Conventional Boiler VS. Combi Hi Efficiency boiler

crispa1

Hello, and good morning everyone, I need advice on what system I should go with as my 33 yr old Weil Mclain gas powered boiler/water is not as efficient anymore. The problem I have with my set up is that my 85 yr old chimney has never had a liner installed, and my flue vent on my separate hot water goes out the wall, and elbows back in the side of the chimney outside. The 4 hvac companies all pointed that once the twp inspector notices that, Id' definitely be questioned about it. It was already like that when we bought the house back in 2001, and was never red flagged by our home inspector. SO, my 2 options are to install with a weil mclain cg4 A conventional boiler, put a liner on the chimney, and replumb the gas flue vents of the boiler, and the 1 yr old hot water40gal/40k btu tank into a Y that will go into the side of the chimney/inside of course to pass inspection. The 2nd option is to install with a Lochinvar noble 150k combi boiler, thus eliminating the problem with the weird gas vent of the hot water tank. I can just sell the like new hit water tank locally on fb marketplace/clist. My other concern is the cost of maintenance of the Lochinvar combi should I decide to go with it, as our old trusty boiler never really was maintaned all that often, except for the occasional burner cleanup. Our house is only 1 zone, and about 2100 sq ft with only the 1st and 2nd floors heated with cast iron radiators. THX for any inputs shared. The current boiler/110k/66 pct afue is working as it should, just thinking of getting it replaced before it **** the bed. Stay everyone.

crispa1

crispa1

As you can see the flue vent of the hot water tank is going out to the outside wall, and elbows back into the side of the chimney.

PC7060

How many radiators?  How well insulated in the house?

GroundUp

I wouldn't even think about a combi, personally, but that's just me. Maybe something like an 80k or 110k Noble heat-only with an indirect water heater? Better efficiency, more hot water, and less maintenance

EBEBRATT-Ed

The discussion about cast iron versus mod con goes on here all the time. Neither one is right or wrong. CI is cheaper, lasts longer parts cheaper less maintenance. Mod con more efficient in most cases parts and maintenance cost more and probably have a life of maybe 15 years

crispa1

In response to pc7060, the house has 8 radiators and is moderately insulated. Aluminum siding. thx

JakeCK

I just want to point out that further insulating and air sealing your house prior to a boiler upgrade and then right sizing the new ci boiler would probably net you both a lower gas bill, and lower overall installed and maintenance costs over the life of the boiler. Going with a mod-con you have to be aware of the law of diminishing returns. Sure you can insulate and air seal and get a nice efficient mod-con that might save you an additional 15% on your gas bill over the ci. But if by insulating and airsealing and then sizing a new boiler to that already lowers your average winter gas bill to say under 100, thats only 15 dollars saving for maybe 6 months every year. 

How much does the annual maintenance cost for a mod-con?

If you want to reduce your costs that additional 15%, there are other cheaper, longer lasting means to do so.

How old is that gas hot water tank?(some how missed that it is only a year old) 

Does everyone in the house take showers?

JakeCK

Actually, what makes you believe your current boiler is less efficient now than when it was new? My 35 year old WM is still ~80% efficient today. 

Even with your hot water tank being new you'll probably be better off improving the building envelope and installing a reverse indirect tank in combination with ci boiler. Or a hybrid heat pump water heater. 

Is your boiler really only 66% efficient? How old is it? 

PC7060

crispa1 said:

In response to pc7060, the house has 8 radiators and is moderately insulated. Aluminum siding. thx

What’s the age of the home?  Is there a rad in every room? Large or small?

As @JakeCK said, modcon require higher levels of maintenance versus CI so they are really only cost effective if you can configure your system to operate at low temperatures to maximize the time the boiler is operating in condensing mode. 

Many house built in the 1920s after the 1919 flu pandemic were equipped with large radiators in all room.  Combining those large rads with addition of insulation and you can get a home that can be heated with water temps varying from 90-120F which is perfect for a ModCon. 

But if low temp operations can not be reasonably achieved, a CI boiler will provide long years of service at similar levels of efficiency as a ModCon with potentially lower installation and maintenance cost.    

Of course, you will need to make sure the boiler piping is set up properly to ensure the return water is greater than 140F because condensing flue gas is not a friend of CI boilers. 

crispa1

JakeCK said:

I just want to point out that further insulating and air sealing your house prior to a boiler upgrade and then right sizing the new ci boiler would probably net you both a lower gas bill, and lower overall installed and maintenance costs over the life of the boiler. Going with a mod-con you have to be aware of the law of diminishing returns. Sure you can insulate and air seal and get a nice efficient mod-con that might save you an additional 15% on your gas bill over the ci. But if by insulating and airsealing and then sizing a new boiler to that already lowers your average winter gas bill to say under 100, thats only 15 dollars saving for maybe 6 months every year. 

How much does the annual maintenance cost for a mod-con?

If you want to reduce your costs that additional 15%, there are other cheaper, longer lasting means to do so.

How old is that gas hot water tank?(some how missed that it is only a year old) 

Does everyone in the house take showers?

Hello, and thx for replying. The hot water tank is barely a year old, and 3 adults take showers at different times of the day. My main concern really is the cost of maintenance of a combi boiler vs a conventional one, as I had stated that with my current Weil mclain, 32 yr old unit, it fires up every year since we moved in 2001. Only maintenance done was the occasional burner cleanup.

crispa1

JakeCK said:

Actually, what makes you believe your current boiler is less efficient now than when it was new? My 35 year old WM is still ~80% efficient today. 

Even with your hot water tank being new you'll probably be better off improving the building envelope and installing a reverse indirect tank in combination with ci boiler. Or a hybrid heat pump water heater. 

Is your boiler really only 66% efficient? How old is it? 

Hi, and thx for replying. The afue rating is stamped inside the boiler unit at 66 pct/105k btu in.

hot_rod

I would say a 33 year old boiler has server the home well. It's maybe oversized? Certainly will be with structure upgrades.
A chimney thru the roof sucks heat energy from the appliances connected when they are not fired, both the water heater and boiler. If the boiler doesn't have an operating vent damper, could be a considerable amount of your heating dollars going up, where Santa comes down


A new cast boiler, indirect and chimney reline may cost more than a mod con or combi?

With a good quality mod con or combi you get a lot more control parameters to size it to the homes ever-changing load, so cycling drops considerably compared to a cast that is only correctly sized a small period of the heating season. If at all.

I've lived 15 years with an early combi with no issues, had two others also. Maintain them like you would a new vehicle or any other mechanical device and 15 years is a reasonable life expectancy.

With a combi, be sure the DHW production is adequate for your lifestyle.

crispa1

PC7060 said:

crispa1 said:

In response to pc7060, the house has 8 radiators and is moderately insulated. Aluminum siding. thx

What’s the age of the home?  Is there a rad in every room? Large or small?

As @JakeCK said, modcon require higher levels of maintenance versus CI so they are really only cost effective if you can configure your system to operate at low temperatures to maximize the time the boiler is operating in condensing mode. 

Many house built in the 1920s after the 1919 flu pandemic were equipped with large radiators in all room.  Combining those large rads with addition of insulation and you can get a home that can be heated with water temps varying from 90-120F which is perfect for a ModCon. 

But if low temp operations can not be reasonably achieved, a CI boiler will provide long years of service at similar levels of efficiency as a ModCon with potentially lower installation and maintenance cost.    

Of course, you will need to make sure the boiler piping is set up properly to ensure the return water is greater than 140F because condensing flue gas is not a friend of CI boilers. 

The house is 85 yrs old/built in 1936. Yes, every room has a radiator. All windows are made of vinyl.

JakeCK

crispa1 said:

Actually, what makes you believe your current boiler is less efficient now than when it was new? My 35 year old WM is still ~80% efficient today. 

Even with your hot water tank being new you'll probably be better off improving the building envelope and installing a reverse indirect tank in combination with ci boiler. Or a hybrid heat pump water heater. 

Is your boiler really only 66% efficient? How old is it? 

Hi, and thx for replying. The afue rating is stamped inside the boiler unit at 66 pct/105k btu in.

wow... at 66% 105k btu/h input thats a little over 69k btu output. It actually sounds like it was sized with in reason for the size and age of the house.

is that the ibr or doe rating?

What model boiler is it? Any pictures of the boiler its self? Maybe some pictures showing the entire area around it? 

crispa1

hot_rod said:

I would say a 33 year old boiler has server the home well. It's maybe oversized? Certainly will be with structure upgrades.
A chimney thru the roof sucks heat energy from the appliances connected when they are not fired, both the water heater and boiler. If the boiler doesn't have an operating vent damper, could be a considerable amount of your heating dollars going up, where Santa comes down


A new cast boiler, indirect and chimney reline may cost more than a mod con or combi?

With a good quality mod con or combi you get a lot more control parameters to size it to the homes ever-changing load, so cycling drops considerably compared to a cast that is only correctly sized a small period of the heating season. If at all.

I've lived 15 years with an early combi with no issues, had two others also. Maintain them like you would a new vehicle or any other mechanical device and 15 years is a reasonable life expectancy.

With a combi, be sure the DHW production is adequate for your lifestyle.

Hello, and thx for replying. So, how often do you get your combi serviced then, and how much is the cost? Does it include cleaning the main burner? I say this bcoz I saw a YT video from a Lochinvar rep explaining the service procedure on a noble model.

hot_rod

crispa1 said:

hot_rod said:

I would say a 33 year old boiler has server the home well. It's maybe oversized? Certainly will be with structure upgrades.
A chimney thru the roof sucks heat energy from the appliances connected when they are not fired, both the water heater and boiler. If the boiler doesn't have an operating vent damper, could be a considerable amount of your heating dollars going up, where Santa comes down


A new cast boiler, indirect and chimney reline may cost more than a mod con or combi?

With a good quality mod con or combi you get a lot more control parameters to size it to the homes ever-changing load, so cycling drops considerably compared to a cast that is only correctly sized a small period of the heating season. If at all.

I've lived 15 years with an early combi with no issues, had two others also. Maintain them like you would a new vehicle or any other mechanical device and 15 years is a reasonable life expectancy.

With a combi, be sure the DHW production is adequate for your lifestyle.

Hello, and thx for replying. So, how often do you get your combi serviced then, and how much is the cost? Does it include cleaning the main burner? I say this bcoz I saw a YT video from a Lochinvar rep explaining the service procedure on a noble model.

Yes I do my own service. I'm embarrassed to say that 15 year old combi was only serviced twice over the time I owned it. It was very clean both times and analysis was within the required range. The years just slipped away. In my experience the biggest factor is the air they breathe. If they recycle flue gas or inhale dust and pollen, cleaning will be more of an issue.

if you are a technical person, and want to spring for a combustion analyzer, as you can see, the cleaning is more time consuming than complicated.

crispa1

JakeCK said:

crispa1 said:

Actually, what makes you believe your current boiler is less efficient now than when it was new? My 35 year old WM is still ~80% efficient today. 

Even with your hot water tank being new you'll probably be better off improving the building envelope and installing a reverse indirect tank in combination with ci boiler. Or a hybrid heat pump water heater. 

Is your boiler really only 66% efficient? How old is it? 

Hi, and thx for replying. The afue rating is stamped inside the boiler unit at 66 pct/105k btu in.

wow... at 66% 105k btu/h input thats a little over 69k btu output. It actually sounds like it was sized with in reason for the size and age of the house.

is that the ibr or doe rating?

What model boiler is it? Any pictures of the boiler its self? Maybe some pictures showing the entire area around it? 

My fault about the afue rating. Upon closer inspection, the numbers states that it's at 86 pct DOE

crispa1

hot_rod said:

crispa1 said:

hot_rod said:

I would say a 33 year old boiler has server the home well. It's maybe oversized? Certainly will be with structure upgrades.
A chimney thru the roof sucks heat energy from the appliances connected when they are not fired, both the water heater and boiler. If the boiler doesn't have an operating vent damper, could be a considerable amount of your heating dollars going up, where Santa comes down


A new cast boiler, indirect and chimney reline may cost more than a mod con or combi?

With a good quality mod con or combi you get a lot more control parameters to size it to the homes ever-changing load, so cycling drops considerably compared to a cast that is only correctly sized a small period of the heating season. If at all.

I've lived 15 years with an early combi with no issues, had two others also. Maintain them like you would a new vehicle or any other mechanical device and 15 years is a reasonable life expectancy.

With a combi, be sure the DHW production is adequate for your lifestyle.

Hello, and thx for replying. So, how often do you get your combi serviced then, and how much is the cost? Does it include cleaning the main burner? I say this bcoz I saw a YT video from a Lochinvar rep explaining the service procedure on a noble model.

Yes I do my own service. I'm embarrassed to say that 15 year old combi was only serviced twice over the time I owned it. It was very clean both times and analysis was within the required range. The years just slipped away. In my experience the biggest factor is the air they breathe. If they recycle flue gas or inhale dust and pollen, cleaning will be more of an issue.

if you are a technical person, and want to spring for a combustion analyzer, as you can see, the cleaning is more time consuming than complicated.

I am a retired Honda mechanic, but have no experience in doing maintenance on these type of boilers. Just trying to justify the cost of its maintenance service vs a conventional boiler. Thx

JakeCK

Yea that isn't a 66% efficient boiler. Its doe rating is over 80%. IBR rating is 15% less and is if it is outside of the structures envelope and all heat coming from the boiler jacket and near plumbing is lost to space. Doe assumes it is with the envelope. Being in a unheated basement kind of puts it in a middle ground between those two. Some heat is lost through the foundation to space but more of it than not makes it upstairs.

JakeCK

I will say Hot_rod is a bonafide expert so listen to him. I'm just a nerdy homeowner. 

@hot_rod you really think a combi mod-con would be more cost effective? 

Doesn't a buffer tank paired with a ecm circulator and operated on outdoor reset allow one to modulate a ci boiler very effectively? I would think running a boiler for maybe one continuous burst to heat the buffer tank would eliminate almost all standby losses when compared to a modcon. and once annual costs to maintain are taken into account...

I guess it one would have to run the numbers and see what way it leans. 

I'd see what the supply temps needed are and maybe an air source heat pump with aux boiler would be effective? 

Steamhead

Keep it simple. Stay with a cast-iron boiler and line the chimney. This compares favorably to all the added moving parts in a mod-con- ALL of which will require servicing at some point.

A stainless-steel chimney liner (at least the ones I've seen) goes in in one piece, so no joints to leak, and will outlast all of us. A cast-iron boiler will last for decades. Mod-cons- not so much.

hot_rod

pretty pretty much all boilers have microprocessor controls and ignition systems if some sort. Mod cons have a inducer fan that differs from a conventional boiler

If you go with a combi it will have a 3 way zone valve or additional pump. A mod con with indirect is fine, more $$

Would  you buy a carbureted Honda, or recommend one if they were available?

JakeCK

hot_rod said:

Would  you buy a carbureted Honda, or recommend one if they were available?

Hey now, there is nothing wrong with a carburetor. They can be just as efficient as electronic fuel injection. You just have to make sure you have it tuned right for the temperature, humidity, elevation, etc, etc.... and make sure to drive at a constant speed of about 40-50mph. That last part is true for just about any vehicle though.

crispa1

Thx all for all the inputs shared so far. I do appreciate it. As I am getting more educated about this, with my current setup of 8 old school cast iron radiators, and a CI boiler, I think that I am leaning towards the conventional install as long as I can get a guarantee from the installer that the Y venting of the hot water tank, and the new CI boiler will pass twp. inspection. Any more ideas shared will be greatly appreciated. Stay safe everyone.

crispa1

Happy Thxgiving everyone. Well, the installer's technician stopped by yesterday, and took a closer look at the chimney. He took pics from the elbow vent of the hot water tank from the outside wall of the chimney, and showed it to me. He explained that the reason why the gas flue of the hot water tank is routed outside that goes back in the chimney is bcoz, the bottom of the chimney is too tight to share it with the boiler's vent, if that makes sense. SO, he suggested that if I still want the conventional boiler option, I would have to get a power vented hot water tank which is going to cost another 1400 dollars. My hot water tank is barely a year old. Then, later on, I googled options of retrofitting my atmospheric hot water tank with a power vent motor assy.. Found out that Rheem makes one. JUst not sure that it can be safely modded to my non power vented tank. It's almost impossible to get through Rheem's tech support or email. SO, with all this findings, am I better off with just choosing the LOchinvar Combi boiler, and just deal with the maintenace cost? Thx all for any inputs shared. Good thing that the tech took a closer look at the Y venting proposal that his sales consultant suggested to me. Today was supposed to be the day of the install. Everything is on hold contingent to my final decision.

crispa1

Granted that both the sales consultant, and technician gave me heads up that they were not trying to sell me a 1400 power vent, bcoz, the tech insisted that he takes out boiler and hot water tank connections to the chimney to investigate it more. And as I had said earlier, the pics don't lie, drilling a vent hole on the side of the chimney right next to the hot water tank, pls see pics above, was not going to work with a new liner installed.

hot_rod

I have run cast radiators down to 120F, which put you in high efficiency condensing range, with a combi mod con.
It makes for a nice comfortable heating systems if you can keep the radiators warm all the time and modulate the supply temperature with indoor and outdoor reset. It's possible you could modulate those radiators from 90° up to whatever SWT is required on a design day. Maybe even run in condensing mode on a design day if you have enough radiator surface.
Throw some radiant floors in the kitchen

JakeCK

crispa1 said:

Happy Thxgiving everyone. Well, the installer's technician stopped by yesterday, and took a closer look at the chimney. He took pics from the elbow vent of the hot water tank from the outside wall of the chimney, and showed it to me. He explained that the reason why the gas flue of the hot water tank is routed outside that goes back in the chimney is bcoz, the bottom of the chimney is too tight to share it with the boiler's vent, if that makes sense. SO, he suggested that if I still want the conventional boiler option, I would have to get a power vented hot water tank which is going to cost another 1400 dollars. My hot water tank is barely a year old. Then, later on, I googled options of retrofitting my atmospheric hot water tank with a power vent motor assy.. Found out that Rheem makes one. JUst not sure that it can be safely modded to my non power vented tank. It's almost impossible to get through Rheem's tech support or email. SO, with all this findings, am I better off with just choosing the LOchinvar Combi boiler, and just deal with the maintenace cost? Thx all for any inputs shared. Good thing that the tech took a closer look at the Y venting proposal that his sales consultant suggested to me. Today was supposed to be the day of the install. Everything is on hold contingent to my final decision.

If you're going to spend that much to replace a new hot water heater just have them install an indirect or heat pump water heater and side step the venting issue altogether. And then sell the current tank on fb market place or something. I'm sure someone would pay a couple bucks for an almost new tank.

jinbtown

People saying "Oh, you save maybe 15% with a modcon" have got to be smoking some good stuff!

OP, I was in your position with a Peerless boiler that was IBR/DOE rated around what yours is. We switched to a Noble combi unit (hot water disconnected since we have an 80 gallon heat pump water heater). We are currently using 50% less propane in our 2500 sq ft two level home in zone 6, north-central NH. I'll lose a super minor amount of efficiency as my ODR curve climbs into higher water temps as temps drop, but for two months now I've used $300 less in propane and I expect I'll save about $2000 over the course of the heating season. We're switching to geothermal eventually and when we do the Noble will go on heated driveway duty.

By the way, I tore the Noble down to single parts, to where I had the bare heat exchanger out, and it is excellently made, super robust, the fire tube takes almost no maintenance. Even the Lochinvar training for HVAC guys is available on youtube and cleaning is literally open the top of the heat exchanger, vacuum it out, spray it down with vinegar and run a scrubby pad around it and rinse it out with water. That's it. I can do that in 45 minutes. The old Peerless boilers we had in the basement ALSO required yearly maintenance to the burner tubes, replacing circulator seals, replacing dripping ball valves. Comfort levels were LOW with 180 degree water blasting through our baseboard. Now we have 18+ hours per day run times at 10-15% fire rate with water temps around 110 degrees most days and 120 degrees most nights. The thermostat essentially acts as a high limit switch, the only time the boiler shuts down is when we have our nightly setback. We switched to this Noble and also deleted an entire chimney from basement to roof, reducing our roof penetrations, one less place to leak in our extremely cold and wet climate. We literally could not be happier with the switch. Converted the Noble to propane for $55. We also replaced dual propane atmospheric vent water heaters that were $560 EACH with a single Bradford White Aerotherm 80 gallon that uses $160 a year in electricity. JUST DO IT.

crispa1

jinbtown said:

People saying "Oh, you save maybe 15% with a modcon" have got to be smoking some good stuff!

OP, I was in your position with a Peerless boiler that was IBR/DOE rated around what yours is. We switched to a Noble combi unit (hot water disconnected since we have an 80 gallon heat pump water heater). We are currently using 50% less propane in our 2500 sq ft two level home in zone 6, north-central NH. I'll lose a super minor amount of efficiency as my ODR curve climbs into higher water temps as temps drop, but for two months now I've used $300 less in propane and I expect I'll save about $2000 over the course of the heating season. We're switching to geothermal eventually and when we do the Noble will go on heated driveway duty.

By the way, I tore the Noble down to single parts, to where I had the bare heat exchanger out, and it is excellently made, super robust, the fire tube takes almost no maintenance. Even the Lochinvar training for HVAC guys is available on youtube and cleaning is literally open the top of the heat exchanger, vacuum it out, spray it down with vinegar and run a scrubby pad around it and rinse it out with water. That's it. I can do that in 45 minutes. The old Peerless boilers we had in the basement ALSO required yearly maintenance to the burner tubes, replacing circulator seals, replacing dripping ball valves. Comfort levels were LOW with 180 degree water blasting through our baseboard. Now we have 18+ hours per day run times at 10-15% fire rate with water temps around 110 degrees most days and 120 degrees most nights. The thermostat essentially acts as a high limit switch, the only time the boiler shuts down is when we have our nightly setback. We switched to this Noble and also deleted an entire chimney from basement to roof, reducing our roof penetrations, one less place to leak in our extremely cold and wet climate. We literally could not be happier with the switch. Converted the Noble to propane for $55. We also replaced dual propane atmospheric vent water heaters that were $560 EACH with a single Bradford White Aerotherm 80 gallon that uses $160 a year in electricity. JUST DO IT.

Thx so much for your detailed opinion. This is a vote of confidence for me. I'll just sell my barely 1 yr old hot water tank on FB marketplace. I'm sure someone will snag it up for 50 pct off what I paid for.

EBEBRATT-Ed

There is no right or wrong between cast iron and mod con. They both have pros & cons. Homeowners need to educate themselves as far as maintenance costs, longevity, rebates, installed cost & the real efficiency

flat_twin

Five years ago I had the same decision to make. Chimney needed a liner, the old fuel oil boiler was toast and natural gas had just become available. We have 10 cast iron rads, big pipes, 1740 sq ft home. I went with a mod con boiler/ 40 gal indirect water heater (didn't want a combi) and spent the first couple heating seasons dialing it in. The cast iron rads do just fine with low supply water temps. Other than making domestic hot water the boiler is always in the condensing range. Supply water temps range from 88 to 142 degrees to cover outdoor temps down to -20. You can add up the EDR of your radiators, calculate their max output and see how that compares to your heat loss. In our case our rads are capable of 102k btu @ 180 degree SWT but our heat loss is only 64k btu per the Slant Fin heat los app. A fuel usage calculator put our heat loss even lower at 58k btu. Either way it's a perfect match for a mod con boiler.

crispa1

EBEBRATT-Ed said:

There is no right or wrong between cast iron and mod con. They both have pros & cons. Homeowners need to educate themselves as far as maintenance costs, longevity, rebates, installed cost & the real efficiency

As with my situation, if I go with a conventional boiler and a power vented hot water tank, it will only be a difference of $230 dollars on the total bill. I'll just have to educate myself on maintaining, and programming the Combi boiler. It'll be fun. Thx for your input.

Jamie Hall

Efficiency claims and fuel savings. Well... what is usually left out is the "all else being equal" part of the analysis. First, there is no question that if you can run a condensing boiler consistently in the condensing range, you will save fuel: if you are well into the range, you can recover about an additional 10% of the heating potential of the fuel.

It is entirely valid to say that a non-condensing boiler, properly tuned, will have a peak thermal efficiency of around 85%. A condensing boiler, properly tuned and operating in the condensing range, will have a peak thermal efficiency of around 96%.

The physics and thermodynamics of combustion set those limits, not advertising.

Now, however, it is quite possible to lower those efficiencies. If I wanted to be really nasty to the systems I maintain, I could probably lower the thermal efficiency of my boilers to around 45% to 50% without there being a visible change in operation -- all I'd have to do is misadjust the air/fuel ratio.

And this is where the all else equal comes in when someone says they saved 50% of their fuel by changing from brand Y to brand X. How well maintained and adjusted was brand Y? What were the actual instrument calibration test numbers for brand Y? Usually, crickets...

This is not to say that one can't indeed save a good deal of fuel by switching boilers from an old, inefficient model to a newer, more efficient one. One can. Again, to give examples from two of the systems I maintain, in one a switch from an old (1948) hot air furnace to a mod/con hydroair system (2019) is saving close to 40% on fuel -- to nobodiy's surprise. In another, swtiching from an old (1930) steam boiler to a modern (2015) steam boiler has saved roughly 50% in fuel.

Robert_25

crispa1 said:

EBEBRATT-Ed said:

There is no right or wrong between cast iron and mod con. They both have pros & cons. Homeowners need to educate themselves as far as maintenance costs, longevity, rebates, installed cost & the real efficiency

As with my situation, if I go with a conventional boiler and a power vented hot water tank, it will only be a difference of $230 dollars on the total bill. I'll just have to educate myself on maintaining, and programming the Combi boiler. It'll be fun. Thx for your input.

Combi boilers & tankless water heaters do not tolerate hard water well. If you have over 12 grains per gallon of hardness in your water you will likely need a softener.

As for conventional cast iron vs. modcon, there is at least one option in-between: https://www.weil-mclain.com/sites/default/files/field-file/GV90+ Brochure - Gray Boiler 0521.pdf

Robert_25

jinbtown said:

People saying "Oh, you save maybe 15% with a modcon" have got to be smoking some good stuff!

The old Peerless boilers we had in the basement ALSO required yearly maintenance to the burner tubes, replacing circulator seals, replacing dripping ball valves. Comfort levels were LOW with 180 degree water blasting through our baseboard. Now we have 18+ hours per day run times at 10-15% fire rate with water temps around 110 degrees most days and 120 degrees most nights. The thermostat essentially acts as a high limit switch, the only time the boiler shuts down is when we have our nightly setback. We switched to this Noble and also deleted an entire chimney from basement to roof, reducing our roof penetrations, one less place to leak in our extremely cold and wet climate. We literally could not be happier with the switch. Converted the Noble to propane for $55. We also replaced dual propane atmospheric vent water heaters that were $560 EACH with a single Bradford White Aerotherm 80 gallon that uses $160 a year in electricity. JUST DO IT.

Your situation is a great example of what can happen when a bunch of other issues are corrected along with a boiler replacement. To Jamie's point above, nothing else in your system was left as it was before when you switched to the high efficiency boiler. Just switching to the heat pump water heater probably knocked your gas bill down considerably. I am not arguing that high efficiency boilers use less fuel, just commenting on it is really tough to say how much they save because it is a rare situation where someone replaces a conventional cast iron boiler that was properly sized & maintained without making other changes to the system.

Hot_water_fan

In addition to the savings from condensing, the lower water temperatures help decrease idle losses, which can be very significant. Modulating helps with that too - increase run time and you'll decrease idle time. The efficiency differences between any boiler at steady-state on and the same boiler cycling are usually huge. There are other ways to limit idle losses, but the ODR and modulation enhances this.

crispa1

Robert_25 said:

crispa1 said:

EBEBRATT-Ed said:

There is no right or wrong between cast iron and mod con. They both have pros & cons. Homeowners need to educate themselves as far as maintenance costs, longevity, rebates, installed cost & the real efficiency

As with my situation, if I go with a conventional boiler and a power vented hot water tank, it will only be a difference of $230 dollars on the total bill. I'll just have to educate myself on maintaining, and programming the Combi boiler. It'll be fun. Thx for your input.

Combi boilers & tankless water heaters do not tolerate hard water well. If you have over 12 grains per gallon of hardness in your water you will likely need a softener.

As for conventional cast iron vs. modcon, there is at least one option in-between: https://www.weil-mclain.com/sites/default/files/field-file/GV90+ Brochure - Gray Boiler 0521.pdf

Would descaling it yearly help out at all? thx

hot_rod

De-scaling is fairly simple with one of the many kits available. as long as service valves are included, it's basically a few garden hose connections to hook up and pump the descaler thru.

You will start to see tankless and combi manufacturers offering or including phosphate dose products to also help with scaling. the phosphate locks up the scaling minerals to help prevent scaling. possibly a better option to a softener.

crispa1

hot_rod said:

De-scaling is fairly simple with one of the many kits available. as long as service valves are included, it's basically a few garden hose connections to hook up and pump the descaler thru.

You will start to see tankless and combi manufacturers offering or including phosphate dose products to also help with scaling. the phosphate locks up the scaling minerals to help prevent scaling. possibly a better option to a softener.

Thx, I will ask my hvac contractor as to how much extra this is. I know that part of the service valves are included in the install as I had mentioned it, and he said that they will install it.