Piping options for new boiler.. advice needed

super_snop

Hello all. Over this winter I’m figuring out a plan for a new boiler setup for my home. I will do the upgrade over the summer time so I’m not rushed. I’m leaning towards a Buderus G115 3 pass with a Riello burner. I currently have 2 zones of 3/4 copper fin tube (1st, 2nd floor), and do not need DHW. I plan to pipe my new system with 1 circulator and the taco zone sentry valves. Obviously with my new setup I’m hoping to save oil. My current boiler is way oversized and short cycles like crazy.  I spoke to a few guys I know in the industry and nobody agrees on how to set up the piping. I would like to utilize an outdoor reset but I worry about flue gas condensation. One guy I know says don’t worry about it because its a low water mass system, the other guy says pipe it primary/secondary. I’m so confused. Any opinions or guidance would be greatly appreciated. 

hot_rod

We need to know the heat load number. Did anyone do that calculation?

HVACNUT

Can't go wrong with P/S piping. 
Buderus claims you can't shock the block by having an 1-1/4" supply, 1" return, and some kind of elastic infused in the cast iron. 
You can also set up the boiler circulator to hold off until it reaches a minimum temperature (not sure but I think the Hydrostat 3250 Plus is offered, or are you getting the R2107?) and have the system circulators run as long as there's a demand, no matter what the boiler temperature is. 
.70 GPH firing rate in the 3 section, and at 8.7 gallons, it's not exactly low mass. I wouldn't frett none about condensing the flue gases... but how's the chimney? Need a stainless liner?
Buderus specs -.02 breach. Do you have the instruments to test and commission the boiler and burner?
How are you making DHW now?

EBEBRATT-Ed

@super_snop

Because I am old and conservative and don't like cracked boilers I would pipe every boiler with primary secondary. I just think boilers are happy and last longer with the correct flow going through them at all times.

Now if your secondary flow is less that the boiler flow the boiler will be protected. If the secondary flow is larger than the boiler flow you could put in a diverting valve to let the boiler warm up.

I don't care for the aquastat cycling the pump

super_snop

hot_rod said:

We need to know the heat load number. Did anyone do that calculation?

I haven’t gotten around to doing it yet. I planned to use the slant fin app to do the calculation. Kind of in a weird stage with this house. Bottom floor is 80% renovated. Everything new (windows, doors, insulation). Needless to say its a work in progress 😂. My current setup is an old thermodynamics S125, running a 1.0 nozzle

super_snop

hot_rod said:

We need to know the heat load number. Did anyone do that calculation?

I haven’t gotten around to doing it yet. I planned to use the slant fin app to do the calculation. Kind of in a weird stage with this house. Bottom floor is 80% renovated. Everything new (windows, doors, insulation). Needless to say its a work in progress 😂. My current setup is an old thermodynamics S125, running 

super_snop

HVACNUT said:

Can't go wrong with P/S piping. 
Buderus claims you can't shock the block by having an 1-1/4" supply, 1" return, and some kind of elastic infused in the cast iron. 
You can also set up the boiler circulator to hold off until it reaches a minimum temperature (not sure but I think the Hydrostat 3250 Plus is offered, or are you getting the R2107?) and have the system circulators run as long as there's a demand, no matter what the boiler temperature is. 
.70 GPH firing rate in the 3 section, and at 8.7 gallons, it's not exactly low mass. I wouldn't frett none about condensing the flue gases... but how's the chimney? Need a stainless liner?
Buderus specs -.02 breach. Do you have the instruments to test and commission the boiler and burner?
How are you making DHW now?

I have a 3250 plus now on my current boiler. If you use it to cycle the circ you can hold off until the boiler hits 120 degrees. I have been very happy with the aquastat. My current setup uses separate circs and are currently controlled with an SR taco control. Even though I don’t make DHW with the boiler I still keep the boiler as a warm start maintaining some temperature throughout the winter. It is old and I don’t trust cold starting it. I’m currently making DHW with a 80 gallon hybrid heat pump water heater (best investment I ever made). The chimney is in good shape and already line to the top with a 6” stainless liner.   As far as commissioning the new boiler. I plan to install everything and have one of my buddies in the industry do the startup and combustion analysis.  I have been kicking around all this for a while. I have just gotten so manny different opinions. 

SuperTech

I vote go with primary secondary piping. Use the 3250 and skip the R2107. Can't go wrong with primary secondary piping as long as it's done correctly. There's a great book on the subject, Primary Secondary Pumping made easy by Dan Holohan. 

super_snop

SuperTech said:

I vote go with primary secondary piping. Use the 3250 and skip the R2107. Can't go wrong with primary secondary piping as long as it's done correctly. There's a great book on the subject, Primary Secondary Pumping made easy by Dan Holohan. 

I have read it as well as “pumping away”. Great books. I think I have made up my mind. P/S it is. 

HVACNUT

I wouldn't worry too much about the heat loss calculation, unless the 3 section undersized. You're not going to find many oil fired boilers in the U.S. with less than 95K input. You could always add emmiters. 

Correction. There are lower input boilers, like the Peerless WBV-3 with a Riello F3, but it's a pin boiler with minimal block insulation. 

hot_rod

An oversized cast boiler on a fin tube job? How many feet of fin tube?
Really no need for primary secondary, the manual shows direct pipe

p/s piping in itself does not provide return temperature protection and with that boiler on a system like yours I doubt return temperatures will be an issue. Are they with y the current boiler?

super_snop

hot_rod said:

An oversized cast boiler on a fin tube job? How many feet of fin tube?
Really no need for primary secondary, the manual shows direct pipe

p/s piping in itself does not provide return temperature protection and with that boiler on a system like yours I doubt return temperatures will be an issue. Are they with y the current boiler?

I will measure the fin tube and get back to you. My current boiler is rated at 149k btu IBR AND 130k btu net. From what I have seen this is oversized for my home. The boiler short cycles and will run for only a few minutes set at 180 hi limit with a 20 degree differential. Last year i did add the hydrolevel 3250. I currently run 180 high limit, 140 low limit, and use the thermal targeting feature (without ODR). Set up this way has saved me a bunch of oil over my previous no frills aquastat. I hate that I even have a low limit set but it was my choice to maintain some temperature because I’m terrified of flue gas condensation.  Overall my system is running well but I would love an upgrade if it would save me more oil. 

hot_rod

Nothing good comes from a boiler short cycling like that. Poor efficiencies, wear and tear on electro mechanical components... And mental toll it takes on the person listening to it. As @HVACNUT mentioned, the smallest possible oil fired may still be too much,

Certainly no need to put more boiler than the fin tube can move into the space.

Here is how I’d pipe it.

super_snop

hot_rod said:

Nothing good comes from a boiler short cycling like that. Poor efficiencies, wear and tear on electro mechanical components... And mental toll it takes on the person listening to it. As @HVACNUT mentioned, the smallest possible oil fired may still be too much, Certainly no need to put more boiler than the fin tube can move into the space. Here is how I’d pipe it.

Thanks for the input. Very helpful. I measured the fin tube. I have a total amount of 125 ft of fin tube plus one beacon morris k84 kickspace heater. I looked up the specs on the kickspace heater. I run it on low. Its rated for 7514 BTU at180 degrees at a 3GPM flow. 

super_snop

I should also add that 125 feet is just the fin tube element. I have many more feet of bare pipe running in the walls and unfinished basement. I assume that some type of loss from bare pipes in unfinished spaces. 

hot_rod

At 550 btu/ ft you have 68,000 plus the fan unit, call it 75,000 btu/ hr of heat emitter at AWT 170F. A 90,000 btu/ hr boiler would be as close as you can get, perhaps
A heat load calc would determine what is actually required. You may not need  to run 180 SWT.

super_snop

If I have a moment today I’m going to try and do the heat loss calc with the slant fin app. I see in your piping diagram you have a delta P circulator. How do they work?

hot_rod

A delta P circulator will increase or decrease flow rate as zone valves open and close.

super_snop

Dies a delta P pump need to get adjusted or does it have some type of sensors similar to a delta t pump? 

hot_rod

super_snop said:

Dies a delta P pump need to get adjusted or does it have some type of sensors similar to a delta t pump? 

The control logic is built into the pumps brain 
Set it to the pressure mode and is senses flow requirements. Some brands have Auto Adapt that learns the systems needs

super_snop

I took a look at the grundfos alpha II. Has a bunch of different settings. Any chance you might know how I would set up that pump? It has an auto adapt function but it states it is for two pipe systems. 

hot_rod

I think you have a two pipe system, unless you have a diverted tee, aka monoflo tee system?
If so start with Auto Adapt, it takes a few days or week to adjust to the system.
Or one of the constant differential modes.
It’s always good to know why or how to select and dialing any pump, especially the smart ones. Download Caleffi Idronics 16 for a good explanation of the how and whys.

super_snop

Perfect thanks!  Only place I have a monoflo tee is the return side of the kickspace heater. I’m looking forward to planning out my new system and installing it during the warmer months when time permits. As of tight now I think I will be purchasing a Buderus GG115 with a riello. I’m a little hesitant to go with the riello because I have never really worked on them. I only have some experience with the beckett AFG. You guys are super helpful and I really appreciate all the input. 

super_snop

Finally got around to calculating heat loss with the slant fin app. I was surprised to see heat loss calculated a 47,788 btu/hr. I used a 10 degree exterior design temperature with an interior design temp of 68. Does this sound correct for a 2 story 2100 square foot home located on Long Island? The house was built in 1987. Half the house has been renovated with new windows. 

DJD775

Sounds about right for where you live. I have 2500 square feet in RI and mine came out in the low 50's.

super_snop

Now im thinking of going with an even smaller boiler. Because I have approximately 75k btu worth of element does that mean that i shouldnt size the boiler smaller than 75k btu even though the heat loss calc came in right under 50k?

hot_rod

Isn’t the 74,000 the smallest offered in that brand and model?

super_snop

hot_rod said:

Isn’t the 74,000 the smallest offered in that brand and model?

Yes the G115WS3 is 74k btu/hr. The WS4 is a 95k.