baseboard fin for emitters for condensing boiler

Unknown

What exactly is a "non condensing low temp cast iron" boiler?

If it's cast iron and not condensing, it's not low temp... typically. I am aware of only one exception and it's not made by buderus.

Bob LaRochelle

condensing boiler

a family relative had a heating contractor check out her 25 yr old wm boiler and wants to replace it with either a w/m ultra or a buderus gb42. She has copper fin baseboard for emitters.Is this be a good idea or should she consider a low temperature boiler with an outside setback instead? Thank you, Bob

Brad White_191

Both

of the boilers you mentioned I would consider to be low temperature and with outdoor reset (ODR). Did I miss the alternative?

There is no issue using baseboard with condensing boilers. Even if sized for 180 degree water there are enough hours where, with ODR, to make condensing viable for enough hours to show a payback. Now, most houses I know fortunately have more radiation than heat loss, so your high temperature needs (your high starting point), will be lower and your condensing range will be nearly the entire season.

You just have to calculate your heat loss and do a take-off survey of your radiation and compare them. Find out at what water temperature you can satisfy your home heating with the radiation you have on the coldest day.

Bob LaRochelle

both

Brad, I have a non-condensing low temp cast iron buderus boiler. I used panel radiators w/trvs upstairs and baseboard fin down stairs. I wondered if she could
use that type of boiler instead. I wish I put the panel rads downstairs also, I may change that later on. She has to keep her baseboard so I didn't know if she had to go the extra distance with a condensing boiler with that type of set up. Thank you , Bob

KHogan

Condensing boilers in upstate NY - Are they worth it?

Brad - I saw this string and this is the exact issue I am struggling with. I just purchased a 100 year old, 4000 sq ft apartment building in upstate NY. I am looking to replace the 50 year old boiler and I am wondering if I will be able to take advantage of the efficiency of a condensing boiler even with outdoor reset control. I would really love to find a case study for the northeast.

Here is a sample of the calcs I did for the radiators on the second floor. These calcs are assuming 170 degree water = 150 btu/sq ft of radiation
Apt 1 - 195 sq ft of radiation * 150 btu/sq ft /410 sq ft = 71 btu/hr
Apt 2 - 151 sq ft of radiation * 150 btu/sq ft /470 sq ft = 48 btu/hr
Apt 4 - 174 sq ft of radiation * 150 btu/sq ft /457 sq ft = 57 btu/hr
Apt 5 - 135 sq ft of radiation * 150 btu/sq ft /425 sq ft = 47 btu/hr

My energy auditor calculated the heat load for the second floor to be 29 load, per SF Btu/(Hr-SqFt). The apt with the least radiation still appears to provide significant more radiation then what is needed.

I found a chart that compares water temperature to radiator output. http://www.colonialsupply.com/resources/radiator.htm

It look like if I use 150 degree water my output will still be 35 btu/hr. The water would return around 130, which is just barely within the condensing range.

Is my methodology correct? Do you think a condensing boiler would be worth it, or should I stick with a traditional boiler, add TRVs, and tighten up the building with air seal and more insulation.

Thank you for your help,

Kevin

Unknown

Read this

Kevin, perhaps it will help a bit more,, its been posted many times.

Dave

Brad White_191

Dave has your back

and posted what I would have. A good study. Thanks, Dave.


Kevin, I think that you are in a good position and have used the correct methodology- finding the "least radiated apartment" in particular.

Do proceed and tell us how it goes!

Brad White_203

I think he means

one with some internal circulation and return water dilution such as in the DeDietrich, Buderus or Viessmann line. While not condensing, they are more forgiving of lower water temperatures for longer periods of time than conventional cast iron boilers that I know of. Still, I insist on return water protection and I see where you are coming from, Rob.

Andrew Hagen_4

Modulating and Condensing

The only additional point I would like to make is that the 140°F rule of thumb for a fixed-input cast iron boiler flue gas condensation does not necessarily hold for mod/cons. The modulating burner makes it possible to condense at temperatures above 140°F. That is why nearly every condensing boiler modulates the burner.

In my opinion, they should be known more as "modulating boilers" than "condensing boilers". The major benefit is from the modulation because it makes harnessing the latent heat in the flue gas possible along with the other benefits of modulation. It's just semantics, but I think it's a point worth making.

Brad White_203

I agree, Andrew

Modulation is the largest benefit (avoiding cycling for one thing). Condensing is a bonus.

PJO_5

I did this same thing...

about 18 months ago.

Two of three apartments in a single building were heated by an oversized W/M cast iron oil-fired boiler that was 30 years old. There was also a 15 year old 50 gallon gas HWH...yes, gas and oil in the same room!

Replaced it with two Munchkin Contender T-80s and had TT Smart 30 gallon indirects with each. The six or eight gallons of boiler water in the outside tank is perfect for avoiding short cycles for HW.

The bottom floor has 35kbtuh heatloss, and the top floor has 45kbtuh, so the sizing was for hot water...but the modulation covers that anyway.

The baseboard is oversized in nearly every room, and in the two rooms it is close it's still comfortable. The boilers run at 170 (max setting) for a short time and then modulate to match the load...in the words of Billy Ocean many years ago it's "simply awesome."

Hope this helps, PJO

Bob LaRochelle

baseboard emitters w/ low temp cast iron boiler

I should have clarified my system a little better. I have a buderus cast iron boiler w/ a r2107 controller with outside reset. This boiler allows for return temp of 104 degrees. If the water goes below that the circulators stop until it reaches 104 or above. Because I have panel radiators w/trvs upstairs and basebord fin downstairs I feel that there is a definite comfort difference between the two. I wish I would have gone with the panel rads downstairs also because of the comfort difference of constant circulation of lower temp water.

Brad White_191

I can see that...

Panel radiators have a higher radiant output (no fooling! than their convective counterparts downstairs.

You will feel warmer with more radiant output versus what is mostly convective and on what is usually the coldest floor of any house (where cold air tends to leak in).

Absent individual zoning or radiator controls, there is no way to compensate for the comfort.

Constant circulation is a good thing but your system sounds like it is directly coupled, thus you cycle your circulator based on your boiler limitation.

One way to compensate for the comfort disparity is to decouple the radiation loop and make that constant circulation, then inject hot water from the boiler circuit to maintain temperature.

It will not make it perfect but will take care of the swings when the pump stops. Not sure I grasp it all, but this is what I am gathering might be happening.

TK03

The boiler condensation temp is a feature of O2 or CO2 settings. The Co2 or O2 sets the condensing temperature. I will have to find the chart but for natural gas I believe that 9.5% C02 the condensation happens about 126f. Modulation plays very little if anything for condensing in the boiler which gives us about 9.6% more heat of what the gas puts out. What can happen at low modulation is some condensation in the vent as the flue gases hits dew point especially if it is done concentric. This does not give you the 9% of heat you get when condensation happens in the boiler.

KHogan

Condensing boilers in upstate NY - Are they worth it?

I just wanted to thank everyone for their input - it has been very helpful. I will bug you once again once I have my estimates in to get your opinions on boilers and items to go over with the contractor before installation.

Kevin