Removed Baseboards Nozzle PSI Change to Accommodate - Sanity Check

GregBl

Hello,
We recently completed extensive remodeling that involved removing walls and major kitchen reconfiguration. In the process we removed approximately 12ft of baseboards and one under counter heater (HideAvector HAV-48 - only one speed I assume was high). My understanding is that each ft of baseboard accounts for ~500BTU/hr and @ 170F inlet temp, the HAV-48 would be ~ 4500/BTU/hr. So a total heat load reduction of about 10,500 btu/hr.

Problem is that the burn cycle seem short (~3 minutes once boiler stabilizes and there is still a demand for heat). Notice this mainly in the morning when 1st floor is demanding heat after being turned down over night. Also, more noticeable when outside temps are warmer.

Burner is running a 0.85 nozzle (80A) with oil pressure @ 140psi. Just considering oil psi (and assuming a constant efficiency of 100% (I know this isn't possible - however, I'm just looking at the relative change for different psi settings and assuming the real efficiency will be constant), a 0.85 nozzle @ 140 psi produces 141,400 BTU/hr. Since I have a reduction of heat load of 10,500 BTU/hr then should I reduce the pressure to 125psi (133,000 btu/hr - a reduction of 8400 BTU/hr)? My thinking is that I shouldn't go much lower to account for times when every zone (I have 5 total) are calling for heat or outside temperatures are lower.

Other than the cycle time, system is running well (cleaned, filters changed, nozzle changed and combustion tuned to specification every year).

So, first, is my logic correct and should I change the psi? Should I wait and check heat cycles when there is more demand on the system (e.g., colder temps)? Should I just not worry about it and move on?

Thanks!

P.S. Please, no snarky comments.

STEVEusaPA

You're boiler is short cycling because it's oversized, and the multi zones aren't helping.
I wouldn't lower the nozzle pressure. Higher is better for atomization and combustion.
If you were to lower the psi, change the nozzle, it would require a full combustion test when you are done to adjust draft, smoke, excess air, etc.
Just dropping the nozzle size (there are plenty of threads on this site) may make your boiler less efficient.
Boiler is sized to the heat loss of the house, not the radiation, although you can consider it in different scenarios.

The only way to correct this is a properly sized boiler and buffer tank. Anything else is only a band aid, and will help, if at all, only a little-might even hurt.
If you go with a buffer you can also take advantage of ODR.

GregBl

Thanks, Steve!

EBEBRATT-Ed

@GregBl , why not put some radiation back in and leave the nozzle alone? Your heat loss for the house didn't change but you took out 10,000btu worth of heat.

That's a pretty big chunk. How will it heat in cold weather?

GregBl

@EBEBRATT-Ed , we removed walls and opened up the living space. In addition, one outside wall (to the garage) that had a register, is now covered with cabinets (floor to ceiling). In addition, upper cabinets on the outside wall now go to the ceiling. Regarding cold winters, I live in NE and have not had any issues heating the new space. As a matter of fact, the temperature is more constant when moving around the first floor!

HVACNUT

What's the models of the boiler and burner?
Do you know the heat loss of the home?
Do you have an indirect water heater?
You might be able to put in a nozzle to match the heat loss and pipe in a boiler bypass to prevent condensing.
Like @STEVEusaPA said, any changes to the burner needs a combustion analysis and smoke test.

GregBl

@HVACNUT , boiler is a Peerless WB-3 cira 1992 (yr house was built); burner is a Beckett AFG, heating is via FHW.
No, I don't know heat loss; however, I'm going to do the calculations. Will be good to understand this.
Yes, it is indirect with a 30 gal heater in parallel with an 80 gal storage tank.
Tuning the system after a nozzle change is not a problem.

HVACNUT

@GregBl, why do need 110 gallons of DHW on hand?

GregBl

@HVACNUT - The previous owner had this installed. My assumption is that it was added when a jetted tub was added.