Perry's 2 month Vitodens report (Viessmann)

Mike T., Swampeast MO

Nope, not referring to a high temp system.

After the first couple months with my Vitodens I had similar degree day compensated fuel savings and reported here speculating that it might even get better as the winter progressed.

Someone told me to expect a bit less as the weather got colder--they were quite correct! They gave the same reason--traditional old boiler got a bit better as load increased while mod-cons get a bit worse.

My system has NEVER seen a <I>supply</I> temperature above 140°F--typically much lower.

During especially mild months, I've seen nearly 60% fuel savings. "Worst" I've seen is about 40%. It's the dismal efficiency of the old cast iron boiler in moderate weather that makes up most of this difference. There is a difference in efficiency of the Vitodens, but not nearly as significant.

Perry_2

Perry's 2 month Vitodens report (Viessmann)

Just got my second gas bill:

By combining two months I get 1678 Degree Days and 192.9 Therms used.

The degree days compare almost exactly with 2003 (1651) and 2005 (1669): Past fuel use in 2003 is 348.4 therms and in 2005 is 348.1 therms.

This translates to a 45% reduction in fuel use for the same basic weather and home heating.

1st Scary thing is... the Vitodens 6-24 is oversized for my application and actually spent much of the last 2 months cycling on and off because the minimum fire rate is more than I needed a lot of the time.

2nd Scary thing is... I have been running the house at constant temperature and have not yet enabled the night setback function - or turned down the heat when I'm gone for a weekend (as I havn't had time to play with it). That will reduce things more as I will get there.

Jan, Feb, and March are the coldest months of the winter and I expect the Vitodens to spend more time in constant fire mode - and better efficency yet... 50% or better fuel use reduction would be nice (and I think achivable).

My System for comparison: 1700 Sq Ft (living area) house with full basement; built mid 1950's Wisconsin (halfway up the state). Monoflo T system, Cast Iron Baseboard. Vitodens 200 6-24 with outdoor temp sensor, Low Loss Header and secondary circulator, RS Control (Indoor thermostate feedback - and NO TRV's installed), Domestic Hot Water with Vitocel 300 tank.

I sure wish that Viessmann had 3-24 model. I'd really be killing the fuel use.

Hope that helps people understand what can be done (and yes, you can use indoor temperature feedback with the Vitodens - just like an old fashion room thermostate: The vitodens has several possible control methods - pick any one of them and it works).

Perry

jp_2

previous system?

what was the previous system?

How old?

previous DHW ?

no change in DHW usage?

what sort of set back used before?

interesting.........

Perry_2

Previous system

Original 1954 Crane boiler fire tube boiler (with turbulators @ 130,000 Lb/Hr) - set to operate at about 140 F. Had built in hot water loop that had been abandoned in the past. DHW by gas fired hot water heater (which was fairly new - perhaps 8 years old). Thus, previous gas useage was for heat and hot water; and current gas usage is for heat and hot water.

No change in DHW usage.

I typically manually set the thermometer back a few degrees during the night, and turned the heat down to about 55 F when gone for a weekend. Currently I have not done any turndowns of the new system.

So I think it is a pretty valid comparison.

I have lived in house for 6+ years and have detailed gas usage records tracked in a speadsheet that I set up several years ago (and I dug up all my past bills to create the full record at the time I set this up).

Perry

GW

compare

It’s not always black and white. Might you agree that a 1950's boiler could be running "good", while another 1950's boiler might be running like a limping old dog?

Great news though! It's nice to see people excited about their fuel consumption. I buy my oil the first day of the month for the simple reason you are discussing. The Viessmann Vitola keeps my costs down. Regrettably and for better or worse I can't compare it to the previous system because I yanked the 25 year old unit when I moved in. Also I can't buy oil in these mild months because I have a hunch my oil company doesn't enjoy dropping 70 or 80 gallons. Oh well, if that's my biggest heating problem I think I'm doing pretty good.


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[Deleted User]

Congratulations..

on reducing your carbon foot print.

Sounds like your energy savings are in line with what we see. 30 to 50% reductions is the norm.


Keep us posted.

ME

Perry_2

Hmmm....

The first winter I had the local heating contractor come out (the one everyone in the area says is really good) and tune it up. There were some minor repairs to the burner, and I asked about installing a modern burner. This was already the second burner in the boiler and I was told that it was working great (and yes he tested the exhauste with a digital combustion meter) and that I would not gain much with a new burner.

I have no reason to suspect that the water side would have been extreemly fouled as the system was "tight" and the city water arround here is fairly soft. In the last several years I have had a valve leaking and the boiler did require some makeup periodically (I did this manually a couple times a year to bring system pressure back up). That valve has now been replaced.

Prior to that valve leaking, my guess is that the system essentially ran on the original water for decades, then on the replacement water when the series 100 pump was replaced.

Perry
Perry

GW

clarify

Hello Perry,

I was more referring to the combustion than the water in the system.

We've pulled out some boilers that were simply filled with crud. Crud is a good insulator, so it stands to reason a crudded up boiler is very very inefficient, very hot flue gas, etc. Possibly very dangerous.

So why did the guy recommend a modern burner? I missed that part. I'll throw that pitch out there if the burner is some obscure beast; I refuse to dicker with dinosaur burners (Economite and Carlin- fine!). But at the end of the day, a new boiler is the best move!

In my line of work, I sometimes crack up at the occasional person who expects their 50 year old beast to just keep on ticking (safely). Once in a blue moon we'll get a disdainful comment "what do you mean you can't fix it..."!

I love this job, something new around every corner!


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GW

Perry_2

Gary

The heating contractor did not suggest replacing the burner. I am the one who asked about it based on my experience with industrial boilers. His answer to my question was there would not be much gained by changing the burner as the existing one worked well and was appropriately sized for the boiler.

As to why I replaced the boiler. I live near Lake Michagan and we often have "lake effect" conditions. This can either help you or hurt you depending on the time of year. But, one thing that comes up with some degree of frequency is a swirling pulsing wind as the land weather pattern and the lake weather pattern tussel with each other. During this swirling pulsating winds I noticed about March of last year that I was getting exhaust gasses leaking into the basement (spillage). Now I had the boiler and venting checked when I noticed it and there was no unusual levels of CO (the burner was doing OK); but you could feel the pulsations of the wind down in the basement in the draft hood. I decided that I would not go another winter with that condition as it did affect my asthma - and just avoided the basement whenever the wind was like that. Thus, I planned to change the boiler in the summer and stashed about $6000 for it (it endid up costing a lot more..).

This actually fit into my long term plan to replace the boiler and tear out the chimney for space and to be able to run summer A/C ducting to the second floor someday. I did relocated the new boiler and water heater to one side of the basement - which frees up a lot of room in the center of the basement (and more will be freed up whenever the chimney is removed at some future year).

I have always known that I should be able to do better on efficiency than what a 50+ year old boiler had. I did not konw about mod/cons and what could be achieved. Now, thanks to the Wall - I do.

Perry

Mike T., Swampeast MO

Despite the cycling, you'll probably find that relative efficiency decreases a bit as the weather gets colder. I know such certainly happens in my house. The efficiency of the conventional boiler increased with increasing load while the Vitodens efficiency decreases with increasing load due to less condensation and slightly reduced efficiency with increasing output.

D107

So that's an average of .115 therms per degree day

Do the pros have some kind of benchmark number they can use for efficiency? Obviously it would be even lower if you had set back at night, and, as Mike T suggests, colder weather may raise these numbers. Also it would vary on what your indoor temperature is set at.

Always good to read your reports Perry,

David

GW

Don't read this, it's technical!

Mike, you must be reffering to a high temp system with this reply?

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jp_2

perry

think you can estimate your differences by also switching from DHW stand alone and the indirect? you know, estimate your hot water useage with the old 65% eff. tank heater.

it should drop your true heating estimate gains.

Robert O'Brien

Excellent!

That should provide a very nice ROI as well as more comfort and DHW. A real world example of why AFUE is useless!

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Rodney Summers

JP that is more like 30% eff for a standard water heater with all the standby losses

Brendan

Perry_2

Hot water use is:

I quickly learned to shut off the boiler for the summer which also shut off the pilot light, and then I relit it when it was time to start the heating system.

With 6 summers of data (3 months per year), my previous hot water gas use was remarkably consistent at an average of 10 therms per month.

Next summer I'll let you know how much it declines.

Perry

Rob_32

last 6 weeks

David, I'm doing 0.089 therms/dd. See the thread on "outdoor reset savings"

Perry_2

Dave... a simple mistake

Dave:

I belive you mean 0.115 term per degree day.

Note - not sure how valid comparisons are between houses.

My 1954 house has 2" of rockwool insulation in the walls - and is not the most air tight thing out there (certainly not by modern construction standards). The attic is also poorly insulated according to the original prints (again 2") with no access to it.

I have replaced the windows on two sides of the house - and you can really tell that the others leak both air and heat.

My parents house - built about 5 years later was much better insulated than this - and had tighter windows.

It all adds up - and while replaceing the windows on the other two sides of the house is on the list - that is another $10,000 project.

House: A structure that you continue to poor money into to retain its value...

Perry

D107

yes, thanks I guess it's therms per degree day

Yes you first have to make comparisons at your own house as you tighten the envelope and install new boiler, hwh. I was trying to get at a reasonable goal for all of us to aspire to--within reason. Obviously with new construction much greater savings are possible--though not always achieved if the construction is shoddy. I think Constantin says his blower door test is down to .2 ACH --on a retrofit I believe--which is astonishing. So with therms per degree day I was looking to see what's considered a solid effiency level given a mod con, good piping, indirect hwh, great controls, insulation, etc. It would seem that .050 therms per DD is attainable.

Thanks,

David

Perry_2

But is it wise - very low air change numbers.

very low air change numbers scare me. Indoor air polution issues, trapped moisture and mold growth, etc.

I believe that the recomendations are still in the range of 1 ACH per hour.

When I had the house tested in 2001 it was at sevearal ACH when I bought it (don't remember the exact number and I do not have the report handy). I then sealed up the worst issues and have been working on some of the others. I admit that I have not had it blow door tested since then - something I probably should do. I Had thought that I would hold off until I changed the windows on the other two sides of the house.

What would be more informative would be a comparison that listed known ACH and therms/degree day. That would form a basis for a much better comparision of what it takes to heat a house with a reasonable ACH.

Perry

Brad White_160

ACH Rates

The 1.0 ACH rate is a fair average default for calculating infiltration (uncontrolled ventilation) when doing heat loss calculations in existing houses, Perry.

Some as we know can be 2.0 or higher but once improved, 0.75 to 1.25 has been demonstrated by blower door testing. A lot of variables to be sure, but one has to start somewhere!

1.0 ACH is excessive from an energy standpoint if it is considered the rate for mechanical ventilation.

Canadian studies have established ACH rates of 0.35 as a basis for use by heat recovery ventilators. Granted this is a minimum and the inside contaminants, moisture, VOC's etc. still have to be taken into account. I defer to Canadian studies given their climate and strong energy policy.

Constantin

First off, congratulations Perry!

I am so pleased that your install is saving you lots of fuel and that you're pleased with your heating plant.

As for the infiltration numbers mentioned by David, yes, they are correct - 0.20ACH per blower door, with some obvious improvement areas in the works (bad seal around the mail slot, for example). Cutting the infiltration to these levels went a long way to reduce our energy footprint by the 4x I estimated using HVAC-Calc and via observation (i.e. a 200kBTU Williamson furnace couldn't properly heat a 1/3 smaller conditioned space).

Now, for the ventilation requirements, we do have two TRVs here (an ERV/HRV combo from Nutech sold under the Lifebreath brand) that cycle on and off on a 20/40 schedule. They also go into high-speed mode whenever a bathroom is occupied and evacuate entirely out of them. It is one reason that even during the shoulder seasons the bathrooms will clear of dew in little time compared to bathrooms I was used to.

A performance enhancement would be having the AC outlets somewhere else in the room, not within 2' of the TRV inlet as installed by my HVAC contractor (GRRR!). That would allow more inside air to get entrained instead of short circuiting from the supply duct to the TRV inlet. Yet, we seem to do OK, considering that any dew clears within 10 minutes at most. Dew is worst in the shoulder season when neither the AC or the heating system is operational.

Another thing I did was to set the AC system to run the air handler at 30% speed for 20 minutes every hour. That ensures that air moves around and can make it's way from the TRV outlets in the return ductwork to the various rooms. So far, I am very pleased with the system. In the future, I hope to coordinate the TRV and AH runs so that I get maximum performance. But who knows when that will happen.

I believe the minimum requirement is 15-20cfm per person. We exceed that with "natural" infiltration (~160cfm), so I could theoretically just run the TRVs to purge the bathrooms during occupancy. I'll experiment and get back to you. Having a fresh house to come to every night is a joy indeed, however.

And lest anyone think that 0.20 ACH is an amazing number to aim for, I disagree. This is an old house with 1/3 the glass being original wavy stuff set in original sashes that have plenty of "play". Had I replaced all the windows and filled the counterweight cavities, then our results would likely have been even tighter. But that is not why one moves into an older home, right?

Ray Moore over at breaktime builds houses that achieve 0.038 ACH. That puts our work here in perspective.