We have lived in our 3000sqft house for 10 years now. Our existing natural gas heating system is a disaster and should have never passed inspection. It is completely unsafe, unreliable and has been a headache (literally)

Our radiant floor is fine. We have Gypcrete throughout the house with porcelain tile. No other floor covering except for laminate floor on the stairs.

Our boiler however is WAY over sized. It has no controls and no mixing to provide proper temps to the floor. It is a copper heat exchanger Teledyne Laars. We have a 43 gallon sidearm off the boiler.

Being that we are not mixing, we have to have to run the boiler at 130 degrees to keep the floor from getting to hot. This is the crux of the problem.

We have horrible stack corrosion because the boiler really never gets the moisture out(bad). The boiler has a 6" exhaust tapered to 4" Type B vent(bad). It is side wall vented. The power vent was mounted mid stream(very bad). We have replaced all of the vent twice now. I moved the fan to as close as I could to the exterior. We have had instances of CO alarms because of leaking vent pipe (very bad)

Well I want to do this right. We have been talking to numerous contractors about replacing the boiler with a modulating condensing boiler. Quotes have ranged from 7k to 17k (ouch)

Two have recommended replacing the boiler and utilizing a indirect hot water heater.

One has said it would be ok to keep our current sidearm.

One has recommended to replace the boiler and put in a separate tank less hot water heater.

They are all proposing using high quality boilers such as Viessmann, Triangle Tube and Buderus.

Anybody an expert?

It makes no sense to use the inferior, outdated, low-efficiency "tankless" water heater, when you have no less than seven 95% AFUE modulating condensing (ModCon) boilers to choose from. Each is compatible with your existing indirect-fired (companion) domestic hot water heater and the most efficient and durable water heater on the market today.

All ModCon boilers are indirect capable and have built-in outdoor reset, increasing comfort and operating efficiency at once.

Choosing a contractor is the key to high efficiency boiler success.

How to choose a contractor.

First, call the listed number in your phone directory and ask whomever answers if they install radiant floor heating, condensing boilers etc. If they hesitate, or don't know, move on.

Once you get a positive response, ask how many radiant floors or Mod/Con boilers they have installed in the last year; or the last 5 years. If they hesitate or don't know, move on.

Ask if the contractor provides a heat load analysis, if they hesitate or don't know, move on.

Ask your prospective contractors about your choices, if they have a website their pictures are a testament to their professionalism, if they try to discourage you - for questionable reasons - from buying Mod/Con boilers or radiant floor heating systems, move on.

If you find a person who affirms their knowledge and experience, ask them to come out and look at your project. Though I often give people ballpark quotes over the phone, it is a practice that is legitimately frowned upon by the industry and it does not reflect poorly on the contractor if he prefers to look at the job before he talks about price. I sometimes charge a modest fee for a consultation, which I deduct when a contract is signed. Remember what free estimates are worth.

Now that you have qualified your prospective contractors (three should be enough) it is time to invite them over. If you plan to have your spouse help you in your decision it is a good idea to have them with you when the contractor shows up. Do some homework. Make notes about your current heating system both good and bad e.g. bathroom is an always cold, fuel bill high, but the boiler never quit working. Think about what you want from your next heating system and tell the contractors about it.

I would admonish you to stay away from glad-handed salesmen from your local gas provider, department store or big box hardware stores. They are not qualified to specify, install or service the equipment you are interested in. They sell you a product, mark up the job and sub-contract the installation to a licensed - low-bidder - contractor that you will probably not speak to until the job goes in. Much of my work involves following around such contractors and correcting their mistakes, both trivial and serious.

Contracts do not have to be fancy but should include language you understand and agree with. One-year parts and labor is standard in the industry. Licenses and permits are fine, but the majority of contractors and inspectors have zero experience with new technology. Their job is to make sure codes are enforced to assure safety. Unfortunately the code usually lags behind the industry a decade or more. It is not a good idea to depend on a code inspector to guarantee a sound design or application.

I am personally more interested in a contractor who has been to factory training for condensing boilers and radiant floor design seminars or certification, a current Certificate of Insurance and a solid and recent referral from a General Contractor or satisfied homeowner. Don't forget the mechanic's lien waiver when paying the final bill.

As contractors pay for their membership to all affiliations, I do not put much stock in Associations or BBB Membership etc.

www.badgerboilerservice.com

I wish. I live in a small town of 3,000 people. There is only one contractor in town who has ever installed a mod/con. Two of the other quotes, I had to pay them to drive 40 miles to get here. The fourth was a German trained heating expert. He came out of the goodness of his heart, but I don't think I could afford the $17,000 he quoted.

Paying people to drive is not the issue really.

Getting a comfortable efficient system is the goal I set for my customer rich and poor. I install Viessmann AND Munchkin boilers, (the most expensive and the least expensive 95%AFUE boilers on the US market) both are a good value if you goals are long term and focus correct.

This decision requires long-term thinking.

I should say, I have no problem paying someone to take a look. What I am having trouble with is finding someone who is experienced, confident and will do quality work.

$17,000 is a little higher than I can afford (by about $5,000)

Other than that, I would go with him. He has installed over 200 Viessmann boilers.

If the boiler isn't totally shot, you can probably get more mileage out of it and be rid of the syptoms by installing a "reverse indirect"  buffer tank (that has an internal heat exchanger for heating potable hot water.)  If the floors are fine with 120-130F water, that's the temp you'd be looking to maintain the potable water anyway, and that would be the point of hydraulic separation between the high temp boiler loop and the lower-temp slab-loop. With the tank's aquastat set to the the radiation/DHW temp requirements the boiler could then run at higher output temp, and it's return water temp will be near-condensing, whereas if you're currently running the return water from the slab directly into the boiler it's well into the condensing zone, even if plumbed with a "boiler bypass" pipe to mix some boiler output water into the return stream to save the boiler.  The cooler the return water entering the boiler, the bigger condensation issue you'll have, but at your altitude even 120F return water won't likely cause a huge condensation issue (but 110F return water will, big time.)

Alternatively you could keep the sidearm for the DHW, and install a less massive hydraulic seperator that would allow you to run lower temp on the radiation but keep the boiler loop could set up to run at much higher temps

IIRC the Laars Teledyne copper tube boilers are all in the 85-87% AFUE range, in which case B-venting would be out entirely- it needs Z-vent/stainless. (Indeed, it shouldn't have passed inspection on day-1, independently of the temp you were running it, which only made the problem worse.)

If it's possible to retrofit the existing boiler into something reasonable for under $4k (and I'm thinking it might) it'll be hard to rationalize going for a full-on boiler swap.  The thermal mass of the gypcrete radiation is high enough that it shouldn't suffer too much efficiency-wise from being oversized, if the retrofits are reasonably designed & implemented.

Many boilers will have issues running in Leadville due to the 10k'+ altitude.  Make sure whomever takes it on has more than a passing notion of what that's all about, and isn't a first-timer for a high altitude installation.

I'm betting you can get reasonable 80%+ performance out of your Laars or a mid-efficiency cast iron boiler by..

A:replacing all B-vent with Z-vent (which isn't cheap), and


B: running it primary/secondary into a reverse-indirect or temperature controlled buffer  (over 120F)  roughly configured like this:



But inspect the heat exchangers on the Laars before deciding which way to go- if it's been getting 100F return water forever there's a chance it has condensing corrosion on the copper fins and may be ready to crap out.  (Hopefully it's at least plumbed with a boiler bypass, which would limit that sort of damage.)


Whatever you do (new boiler or old, condensing or cast-iron) running either the existing sidearm or a reverse indirect/buffer will be more efficient that running a separate tankless heater for hot-water only.  A standalone tankless can be as-expensive as a boiler installation (with as many issues), and it's output is likely as big or bigger as your heating boiler's, which may require you to upgrade your gas lines to be able to handle the combined capacity.  The Laars + sidearm is probably already more efficient when heating hot water than a standard-efficiency tankless (or at least "in the range").

A $7k install for any mod-con would be on the low side in my neighborhood, and small difference in AFUE numbers notwithstanding, might be the optimal solution here, since your high mass/low temp radiation is now an asset rather than a liability to work around.  But it won't likely run at it's sea-level AFUE rating due to the lower exhaust dew point at the atmospheric pressure & leaner mixture it'll be operating at in Pb-town. Some tankless HW heaters crap out at 10k' too, for similar reasons.

The boiler heat exchanger is fine. It is easy to look at by taking the sheet metal off the boiler.  However the sheet metal after the heat exchanger is rusty.

My concerns with keeping the boiler are:
It has a 6" exhaust, and I am trying to stuff it down a 4"stack
The existing exhaust exits the house below a functioning window. I could relocate it.

My boiler chemistry looked good last winter, However the sidearm is now 13-14 years old. What are their lifespans?

I will probably be taxing the system more so in the future as I am the father of 3 month old twins.... More hot water usage, zones turned up that were kept at 55 degrees.

I have two top contenders for installers/problem fixers. One is a local Leadville who has installed 8 Buderus/Rinnai combinations. I am not very enthused about the Rinnai. I haven't talked to him in the last few days, but I would imagine he would use an indirect HW if I insisted. I just don't think I should have to insist.

The second person, is from Summit County and has very right answer (that I have learned over the last 10 years dealing with this system). He has installed 200+ Viessmann boilers. He has numerous factory trainings and has years of experience in Europe. Its just a hard $$$ to swallow.

Other than that, I haven't found anyone else I would consider using. Although I haven't tried, the economy might help me know as companies from the ski are might be willing to travel to Leadville now.

Buderus/Rannai ?

Buderus is the biggest boiler manufacturer in the world and they make a fine indirect. The average indirect will lasts 30 years with soft water or regular service. There is no reason whatever to install a tankless low-efficiency water heater when you have a 95%AFUE burner in the house.

The ModCon with indirect is the best domestic hot water heater in North America.

Buderus or Viessmann you will get what you pay for if the contractor knows his business. I would ask about factory training on any ModCon install.

That is a concern of mine.  If he really knows his stuff, why is he even considering a tankless in addition to the mod/con?

He is clearly misinformed. I would eliminate any candidate who neglects to offer an indirect or does not offer a computor generated heat load analysis. It makes for a short list (even here in Minniapolis) but you will end up with the smart guy and a sound investment in GREEN comfort.

Yeah- I have no issues with Buderus, but pairing it with a Rinnai is ridiculous. A 43 gallon sidearm (assuming that's an internal volume, not a gpm rating) is more massive than many indirects, with much higher heat exchange capacity. It should have livespans of several decades, and chucking one that's less than 15 years old would be a real waste. I'f it's truly that massive, it might be impressed into use as a hydraulic separator (as in the system sketch in my prior post).

The output of the Rinnai is probably bigger than your space heating design day load, and it's technology is very similar to the Laars (it's just a water tube boiler with different control constraints), and running it in on-demand mode as a water heater is guaranteed short-cycling. Every draw less than 3 gallons is below the EF rating for efficiency, and draws under 1 gallon (like hand-washing) are no better than 60% efficient. With 43 gallons of thermal mass to work with the boiler will have a significant burn, and the fractional loss of ignition cycles, flue purges and heat abandoned in the boiler will be quite low. It may be marginally less efficient than a Rinnai in the summer, but during the heating season all burns will be warm-starts, and half the abandoned heat water-heating burns will be usable space-heat. (If I'm misunderstanding the sidearm number, it's at least true for a 30-50gallon indirect. A 3-6 gallon hot water coil probably isn't enough mass to keep the efficiency up, however.)

It's unlikely that a mod-con will run at 95% combustion efficiency (let alone AFUE) at your altitude, but it'll hit 90-92. Most boilers are rated for performance at 2000' altitude. Viessman has standard kits for running them above 6k' that reduces both input & output BTUs to run it more efficiently & safely at altitude, some "high altitude" versions have altitude sensing for auto-adjustment. I haven't looked at the derating curves recently, but IIRC it's on the order of a 30-35% reduction in total thermal output to run them at 10K vs. 2k'. The derating for altitude is more severe for mod-cons because the dew points at which the exhaust will condense is more than 10F cooler at 10K' than it is at 2k', a function of both the air pressure and the dilution air mixture required for complete combustion having less CO2 content in the exhaust which further lowers the dew point. You need the condensation to occur in the heat exchanger, (not the flue) to get the benefit, and (wild-assed guesstimation herer) you'd probably need sub-85F return water to actually hit 95% efficiency in your location. (You might get there with a slab- but I wouldn't assume that.)

The Laars isn't dependent upon condensation for efficiency. It will likely have to take a ~20-30% hit in total thermal output to get it to burn properly, but probably still runs ~85% efficiency as long as it's not short-cycling (but you'd have to fix it's venting and operating temp issues. Also, the output of any boiler at 10k' will be well under it's sea-level rating, even when properly adjusted. If the Laars hasn't been adjusted for altitude it's likely running too rich, resulting in higher CO in the exhaust. Properly adjusted the CO content of the exhaust would be quite low, and a leaking vent of a properly operating boiler would increase the indoor humidity, but not necessarily trip the CO alarms (which makes me think the original installer may have been clueless on that front as well...)

I will never see a return on investment as my house is well insulated/has a lot of solar gain and a lot of thermal mass. My gas and electric combined peak at $240 in the dead of winter. I run at $80 most of the summer. Even if I cut my gas use in half (impossible) I would only save at best $75 in a month.

So I am not asking these questions to reduce my energy use (a very good side benefit though)... I just want a safe and comfortable heating system with some hot water for showers...

Is it worth redoing the controls and plumbing (mixing and exhaust) on a 15 year old boiler? Should I worry about the sheet metal on the boiler? Would it be wiser to find another boiler like I currently have? I am guessing to fix what I have is going to be 4-5000 plus possibly a $1500 boiler replacement.

Or does it make sense to step up to a mod/con at a minimum of a $10,000 investment?

$75/month adds up- what do you estimate the savings would be per year? For me the difference in operation costs between an 80% low-mass boiler and a 95% condensing boiler is well under $200/year, and not worth the difference in up-front cost (except maybe as a DIY project with a discontinued bargain-basement mod-con.) YMMV.

First, do a heat-load analysis to determine the whole house heat load on the coldest day of the year. (Manual-J style, don't try to do fuel use & boiler efficiency to measure the heat load, as can be done at lower altitude where the parameters are better known.) If you don't do it yourself, have competing contractors submit their own, and question them on how the numbers are derived. A "right-sized" mid-efficiency cast iron boiler plumbed primary secondary w/mixer for the low temp radiant + an indirect should be under $10k, installed from scratch.

Alternatively, using a tankless hot water heater as a boiler with & a reverse-indirect as a hot water heater/hydraulic separator can get you there for ~$5-6K. (Set up slaved to the indirect's aquastat with the flow & delta-T on the boiler loop set to about your design day heat load or slightly above, then it will modulate up under domestic hot water flows, but otherwise it'll modulate within a range on heat loads. There are other design issues when using an on-demand HW heater as a combi-boiler too- only go this route if you have confidence in the designer/installer. Some solar heating contractors are on top of it though, having used tankless water heaters as backup to the solar storage, which is a nearly identical problem.)

It's possible to plumb the existing boiler with the rest of the components such that a replacement boiler would be pretty much a drop-in. An indirect will last decades. Copper tube boilers are typically good for 25 years+ if not abused, and the sheet-metal isn't typically very important. Setting it up so that ANY boiler (cast iron, copper, mod-con, tankless HW) can be used won't necessarily be wasted, since it'll outlast the boiler. A mod-con driving an ErgoMax/TurboMax or similar will be limited to ~90%, efficiency, but that approach gets the most out of a cast-iron or copper-tube boiler by reliably blocking short-cycling, and combine & lenghten DHW & heating burns to get closer to the boiler's steady-state efficiency.

It's a system-design & integrity of installation issue more than a simple boiler-replacement. Plumbing in a more appropriately sized boiler where the Laars now stands is no guarantee that the problems are all solved just by the re-sizing of the boiler. The design has to be fixed, and that can happen with or without replacing the boiler. If it's just sheet metal damage on the Laars, re-commissioning it with more appropriate placement, venting & plumbing is likely to get you at least another decade out of it, maybe two, and when it's time, another boiler can be installed without reinventing the whole thing.

The fly in the ointment for you is finding the contractor who fully understands the altitude issues, beyond just buying the "high altitude" version. "High altitude" means "up to 4500 feet", for some manufacturers "up to 6000 feet" for others, or "over 6000 feet" for still others. What might work as standard practice in Denver or Durango won't necessarily work un-modified up in Leadville. The market for boilers installed above 10K' in the US is quite small- I would hope that somebody in the biz local to you is more on top of it than a flatlander like myself.

I am having the fellow who has answered all my questions (properly!) and asked a lot that I did not know to ask come over tomorrow. Here is his website http://heatmeister.com/ I do have a very good feeling about Richard. We will see if I need to break open the piggy bank to afford him.

The sidearm (indirect hot water heater) is Amtrol 43 gallon. It was put into service 5/1994 according to their website.  It has a HDPE liner.  I did have an exciting discovery today and found a section of PEX where I could finally see a standard stamp along with Manufacturer and type. I have Oxygen barrier pex. Sure widens my choice for boilers.

I know that this is not just a boiler size issue. The current install is completely screwed up. Unsafe and Unreliable. At what point do I cut my losses? I am leaning towards boiler replacement as it will be a fresh start and I won't be doing this again in 5-8 years.

Water for the system? Anitfreeze or not?

I am thinking about heating my garage. I don't want to heat it too hot and I would prefer not to have to keep the heat on all the time in there.. I have gas plumbed in to the garage already. Hydronic coil heater? Infra red tube? Unit heater?

I have had multiple heat load calcs done and I am in the 90,000 btu range

If it hasn't had any problems/issues to date, the Amtrol should still have decades of life ahead of it- recommission it with the new system. If you have hard water, you might want to de-scale it while you have the system apart, and plumb it with isolating valves & ports to be able to de-scale it as-needed without hacking into the plumbing.

Unless you leave the place for a week at a time during the heating season your chance of freeze-up is low. Anti-freeze reduces heat transfer efficiency, and breaks down over time creating chemistry issues. Don't use it unless there's a very good reason to.

If there's chance of freeze-up in the not-always heated garage, a hyrdonic solution isn't the best. A ~75-80% efficient wall-furnace is probably your best bet for a low cost, low maintenance intermittent heat solution.