Input wanted on first heating system

[Nathan901]

Florida plumber transplanted to New York. Working with general contractor now and doing plumbing install on new projects. Took my first swing at a heating system and am looking for input on what I have so far.

Be nice

 

[Dana]

The expansion tank does a lot more good if it's installed in close proximity to (preferably in a straight line with) the pumps.

What is the design heat load, and the individual zone loads?

What type, and how much radiation is there on each zone?

What is the boiler model number?

It seems unlikely that radiation on the individual zones is sufficient to avoid short cycling the thing into an early grave on zone calls, but maybe- to the math. The napkin-math version of what it takes lives here.

 

[Sponsor]

 

[Nathan901]

Heat loads and units were sized by local company. The boiler supplies two air handlers, a large basement of radiant heat, and one zone of baseboard.
Modulating unit, 105k btu.

 

[Dana]

Heat loads and units were sized by local company. The boiler supplies two air handlers, a large basement of radiant heat, and one zone of baseboard.
Modulating unit, 105k btu.

The local company may or may not have competently calculated the heat loads . Unless this is a very large (5000'+ ) or very leaky (little to no insulation, antique single pane windows), my suspicion is that it was not done correctly. A 105KBTU/hr boiler is ridiculously oversized for almost all houses in the US, but may have been sized for the (also oversized) air handlers.

The minimum modulated output is more important than the max. Without the model number I can't look it up, but what is the MINIMUM BTU-input (or output) of that boiler?

When it comes to serving micro zoned radiant (what type of radiant? how big is each radiant zone- radiation-wise?), it can short cycle on zone calls the boiler even with high-mass concrete or gypcrete radiant. But it becmes even more problematic when serving low-mass heat emitters such as baseboard.

A 105K-in modulating condensing boiler with a 5:1 turn down ratio can only throttle back to 21,000 BTU/hr-in, and at the ~120F average water temp needed to deliver 95% efficiency it can't drop below ~20,000 BTU/hr out. For a typical fin-tube baseboard zone to deliver the 20KBTU/hr without cycling the boiler on/off it would need more than 90' of baseboard. If it only has half that much baseboard on the zone it will short cycle pretty badly on that zone, and less than that becomes a short-cycling boiler & efficiency killing nightmare.

Very few modulating condensing boilers have sufficient internal thermal mass to suppress short cycling, and the system may need a high-mass buffer tank or thermally massive hydraulic separator to fix it.

 

[Fitter30]

Can't see where the expansion tank is piped but i agree with Dana it should be on the suction side of the boiler pump. What type of valve is that feeding the floor radiate heat. Baseboard and fan coils need a minimum 120* , radiate 5-10* over room temp. You have to be a ua plumber beautiful work.
Whats the galvanized pipe and valve header for?

 

[Nathan901]

The air handlers are pretty big because ceiling heights are nearly 20 feet in areas, multiple sliding doors and windows over 8 feet long. Almost a 5000 square foot home I believe.

The expansion tank was piped into the port of a tee under the air separator, with the regulator and back flow for make up water downstream. Being that i mounted the expansion tank to the ceiling, i put an isolation valve with bleeder to be able to purge and service the tank without interruption.
That’s a thermostatic mixing valve to feed the radiant floor manifolds.
Galvy manifold is for propane to feed fireplaces and a few other things.