Maximum temperature problem with new Viessmann Vitodens 222-F

alexzaslavsky

Hello,
we have a new Vitodens 222-F gas heating system. During the recent cold snap (0 F outside) we found out the boiler temperature does not go above 165 F, no matter what heating curve settings are used. It does go to 190 F easily during in flue test mode, so it does not seem to be a combustion issue, but something to do with the programming. Our installer is puzzled and the house is very cold, even though the boiler is working all the time.
Any suggestions would be appreciated, thanks, AZ

unclejohn

Is the boiler running non stop and can not get to 165*F or is the boiler hitting the target temp of 165*f and shutting down?

alexzaslavsky

During the cold snap, the boiler was running non-stop at 165 F but would not go any higher. It seemed impossible to make it go higher, regardless of the heating curve settings (according to which it should have been running at 190 F or 195 F).
Today the outside temperature is back to around 30 F and the house is acceptably warm, but this failure to go above 165 F is likely to cause trouble during the next cold snap.

unclejohn

Sounds like you have a undersized boiler.

GW

Sounds like there's a programming issue, you should contact the local Viessmann rep.

Paul48

That boiler has a maximum adjustable hi-limit of 165 degrees. According to their documentation. What is the heat loss of the house?

GW

165!?

icesailor

Did they use ACCA Manual "J" as the tool for determining heat loss? Or properly applied AHRI/IBR like the Slant Fin. You might have just found the differences.

Have you accurately measured the supply and return temperatures for what the delta T is? If the water leaving the boiler is a true 165 degrees, and you DO have a 20 degree drop/Delta T, the last radiators/emitters are seeing 145 degree water.

Was this a new boiler replacement? Did the installer/winning low bidder do a complete and thorough heat loss calculation of the structure and a measurement of the output of the available heat emitters?

Ay-yup, you could always turn them old cast iron boat moorings up to 200 degrees t' see what happens when the house was cold. Oil or gas. Old guy said, "Them 6-pack beer coolers, you can't get more'n a 6 pack in 'em and and ya can't shut the lid with bottles."

Kind of like undersized beer cooler boilers hung on a wall. Maybe some of you young smart guys will get why some of us old dumb guys always left something "extra" for heating domestic hot water. It sure came in handy when conditions went way below what was considered design day. Especially the salesperson at the supply house. In spite of what some read everywhere in the Internets, Lennie wasn't trying to screw someone to make more money, he was just trying to Cover His @$$. Yours too. (Or why I learned to do it myself).

Somebody didn't do their homework. What else can be said?

Paul48

By their documentation....Max flow through the boiler= 6.2 gpm. At a 20 degree DT, the math doesn't lie.

alexzaslavsky

I salute the knowledgeable Paul48, after my installer visited Viessmann, it turned out that there is indeed a limit of 165 F set in the programming. This is very bad news for us (and makes a mockery of the heating curve programs -- at factory default settings the boiler should run well above 165 F when it's near zero F outside!); it is also apparently bad news for other people who installed Viessmann's newest boilers -- according to the Viessmann rep, we are not the only complainers.
The boiler is supposedly the most powerful 222 model, 35 kW. We do have a fairly large Victorian house that could be better insulated, but could it really be that no gas boiler can do the job when it's truly cold outside? Our previous Weil-McLain oil boiler burned through a lot of oil but could handle any outside temperature.
Can anything be done, besides begging Viessmann to somehow remove the 165 F limit? Thanks for any advice, AZ (who should have known better than to get a fully digital model that cannot be manually overridden)

James Day_2

All of the vitodens 200 lines have a capped temperature of 167 degrees. It is in the programming and cannot be changed. The installer should have done a heat loss calculation and measured heat emitters to ensure that this would be sufficient with the lower water temperatures.

Paul Pollets

This is a condensing boiler. It is designed to provide maximum efficiency when the heating demand load is designed for 140 on average coldest days of the year. That means the heat emitters have to be calculated correctly or the house won't heat correctly. The boiler should not be sized to run at 165. When the boiler is forced to run at max limit, it can fault and create further problems. That's misusing the condensing features of the appliance. Sounds like someone didn't do the math...

jim_94

We've put a few of these in. You have to make sure you have enough baseboard or add more if you don't. They work amazing with radiators. It is a great unit. Most of Viessmann's controls are designed for 167. Although I believe the basic models go higher and the commercial ones do as well.

jim_94

Not true. We put one in on existing baseboard and did not add any and it made it through the recent cold snap (going below 0) without one call for lack of heat. Some houses have too much baseboard for a 180-190 degree boiler and will work with a 165 degree max temp boiler on the coldest day and purr along at low temps most of the time. It depends on the house. You just have to check the amount of radiation before you put it in. Most older cast iron radiator systems were designed to work with 150-160 max temp back in the day. We've had no problems with ones on radiator systems. It all depends on the house and it's radiation as well as what design day temperature was used. On new systems we always design to -10 so that when these cold snaps come we're safe and we use either a Tekmar TN2 system with a cast iron boiler or a condensing boiler(sometimes with and sometimes without the Tekmar depending on the boiler)

unclejohn

So don't sell a condensing boiler if you don't design the system to work at a max return temp. of 136*F. Or is this the start of something new MCTA. [ manufactures covering their @sses. Home owner says; We bought a condensing boiler and it only condenses x amount of the time. I want my money back.

jim_94

And I'm sure it's a great boiler. Never put one in personally and I'm not here to argue, was simply explaining that the Viessmann does work in a installation with enough heating emitters. Everyone has their own preferences for boilers and what they like to use.

jim_94

Hatterasguy said:

jim said:

Not true. We put one in on existing baseboard and did not add any and it made it through the recent cold snap (going below 0) without one call for lack of heat. Some houses have too much baseboard for a 180-190 degree boiler and will work with a 165 degree max temp boiler on the coldest day and purr along at low temps most of the time. It depends on the house. You just have to check the amount of radiation before you put it in. Most older cast iron radiator systems were designed to work with 150-160 max temp back in the day. We've had no problems with ones on radiator systems. It all depends on the house and it's radiation as well as what design day temperature was used. On new systems we always design to -10 so that when these cold snaps come we're safe and we use either a Tekmar TN2 system with a cast iron boiler or a condensing boiler(sometimes with and sometimes without the Tekmar depending on the boiler)

How do you explain the 40 DT that you get with the Viessman? You only get an average SWT of 145°F if you need the full 125K.

If you have emitters that can provide 125K at 145°F, I have to say that's truly a rare situation.

The only way this works is if the boiler is 2X the size required for the heatloss.

You size the radiation for 150 degrees on design day. Or if doing a replacement you measure the radiation to see is it can do a design day at 150 degrees. It's not the boiler that is oversized, it's the radiation that is if you compare it to radiation designed for 180 degrees.

We do it and it works.

We also use buffer tanks so that you have a mass of warm/hot water to pull from and can keep pulling from when the boiler goes into priority for DHW because you do not have to tie the zone controls in the Vitodens 200 series boilers as it is always keeping the boiler at temp based on the outdoor temp(similar to the Buderus ecomatic control)

Paul48

Alex.......Don't shoulder this problem, yet. What is the installer doing to make this right? He has the responsibility of knowing the equipment he installs.

Paul48

Have a look, and see if you can figure out what this boiler will actually put out. I'm embarrassed for Viessmann.
http://www.viessmann-us.com/content/dam/internet-ca/pdfs/wall-mount/Vitodens_222-B2TA_tdm.pdf

Paul48

Look closer...they say max 6.2, then proceed to give higher flow rates. And it's not pages apart...it's lines apart. Its DOE rating is based on 140 supply and 120 return? If this was a first offering for this company, they'd be out of business in a year.

Gordy

Where's Chris? He's a V guru.

I,suspect the high limit is protecting the longevity of their HX?

The 40 degree delta is keeping the boiler efficient

6.2x40x500= 124000 btus. The secondary only cares how many btus are available. The primary conveyer belt is making or has the ability to produce 124k at 6.2 gpm 40* delta @ 165.

If the heat loss is more than 124k it's simply not going to work.

Gordy

Where's Chris. Chris where are you you you? "Echo"

So,if your system supply is 165, and return is 125 then you are delivering 124k no? 145 AWT can be doable if the emitters are sized right. Some one did not do their math exercises. Or their system side circ selection is not doing well. Or the emitters are under emitterized. That's what V will say, and stick to it.

Gordy

you have to think German. Believe me they are never wrong it's in their genes.

Gordy

So ya know what I mean......gramps was German. I have my moments.

Gordy

If you want a Viessmann than you have to know its parameters, and design with in them. Not viessmann design around yours. American boilers allow more latitude for that is all.

Gordy

I believe that having 190ish in the odr parameters is deceiving, but then who really uses that high of a curve.

Gordy

That's an industry best kept secret.

Alan (California Radiant) Forbes

The old Vitodens boilers had "External Heat Demand" terminals; when jumpered, it allowed the boiler to fire to 180°.

We just finished a radiator job, designed the radiators for 180° and realized that the Viessmann 200-W only heats to 167°. It's been awhile since we used a Viessmann and I wanted to get back to using them because I like them so much, just forgot their limitations, i.e. 167° max. Luckily, we discovered the error in the design stage and upsized the radiators; the wife was not happy with larger radiators, but she loves them now.

xxoo

GW

we've done dozens of the 200 series, these boilers will fire way above 167. The new 222-F is a new one, i have not installed that one.

alexzaslavsky

Dear experts (and especially Paul48),
I am learning more about boilers, but it's quite a costly lesson. I will ask, but I doubt that my installer did a careful heat loss calculation -- but there was seemingly no reason to do one. The Viessmann Vitodens 222-F (with nominal 125K BTU capacity) was replacing a Weil McLain WTG0-4 oil furnace with 125K BTU capacity! I am the one who insisted on the Viessmann (because a friend had a Vitodens 100 installed -- very economical and very quiet). Now I have a very quiet boiler (with excellent hot water service), but with the 165 F upper limit it looks like I am in real trouble.
Given that the major mistake has already been made, questions to the expert community:
1) Is it correct that installing higher-speed circulator pumps might help (currently I have 4 zones with small 4 GPM Grundfos pumps -- should some or all be upgraded to higher capacity)?
2) Is there any hope of overriding the 165 F limit?
3) Might installing a lot of insulation (old Victorian house, no insulation in the external walls as of right now) help -- this would be real money, but I was thinking of doing it eventually anyway?
Many thanks and I wish I had asked some of these questions before the gas conversion! AZ

Paul48

Alex........There is something else going on here, that we can't see. Regardless of our likes or dislikes for that particular boiler, you can get 114k btus out of it. It has either been piped incorrectly, or it is pumped incorrectly.
In the meantime, run all your zones at a temperature, as though you are using that space. Don't use night setbacks. They are a no-no with properly operating mod/cons.
There is a saying that everyone here is familiar with," A btu is a btu". That boiler is going to require careful consideration of pumping strategy, and it will work. Adding insulation, down the road will only improve how well it works.

Paul Pollets

When there's no low loss header and sensor installed, the boiler will not provide adequate flow rates.

icesailor

Hatterasguy said:

I worked for a German company for 10 years. I told them they were wrong on numerous occasions.

One occasion was once too many...................no regrets!!

A careful perusal of the history of the War in Northern Europe will show how true that statement is.

And Pete Seeger was ostracized for trying to sing a song "Waste Deep in the Big Muddy and The Big Fool Says to Push On" on National TV. (During the Viet Nam War Era).

Paul48

When I was in 5th grade, a new(German) kid came into our class. I said to him,"we kicked your asses in the war". He responded, "we didn't do too bad, for a country the size of Ohio". Needless to say, I dropped the discussion.

Jamie Hall

Switch to steam and relax and enjoy...

Paul48

He heated the house with a boiler with the same. or slightly less, rated output before. It has to be how he is moving the btus...no?

Paul48

Hopefully, they haven't "upgraded", and replaced the CI radiators with fin-tube. That could be the game-changer.

GW

this has been blown out of proportion, if the emitter system needs 180 on a design day and the boiler only makes 165, end of story, we can talk about flow rates till the cow comes. No normal hi temp system can unload 40 degrees, that makes no sense----UNLESS is was designed that way. How many people have changed a boiler in an existing home and found 40 DT, and all the rooms are comfortable?

YES, dropping your heat loss will positively 'help', of course it would, and you'll save fuel forever. Get a guy in there that knows how houses lose their heat, a guy with a blower door and IR cam means you found a pro.

icesailor

Paul48 said:

When I was in 5th grade, a new(German) kid came into our class. I said to him,"we kicked your asses in the war". He responded, "we didn't do too bad, for a country the size of Ohio". Needless to say, I dropped the discussion.

Considering that Germany lost 25 million killed and Russia lost 65 million killed, and we, the USA had 400,000+ killed, they didn't do bad in loosing.

War is stupid and deadly.

BobC

War is the failure of diplomacy. the big shots can't agree and the little guys pay with their lives. Every time I hear a member of congress pound the table and demand that troops get sent in it makes my skin crawl - we should be sure their kids are in the front lines.

Bob

alexzaslavsky

Glad to hear there may still be hope due to pumping issues and thankful the experts are still interested in my troubles.

A couple of folks brought up the "emitters": we have standard forced-water baseboard (pipes with fins), they have not been changed in any way. It's a 3-story Victorian house + semi-subterranean finished basement, so 4 zones total.

Also, regarding comparisons with the previous Weil McLain oil burner (with the same nominal 125K BTU capacity), I do not want to give the impression that the old furnace handled the job easily. During a true cold snap (a couple days with outside temperature of around 0 F), it would be firing nearly all the time and still the living room temperature would drop from 68 K (thermostat setting) to something like 65 K. And the oil consumption was fierce (1500 gallons per year). But the current situation with the Viessmann is much worse, at least as far as comfort is concerned.

I will take some photos of the piping tomorrow and post them. Thanks to everyone, AZ