1961 KEWANEE BOILER CONTROL UPGRADE

JUGHNE

Ideas are welcome for updating controls on school house heating system.

The owners need a budget plan for improving efficiency of this hot water system:

1961 Kewanee 3R6FO, output rated at 792 MBH (23.6 HP) converted from oil to

Adams Speedflame NG power burner--HP 800 (800,000 to 300,000 BTUH)

NG meter clocked @ 514,285 BTUH input. Combustion test shows 313.2 temp. stack--6% oxygen--2 ppm CO--3ppm CO air free--85.2 % Eff.gross-35.8% excess air --8.35% CO2--86.7* amb temp.  (Testo 320 is a new toy for me, so does this sound to be possibly correct)

Boiler stays hot for entire heating season (manual shut-off). Honeywell reset control installed. (quite old).

Pump pushes thru boiler; is B&G PDI 121 1/2 HP 6.5 amps 120VAC.

Pumping control is outdoor T-stat-- off at approx 60* . There are 2 pumps with flow switch to start back up pump in case of # 1 failure. (pumps do not alternate) 

 There is a B&G FAS 2" flow control installed for each pump.

Emitters consists of commercial baseboard running nearly the entire length of the building  (north/south sides) with a Nesbitt Syncretizer (fan coil) installed in each classroom.  There are 10 convector units for hall & RR etc. use.

There is a pneumatic control system consisting of 6 Powers day/night T-stats.(Most work fairly well) .  Also is a manual master "day/night" switch in the boiler room.  

Building is 137' X 70' = 9,590 sq feet on slab, no bsmt or attic.  1961 insulation is minimal.  Masonry walls thru out.  Only 1 classroom is in use daily M-F.  The entire building is in use only on Wednesday.  The master night/day control is set to night except for Wed.  The M-F classroom sets its T-stat to "day" as needed.

Issues:

1.  Need boiler temp control that will maintain return water temp to avoid condensation. (A 1 1/4" manual by-pass was installed to maintain return temp and avoid high head on the pump, some automatic control would be good. )

2. Most balancing valves are throttled down to slow flow.  On "day" mode the fan coil valves open and there is more flow needed for Wednesday.----Is this a place for ECM pumping?  Pump must maintain some water flow thru out all emitters to avoid freezing.

3. Power burner orifice can be down sized as I have not noticed constant operation on coldest days. (checked daily).

Thanks for any direction provided !!

SWEI

Questions

Can the burner be modulated or fired two stage?



New controls (Tekmar, Heat-Timer, or DDC) and ECM pumps would make a huge difference.



I assume the baseboard is parallel piped - are the fan coils piped off the same supply/return lines or is there a separate loop for those?  Two reset curves might be helpful.

JUGHNE

Answers for SWEI

Thanks for quick response;

Burner is on/off; pretty basic burner.

Fan coils piped parallel with all else, but water flow thru fan coils & motors controlled by day/nite system.

Thanks again.

tim smith

Re: upgrades etc

You might want to check on their annual useage for entire bldg and see if there is any energy efficiency grant money available from your utility. You might be able to make a case for a new High efficiency condensing boiler, maybe a Triangle Tube PT399 or Lochinvar WHN399 if that will meet the building load which I think it is very close to being able to. I usually see a 25% reduction in fuel bills when going from older firetube boiler to condensing. Just a thought? You could probably leave old boiler in place for now to keep cost down to help justify the change out.