Tuesday February 18 is a 17 degree Farhenheit What to look for

newinnj

Hi,

I have a Navien NHB-150 boiler. Everyone on this forum has helped me with my setup the house is warm and right now it's running pretty good. What should I look for in getting info to the forum so I can get an answer that the oversized boiler (I just have to grow to love it since it works and I will not be replacing it) that it's optimized as best as it could be. Is it me just sitting in front of the boiler on a cold day and take down supply side and return side temps at the boiler or the manifolds? Record the circulating time versus the boiler firing length of times?

1800 square feet of living space with insulation done with door blower test etc.

2 active zones for staple up wood floor on two levels.

one zone - one loop Walkout basement 600sq

second zone - three loops. main living area. 1200sq

One indirect tank for about 50 gallons.

Thanks for pitching in. Also thanks for the help on my last question about a week back that was the icing on the cake in getting the system to really working pretty good.

newinnj

oops some more info.

I have another apartment on top of my unit. One side of my unit is another building butted up to mine. I live in a multifamily walkup.

EBEBRATT-Ed

The first thing I would look at is the boiler run time. A properly sized MOD CON should run 24/7 when the weather is cold.

If it doesn't the boiler could be oversized or the controls may need adjustment.

hot_rod

The boiler has a 15-1 turndown, down to 10,000.

Also you can limit its SH firing down to 20% so it should not be oversized. Essentially you can make that a 27,000 BTU/hr boiler.

On the coldest day, set the SH down as low as it can go and maintain the temperatures you desire in all zones.,

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Hot_water_fan

Long run times with low return temps. Please don’t spend too much time sitting in front of it

EdTheHeaterMan

I can guarantee you that there are no professional HVAC or Plumbers that have sat in front of a boiler on the coldest day of the winter and record the temperatures and the cycles, so that they can set it for the most efficient operation. They are all too busy that day and night solving no heat calls for their customers.

That said, what do you expect to accomplish with this exercise?

DCContrarian

With a modulating boiler I'd be more interested in what it's doing when it's 45F out.

newinnj

Thanks for the inputs. My concern is that if the boiler is short cycling. A common theme on a lot of posts other than mine is an oversized boiler because no heat calc was done. About five years ago I had the system installed without any heat calc. There were issues with the install and with this forum assistance the system is getting better. DC's point is also good to check when it's warm outside. The boiler on a cold day will circulate all the time and the burner will fire up literally for five seconds and stop and then 20 seconds later will fire up for five seconds and stop. I don't know if everyone will consider that short cycling or not. In any case with the boost option turned off and the water temp is staying within the max of wood floor the firing cycles now are longer. I am thinking that is an improvement. The default setting which Hot Rod mentioned was set at 100%. I just turned it down and the lowest it will go is 50%. At this time the circulators are always running and every 3 minutes the burner will fire up for about a minute. Tomorrow morning even a colder day about 15 fahrenheit.

newinnj

Disregard the default setting I mentioned. Wrong option. That was reset back to what it was. The setting hot rod mentioned is default at 30.

newinnj

hot_rod

some boilers also have an anti-cycling setting. After the boiler runs, a timer prevents it from firing again for the time you enter, 10 minutes for example.

But the burner on time is what it sounds like in your case? Look for plugged strainers that could be preventing adequate flow through the boiler.

JMWHVAC

Your boiler running for only a minute is not ideal. The space heating min capacity must be set as low as it goes. I would set the "Burner off differential" to 12* or more. Set the "low burning time" to approx 3 minutes. Set the Acceleration time to maybe 8. See what that does.

newinnj

Thanks. I have set most of the parameters and will report back.