Observations: Balancing Orifices and Tekmar 279 Control

Dave in QCA

OK, I don't have a data logger or other electronic gadgetry, but I thought that my observations of the my system operation, now that the weather has actually gotten cold, would be of interest.  For reference, a previous long and continuing thread on progress made with my system is at <a href="http://www.heatinghelp.com/forum-thread/131216/The-Best-Heating-System">http://www.heatinghelp.com/forum-thread/131216/The-Best-Heating-System</a>

Also, I would like to note that I do not have the tools and/or the ingenuity necessary to produce my own orifices.  I purchased cup orifices that were stamped out of sheet copper and pre-drilled according to me radiation needs.  I obtained the orifices from Tunstall, Inc. and I found them to be very good to work with, prices reasonable, and very quick to turn around some additional orifices when I accidentally mangled a few during installation.



Observations of system operation were taken at 10:00 AM on January 3.  Overnight temperatures had dropped to 10F, the coldest day we have had this season, which has been a remarkably mild one.  When I started the observations, the Outdoor temp was 20F

System had finished a steam cycle about 45 minutes prior to the beginning of this cycle.  Room Target Temp = 71F.  Cycle length 60 minutes. 

At start of cycle,  1st floor South = 72F

                          1st floor North = 71F

                          3rd floor = 71

Note: sun was shining and the south unit has a very large wall of windows that shine in on a floor finished with dark brown Mexican style floor tiles, which normally produces a good solar gain.

0:00 minutes:seconds      boiler starts, Tekmar indicates 26% cycle

2:50                                boiler begins to steam

5:00                                1 oz pressure showing at boiler

6:20                                steam reaches end of main, heating cycle begins

8:07                                2 oz pressure

9:20                                4 oz pressure

11:00                              6 oz pressure

14:14                              8 oz pressure

14:50                              cond pump cycles, pressure drops to 6 oz

17:10                              8 oz pressure

18:20                              8.5 oz pressure

18:28                              cond pump cycles, pressure drops to 6 oz

20:30                              8 oz pressure

21:42                              cond pump cycles, pressure drops to 6 oz

21:56                              boiler shuts off

TOTAL length of steam cycle, 15.5 minutes which = 26% cycle



End of Cycle Room Sensor Temps

1st floor south, 73F  (solar gain)

1st floor north,  71F

3rd floor,          71F



Orifices allow steam to arrive at each radiator at the same time.  Orifices meter the flow of steam into each radiator. 

Total Connected EDR = 1383

Figuring 0 for pickup factor (because of orifices) and 10% for piping losses, and using 225 BTU/sq ft for as the calc for radiation (because 240 BTU/sq ft is based on 2 psi, which carries a higher temperature),  I would need a firing rate of 423,000 BTU input on an 82% efficient boiler to provide the steam required to come up to a supply pressure of 8 oz in the mains.   My present boiler is firing at 525,000 BTU input which brings the mains up to 8 oz  and remains in equilibrium.   This boiler is rated at 1,050,000 BTU input, and I realize that this amount of down-fire on this boiler is very inefficient.  According to the calculations, I may be losing another 100,000 BTU due to ineffiency of the boiler firing at a low rate,  but the setup is heating the building better than ever before, and cost when accounting for difference in heating degree days, is actually lower as well.  Future plans to change out the 36 year old Pennco Atmospheric and install a power-burner type wet base boiler, properly sized for the load should bring great savings.  I am guessing at a five year payback, but more urgent projects are currently consuming all income from the property.



Next projects are to Remove all main venting.  (Dave pauses until the sounds of astonished gasps and muttering at the back of the room quiets down.)             I plan on replacing the main venting with Mepco 1E traps piped as crossovers.  Given the temperature of the air in the mains at the beginning of the cycle, which is warm enough to interfere with the proper operation of my Gortons, I have experimented and found that 1 Mepco 1E will actually provide much fast venting.  In addition, I will remove the condensate pump and re-pipe the returns and create gravity return and also one central point of venting on the return piping.   I will fit the vent with a swing check, (to enable vacuum) and no other vent device. (This is one of the setups shown for the Dunham systems)  All traps are working and are being maintained so I don't have to worry about steam blowing into the boiler room.  The vaporstat at 10 oz prevents the backing up of condensate in the returns.  I will also reconnect the dunham equalizer line that runs between the steam main and the return piping, with a swing check that allows one way flow from the return to the main.  This will allow the strong vacuum that is formed in the mains to be transferred to the return piping which assists the condensate in flowing back to the boiler. 

When I get to this point, I plan to experiment with vacuum operation and I will report my observations at that time.



Happy Steaming in the New Year!

gerry gill

Cool!

Sounds like a great system! and i love the tweaking your doing! especially the orifice report. Great job!!