Condensing vs. Traditional

Jack

to this. You could install a Rinnai Energysaver Direct Vent wall furnace in each apt, 83% AFUE, modualating gas valve and blower. Cool to the touch. Nice! Sub meter the load to the tenants. Hot water with an R50LSi Rinnai direct vent water heater. Everything will be new.

To assist in moving air from one room to another check out the Tjernlund Airshare. I have done several tens of thousand Rinnais over the years and they work exceedingly well. My normal disclaimer applies here. I, fortunately, represent Rinnai in New England! Happy Holidays!

KHogan

HELP - Condensing vs. Traditional Boilers

I recently purchased a 100 year old, 4000 sq ft apartment building with 7 apatments. I planned on replacing my 50 year old boiler with a high efficiency boiler. The heating system was originally a steam gravity system(now NG hot water), so some of the piping has a large diameter. There is a lot of water in this system and the pipes are old, but appear to be in good condition. I have had several contractors provide cost estimates. The two contractors that seemed the most experienced gave me two very different opinions so I was hoping to get some of yours.
Contractor 1 recommends a Traingle Tube Prestige model 250 natural gas modulatingcondensing boiler, with a 50 gallon Triangle Smart Tank. This boiler has an AFUE of 95%. I have looked at the reviews for TT on this forum and you guys can’t say enough good things about them. I have about twice as much radiating capacity in my boilers as I need so I would be able to supply water that is 140-150 degrees instead of 180.
Contractor 2 recommends a Burnham gas fired power vented, cast iron based boiler with 84.5% efficiency installed with a Alliance Hydra-Stone indirect water heater 50 gallon capacity. He usually uses Munchkin or Weils Mclean for high efficiency. The reason he is not recommending the high efficiency boiler is because of the size of the piping and the potential for debris and sediment in the pipes. He believes a condensing boiler would not be the best choice for long term reliable service. The Burnham is still energy star rated and is $10,000 less installed.

What is your opinion? Is there a lot of servicing and maintenance costs with high efficiency boilers? Munchkins have much smaller openings than the TT so maybe sediment would not be an issue with the TT. I have read that condensing boilers may require a significant investment 15 years after installation, compared with traditional boilers.

Charlie from wmass

Which contractor did a heat load for the boiler sizing? Which one seems most familiar with their product? The concerns are real but also the condensing boiler can do well with a system like yours IF it is installed and maintained correctly. Was your system formally steam or was it Gravity Hot Water?

tim smith

I do lot's of apartment buildings and have converted many

to TT Prestige boilers. It is a great fit for this application with oversized radiators etc. Service probs are nil. Make sure they pipe properly. Put large Y strainer or bucket strainer on but the TT heat exchanger is not prone to blockage as it has a higher volume heat x than any of the others. You will be happy as long as you have a decent installer on your side. Make sure they set up the outdoor reset properly and it will purr along. Tim

KHogan

Condensing vs Traditional Continued

Thank you for your response. What are some items for them to consider when piping? They do not plan on putting in a primary and secondary loop, since the boiler is sized to take the quantity of water delivered. They are going to install a valve at each branch to help regulate the heat in different areas of the building. I will make sure they install a strainer as you suggested. Any additional piping considerations?

The TT rep told me that setting the outdoor reset is easy. They will install and then show me how to change the target temp. I am going to start with a high temp and then lower the temp in 5 degree intervals until I am not getting 70 degrees in each apartment. Is there more to it.

Thanks,

Kevin

Buzz G.

DIRT IN THE OLD SYSTEMS

I used the Spirotrap and find it is really good at getting the dirt out and protecting the HX in my new boiler. It is easy to check to see if there is any sediment and is set up so somebody doesn't accidentally open it.

Empire_2

Tim , Been a long time..How's thing's?

Any way's Changing from steam to HW no big deal, but make sure that all your radiation is accounted for and Be SURE that you pay special attention to the 3" or larger mains. Primary/Sec. is basically a must here. I say that just for the mere fact of what happens to you water velocity as you go from :Say" 1 1/2 to 3" or 4". Your flow will drop like a rock and move slower than molasses...:-) I personally would check you total radiation/Heat loss on the structure, Select the appropriate system, either Hi or mid, but unitize a separate Loop pump since you are going to loose velocity due to the larger mains. To move your heat content of the 20 to 40* Delta T....(It all depends)to all areas, you have better have thought of what these larger pipes need to get the water there without loosing it's design Del/T...

Thermal shock if excessive can be just that....A Thermal Shock to your wallet....:-)


Mike T.

Steve Ebels_3

I'd go condensing

There is virtually no chance that fuel prices will stay where they are as I type this. I'll make a prediction that the next time they spike we'll see them even higher than they were this summer.

While you may see a bit higher maint costs with the M/C boiler, the ROI is too good to ignore. Nearly all the systems that we have upgraded to this technology have provided dramatic reductions in operating costs. Many were over 35% less than the typical CI boiler with standard control technology which is much the same as the Burnham system proposed to you.

On the subject of debris in the system, others have suggested strainers or other similar devices and I would agree 100%. You might ask your installer to check out the air sep/dirt screen combo that Caleffi makes. We've used several and they definitely perform well.

TK03

I would go conventional for 10k difference. When you add that plus needed service every year or two and more expensive parts. Size properly, pipe properly and use ODR and savings will be more with conventional in life cycle costs.
With the above installation I will normally save owners 25% - 40% on fuel. I also like two stage ODR bring on boiler pump on stage one and fire boiler on stage 2.