Condensing combi-boiler operation cost...

Skyline

When my 20 years old TriAngleTube non-condesing combi-boiler started to leak internally, there hasn't been much choice, but to replace it. Based on the recommendations by a handful of installers/plumbers, it's been hard to say no to the condensing combi-boiler and the much emphasized savings in utility bills.

Selecting one of the best combi-boiler made by Viessmann had been the result of "might as well get the good one" mantra. While I have not regretted my selection yet, it worth for comparing its operational cost to the TriangleTube for the same time period:



Based on the first five month of operational cost, there's certainly a decrease in the overall cost of the utility bills. The savings is greater for the NG, the only one that the energy efficiency rating is calculated by. The rating does not account for electricity utilized in calculating the efficiency rating. For some reason, electricity is not viewed as energy? Anyway...

The NG over all saving for five month had been ~11%; conversely, electricity cost increased by ~5% for the same time period, giving an overall saving of ~5.5% for the utility bills. There's no question that the savings is there, not to the level emphasized by pros, but it is certainly there.

The image does not show that temperature had been set to 70F for the day and set back for the night to 68F.

As the outdoor temperature decreased during this five month period, more and more times the boiler's frost protection (32-37F) had been activated. During the month of February, the frost protection had been activated 60-70% of the times. This "feature" is probably single handedly responsibly for most of both energy source utilization increase.

The frost protection "feature" draws 160-170W when activated, observed via the UPS and "Kill-a Watt" devices. It is questionable, if it makes sense to activate this feature for indoor installation when the outdoor temperature falls to 32F or below. Bringing in the low temperature outdoor air via the intake pipe will lower the internal boiler temperature rather quickly, that triggers firing up the boiler. I did not want to shut off this feature during the first winter season, but it'll be off by the end of this year.

Maybe my research on boilers should have been done prior to selecting a boiler. With the given 70 years hold house, CI and basedboard radiators' limited heating surfaces, average at best insulation, etc., a non-condensing boiler would probably had been a better choice. Based on what I know now, I would have started with improving insulation, increase the heating surface and the select the boiler based on the needs.

Over all, I do like the comfort, unlimited DHW and low operation sound this boiler has. The latter one had been one of the deciding factor selecting this boiler, since the boiler room is part of the ranch style house that has no basement.

Zman

Do you have outdoor reset set up and have you experimented with how low you can go?
What is the thinking behind the frost protection mode?
Is this a baseboard or infloor heat system?

Skyline

Zman said:

Do you have outdoor reset set up and have you experimented with how low you can go?
What is the thinking behind the frost protection mode?
Is this a baseboard or infloor heat system?

The frost protection is a default settings for this Viessmann boiler, that rather complex to change, especially since I don't know how to change it. In addition, for the first year I didn't want to change it for various reasons.

The house has two zones with tstats and circulators. Zone #1 is cast iron radiators and zone #2 is baseboard radiator. There's no infloor heating in "this old house"...

The outdoor reset originally had been set @1.4 and yes, I did experiment with the settings. This setting impact the length of the run time, when the tstats call for heat. The initial 1.4 value was too low for 55-65F outdoor temperature and had been bumped up to 2.2, or 2.4. As the outdoor temperature dropped, this value had been dropped as well, falling back to 1.4 by the month of February. It's been more of an experiment, since the outdoor temperature fluctuated during the last five month between 10-65F. The same outdoor reset all the times is not suitable for the heating media with various outdoor temperatures.

I am not a fan of the long heating cycle, since some of the savings in NG is offset by the electric bill. As it is, the frost protection offset the NG saving by 18-20%. For the next winter, I'll probably use 2.2-3.0 outdoor reset for the winter month, with the frost [protection disabled.

And again, the house been comfortable during the last five month, with even temperature all around and unlimited DHW. This had been the case all the times with the replaced non-condensing combi-boiler.

PC7060

The long heating cycles are where you get the efficiency gains. Did you switch out the pump to a ECM.  My Grundfos Alpha2 pump rarely draws more than 8 to 9 watts; probably about 5% of the power draw of the huge B&G pump it replaced. 

bucksnort

So how long do you figure the payback is? I'm not spending 3X's to save pennies.

Skyline

PC7060 said:

The long heating cycles are where you get the efficiency gains. Did you switch out the pump to a ECM.  My Grundfos Alpha2 pump rarely draws more than 8 to 9 watts; probably about 5% of the power draw of the huge B&G pump it replaced. 

Even if the house would have large, conductive heating surfaces such as radiant floors/walls/ceilings and good installation, I'd probably wouldn't agree with you. Based on my experience with the frost protection, where it's been active for long time, the long cycle's efficiency gain would more likely be offset by the increased electricity utilization. I'd love to test it, but that's not an option for me with the radiators and the heat-loss ratio for this old house.

I cannot measure what the new Taco 007e™ ECM circulators draw. My guess is around 15-20W each, based on the frost protection cycle drawing 160-180W drawing by itself. When the heat is on in both zones, it's around 200-210W electricity utilization. In retrospect, the zone valves would have been a better option since the boiler has a circulator for the heat anyway. That's on the installer, since at the time I did not even know about this option. That's not the only thing what the installer did wrong, but that's another discussion.

bucksnort said:

So how long do you figure the payback is? I'm not spending 3X's to save pennies.

Thanks for the laugh , actually, I should have cried instead...

Based on what I have seen/experienced so far, the yearly savings will probably be offset by the yearly maintenance cost of the boiler. That's just my estimate, based on the five month energy utilization so far. The summer energy utilization, with DHW utilization only, could provide more efficiency/saving but that remains to be seen. So does the longetivity of the Veissmann boiler, somehow, I have doubt that it'll last for 20 years. Just the maintence cost for this boiler will be around $6K for 20 years, that's a low estimate, if it would last that long.

I am not certain from where you've got the "spending 3X's" for the condensing boiler? I did have one quote for non-condensing boiler installation, that had been 20% less, than the Viessmann boiler. The quote was by the company that installed the former TriAngle Tube non-condensing boiler, probably a rip-off. The plumbing supply house listed the boiler quoted at half the price.

bucksnort

Without knowing your costs it's hard to make hard facts. Half price to you could be full price to the slob 2 homes down the street. We can't discuss price. But spending $300 a year for maintenance if you're saving say $250 makes sense if you feel good about saving fuel but then spending that on maintenance. I looked at 95% mod/con units and then the next model boiler up from what I have now that has given me 33 years pretty much trouble free fell in my lap for cheap.
Yes, the new boiler is only 88% efficient, doesn't need $300 a year to flush out even though I could do it for materials. It's cool how you have costs down to the last penny. My 7% I could save each year would amount to $100 if I went with a mod/con. My old skool went 33 years, heck the Taco still purrs along like day one.
I could save $$ if I put in ECM Tacos but I'm hesitant because of my old pipes. But I have clear water now. If I put the ECM's in and 5 years down the road sheit the bed because the magnets in them attracted rust because I didn't install a magnetic trap ($250) make it worth saving $50 in juice.
That's why I asked what the payback costs are. My situation is different then you. I'm staying old skool. What's that 65" dashboard display gonna cost in the new BMW when it craps out?
Sometimes saving $$ has a comfort level over going old skool but only you can decide. Heck, in 20 years we may have "free" abundant electricity and everything now will be obsolete. Ford is going all "green" by 2035 so what do they know that we don't?

Skyline

@bucksnort...
In my view, replacing a boiler does not have an ROI; one either has heat, or don't. Cost of the replacement did not matter that much to me and won't matter down the road. Granted, for my circumstances the non-condensing boiler would had been a better choice, for 20-30% or less, with its much lower maintenance cost.

Thanks for the heads up about the Taco ECM circulator. If it fails down the road, I'll replace them with zone valves, that should had been installed on the first place.

The condensing boilers can run efficiently, but it is certainly not "set it and forget it" type of operation. The Outdoor Reset (ODR) is a double edge sword. One could set the ODR for 55-65F outdoor temperature and the efficiency is there. The efficiency will not be there, when the outdoor temperature falls in the 45-55F range. It's even worse, when the outdoor temperature keeps falling below. I live in the area, where the outdoor temperature could flactuate from 10F to 55F, or the reverse, within a day or so. A single ODR will work, but either forget the comfort, or the efficiency.

If you look at the first five month operational cost for the Viessmann boiler posted earlier. There has been substancial savings for the first couple of month. The reason being is that, I've changed the ODR frequently, based on the weather forecast and my outdoor temperature provided by my weather station. The result speaks for itself, but gets old in a hurry. By last couple of month, the ODR had been changed maybe once a month and it shows.

It's not the first time, that Ford's vision for the future had been wrong and won't be the last. The current electricity infrastructure has problem managing the demands at times in the US. Just look at what happened in Texas couple of weeks ego. For all electric vehicles, the electricity infrastructure needs to be updated and that's a tall order for the next 15 years...

bucksnort

You still will need a Taco or whatever with zones. I understand the ROI and all. If you're happy whatever the cost is a bonus. Say you sell in 3 years. People looking at it for the most part will only care how old it is, not how many gizmos it has. My friend just had a mega solar system put in. Brags about ROI which is very liberal. Guy will be gone in less that 3 years so ROI goes out the window. Since he would die if the power goes out he just put in a 12K Generac. When the home is sold in 3 years the cost will not be recouped unless the new owner thinks the panels are the cat's meow. I would look at it as a liability down the road. My payback in years is what I'm looking at. My old boiler has cost me about $75 a year.

Paul Pollets

Take the boiler off frost protection. The combi boiler cost and efficiencies somewhat depend upon DHW usage. If there's 5 adults using the hot water, costs will be higher, maybe significantly higer, than the 30% usually associated with DHW usage.

Skyline

@bucksnort...
The dwelling is 1,300sqf, ranch-style house. I seem to recall that the internal circulator could handle upto two zones, but will check.

When your boiler is broken, there's no long term planning. I am more than satisfied with the even comfort and unlimited DHW that the Veissmann boiler provide. There are some aspects that I don't like, but they will be remediated sooner of later.

@Paul Pollets...
There are two people living in this house, albeit my better half probably should be counted as two, or maybe three. She takes half an hour, or longer showers; that had been one of the consideration in selecting the boiler.

Taking off the frost protection seems rather simple, just change two of the default settings via the "coding level 2":

1. A3:2 --> A3:-9
   
2. A3:0 --> A4:1
   

This is based on Viessmann's service instraction for my boiler:



I just didn't want to make the changes during the first year, especially during the first winter. It'll be done during the summer, then next winter will show changes in the operation cost. It'll be interesting to compare the years, more likely will show the actual cost of the frost protection.

I just wish there would be a virtual "coding level 2" to practice, prior to changing the values. That would make it much easier. Also, backing up the configuration to the USB flashdrive would be nice, especially, if the configuration could be restored from there. The boiler does have a USB port, so backup/restore should be an option.

Yes, I do have extensive IT background, Vitoden is just a single task computer, probably with either an ASIC chip and/or SoC.