old school cast iron or new school wall hung 95%

lowercanada

Hello....senior (;-) citizen who's been building and fixing things going on 55 years, know enough to usually get things done, without too much dangerous involved....
Friend called the other day, no heat, could I drop over and have a look....
Small, ~20 year old (maybe) Teledyne Laars HW boiler, small house, zoned second and first floor, each floor with two loops of fin tube......
Pilot's on, power's on, Tstat good, electronic draft damper working, roll-out not tripped.....
Power unit off, turn gas valve to off. attempt to relight pilot, gas valve won't turn back to pilot, knob "feel" not smooth......
Here's where it gets tricky.....I don't know what faulted, but pretty clear the gas valve is shot.....and there's a two week lead, unless expedited, for the $250 replacement.

In any case, although I might tackle the job in my own house, time to call in local pro's....
Who sold my friend on a wall hung 95%, to be installed on Monday (it's Friday night as I post this)
Now, the selling point was "High Efficiency".....Although it's likely friend won't be in house long enough to hit the break-even point.
Also of note, installation is boiler and gas water heater side by side in basement with a very nicely done (smaller flue feeds higher than bigger flue) combined flue into brick (presumably tile-lined) chimney.
The pro's wanted to upsell a new water heater in the deal, like-for-like, gas fired storage unit.
Friend declined.

I asked whether they mentioned lining the chimney after the furnace was gone----nope.
Asked whether they offered up a like-for-like boiler option....yep, roughly same price, friend bought into the "better efficiency" and "it will be a selling point if I sell in a few years".

Full disclosure, I'd probably have decided the same way if I were under the gun....

But the more I think about it, the more I think the best answer would be the old fashioned one....
--simpler tech....
--and simpler circulation and piping design, if any is even necessary (new 95% boiler would have own internal modulating pump, and the installers manual only shows a model # for said pump, no performance #s, no guidelines as to when an additional circulating pump is needed)---existing system has a single two speed newish Grunflos and a little Weil or similar would be pretty much a drop in.....
--cast iron exchangers.....
--no solid state control boards....

.....now, it's quite possible with a little work and TLC the old boiler could last 5 more years, but that's not gonna happen.....which is too bad....and the 95% is probably a done deal, but....

what would you choose, and why?

bucksnort

His payback is he'll have heat now.

EBEBRATT-Ed

Half & Half on this forum will go cast iron (me included) the other 50% would go mod con.
There is no right or wrong choice

CI is less money, probably last longer

any competent person can service it, parts less $

Mod cons need some one to service it that really knows the equipment a better technician
parts are more $ and not always quickly available

Some mod cons parts become unavailable after 15 years or so

They both have pros & cons

Mod cons modulate the flame which is better for efficiency and less starts and stops.

But efficiency wise the gap is more narrow then they would have you believe. If a mod con heats baseboard like you friends house it won't condense much where the increase in efficiency comes from. That's because baseboard systems run at higher water temps

So it's probably 82% for cast Iron and 87% for a mod non not 95% like they say

In the long run the quality of the installer is more important than the boiler. The best boiler won't run right with a lousy install

psb75

Don't forget to pay close attention to SIZING of the boilers. Make sure this is directly related to the HEAT LOSS of the building. Be wary of oversizing of the boiler esp. with a mod-con boiler --consider its modulation and turn-down ratio. Efficiency will be lost if the mod-con cannot "con" or condense (with return water being under 130F), as is the case often with high temp. baseboard heat emitters. In which case an appropriately sized cast iron boiler may perform as well, for longer period of time with easier and cheaper repair bills.

SuperTech

Unless it's for a low temperature application like radiant flooring I would avoid the mod con. I like being able to easily fix boilers with readily available standardized parts. I probably could easily fix that Laars boiler with a universal replacement Honeywell gas valve on my van. I like how long the cast iron boilers last. I had a Buderus GB142 last week, not even 15 years old and is leaking water from the aluminum block. This Buderus was used to heat hydronic air handlers and an indirect tank.  

Gotta use the correct boiler for the type of emitters the house has, and size it correctly. Unless your friend is really only going to be in the house a few more years and doesn't care about how long it lasts.

Skyline

There's no payback with heating, it is part of the overhead for owning a house.

On the other hand, there's a difference in overhead cost for CI and mod-con boilers. It's start out with acquisition cost, that's higher with mod-cons. The operational cost, or energy utilization, is lower with mod-con, but the yearly servicing requirement wipes out the savings and then some. Let me give you an example...

A little over a year ego, I've replaced my 20 years old TriAngle Tube with a Viessmann, both combi-boilers. With the exception of one contractor, all of them pushed for the high efficiency mod-con boilers, citing a lot of savings.

My NG company has historical energy utilization data and as such, I've compared NG utilization between the different type of boilers for a year. The result was, yes, there is a saving of 250 bucks over a year with the mod-con boiler. Is that a lot? No, not really, especially when the first year service cost was slightly over 300 bucks. Then add to it the three boiler parts for a midge under 300 bucks, just in case they'll be needed. These parts, and my money, are sitting on top of the boiler. In 20 years, the service cost for the TriAngle Tube boiler was around 800 bucks, mod-cons cannot compete with that.

The Viessmann service manual tells you all you need to know about the heat emitters:



But you don't see this until you have the new boiler.

With baseboard and CI radiators, there isn't much condensing in the mod-con boilers during winter month with baseboard and CI radiators. It's in the shoulder month where most of the saving comes from. That and the on demand DHW, instead of atypical CI combi-boiler keeping the DHW at the right temperature all the times.

With that stated, I do like my Viessmann boiler in "this old house", even if the yearly service cost wipes out the savings in energy cost. It's quiet, keeps my house at even temperature and provides unlimited DHW. Would I replace it with another mod-con boiler in 10-15 years, when this one stops working? The chances are, that I won't have a choice by that time, the CI boilers are hard to come by even now...

Skyline

SuperTech said:

Unless it's for a low temperature application like radiant flooring I would avoid the mod con. I like being able to easily fix boilers with readily available standardized parts. I probably could easily fix that Laars boiler with a universal replacement Honeywell gas valve on my van. I like how long the cast iron boilers last. I had a Buderus GB142 last week, not even 15 years old and is leaking water from the aluminum block. This Buderus was used to heat hydronic air handlers and an indirect tank.  

Gotta use the correct boiler for the type of emitters the house has, and size it correctly. Unless your friend is really only going to be in the house a few more years and doesn't care about how long it lasts.

I wish the contractors, giving me quotes for CI boiler replacement, were like you. Neither of them talked about the type of emitters and I only learned about them, after getting the mod-con boiler...

Hot_water_fan

Depends on the house, system and climate. Boilers are usually oversized and don’t come anywhere close to their advertised efficiency numbers (no shade to AFUE, it’s so difficult to capture this number and people are fallible). Low idle loss and low water temperatures are two keys to an efficient system and a modcon can provide those easier than other options. A modcon could easily pay for itself in the right situation. Or not. I don’t think homeowners care the slightest about payback either way. 

Ironman

The real issue that your friend has is that you can’t orphan that water heater on the old chimney like they did. It won’t vent properly unless the chimney is properly re-lined for the lower btu input of the water heater.

I don’t know why installers can’t read instructions or get some education about their trade.

He should probably just go ahead and install an indirect.

Skyline

Hot_water_fan said:

Depends on the house, system and climate. Boilers are usually oversized and don’t come anywhere close to their advertised efficiency numbers (no shade to AFUE, it’s so difficult to capture this number and people are fallible). Low idle loss and low water temperatures are two keys to an efficient system and a modcon can provide those easier than other options. A modcon could easily pay for itself in the right situation. Or not. I don’t think homeowners care the slightest about payback either way. 

Modcon, with its life expectancy, yearly service cost, etc., will not pay for itself. That's definitely true for most houses, with baseboard and/or CI radiators. Maybe in the right circumstances, but even then, I have some doubts that it would pay for itself.

Hypothetically, if my Viessmann modcon combi-boiler last 15 year, big if, the total cost will be more, than my 20 years old TriAngle Tube non-condensing combi-boiler had been. Just the yearly service for a modcon will be close to 5K for 15 years. That's, if nothing else will break in it during this time.

People, especially contractors, stating that "modcon will pay for itself" is just downright misleading. Especially, when they are giving me a quote for "this old house", after evaluating my heating system.

Hot_water_fan

Modcon, with its life expectancy, yearly service cost, etc., will not pay for itself. That's definitely true for most houses, with baseboard and/or CI radiators. Maybe in the right circumstances, but even then, I have some doubts that it would pay for itself.

Whatever, I’m not trying to argue. Obviously, not all situations are the same. Some will pay back, some won’t, but payback is hardly important to most homeowners. 

psb75

I have two houses in southeast Michigan. #1.) is a large midcentury modern 1960-vintage (unimproved energy-wise with minimal insulation), lots of glass, high ceilings, and much baseboard. It has a Viessmann W200 B2B 145mbtuh wall-hung with large indirect tank. It does a wonderful job of heating all year, but ONLY condenses in the shoulder seasons. It needed a new motherboard due to an electrical brown-out, and regular service, new refractory in heat exchanger and new ignition consumables --in 10 years.
#2.) is a completely renovated large 1855 vintage, well-insulated farm house. Well insulated but still has old windows. 20 cast-iron radiators. It has a Viessmann 222F floorstanding, modcon combi, 130mbtuh. It works wonderfully with no thermostats, on outdoor reset only. Replaced heat exchanger under warranty.
It condenses year-round. 8 years in service.
It is not easy to find Viessmann service in southeast MI. Tech support from RI is good however. Parts are not "on the shelf." Must be ordered. Viessmann equipment comes w/ a high price-point. Well engineered w/ homeowner AND serviceperson in mind.

GW

“Mod con will pay for itself” 

son of a gun- that’s extremely bold. Perhaps not a lie. Several factors have to line up for this to be factual (not misleading)

“Selling” has been around for quite some time. I’m a little more conservative so I don’t have to “take back what I said” all that often. 

I’ve dealt with vendors/reps that “embellished“ till the cows came home. It’s just the toils of living in a 1st world nation. 

GW

I bring up automobiles all the time in my conversations with people. When I get this question, (what’s the payback period) I’ve been saying “what’s the payback on your car in the driveway? There is no payback to speak of”. Then I will proceed to do some quick math, and share with them some expected savings.

If I’m feeling extra spicy I’ll even proclaim what I think the value of their car is. I’m not often in that mood.😆 “ what’s the payback period on your $40,000 car?“ 

it’s a little rough, but the message gets delivered.