Recommendations for new boiler. Lots of info and pictures in post

bentley199

I've found this site extremely helpful so I thought I'd ask for your suggestions on brand/model for my boiler replacement.  My father will be helping me do the change out.  He has 40+ years working on refrigeration, heating, steam and chilled water systems.  I'll be the muscle and he's the brains.  Most of his work is on much larger equipment and in a different state/climate.

The house is in the Colorado mountains at 8,300 ft elevation.  4000 sq ft, ~350 sq ft is insulated, unfinished storage/mechanical space.  It's 4 bedrooms, 1 full bath, 2 3/4 baths and 1 half bath.  It was a custom build in 1995.  2x6 exterior walls and fairly tight.  Lots of big double pane windows overlooking the mountains.  Some of the pane seals are bad, we plan on changing all 33 windows and 4 exterior doors in a couple years.

The existing heating system consists of a natural gas Crown CXE-5 boiler with 5 zones, 4 space heating and 1 DWH.  DHW is supplied by a Vaillant VIH 190/3, 50 gallon indirect tank.  Both the boiler and indirect are original to the house (27 years old.)  The boiler is set up with separate supply and return manifolds.  The flue is 3 stories of 4" b vent through the roof.  There is 130ft of what I think is slant fin e75 fin tube split up on the 4 zones.  

The boiler is 150k btu in, 125k btu out.  The manual list the elevation derate at 4% per thousand feet above sea level.  If my math is right, that comes out to 90k btu output.

The chart I found for the fin tube list 580 btu per foot at 180° so heat output for all of it would be about 75k btu.

I was going to do a heat loss calculation on the house but stopped once I calculated the fin tube output.  With those numbers I figured that there was no reasonable way I could use a condensing boiler without changing the heat emitters.  We don't have much short cycling and everything heats good in the house so the boiler sizing seems pretty accurate. 

We've had several problems with parts breaking, valves leaking and in my opinion, some poor quality service work before we bought the house in 2019.  With a baby on the way, I want to replace the boiler and indirect this summer to give a little more peace of mind and prevent more winter breakdowns.  All external values and parts will probably be replaced as well.

It seems I'm limited to another CI boiler with draft inducer to reuse the 4" b vent.  Rebuilding the piping around the boiler isn't an issue since I'll be replacing the valves as well.

All that said, if this was your house, what boiler and indirect would you pick?  Thanks in advance

Ironman

Your baseboards have an output of about 65k btus: You have to use AVERAGE water temp which would be about 170* if SWT is 180*.

IDK why that you would assume that a mod/con would not be appropriate. One that’s properly set up with ODR could operate at a SWT which would cause the boiler to condense for a substantial part of the heating season. You only need 180* on the coldest night of the year.

Some will argue that mod/cons are more complex and break more often, but that’s not been my experience. The new cast iron boilers are just about as complex and seem to breakdown just as much. Since you’d need a power vented one, it would be just as prone to failure.

We like the HTP EFTU which I also put in my house. But you have to follow the manufacturer’s piping instructions and do p/s if you have multiple zones. Also, avoid micro zones as they can cause short cycling, even though the boiler has a 10 to 1 turn down.

Hot_water_fan

I don’t think the boiler needs to be replaced - they can last much longer than 27 years. 

If you go with a replacement, you could use a modcon - remember, design temperature is only a few days per year. You could still condense for months at a time. Plus adding high output baseboard/other emitters is an easy addition if you’re doing the work. That’s if your heat loss is actually 75k. May be, may be less.  

Usually the advice is that brand is not nearly as relevant as installer, which in this case is you two! The Idronics journals are a great resource to consult. 

MaxMercy

bentley199 said:

All that said, if this was your house, what boiler and indirect would you pick? 

I have a Slant Fin TR-30 that's been great, but it's only been a few years since I installed it. I'm not a pro however and hopefully you'll get some good advice for brand. Of course, the installation will be the biggest factor for reliability. If you're changing all those valves and controls, you should be trouble free for the most part.

I did a year's worth of reading about boilers, and so did not pick a mod/con boiler because they require a lot more maintenance, have brand specific controls and parts that could be days or even a week or more away when something goes wrong, and they half the life of a CI boiler. From my calculations, a CI boiler is cheaper all around.

Under the best of circumstances, a mod/con will reduce your heating bill by 10 percent. Offset that by replacing the boiler twice in 30 years instead of once, paying a lot more for parts, and more for maintenance and for me, it didn't make sense. Until the legislate them out, I would stay with a traditional CI boiler.

Because there's no gas where I am, I installed a Beckett AFG oil burner and the boiler came with a Hyrostat control. I can get parts for this thing from any local plumbing supply and even the big box stores have most parts for it. Other than an outright catastrophic failure of the sections, I can get this running pretty much any time and for little cost.

bentley199

Thanks for the replies

Interesting to hear about the newer CI boilers breaking down.  I guess with the more electronics, the more failure points?  Or is it something else failing?

Thanks for pointing out using the average water temp.  Makes sense with the temp differential.

The zones in the house are:
Basement 28ft fin tube
Main floor 38.75ft fin tube
Master bed/bath 29.5ft fin tube
Upstairs 34ft fin tube

Most of my wanting to change it out is due to frustration in working on it.  The first problem we had was with the flame roll out switch.  I won't speculate on how it happened but what I found was upsetting.  At some point the roll out was changed to a lower temp switch.  The ~2.5" tall peice of insulation on the front of the burner box was laying on the burners effectively keeping the higher temps away from the switch.  I think the lower switch finally failed because of the huge amount of carbon on the plates blocking air flow.  Took awhile going through velocity boiler works but I got a call back from a very nice gentleman at crown that told me what the correct roll out switch temp was.  Took the front cover off and cleaned the plates.  Didn't take the top cover off because when I disconnected the flue the fan housing flange cracked.  New fan is $400+.  This happened in the middle of winter with an infant in the house.

The control box mounted on the supply line has been changed at some point and rigged to make work.  The burner was kicking off on the safety high limit in it, best I could tell it was well above 200 degrees.  I added a strap on aquastat to provide a high set point control.  Took awhile to figure out how the wiring had been changed but that works now.

There are 3 Honeywell zone valves and two White Rodgers.  I've replaced 1 servo motor in a Honeywell and ordered the parts to replace the leaking seals in one of the white Rodgers.  That is where the corrosion on the boiler sheet metal came from and why the bowl is under it in the pictures. 

The temp/pressure gauge on top is barely readable from the plastic cover degrading. 

The fill valve is broken and won't open.  I made an adapter with a valve and pressure gauge to add make up water through the boiler drain valve to replace the leaking water from the zone valve.  The boiler drain valve leaks when it is open.  Not sure I would be able to unscrew it from the cast iron without breaking.

Spark ignitor cable insulation it starting to show signs or age.

The things I've done are band aids.  We can fix all of the problems, just don't want to throw good money after bad and the cast iron fail next.  From what I saw, the outside of the cast iron looks good.

Would you guys just shut it down and fix the problems or replace it?  Saving some money on gas would be nice but reliability is more of a priority to me than efficiency.  Maybe the way to go is fix what I've and get some more life out of it, then do a condensing down the road at some point. 

Also, what kind I've life span would you give the indirect tank?  I've been told from its age that the coil would be copper and new ones use stainless.  Don't know about the liner.  I get some what looks like green copper oxidation in the sink areators.  It doesn't show up in my well filters so I has to be coming from the system somewhere.  There is no sign of oxidation on the house plumbing.  My only guess is it is coming from inside the tank.  If you dump it on a paper towel and let it dry out, it smashing in my fingers like a powder.

hot_rod

Yeah, that boiler is pretty sooted up, wonder if the burner was ever set up properly for that altitude?
I'd go with a mod con also.
in Colorado Lochinvar, Triangle Tube and IBC have excellent reps and support. Also part availability.

I'd run that tank until it leaks. Those are nice glass lined steel tanks. I believe they had glass coated steel coils inside. A large clean out hand-hole opening on the side. Although rarely used by homeowners

STEAM DOCTOR

Not so sure that I agree about CI being as complex as mod cons. Or breaking down as often. While CI boilers are certainly more complex then they where years ago, they still have a fraction of the complexity that mod cons have. CIs have fewer parts and the parts are typically readily available. Just my experience. 

MaxMercy

STEAM DOCTOR said:

Not so sure that I agree about CI being as complex as mod cons. Or breaking down as often. While CI boilers are certainly more complex then they where years ago, they still have a fraction of the complexity that mod cons have. CIs have fewer parts and the parts are typically readily available. Just my experience. 

Totally agree. Last year I posted here for help for my wife's co-worker who had a 10 year old Buderus mod/con shut down. The guy had three well known professional techs look at it and couldn't figure out what was wrong with it. I got some good advice here but by the time I called him back he decided to replace the whole system (wife was getting tired of living in a 40F house). Since it didn't have an xchgr leak, I'm sure a good tech could have repaired it, but everyone said it had a life expectancy of maybe 12-15 years, which pushed him into replacing it. He plans to move south in 10 years and is hoping the new boiler is still running then.

https://forum.heatinghelp.com/discussion/182503/buderus-gb142-no-heat-update-error-codes#latest

My boiler is about 4 years old and is still being made. It has a Beckett AFG (simple and parts are cheap and available locally), Taco circs (cheap and locally available incl box stores), Taco circ controller (cheap and available incl box stores) and a Hydrostat 3250 (available at any local plumbing supply). Other than a catastrophic failure of the block, there is literally nothing on this boiler I can't fix either immediately with parts I have or within hours with parts I can get locally. This is a far simpler device than a mod/con which has all sorts of one of a kind electronics and sensors.

John

EBEBRATT-Ed

@bentley199

First you should do a heat loss. Why, because you need to know what you have.

Mod con or Cast iron is a toss up as far as I am concerned. Mod cons cost more, replacement parts cost more and parts,,,, you can sometimes have to wait for parts if the distributor does not stock them. Cast iron have few parts to break and parts are more standardized and easier to get. Mod cons parts can be unavailable after 10-15 years as they come out with new models

But the quality of the installation is more important there is not right or wrong choice between a good mod con or a good CI boiler it's just a choice.

Mod cons save energy because they eliminate the on off cycling and only input what you need to offset the load.

hot_rod

what @EBEBRATT-Ed said, mod cons can save energy by modulating, running steady state as much as possible, but also by running in condensing mode for some, maybe much of the heating season.

If you choose a mod con do all you can to run the system at the lowest possible SWT.

Food for thought here.
https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf

bentley199

I'm going to finish the heat loss I started so I know what I'm dealing with.

With a mod con boiler (I've spent a couple weeks researching the lochinvar knight series) I feel like I understand the theory behind it.  Run at a lower temp to keep return water cooler so you can condense the flue gas and recover more of the energy.  Would also run longer but at much lower fire rate than what I have now which is 100% on or off.

Let's say my heat loss is close to my fin tube output.  Fin tube is currently putting out 65k btu at average SWT of 170 (this is how it is set up now with 180 SWT.)  Most of the time I don't need the full 65k, only on the design day.  This winter we have had several different periods where overnight lows were close to or below zero for a week or longer at a time.  This morning was -8 degrees at 6am.  Providing I didn't upgrade the fin tube to something with a higher btu output, the mod con boiler would have to be running well above the condensing range much of the season right?  Would spending so much time hotter than the condensing RWT range, does this lower the lifespan on the heat exchanger?  Seems like it would be hard on the machine.

I've looked for the design temp for my area but haven't been able to find it, zip code 80433.  We have the original blueprints for the house but nothing for the mechanical systems.

Thanks you you input and help

STEVEusaPA

ASHRE says 5° for heat, 91° cooling for Jefferson County, CO

https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/County Level Design Temperature Reference Guide - 2015-06-24.pdf

Hot_water_fan

Let's say my heat loss is close to my fin tube output.  Fin tube is currently putting out 65k btu at average SWT of 170 (this is how it is set up now with 180 SWT.)  Most of the time I don't need the full 65k, only on the design day.  This winter we have had several different periods where overnight lows were close to or below zero for a week or longer at a time.  This morning was -8 degrees at 6am.  Providing I didn't upgrade the fin tube to something with a higher btu output, the mod con boiler would have to be running well above the condensing range much of the season right?

Well depends on what you mean by much. If your heatloss is truly 65k and you have 130 ft of baseboard, you need 500btu/lnft on design day with a delta T of 20 (supply - return temperature). Let's call design day a day with an average temperature of -5. That's the same thing as saying you'll need 500*130*24 = 1,560,000 BTU on a day with 70 heating degree days, or 22,285 btus/HDD. Based on Denver's airport, there were an average of 6100 HDD/year over the past 3 years, which is about 136MMBtu output needed.

With a 20 degree delta T, you could get 250 btu/foot with 130 degree average water temp and 300 btu/ft with a 140 degree average water temp (bumping up delta T to 40). Using the lower temperature, you can cover any load 32,500 btu/hr or lower, which is about 70% of the BTUs needed. For the higher temperature, you could condense for about 85% of the BTUs needed. If the heat loss is slightly less, say 60k, you'd be condensing about 90% of the time. 

Posting some recent gas usage (amount, start and end dates) can help determine the heat loss too.

hot_rod

You can find this Bin data also for your area, showing a 20 year history of "hours of occurrence." If you really want to drill down the numbers. The Idronics I attached above walks you through this data and how to apply it.

Spend $$ on anything reasonable that will lower the load.

No reason not to do a room by room load calc. Know that it is just one point in time. It also doesn't account for internal gains. In case you are mining bitcoins at you home, for example

MaxMercy

bentley199 said:

Would spending so much time hotter than the condensing RWT range, does this lower the lifespan on the heat exchanger?

I could be wrong (and I'm willing to accept a correction here), but my understanding is that the condensing function is what gives these boilers a much shorter life than a non condensing boiler. You can make a traditional cast iron boiler condense, but it won't last long if run that way. Running it at high rate won't hurt it at all but it won't be as efficient as when it's condensing.

bentley199

Haven't figured out how to tag just a username to reply so just typing the names until I do.

@hot_rod ,  I'll be reading those links tonight.  When time permits I've been watching the coffee with Caleffi series on youtube, very helpful.

@STEVEusaPA , thanks for the link.  Jefferson county is about 5200-5300ft and much flatter on the east side, closer to the Denver/Stapleton (in a different county) station listed.  Since I'm 3000ft higher on the western side, it's not uncommon to be 10-15 degrees cooler than the eastern side.  Would you still use the numbers listed or adjust them?

@Hot_water_fan , thanks for the breakdown, going to read it several more times tonight to make sure I understand exactly what you are saying.  Will also post recent gas usage when I get home.
 

hot_rod

MaxMercy said:

bentley199 said:

Would spending so much time hotter than the condensing RWT range, does this lower the lifespan on the heat exchanger?

I could be wrong (and I'm willing to accept a correction here), but my understanding is that the condensing function is what gives these boilers a much shorter life than a non condensing boiler. You can make a traditional cast iron boiler condense, but it won't last long if run that way. Running it at high rate won't hurt it at all but it won't be as efficient as when it's condensing.

If they a sweating they are running a lower temperature and less stress to the metal. The condensate also cleans the metals as it runs off.

I'm not convinced they are shorter lived than non cons? Plenty of failed CI boilers cross this list below 10 years old?
It has more to do with how they are commissioned. Burner adjusted and dialed in with a combustion analyzer. Adequate and clean combustion air, always. Proper pumping and flow rates. Water is in the manufacturers spec, etc.

If anything a shorter life could be contributed to the thinner metals, mistreated wink: .

Ironman

One thing that doesn’t appear in the AFUE ratings between a mod/con (95%) and cast iron (82%) is the savings that the ODR feature produces. It’s not unusual for this to produce another 15% in savings depending upon the application.

Look at the mean temperature for your locale. If it’s about 35* or above through the heating season, a mod/con would be condensing the majority of the time and worth the investment.

Once a boiler is sooted up like yours, it’s very difficult to get it thoroughly cleaned and get the combustion right.

We recently replaced the same model as yours for a customer because the inducer went bad and the cost and time frame to get it were outrageous.

When it comes to comparing a gas cast iron (not oil) to a gas mod/con, things are much different than they were just five years ago; and with fuel prices skyrocketing like they are, a 15% fuel  savings could be substantial when amortized over a 15-20 year period.

Also, consider: though boiler manufacturers recommend that ALL boilers be inspected annually, every fire tube or ECR laser tube that we’ve taken apart to clean after 5-10 years looked very good because the down-fired design has a self-cleaning effect. This is not the case with a Gianonni type heat exchanger which should be cleaned annually. I think a lot of folks lump all mod/con designs together and come to the wrong conclusions about the better ones from doing so.

The brands that hot_rod mentioned are better designed and he’s familiar with reps and distributors in your area. He’s also extremely knowledgeable about hydronics. I’d recommend that you follow his advice.

bentley199

I measured the walls, windows/doors, ceiling and volume last night.  Used the estimator on u.s. boilers website last night.  Using an air exchange factor of 3/4, I came up with heat loss of of of 63.5k btu at at a delta T of 60.  I think my delta T would be a higher value than this (colder design temp.)

My dad and I talked for awhile last night.  He is of the mindset to just fix what is broken and run the existing boiler for longer.  It's a gamble on the cast iron failing buy everything else I can fix much like @MaxMercy said.  We talked about the different factors of why people would go to a high efficiency boiler wether it be for environmental, gas cost, legislative or marketing.  Him and even more so my 99 year grandpa went through tough times and did what they had to do to get by.  Fix what they could and not simply throw it away to buy another one.  I'm fortunate that if I had to completely replace the whole system I could afford to do so but that doesn't mean I need/have to.

For now, we are just going to do that and replace the parts.  There is a good possibility we won't be living in this house 5 years from now which factors in as well.

Thank you all for the information and help.  I'm going to continue to research and learn about hydronic systems so when the time comes, I'll be ready to change this one or one in a different house.

I enjoy learning about different trades.  My job is a journeyman lineman but I try to learn as much as I can about other mechanical work.  This website is a great learning tool and I appreciate it.

As far as the soot in the boiler.  I think most of it was caused by a bad flame from the burner box insulation laying on top of the front 20% of the burner tubes.  We will be taking it completely apart and cleaning it thoroughly followed by a combustion analysis. 

Paul Pollets

Try Richard Graves (Heatmeister) at 970-513-0697. or heatmeister@comcast.net He's highly competent.