almost a crime. Just my
> $.02.
>
> Luke Lefever
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CAST-IRON
ATTN ALL CONTRACTORS STAY IN THE WEIGHT ROOM, CAST IRON WILL OUT-LIVE US ALL !!!!!!0 -
baseboard
That chart is for baseboard, not radiators. Radiators are close to linear.0 -
Now he's shouting.
And changing the subject.0 -
mike - no matter what you do,
since your system is essentially cast iron, be sure to do a good system cleanout - there are plenty of environmentally safe products out there for this - so whoever does your system = make sure an up front clean and flush is included in the price
this is especially important if you are doing a system with outdoor reset (highly recommended) - that will run your system much cooler on warmer days so you want as little insulating gunk on the inside of your radiation as possible
now, while a weil-mclain cv-gold or a Burnham revolution, are officially the correct fit for your system - a WM ULTRA will cost you least to run even though a vie$$mann vitodens is a better boiler (perhaps the best out there) the real world TOTAL operating cost doesnt hold a candle to the ultra especially in your application the ULTRA is the broadest usable temp range boiler out there hey, weil worked on it for 15 years!!!
However if your vendor installs primary/secondary/injection piping with a tekmar control, then a good old slant-fin vsph is the most bang for the buck and will give you through the wall venting
Ps if you pick a vendor who hasnt heard of heating-help send him to us we wont let him fail you
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Now Really, Mr. Garnett...
I take it that you believe a stainless steel HX is inferior to cast iron as far as longevity is concerned? We better call Viessmann and warn them.
Don't get me wrong, there are ways to make stainless fail (or any metal for that matter). However, I believe your outburst requires a bit more qualification to be true.
Here is a Weil-McLain that failed in year 20 or so of its life. Considering that we no longer live in the middle ages, that's about 3.5 less than an average lifetime today. Click on either picture to be taken to a gallery of the failed steam boiler.
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The chart
is for radiators. It is in terms of square feet of radiation. This chart is used for steam to hot water conversions of radiators. The ratings for baseboard are similar. Hope this helps.
Glenn0
This discussion has been closed.
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