Maximum temperature problem with new Viessmann Vitodens 222-F

scott markle_2

Hi friends,

I just took my first rule of thumb burn on this 222-f high limit.

When is the special 175 coding card coming out? I'll take one along with the Vito-com they have been talking about.

Anyway it's not real bad but the clients are older and like it warm, I'm offering an ultra-fin take off … At a reduced price.

I know heat loss ,heat loss. I still maintain that most modulating residential boiler sizing can be done by informed intuition, modeling is great but garbage in garbage out and it's a lot of work to even input garbage. You can't see through the wall (without thermal imaging) or easaly find hidden air movement problems (without a blower door) in a speculative visit. The older housing stock where I live is hugely variable in it's thermal integrity, So I say take some of this heat loss stuff with a grain of salt, real world is real world.

Anyway chris has contributed extensively on this in the past and his advise/warning as I remember it … is to add up all the base or whatever is installed and make sure this radiation is sufficient at the lower Viessmann temperature , even if you know your fine on the total BTU's. It might not cut it @ 165 limit. It's not a boiler sizing problem it's a radiation sizing problem.

Great boiler though…. If you can't heat at 165 you probably should be addressing distribution and or envelope anyway, but it's delicate to explain this to a client in hindsight.

Gordy

The math works out as 156.54 system supply 136.54 system return. 146.54 AWT that's all the nuts you will get. 11.4 gpm.

That's with 165* @ 6.51 gpm at the boiler supply.

alexzaslavsky

An update from the Viessmann 222 owner (victim?) who started this thread.
After listening to the assembled wisdom, I asked my installer to put in additional radiators: to make things easier, he suggested replacing the basement and first floor radiators with larger, heavier baseboard (going from 500 BTU to 1000 BTU/ft). We shall see whether this helps -- right now the night-time temperature is around 20 F and everything is holding nicely. The next steps would be adding some more baseboard and, eventually, insulating the house.

If there is interest, I will report in a few days, we have a storm and predicted cold front coming through. Regards, AZ

Gordy

Always interested in the outcomes, and or resolutions.

icesailor

Insulating the house will give you a far bigger bang for your buck. Insulating can cut your heat loss by X3+.

Its like planning to build a hot rod and buying special high performance tires before you do the modifications. You may never get to the modifications, but you got some hot tires to ride around on.

The horse goes in front of the wagon and pulls it. Not the other way around. The horse doesn't push the wagon.

alexzaslavsky

A results update from the Viessmann 222-F owner who started the thread.

The replacement of baseboard by high-capacity baseboard (from 500 to 1000 BTU/hr) has helped immensely in the basement and on the first floor. In fact, with recent night-time temperatures at 10 F, the first floor maintains nicely at 68 F. So the plan is to possibly replace some of the baseboard on the second floor (one of the three bedrooms is still too cold) and then insulate the house in the summer.

Many thanks to all of you, particularly Paul48 and Hatterasguy (and there are surely others) -- you have been great!

Regards, AZ

Paul48

Alex......Best Wishes and Warmth. As you can see from all the posts, we all learned something from your post. Mostly, it just reinforces the fact that you have to know your equipment. The only good that came out of this for you, is, all the things you're doing will keep money in your pocket, long-term.

jonny88

Really enjoyed this thread.Great help from all involved.Enjoy your new heating system and reap the rewards of a great system.

jdelec

First off, Hi everyone. I will start out by saying I am just an amateur that finds hydronic heating a very interesting subject.
I noticed in your post that you said that your previous boiler had a hard time keeping up when the outside temperature was around Zero degrees. I think you can use this information to figure out the actual heat loss of your house. I will guess that the old boiler had a high limit of 180 degrees. Measure the length of all the base board in the house, the finned part not the case. Then go here http://www.supplyhouse.com/SlantFin-Baseboard-Heaters-1828000 pick the board you are using. Download the brochure. In the brochure is the max output per foot of the base board at a given water temperature. Use the 180 Degree rating at 4 gpm per minute. The Slant Fin 30 line is 680 BTU’s per foot at 180 degrees. Now multiply the number of BTU’s stated by the manufacturer for the 180 degree water temp by the total linear feet of baseboard in the house. 680 BTU’s per foot at 180 degree water temp. by the number of feet of base board you have. If you have 100 feet of base board the formula would be 100 X 680=68,000 BTU’s. By doing this you know that the house needs at least 68,000 BTU’s of energy to be acceptable at Zero degrees. You can take the 68,000 BTU’s and divide it by the total heated square footage of the house and get your BTU’s per square foot. This is useful for adding base board to each room. If your heat loss in BTU’s is less than the output of your current boiler you know your boiler will heat the house without adding insulation. The only thing you would need to do is add more base board. Insulation may be a cheaper choice.
Now we know from Gordy that at 165 degree boiler temp with your flow rates calculate to an actual water supply Temperature of 155 degrees. Look up the BTU reduction for that Water Temp. for your base board. The Slant fin 30 line is about 440 BTU’s per foot at that water temp. In the slant fin’s case That works out to a 35.3% reduction in heat output.( 68,000 BTU’s x .353= 24,000 BTU reduction). That is significant but certainly doable by increasing the length of your base boards if you have the room. In our case we know at full output we get 440 BTU’s per foot so we would divide 24,000 by 440 to get 54.5 extra feet of Base board if you used the Slant fin 30 line.
One thing I do see in your pictures is the way the LLH is installed. If the expansion Tank is on the system supply side and the pumps are pumping away from the expansion tank I would suggest swapping the return and supply output of the LLH. If the pumps are pulling on the return side and pumping into the expansion tank I would move the expansion tank to the primary side of the LLH. Make sure the pumps are pumping away from the tank. Make sure the boiler output side is flowing into the top port of the LLH. Look up idronics 1: Hydraulic separation by caleffi.
My only experience is with a viessman vitodens 200-w 3 boiler cascade system that replaced a 3 boiler cast iron cascade system. The system is in a 27,000 square foot building that was built in the late sixties on a shoe string budget and it still has the original windows. We are seeing a solid 20% reduction in our fuel bill even though the outside reset curve matches the original system reset curve and the outputs are the same a little over a million BTU’s. Max water temp out new system is 170 degrees. (About 37 BTU’s per square foot)It is currently -3 outside with a wind chill of -16 and our residents are as snug as a bug in a rug. I can tell you it is hypnotizing watching the system work seeming to never break a sweat. I know 20% does not seem like much but it saves us 3.5k a year. I hear stories of 40% plus savings but I am thinking that may be stretching it.

3zht

I'm just going to throw this out there. I decided on a Lochinvar over a Viessmann 222F but I think I would have been alright with either.

I have my Lochinvar set so low that my temp is NEVER above 135F...I have been through 15F nights and 135F will heat my house and my garage. I did have to alter the setting on my garage fan aquastat to turn on so low but it does work. I do have alot of baseboards but they're older (1978).

My point is that 165F should be more than adequate to heat your home. The boiler may run alot longer than normal but that's a good thing, that is what they are designed for.

hot_rod

Keep in mind with fin tube in series each section sees a lower temperature, so the btu output per food drops around the circuit, adjust output accordingly

Gordy

It all depends on the whole package.

Oversized emitters.
Types of emitters.
Where insulation upgrades performed after the existing emitters were installed sized to a higher heat loss.

Temperature drops through series loops as @hot_rod mentioned.

If one, or more of these do not fall in favour of the max AWT temp. You could have issues.

Paul Pollets

Since the heat loss or existing footage of baseboard is not known, it's hard to troubleshoot the complete issues. I do see a 3/4" S&R to the inlets of the LLH. That would create a "choke point" and reduce the available BTU's to the LLH. Min. pipe size should be 1" or 11/4". Using zone valves and 1 variable speed pump would have helped the efficiency, but the issue here is available BTU's to the emitters.