Setting Supply and Return Levels on Condensing Boiler

djwcmurphy

Hey guys,

Just had my old electric boiler replaced with a natural gas IBC SL 20-160 G3. Also got my DHW onto an indirect tank.

Install was good and everything is running well, however my installer did not seem to knowledgeable on how condensing boilers actually condense. Slightly concerning, I know, but I'm confident the unit was installed well. He just did not know where to set supply and return levels.

So that being said, when heating my supply temp is about 74C right now but my return is coming back very close to that. Anywhere between 72-74. Does anyone have experience with IBC boilers specifically? I'm heating three zones, one for each floor of the house. How do I get that return temp down to make sure I'm actually condensing as much as possible.

Paul48

Regardless of brand, the requirements for a mod/con to be most efficient remain the same. The boiler should be sized to the heat loss of the home. It's best if the home is over-radiated to allow lower supply temperatures. The boiler should be able to modulate down to the required btus of the smallest zone. The boiler should be running on an outdoor reset curve. I'm sure others will chime in.

Rich_49

Circulators or one circ with zone valves ? Pictures where all is visible ?

NY_Rob

What type of emitters do you have... fin-tube, cast iron, radiant, etc.. ?

NY_Rob

djwcmurphy said:

Install was good and everything is running well, however my installer did not seem to knowledgeable on how condensing boilers actually condense.

That's just incredible, and unfortunately it seems to be a continuously running theme we see all too often lately.

Hopefully the installer was at least bright enough to follow the recommended install layout, etc... and you just need programming guidance.

djwcmurphy

Thanks guys.

Rich, not sure about circulators. I'll post a picture when I get home tonight. I'll describe as best I can right now. The boiler runs in a loop that has DHW and 3 zone valves coming off it. Each zone is one floor of the house. There are 3 seperate pumps in the loop, but they're not all for the zones. I believe one pumps to the 3 zone valves, one for DHW and one on the return.

Rob, we have hydronic baseboard emitters. You are correct as far as install. He followed their layout and adjusted it as necessary for my house. He is a reputable plumber and I'm confident it was installed well, he's just not actually a heating guy and doesn't know the details of how a condensing boiler gets that extra efficiency. So yes, I believe I just need programming advice.

NY_Rob

Nice boiler, lots of features....

I was just looking at the Touchscreen manual- you can connect your boiler to the internet and have a IBC tech remotely configure your boiler.

Looks like the Touchscreen manual (http://ibcboiler.com/wp-content/themes/ibc/pdf/Touchscreen.pdf) walks you through the basic setup for emitter type, zones, desired temps, etc...

djwcmurphy

Yes, I've actually been in touch with IBC already. However, they won't really recommend setting or configure it for me as they say there are two many unknowns. Types of piping, pumps, etc.

He could only say a 20 degree Delta T is ideal

EBEBRATT-Ed

Is the 20 degree delta they recomend in F or C?

Chances are your circulators could be over pumping. This will give you a low delta T across the boiler and not allow as much condensing as possible.

Heat loss of each zone
Rating of heaters in each zone at recommended delta T

For example, if your heat loss for a zone is 20,000 BTU/hr and you run a 20 degF deltaT you would need to pump 2gpm of water through that zone. If you pump more=low delta T if you pump less= higher delta T. This is assuming you have 20,000 btu of radiation installed.

1gpm of water will carry 10,000btu/hour with a 20 deg F temperature drop.

The output of the radiation is based on the average water temp in the baseboard. So 180F supply and 160F return (20degTD) average water temp would be 170 deg so you would check the rating of the baseboard at 170 deg

Don't know if this helps or confuses

djwcmurphy

Ok, here's a picture of the system. You probably don't need the arrows but I made this to explain the loop to someone else.

djwcmurphy

Paul48

You might want to consider having the installer swap that air scoop for a spirovent. Scoops have piping restrictions that spirovents don't. I think it's 18" of straight pipe before the scoop. There is a lot going on in a very small area.

NY_Rob

OP...
Can you verify your installer used/installed the Outdoor Temperature Sensor?

You can look for it's connection on the terminal block inside the boiler or go through the touchscreen menu- you should be able to find a screen that displays your current (or very close to) outdoor temperature, or call him and ask if he did install it.

You can run your boiler with or without the outdoor sensor installed. If he did install it we need to look at and or adjust your ODR (Outdoor Reset) curve.

djwcmurphy

Hi Rob,

I've confirmed that no outdoor temp sensor was installed. I live on the west coast of British Columbia, Canada. At our very coldest we've been getting down to about -4 or -5 C. Do you think the sensor would be beneficial or is that more for areas with a real winter?

NY_Rob

It can't hurt because you can design the ODR curve to give you up to 180F water at whatever outdoor temp you want vs. right now supplying 180F water even if it's a balmy 60F outside.

Using an outdoor sensor my boiler was supplying 133F (56C ) water this morning even though it was 13F (-10.5C) outdoors.
Just no need to use 180F water if you don't have to.

HVACguyinME

> @djwcmurphy said:
> Hey guys,
>
> Just had my old electric boiler replaced with a natural gas IBC SL 20-160 G3. Also got my DHW onto an indirect tank.
>
> Install was good and everything is running well, however my installer did not seem to knowledgeable on how condensing boilers actually condense. Slightly concerning, I know, but I'm confident the unit was installed well. He just did not know where to set supply and return levels.
>
> So that being said, when heating my supply temp is about 74C right now but my return is coming back very close to that. Anywhere between 72-74. Does anyone have experience with IBC boilers specifically? I'm heating three zones, one for each floor of the house. How do I get that return temp down to make sure I'm actually condensing as much as possible.


I’ve installed these boilers and know this control extremely well. I live in Maine and I have set my ODR to 15 above. And then set my designs for baseboard at 170 as the boiler will go to 180 because of the 20 degree dif. 10 up-180, and 10 below 160. If you think your baseboard is over sized and are ok being cold one night set it down to 150 for your design. And then set your WWSD to 70. With minimum temp of 120. This is all done in installed settings. Feel free to Pm me and I can help you out more.

DZoro

Nice install! Agree with the air scoop, it will work fine, but too bad he didn't use a better one.

Have your outdoor sensor installed. Too nice of a system to not take full advantage of it. Don't be afraid of it, study and learn how it works. Lower water temps = more comfort in your home and wallet.
If you go too low you can always turn it up. The worst that can happen is the house temp may not satisfy all day. Then you know your current boiler temp was too low for your house.

You maybe over pumped and not be able to get your delta t down so even more important to have your water temps at minimum load design temps.