Replacement boiler for forced hot water baseboard heating system

[fritzfield]

My natural gas fired Weil-McLain CGI power vented hydronic heating boiler needs to be replaced. It was installed by builder in 2001. The fire box is cracked/crumbling so replacement is needed before fall starts here in New Hampshire. The other component of our comfort system is a 2008 40 gallon gas fired power vented Bradford-White water heater that I have changed anode rod, dip-tube, gas control valve and works fine.

I had a local plumbing contractor - large fleet of trucks - come to give me estimate of project for boiler. They are telling me that I should go with a condensing combination boiler by Bosch that would replace the broken boiler as well as the still-working domestic hot water heater. It does NOT have a crappy "coil" system but seems to have a Rinnai like water heater built in. The estimator said that the cost would be more than retro-fitting the boiler, but not that much more. I haven't got the $ quote yet. I can afford the really "nice" system, but I am happy with what I have now and I can maintain the equipment myself. It seems that just replacing the boiler would be cost effective if I get another 15 - 20 yrs from new boiler, even though I would not be getting the sacrosanct 95% efficiency that boiler manufacturers strive for.

What do you people think about just retrofitting and be done with the job - just a newer model Weil-McLain boiler. Then, replace the water heater when it finally fails which may be a while as I drain about 5 gallons/week and change out the anode rod yearly myself.

Any insight/suggestions would be appreciated.

 

[Greenman]

I'd do the combination unit if it has a small holding tank built in, 5 gallons or so.

 

[fritzfield]

The quote came in at $16K. 10% off if I pay before job starts.

 

[NetWareHead]

In order for you to get the 95% efficiency out of a condensing boiler, the radiation in the home needs to be adequately paired with the boiler and match its characteristics. You wont get into the condensing zone unless you return cold water (I beleive below 120 degrees). Ive heard many stories of guys being sold condensing boilers and paired with old school slant fin convection type of baseboard radiators (judging by your current boiler, sounds like you have these in your home). If you dont deliver cold water back to a condensing boiler, you will never acheive the efficiency ratings you were sold and have just wasted money. Besides natural gas is pretty cheap so I dont mind saving thousands of dollars up front and straying with an 80%+ efficiency boiler vs spending $16K for a fancy condensing high efficiency boiler that promises 95%. Not saying there is no place for condensing boilers and they are perfect for high thermal inertia applications like in slab radiant floor where the return water will be what the boiler is asking for, I'm not an HVAC guy but know enough through my own research as I had a boiler replaced recently; so take my writings here with a grain of salt and do your own research.

You have a 2008 vintage water heater that will in the next 5-10 years likely need replacing and IMO its prudent that if you are replacing the boiler now, to factor in for domestic hot water replacemnt as well. You can only replace the anode rod so any times on a standard tank before somethign else expensive also goes. What I did was get a non-condensing boiler, also a weil mclain cgi natural gas unit; my radiation in habitable areas is baseboard convection. I had the hvac guy plumb a circulator for this zone and then plumb an extra zone with a circulator for the hot water heater to stay dormant. My standard gas fired water heater was kept in service until its death. When that time came, I replaced that tank with an indirect fired water heater (a Superstor) and used the dormant zone on the boiler for this to heat the tank. Im not a fan at all of the tankless water heater systems, whether separate or built in to the boiler as a combi unit. I'm also in NH and we have hard water which degrades the internals of these heaters. IMO you should should stick with your second idea but consider plumbing in for a future indirect. Mine works very well with my weil-mclain and I have limitless hot water without worrying about what hard water is doing to my system. Ive been very happy with my Superstor and comes with a lifetime warranty.

 

[fritzfield]

NetWareHead - thanks for the info/insight. Sounds like that is what I want to do - get another conventional boiler and rough in a separate zone for an indirect water heater when the current stand alone fails.

 

[fritzfield]

So, I plan to just get a conventional boiler, direct vent, sealed combustion. No outdoor reset. The Burnham ESC-4 was the recommendation. One plumber wants $7500 another $ 9k. The 9k guy also quoted 3k more to add a Burnham SL indirect water tank that would replace a gas Bradford-White water heater that is 10 yrs old. Also, everyone wants to replace the yellow flexible gas line w/ black pipe. Any thoughts about Burnham vs. Weil-McLain vs. Buderus?

 

[NetWareHead]

The 3k more for just the indirect WH sounds about right. How is the warranty on that model? No experience with it personally, but I did mention the superstor earlier and one of its perks is a lifetime warranty. Otherwise most indirects in that price range should be fairly equal.

I dislike that flexible yellow gas piping. Black threaded pipe, while labor intensive and messy to install works much better and is safer than CSST. None of the plumbers and hvac guys I use will install CSST.

The Burnham ESC4 boilers look to be discontinued from the limited googling I did so keep that in mind.

Buderus is a German boiler manufacturer that are built and run very well but my understanding is you pay a premium for the quality. In terms of quality and where money is no objection, its Buderus at the top, WM in the middle and Burnham at the bottom. The question is, how much will you gain? How long are you going to stay at the home? If you will own it for a long time, if you value a high quality piece of equipment that is easy to service and more efficient, go for the better boiler.

 

[fritzfield]

Is the superstor the gold standard in indirect water heating?

 

[NetWareHead]

Is the superstor the gold standard in indirect water heating?

Probably not the best aka gold standard. I might give that nod to the Veissmann ($$$). Think I remember reading they offer a stone lined tank that offers better insulation and great resistance to poor quality incoming water (pH, hard water etc...). With a cleanout so the tank insides and coil can be cleaned or replaced. Its way expensive and so heavy your plumber will hate you for making him haul the thing into your basement.

I think the Superstor is one of the better than average ones. Lifetime warranty. No anode rod needed; entire tank/internals are made from 316L stainless steel, no glass lined tank to rust out like typical WH. Efficient finned cupronickel heat exchanger. And great insulation (2 inches all around), losses of only 1/2 degree per hour of stored hot water. Can be ordered with a secondary input/output for solar/multi-energy applications. With 1 inch boiler connections so with the right circulator and boiler combinations, you can really pump a TON of BTUs through it and have practically unlimited hot water. Ive seen them in plenty of installations and so far I haven't found a pro that doesnt like them.

There are other good indirects. I hear triangle tube makes another good one. Chat up your plumber and see what he supports/recommends. Best indirect is useless if the installer has not sized correctly to customer needs, not taken into account the water supply requirements or is just unfamiliar with the install & maintenance.

 

[paperfist]

Indirect is like heaven if you like hot water showers to last all day

And do t forget OP there’s probably energy rebates to get from your energy provider and they usually pay out more when you buy better equipment.

 

[herm0016]

Netware is correct. i have been doing some research about this as we are looking at getting a 1970s boiler replaced. i have had 2 guys quote me the expensive 95% boilers, and the 3rd guy told me all about the efficiency problems. our house was built in the 60's and does not have enough radiator length to run at a less then 180 degrees output. you need roughly 75% more length of baseboard to run at 135 which is about the top that you can get the 95% efficiency form the high cost boiler.


we plan on replacing the 50 gal tank with a gas tankless when it needs to be replaced. I can put in the tankless for around 1k, much less than an indirect setup.

 

[paperfist]

Netware is correct. i have been doing some research about this as we are looking at getting a 1970s boiler replaced. i have had 2 guys quote me the expensive 95% boilers, and the 3rd guy told me all about the efficiency problems. our house was built in the 60's and does not have enough radiator length to run at a less then 180 degrees output. you need roughly 75% more length of baseboard to run at 135 which is about the top that you can get the 95% efficiency form the high cost boiler.


we plan on replacing the 50 gal tank with a gas tankless when it needs to be replaced. I can put in the tankless for around 1k, much less than an indirect setup.

The indirect is basically using free heat generated by your boiler that’s heating your house. Have you considered those long term savings compared to tankless?

 

[herm0016]

How is it free, esp. if i opt for at 85% boiler due to the above and i can run a 95+ tankless?
you are still using heat that would otherwise go to the rooms to heat the water. plus, in the summer the boiler will be running at 85% heating water while the house is not calling for any heat. or i could run the 95+ tankless and have the pump and such on the boiler totally off. I shut off the pilot light on our current boiler in may and lit it last week. i really dont think there is any energy savings or cost savings even after 20 years.

The indirect is basically using free heat generated by your boiler that’s heating your house. Have you considered those long term savings compared to tankless?

 

[NetWareHead]

The indirect is basically using free heat generated by your boiler that’s heating your house. Have you considered those long term savings compared to tankless?

Its not free heat. The indirect needs its own zone off the boiler and is triggered by temperatures in the indirect tank as read by an aquastat. The boiler fires, the zone valve opens or circulator runs for the heating loop and this way the boiler heats water in the tank for domestic hot water.

How is it free, esp. if i opt for at 85% boiler due to the above and i can run a 95+ tankless?
you are still using heat that would otherwise go to the rooms to heat the water. plus, in the summer the boiler will be running at 85% heating water while the house is not calling for any heat. or i could run the 95+ tankless and have the pump and such on the boiler totally off. I shut off the pilot light on our current boiler in may and lit it last week. i really dont think there is any energy savings or cost savings even after 20 years.

My thought process was opposite of yours and I wanted to keep my boiler running in the summer even if its just to make hot water. Think of a car that sits around for months without starting. During idle times is when many components go bad. And you dont find out your boiler has a problem until that first chilly night when the thermostat makes its first call for heat of the season. Id rather find out we have problems when the service techs are in their off season and can easily schedule me in.

 

[paperfist]

Its not free heat. The indirect needs its own zone off the boiler and is triggered by temperatures in the indirect tank as read by an aquastat. The boiler fires, the zone valve opens or circulator runs for the heating loop and this way the boiler heats water in the tank for domestic hot water.



My thought process was opposite of yours and I wanted to keep my boiler running in the summer even if its just to make hot water. Think of a car that sits around for months without starting. During idle times is when many components go bad. And you dont find out your boiler has a problem until that first chilly night when the thermostat makes its first call for heat of the season. Id rather find out we have problems when the service techs are in their off season and can easily schedule me in.

The boiler is already running to heat the house and as you know boiler temps are high so indirect heats up fast.

 

[NetWareHead]

Netware is correct. i have been doing some research about this as we are looking at getting a 1970s boiler replaced. i have had 2 guys quote me the expensive 95% boilers, and the 3rd guy told me all about the efficiency problems. our house was built in the 60's and does not have enough radiator length to run at a less then 180 degrees output. you need roughly 75% more length of baseboard to run at 135 which is about the top that you can get the 95% efficiency form the high cost boiler.


we plan on replacing the 50 gal tank with a gas tankless when it needs to be replaced. I can put in the tankless for around 1k, much less than an indirect setup.

This is a good graphic to share concerning the bolded text. You get remarkably less BTU ouput from baseboard fin at lower temps so it makes sense to need more linear footage to satisfy the heating demand of the structure. Its such a radical departure, these condensing boilers, from established practice. Conventional boilers deliver hot water at 180+ to the heating loop and are tuned/sized to not allow water below a certain temperature to return to the boiler, at risk of cracking the heat exchanger from thermal shock at worst or the moisture condensation causes premature corrosion shortening system life. Condensing boilers demand low temp return and by condensing the moisture out of the hot exhaust, utilize the latent heat available when the moisture undergoes a phase change from gas to liquid and pass that heat to the heating fluid. AFAIK, you can return high temperature water to a condensing boiler but will forgo the extra efficiency and it may operate at somewhere in the 80s efficiency. This is also why condensing boilers have their exhaust mechanically vented with a fan to atmosphere; the exhaust is so cold at this point that it no longer has the buoyant effect of hot exhaust and wont be able to rise up and out of a chimney on its own. Another reason why these boilers can be vented with simple PVC piping.

 

[NetWareHead]

The boiler is already running to heat the house and as you know boiler temps are high so indirect heats up fast.

Right but its not "free" heat. And the indirect zone is independent of other zones and can trigger a boiler cycle all on its own. In the summer, my boiler fires solely to heat domestic hot water even if the other zones in the house are not calling for heat.

 

[paperfist]

Right but its not "free" heat. And the indirect zone is independent of other zones and can trigger a boiler cycle all on its own. In the summer, my boiler fires solely to heat domestic hot water even if the other zones in the house are not calling for heat.

Ok free isn’t the ideal word, but it’s pretty close. It’s a separate zone, yes, but like I said the boiler is already making heat especially in the winter so you’re utilizing it to heat domestic water without having another heating source.

I have one too and in the spring and summer with it’s 30 gallon tank the boiler fires up for 6,7 minutes to heat the water I need. I don’t think a tankless can compare. Sure gas is cheap but why have 2 points of failure?

 

[herm0016]

Ok free isn’t the ideal word, but it’s pretty close. It’s a separate zone, yes, but like I said the boiler is already making heat especially in the winter so you’re utilizing it to heat domestic water without having another heating source.

I have one too and in the spring and summer with it’s 30 gallon tank the boiler fires up for 6,7 minutes to heat the water I need. I don’t think a tankless can compare. Sure gas is cheap but why have 2 points of failure?

Tankless only runs when you use the water... does not keep it hot all night while you are sleeping. So if you take a 5 min shower it runs for 5 min. If that's all the hot you use all day, it only ran for 5 min.

 

[fritzfield]

Tankless sounds like a great idea! I have a long 1 floor ranch style house with long runs from the water heater. I have a Jacuzzi tub, dishwasher, washing machine, and a 2nd bathroom with shower. Would a tankless keep up with that demand if everything is going at the same time?

 

[herm0016]

Tankless sounds like a great idea! I have a long 1 floor ranch style house with long runs from the water heater. I have a Jacuzzi tub, dishwasher, washing machine, and a 2nd bathroom with shower. Would a tankless keep up with that demand if everything is going at the same time?

Not to derail too much...you have to siza a tankless unit to your lowest incoming water temp and gallon per min demand. You can't put the cheap ones here, as you only get 1 gpm at a 60 degree temp rise. Larger and better units get more like 7 or 8 gpm at a 60 degree rise.

 

[NetWareHead]

Not to derail too much...you have to siza a tankless unit to your lowest incoming water temp and gallon per min demand. You can't put the cheap ones here, as you only get 1 gpm at a 60 degree temp rise. Larger and better units get more like 7 or 8 gpm at a 60 degree rise.

And colder climates where the groundwater is near freezing in the winter will demand greater delta T to reach the hot water set point. Im in NH and in the winter is when I actually want a pretty hot shower, I didn't want to spend all this money on a tankless and it could only make the water warm, not hot.

I investigated a tankless and was kinda shocked at what kind of draw they pull down in terms of natural gas demand. The pretty much heat the water passing through it by lighting off a large volume of gas in the heat exchanger; larger than some boilers! The ones I considered had gas demands of 150-175K btus/hour. Thats a 1 inch gas line right there for the distances involved in my house. Actually, since I have other gas burning appliances, I would have had to upgrade the entire line from the meter to 1.25 inch and then tee off of this main line to my kitchen range, boiler etc... Thats a few thousand right there in just gas supply piping upgrade to run a tankless.

I also wasn't jazzed at the idea of the mineral scale the unit internals would accumulate over time; we have hard water here. The tankless sees the same harsh environment that a direct fired tank gas water heater sees. The solution is to descale it once a year or as needed; a plumber has to come and cycle a vinegar solution through the tankless to dissolve the scale. It was here where I figured out the tankless wasnt for me and went with the indirect.

Link to natural gas piping chart http://www.endot.com/OpenFile.aspx?path=21eb7_0.pdf&Type=1&pid=34

 

[paperfist]

Tankless only runs when you use the water... does not keep it hot all night while you are sleeping. So if you take a 5 min shower it runs for 5 min. If that's all the hot you use all day, it only ran for 5 min.

I’m not going to pretend to know a great amount about tankless, but I imagine to get the temps you need on a consistent basis is going to take a lot more energy than even a boiler.

Cool if you take 5 min showers, but it’s not worth my time to get naked for that .

I’m not trying to dissuade you, but with a boiler indirect is pretty nice. It’s basically unlimited hot water.

 

[herm0016]

I’m not going to pretend to know a great amount about tankless, but I imagine to get the temps you need on a consistent basis is going to take a lot more energy than even a boiler.

Cool if you take 5 min showers, but it’s not worth my time to get naked for that .

I’m not trying to dissuade you, but with a boiler indirect is pretty nice. It’s basically unlimited hot water.

funny thing about physics, it takes 1 BTU to raise a pound of water 1 *F.

a tankless uses a very similar amount of energy to heat the water, it just has to do it much faster and thus takes a lot more energy per time.

it uses the same amount of energy that your tank uses if your tank was perfectly insulated, but we know that your tank is not perfectly insulated, so your tank uses more energy because it keeps the volume of water hot all the time, and not just when you are using the water.

 

[paperfist]

funny thing about physics, it takes 1 BTU to raise a pound of water 1 *F.

a tankless uses a very similar amount of energy to heat the water, it just has to do it much faster and thus takes a lot more energy per time.

it uses the same amount of energy that your tank uses if your tank was perfectly insulated, but we know that your tank is not perfectly insulated, so your tank uses more energy because it keeps the volume of water hot all the time, and not just when you are using the water.

Right, but like I said my boiler is already heating my water to keep my house warm so I’m not using 2 systems to accomplish the same thing as you are.

My Buderus is pretty close to perfectly insulated. 1” thick foam 360 degrees around the tank. Even the penetrations are insulated.