Bosch vs. Viessmann Condensing Boiler for old home

phobulous

Hello! Bit of a tragedy happened the week of Christmas and my 1989 Viessman Atola AR boiler died, leaving us without heat. We bought this 1929 fieldstone (SE PA) house knowing it was old and figured this would happen sooner or later. Suffice to say, this house has little to no insulation. It is mostly plaster and lathe, to my knowledge, and the windows are single paned glass. We have cast iron radiators throughout the house, (7 on the first floor, 6 on the second, the 1/2 finished attic is heated electrically). Our home is approximately 3100 sqft.

I've gotten a few quotes and fielded a few options for replacement boilers and wanted a few different opinions. My preferred contractor has recommended the Bosch Greenstar boilers, either combi or heater-only with indirect (I haven't decided, as we hope to start a family soon so it is balancing cost with future capacity). I originally wanted to install the Viessman Vitocrossal 300, as I have read they are quite good with retrofits like our situation requires. My contractor has stated that Viessman, while top of the line, can be hard to service and order parts for and will be harder to service in the growing future as expertise becomes highly niche. He also says that the Greenstar boiler can do pretty much exactly what the Vitocrossal can do.

What do you think? The Vitocrossal seems more thoughtfully designed to deal with sediment and sludge commonly found in retrofitted systems like ours, which is a concern of mine. But I am finding it hard to justify the cost differential if they are, in fact, basically the same performance-wise as my contractor claims.

I'd love to hear thoughts and if you have experiences with either. Thank you!

GW

yes, if Hollywood ever wrote a script, they would pay you for what you typed. Your person definitely has a preference towards the Bosch, and does not feel comfortable with the Viessmann. I install both of those brands. (Somewhere between 100 and 200 boilers, each brand.)

Yes, both are listed at 95% but that’s not the full story

The Viessmann is Extremely reliable. The Bosch is very good, but your guy will want to spend more time conditioning the boiler water. Any boiler in that situation would require the dirt magnet, but especially the Bosch (it’s low mass, not much water in there)

The Viessmann comes with outdoor reset, the Bosch does not (at least not in my area). It would be a true crime to put a non-outdoor reset boiler into that application you have. could he add one to the Bosch? Yes. But I think they stopped making the FW 200 control. So aftermarket it would have to be

If you want the Viessmann, you probably need to keep looking. You did your research, you found the best boiler, now you just need to find somebody that installs them routinely.

Actually, if he did not discuss outdoor reset with you, you should move on anyways. Cast iron is very large mass—-no need to let that beast cool down between cycles. If you have just one thermostat, then you’re going to want to consider full constant circulation with the Viessmann indoor sensor (Vitotrol)

I could opine for quite a bit, but I’ll stop typing😀

Alan (California Radiant) Forbes

For a long time now, boiler manufacturers moved away from large, high water volume boilers and left us installers to deal with micro zoning and short cycling issues. Efforts were made to increase capacity external to the boiler and to hydraulically separate boiler flow and system flow in order to keep the heat exchanger happy. Viessmann has been at the forefront of bringing back a boiler with a decent water content.

The Vitocrossal CU3A is a wonderful boiler. The ones I’ve installed have been problem free. I always insist on keeping essential parts at the job: igniter, flame probe and burner gaskets.

Jamie Hall

@GW makes one exceedingly good point: whichever boiler you might buy, it is the installer that makes the difference in the install and subsequent service — which all of these things require. You need to be quite certain that the installer you select likes and is familiar with the boiler you select — or that the boiler you select comes with an installer who is thoroughly familiar with it and will be around to service it. Not every one is as comfortable or capable with various makes as Gary is!

You also need to be sure that whoever it is has actually evaluated the heat loss of the house and not just casually selected a boiler to replace the one that was there.

Now. You mention single pane windows. One thing which can really make a difference, both in terms of energy usage and comfort, is to install storm windows. I'm a bit of a nut on this, I admit, but I strongly advocate removable storm windows which install from the inside of the house. There are several people who make these; I happen to like these people:

Interior Storm Windows For Older Homes, Churches & Buildings

but there are others. Don't be misled by folks peddling replacement windows. Unless you get the very top of the line replacements, they won't be any better than the storms — and won't last anywhere near as long.

GW

thanks Jamie, there’s lots of high efficiency boilers out there. We politely decline to install and Service many because of a lack of familiarity. But the Bosch and Viessmann- Tis my wheelhouse.

LRCCBJ

. My preferred contractor has recommended the Bosch Greenstar boilers, either combi or heater-only with indirect (I haven't decided, as we hope to start a family soon so it is balancing cost with future capacity). I originally wanted to install the Viessman Vitocrossal 300, as I have read they are quite good with retrofits like our situation requires. My contractor has stated that Viessman, while top of the line, can be hard to service and order parts for and will be harder to service in the growing future as expertise becomes highly niche.

He is being totally honest. It is hard to service if you never installed one!! And it is harder to service in the future if you never installed one!!

FIND ANOTHER CONTRACTOR!!

The Vitocrossal 300 far exceeds the capability of the Bosch Greenstar which has ongoing issues.

LRCCBJ

@Alan (California Radiant) Forbes

The Vitocrossal CU3A is a wonderful boiler. The ones I’ve installed have been problem free. I always insist on keeping essential parts at the job: igniter, flame probe and burner gaskets.

^^^ THIS. PAY ATTENTION!!

EBEBRATT-Ed

Bosch if I am not mistaken has an aluminum HX

phobulous

Ah, thank you all for your input, especially @GW for your insight into the Vitocrossal! I typed in my zip code into Viessmann's contractor locator and it is a veritable desert here, it seems, in terms of contractors who are familiar with Viessmanns. I only know this current contract I am speaking to right now because my home's previous owner had the Viessmann Atola AR installed by them in 1989. It seems like they are no longer as familiar with the brand as they used to be or from a simple lack of demand around my area, but they may be the only way I am able to get my hands on a Vitocrossal. I had not known that the Bosch FW 200 was no longer in production, so thank you for that information! I definitely have my heart set on an outdoor reset so this makes me lean even moreso towards the Vitocrossal. Now to just convince my husband about the price … ;)

@Jamie Hall @LRCCBJYou both make an excellent point about the contractor being just as important, if not moreso, than the boiler itself. I will keep looking to see if I can find someone more comfortable with Viessmann if I can. But in your opinion, assuming I must go with this current contractor due to lack of Viessmann contractors around me—is it better to go with the superior boiler (Vitocrossal) while knowing the contractor isn't as experienced with it, or is it better to go with a slightly worse boiler (Greenstar) but knowing it is within the wheelhouse of the contractor I am choosing?

PC7060

Many skilled professionals on this site. Use the Find a Contractor in your area link at the top of the page.
Good luck

LRCCBJ

 But in your opinion, assuming I 

must

 go with this current contractor due to lack of Viessmann contractors around me—is it better to go with the superior boiler (Vitocrossal) while knowing the contractor isn't as experienced with it, or is it better to go with a slightly worse boiler (Greenstar) but knowing it is within the wheelhouse of the contractor I am choosing?

You can't go with an inexperienced contractor who has never installed the Vitocrossal. That's suicide. If they have a good understanding of the Greenstar and significant experience installing and maintaining it……………that's the contractor to use.

If you have any opportunity to get a photo of a previous installation by the preferred contractor (which they certainly have if they are proud of their installs) it would be invaluable for us to review and comment.

phobulous

https://forum.heatinghelp.com/discussion/comment/1831135#Comment_1831135

Thank you, @PC7060 ! There were only four listed in my state but I have reached out to two. Fingers crossed!

phobulous

@LRCCBJ Thank you! I'm sure everything is a tradeoff but an inexperienced contractor is something it sounds like I shouldn't be trading off for boiler quality, no matter how high end. Really valuable insight, I appreciate it!

Unfortunately, I don't have any of their installation photos on hand. I only have photos of my own home's installation from them in 1989? But I'm not sure how indicative of skill or competence those would show, given how outdated the system is compared to what they would be installing today. I will ask them to see if they can send me recent installation photos!

LRCCBJ

https://forum.heatinghelp.com/discussion/comment/1831146#Comment_1831146

If they have any photos taken in the last year, they are extraordinarily valuable to those who know what to look for and for a general take on the planning and neatness of the installation………thereby showing pride in workmanship.

Also ask them if they stock parts ………and which parts………..for their favorite boiler. If it fails at midnight on a Friday……….you absolutely don't want to hear that it's a week to get the parts. Mod-cons are problematic in this regard. All the parts are unique to a specific mod-con.

GW

Happy new year to all

I’d be careful on how many questions you ask- some personalities can be awkward and almost confrontational. Other personalities can pose the exact same questions with smoothness. I’ve actually backed out of jobs (not started yet) when the questions became seemingly endless (a few times out of thousands of interactions). That’s just me- my MO. Time and energy before the installation starts can often be “forecasted” to mean time and energy after the installation. Certainly not a scientific way to conduct business. The interview process is happening in two directions

Asking for pics- that can be odd. Only trained eyes can decipher this stuff (unless it’s a huge mess). So why make the contractor jump through hoops. Pics don’t indicate control set up at all. Us Wall people love pictures- if you didn’t pick up on that (I may gather energy and post some of my own CU3A jobs)

If the company is very reputable- I’d have them install the Viessmann; they will stick with it and do a good job. If they’re not or you simply can’t get a vibe, just do the Greenstar and get the process over with. What you don’t want is a glitch and down the road you hear “well you’re the one that wanted this boiler “——that would be a bad day

Another morsel- the Viessmann has computerized combustion, the Bosch is completely manual (setting the high and low fire). The conscious tech to go through the steps. The guy is a hurry won’t.

For a tiny fee I’d be willing to be your “friend in Massachusetts that knows Viessmann CU3A”. Just an idea! You’re about to unload some dough- it would be a shame not to get what you want. I can speak with fellow contractors with relative smoothness

LRCCBJ

@GW

For a tiny fee I’d be willing to be your “friend in Massachusetts that knows Viessmann CU3A”.

@phobulous

This is the best investment you could possibly make. Why try to vet a contractor, who might take it "personally" when you can have a fellow who's thoroughly familiar with both machines and will vet the contractors for you!! The potential contractors will speak with him on the same level. Your risk of a bad install drops 90%!

offdutytech

Viessman hands down vs Bosch. It's just a better product. If Viessman is the product you want, then seek out a contractor who specializes in them. Viessman should have list of contractors in your area, if you don't see one listed in the find contractor area here.

GW

At the risk of being a total heat geek—-one of the milestones of a good install is the small details.

This job—-no, I didn’t re-paint the plywood wall. I suppose others may have. Most would not.

in general—-does the new install look like it is the original boiler or has it been “chopped in” ? The answer doesn’t normally impact performance, it simply speaks to the professionalism and that means your heating guy cares; he’ll come back and deal with stuff if there’s a glitch down the road.

Our installs: we cut back pipe much further that the average heating guy, to simply reduce “couplings” . That simply adds to the general aesthetic appeal (professionalism)

phobulous

Happy New Year everyone!! Thank you again for everyone chiming in to recommend one boiler over another and lending their expertise. I hope everyone has a year of easy installs and fixes :)

@GW Absolutely, I'm down to have you talk to my contractor for me for a fee. You're incredibly generous for offering and I'm very touched. @LRCCBJ is correct and I feel the same way. I'd pay to have an expert on my side and some peace of mind! Let's talk :)

And no risk of being a heat geek here! As someone in the middle of getting my PhD I do admire those who go all in and know their craft inside out. Thank you for the pictures and the explanation of professionalism, I see now that it can certainly make a difference. Now if only I lived in MA... :(

Kaos

First step before any brands is to figure out how big of a boiler you actually need. If you are not using about 5000therms of natural gas in a heating season, it is not 200kBTU.

You can take a gas bill from last winter and run through the math here to figure out what you actually need:

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

With cast iron rads the oversizing is not so much an issue but you are paying for more equipment than you need.

With older houses and mass rads, you also want outdoor reset with constant circulation, make sure the installer sets it up. Besides the fuel savings, this keeps the rads at a more even temperature which is good for comfort plus it also stops any banging from pipe expansion.

GW

@kaos I sped though the article, I’m surprised the math didn’t say “take your largest mid winter fuel usage and minus your smallest mid summer fuel usage”

Smallest of course would be the hot water and other appliances (cooking and laundry), which is most often the case

But alas- I’ve never used this approach. It offers good math. The one potential glitch is family A keeps the stat low and runs a wood stove in super cold weather. Joe Contractor uses the math, installs a new system. Family A moves to be closer to their grandkids and Family B has no desire to run a wood stove, and wants a warm home. Joe now has a problem on his hands (well sort of, he has no legal obligation at this moment)

Anyhow, I like the approach

GW

@phobulous shoot an email whenever

gary@wilsonph.com

Mad Dog_2

No contest..Viessman...Laars are very good too above the rest out there. Mad Dog

Kaos

@GW There are arguments for and against summer usage. The fuel use based heat load does not take into account solar gains, so it underestimates peak load. Solar gains in a normal house are not that high so about DHW energy use is probably comparable fudge factor.

If you are heating hot water with a high mass boiler in the summer, the summer time efficiency is extremely low so it over-estimates winter time gas contribution.

Wood heat can be added to the calculation, it is simply another source of BTU. The conversion from cords to wood to BTU into the house has fair bit error (efficiency of stove, quality of wood, quality of burn), so won't be that accurate. Still within ballpark though.

Keeping the thermostat a couple of degrees colder doesn't change the numbers that much when you are working with a 70F delta, nighttime setbacks don't change fuel use much either. Definitely don't use a month when you were away on vacation and the heat was turned down.

For any existing house with unknown construction details and air leakage, it would still be the most accurate boiler sizing. Certainty more accurate than even the best manual J. Won't work with something like an all glass MCM house, so not for every situation but a good check if within the ballpark though.