Replacing old cast iron boiler with - Bosch SSB, Navien, Lochinvar?

LeonardB

Ripped out the old Weil Mclain 210K cast iron boiler and old radiators in my house and wanting to replace it with one of these listed above. I'm in the Hudson Valley and the house is circa 1900, 2 floors, 3 bedrooms. No insulation at all just lathe and plaster. Coldest it gets here is about -9ºF but that only lasts a few days, average is about 10ºF at night

It's 2400 sq ft. and had 12 old school large cast iron radiators in it (7 downstairs, 5 upstairs). Coming from the boiler was 3" cast iron pipe splitting off to 1.5" cast iron going into the radiators.

Attached is the heat loss calc that I did (per floor). I'm leaning towards the bosch ssb 120K boiler and am planning to install hudson reed traditional cast iron radiators with it. Would very much appreciate any input and any opinions at all! Thanks

Tinman

Those large, most likely oversized, cast iron radiators would have been a great match with a mod con in a high temp application.

LeonardB

Steve Minnich said:

Those large, most likely oversized, cast iron radiators would have been a great match with a mod con in a high temp application.

Problem was that there was a lot of water in the system. Had 3" cast iron pipes splitting off to 2" cast iron feeding the radiators.

Zman

Be sure to size the new radiator for low water temps for maximum efficiency.
5-1 turndown is good. The Lochinvar will go to 10-1

pecmsg

As posted on H-Talk
First you need an accurate Manual "J" calculation.


The high gas usage is due to:
1) No insulation
2) High infiltration of outside air (Windows & Doors)
3) Oversized Boiler

Reducing the size of the boiler will lower the high gas usage but only so much. The return on your investment is minimal.

Tightening the envelope has a much larger return on investment.

Sounds like original radiators, I wouldn't replace them.

Ironman

This discussion is also going on over at HVAC-talk.com.

To put it in context, here's my last reply:

[QUOTE=Leonard Bayard;25713515]
Quote Originally Posted by bobboan View Post
Large radiators didn't cause you to use more gas. /QUOTE]

-You're saying that it takes the same amount of gas to heat a high water volume vs a low water volume?-


My reply:
"Think for a minute: where's the heat going? It's going into the radiators which in turn heat the house.

High mass in a system is a good thing as it prevents short cycling, allows lower water temps, and delivers a more even heat.

We do these kind of systems regularly; in fact, they're our bread and butter. We've got 3 old Victorians that were doing right now and all of them are keeping or adding CI rad's with a mod/con boiler (s). You can find posts and pics of them over on HeatingHelp.com.

I'm sorry to have to say this but, You made a big mistake removing those rad's."
Bob Boan


​

LeonardB

I may not be a pro at this but you're not making any sense at all

pecmsg

In a perfect "System" the boiler supplies hot water to the emitters, in this case radiators, at the same rate the house looses that heat.
The boiler, emitters and delivery system of that system MUST all be sized properly of the be issues.

Hot and cold areas, short cycling of the boiler, wasted fuel......

STEVEusaPA

LeonardB said:

I may not be a pro at this but you're not making any sense at all

Then have a pro come over and design it.

I know you're not getting the answer you want, but you are getting the correct answers.
--or--
Don't listen to the experts and you may have to come on here and ask the same people how to fix what you installed that doesn't work as you hoped..

HVACNUT

High mass emmiters, ODR, and large water content= low return temps so the flue gasses condense and increase efficiency and even comfort. If your new piping and emmiters cant get rid of the BTU's along the circuit then it defeating the purpose of a mod con boiler.
As @pecmsg mentioned, the real savings comes with tightening up the house. Windows, doors, insulation.
Makes perfect sense.

LeonardB

STEVEusaPA said:

LeonardB said:

I may not be a pro at this but you're not making any sense at all

Then have a pro come over and design it.

I know you're not getting the answer you want, but you are getting the correct answers.
--or--
Don't listen to the experts and you may have to come on here and ask the same people how to fix what you installed that doesn't work as you hoped..

Well, if you would of read my op, you would of realized I wasn't asking design advice, just opinion on the different boilers

Ironman

LeonardB said:

I may not be a pro at this but you're not making any sense at all

I am a pro and I'm trying to help. Please explain how what I'm saying makes no sense and maybe I can clarify.

To me, you're not making any sense: you've come to two pro sites asking for advice and when it's given, you disagree because you've already made up your mind about how things are. That's not logical or reasonable.

I'm not trying to be mean; I am trying to help you, but if your mind is closed, there's nothing I can do.

I can assure that what I'm saying makes perfect sense to any of the experienced pro's on here because they see the total picture.

pecmsg

The contractor that does all the math calculations for proper design is 100 times more important then the name on the equipment!

STEVEusaPA

I read your OP, and responded on both sites.
Proper heat loss, proper design dictates equipment size (and in certain cases type), piping size/layout and emitters, not the other way around.

LeonardB

STEVEusaPA said:

I read your OP, and responded on both sites.
Proper heat loss, proper design dictates equipment size (and in certain cases type), piping size/layout and emitters, not the other way around.

See? You didn't. I posted my heat loss calc and simply mentioned what size boiler I was looking at.

You could of just said "With that setup, that style of house I've had good luck with this brand". But no, you had to go all keyboard warrior about "proper design" with having even seen the house.

Zman

Your oversized pipes and radiator from the old gravity system were adding mass to the system which would have helped with short cycling.
Granted it takes more energy to warm up the pipes and radiators but you are not actually losing the energy (where would it go?) just slowing the process a bit.
With the new setup, your system will react more quickly and everything will take up less space. I would recommend going with a boiler sized to your new heatloss (after insulation and windows) and find one with a 10-1 turndown.

Brewbeer

Hi LeonardB, you are getting some top notch advice here today, the kind that is worth $100/hr, and you are getting it for free.

Good luck with your project !

Tinman

On the boiler decision alone, my choice would be the Lochinvar 10:1; available in both floor and wall models.

LeonardB

Steve Minnich said:

On the boiler decision alone, my choice would be the Lochinvar 10:1; available in both floor and wall models.

Thanks Steve

Zman

Steve Minnich said:

On the boiler decision alone, my choice would be the Lochinvar 10:1; available in both floor and wall models.

I would second this recommendation.

Ironman

Maybe this illustration will help:
A car gets 30 mpg, but has a 14 gallon gas tank. In order to go farther on a tank of gas, the owner has a 21 gallon tank installed instead. He now pays 33% more to fill the car up. Does he complain that he's paying 33% more for gas because he has a larger tank? Of course not, because he realizes that he's gonna go 33% farther on that tank-full.

It may take more energy to heat a larger volume of water, but that energy is still going to heat the house and the boiler won't cycle as often.

DZoro

Lochinvar would be my choice, as with any system proper complete installation is the key to success and efficiency. The advice given is part of the proper installation. Smart decisions will lead you to a great system.
D

pecmsg

@LeonardB

What your not understanding is ……………..

this is not an appliance that you take home and plug in. It comes in several pieces that must be assembled in your home. That home being very different then almost all others. Because of that uniqueness it is up to the installing contractor and there personnel to get it right. We are the ones that make the difference between brands. What good is Brand X if the contractor doesn't follow the install instructions, best industry practices, Federal, State & local codes.

ChrisJ

What's considered to be the most efficient and most comfortable form of heating? Radiant.

What has the most mass of all heating systems? Radiant.

What has the least mass? Forced air.

What's the least comfortable and often the least inefficient? Forced air.


That and energy cannot be created or destroyed. You're transferring energy from fuel into water and that energy has to go somewhere. All of it. It doesn't matter how much water. There isn't a partial amount being beamed up to the Enterprise by Mr Scott. All of it comes back.

PerryHolzman

I am not a contractor; but a homeowner same as you who dramatically reduced my boiler size and increased efficiency. I used the original radiators and main piping in my house.

It all started with a home energy audit which included an air infiltration test. My house was a leaking sieve... I then spent a week and about 24 tubes of caulk and about 12 cans of expandable foam to dramatically reduce my air infiltration to modern acceptable standards. In my opinion, that is your first step here. Replacing windows may also be a good idea depending on the energy audit results - and ensure they seal the new ones in properly.

Blow in insulation into the walls is next (unless you have knob and tube wiring - then you have other issues).


Then you can size and install a new boiler and modified heating system. I believe that it is likely that tearing out the old radiators and piping was likely a mistake, unless they were unusually degraded. Now you have to pay to replace them. I agree with the comments above that changing the radiators and piping will not change your energy usage.

I wish you the best,

Perry