ASHRAE Journal - September 2009 - 48

We noticed significant burner runtime, making up standby losses, which was especially irritating when we had much higher solar tank preheat temperatures. We added control to the domestic water heater burners to shut them down (but with automatic restart if the tank temperature dropped too low) whenever the solar tank temperatures were significantly higher, saving a lot of gas. Because we had 160 gallons (606 L) of additional solar preheat storage capacity, we had the maintenance staff valve-off and operate only one domestic water heater at a time, which further cut the standby losses. Fine-Tuning the System After we corrected the problem with the solar pump running too long, our flow meter, which clocked one pulse per gallon, showed a thermosyphon, which caused additional reradiation of already stored energy. We suspected the solar loop check valve was stuck open (Figure 3). A new Figure 4: Piping for the tank transfer pump from the project Web site. valve was installed and the problem immediately D5 Solar 710B/D5 Solar 720B disappeared. The Btu logs showed that we had 10 been losing up to 20% of the Btus collected each 9 day before we stopped the PV pump extra runtime and the thermosyphon. 8 After the overheat dump valve was installed, 7 we never worried again about overheating on low usage days because hot water was automatically 6 dumped to prevent reaching 180°F (82°C) storage 5 tank temperature. The most effective sequence was running the dump valve for several minutes 4 any time the tank temperature hit 170°F (77°C) 3 before 4 p.m., dumping about an hour’s worth of collection. We found we could move the time to 2 about 3:30 p.m., which saved water, because the 1 remaining solar collection time didn’t allow the 0 tanks to reach 180°F (82°C). We originally con0 1 2 3 4 5 6 7 sidered stopping the pump when the tank reached gpm 180°F (82°C) but decided it was a bad idea for our system as the collectors would boil and lose glycol, Figure 5: Pump curve for dc solar pump. shutting the system down until it was recharged. After observing that almost 100 gallons (379 L) of hot water since the tank transfer pump was installed last fall. The pump were dumped each weekend in September to prevent overheat- has run for several hours each weekend during the hottest part ing, we experimented by adding a pump to transfer the solar of this summer. heated preheat tank water into the gas domestic water heaters, When we changed solar tanks and added glycol, the solar loop pushing the lower temperature domestic hot-water heater water dropped from 2 gpm (0.13 L/s) on city water to 1.6 gpm (0.10 into the preheat tanks, allowing several more hours of solar col- L/s) on glycol, which proved to be a problem. Several weeks lection in the afternoon (Figure 4). When we started the pump, later the collector temperature was more than 240°F (116°C), we found we also needed to add an external check valve as the there was no flow, and we suspected the glycol was boiling. We donated pump did not have one built in. Our sophisticated con- rushed to the project, found steam coming out of the collector trol logic was not necessary because all we needed was to run output automatic vent, and covered the collectors with a tarp the tank transfer pump for an hour after 2 p.m. in the afternoon, until we could correct the no-flow problem. whenever the pre-heat tank temperature exceeded 160°F (71°C). The glycol expansion tank pressure gauge had dropped to alWe never dumped hot water again on a weekend last fall. As most zero. We could not remove the pump for inspection because of Aug. 10, 2009, the emergency dump valve has not operated the isolation valves also included the expansion tank in the loop. 48 ASHRAE Journal Pump Head (ft) ashrae.org September 2009

ASHRAE Journal - September 2009

Table of Contents for the Digital Edition of ASHRAE Journal - September 2009

ASHRAE Journal - September 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
Getting to Net Zero
Feature Articles
How High Can You Go? Building Height and Net Zero
Lab for Learning
Solar Hot-Water Heating System: Lessons Learned
50th Anniversary—Low Pressure Steam Heating Systems
Building Sciences
Products
Emerging Technologies
People
Classified Advertising
Advertisers Index
ASHRAE Journal - September 2009 - ASHRAE Journal - September 2009
ASHRAE Journal - September 2009 - Cover2
ASHRAE Journal - September 2009 - 1
ASHRAE Journal - September 2009 - 2
ASHRAE Journal - September 2009 - Contents
ASHRAE Journal - September 2009 - 4
ASHRAE Journal - September 2009 - Commentary
ASHRAE Journal - September 2009 - Industry News
ASHRAE Journal - September 2009 - 7
ASHRAE Journal - September 2009 - 8
ASHRAE Journal - September 2009 - 9
ASHRAE Journal - September 2009 - Letters
ASHRAE Journal - September 2009 - 11
ASHRAE Journal - September 2009 - 12
ASHRAE Journal - September 2009 - 13
ASHRAE Journal - September 2009 - 14
ASHRAE Journal - September 2009 - 15
ASHRAE Journal - September 2009 - Meetings and Shows
ASHRAE Journal - September 2009 - 17
ASHRAE Journal - September 2009 - Feature Articles
ASHRAE Journal - September 2009 - 19
ASHRAE Journal - September 2009 - 20
ASHRAE Journal - September 2009 - 21
ASHRAE Journal - September 2009 - 22
ASHRAE Journal - September 2009 - 23
ASHRAE Journal - September 2009 - 24
ASHRAE Journal - September 2009 - 25
ASHRAE Journal - September 2009 - How High Can You Go? Building Height and Net Zero
ASHRAE Journal - September 2009 - 27
ASHRAE Journal - September 2009 - 28
ASHRAE Journal - September 2009 - 29
ASHRAE Journal - September 2009 - 30
ASHRAE Journal - September 2009 - 31
ASHRAE Journal - September 2009 - 32
ASHRAE Journal - September 2009 - 32a
ASHRAE Journal - September 2009 - 32b
ASHRAE Journal - September 2009 - 33
ASHRAE Journal - September 2009 - 34
ASHRAE Journal - September 2009 - 35
ASHRAE Journal - September 2009 - 36
ASHRAE Journal - September 2009 - 37
ASHRAE Journal - September 2009 - Lab for Learning
ASHRAE Journal - September 2009 - 39
ASHRAE Journal - September 2009 - 40
ASHRAE Journal - September 2009 - 41
ASHRAE Journal - September 2009 - 42
ASHRAE Journal - September 2009 - 43
ASHRAE Journal - September 2009 - Solar Hot-Water Heating System: Lessons Learned
ASHRAE Journal - September 2009 - 45
ASHRAE Journal - September 2009 - 46
ASHRAE Journal - September 2009 - 47
ASHRAE Journal - September 2009 - 48
ASHRAE Journal - September 2009 - 49
ASHRAE Journal - September 2009 - 50
ASHRAE Journal - September 2009 - 51
ASHRAE Journal - September 2009 - 52
ASHRAE Journal - September 2009 - 53
ASHRAE Journal - September 2009 - 50th Anniversary—Low Pressure Steam Heating Systems
ASHRAE Journal - September 2009 - 55
ASHRAE Journal - September 2009 - 56
ASHRAE Journal - September 2009 - 57
ASHRAE Journal - September 2009 - 58
ASHRAE Journal - September 2009 - 59
ASHRAE Journal - September 2009 - 60
ASHRAE Journal - September 2009 - 61
ASHRAE Journal - September 2009 - 62
ASHRAE Journal - September 2009 - 63
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ASHRAE Journal - September 2009 - 66
ASHRAE Journal - September 2009 - 67
ASHRAE Journal - September 2009 - 68
ASHRAE Journal - September 2009 - 69
ASHRAE Journal - September 2009 - 70
ASHRAE Journal - September 2009 - 71
ASHRAE Journal - September 2009 - Building Sciences
ASHRAE Journal - September 2009 - 73
ASHRAE Journal - September 2009 - 74
ASHRAE Journal - September 2009 - 75
ASHRAE Journal - September 2009 - 76
ASHRAE Journal - September 2009 - 77
ASHRAE Journal - September 2009 - 78
ASHRAE Journal - September 2009 - 79
ASHRAE Journal - September 2009 - 80
ASHRAE Journal - September 2009 - 81
ASHRAE Journal - September 2009 - Products
ASHRAE Journal - September 2009 - 83
ASHRAE Journal - September 2009 - Emerging Technologies
ASHRAE Journal - September 2009 - 85
ASHRAE Journal - September 2009 - 86
ASHRAE Journal - September 2009 - 87
ASHRAE Journal - September 2009 - 88
ASHRAE Journal - September 2009 - 89
ASHRAE Journal - September 2009 - People
ASHRAE Journal - September 2009 - 91
ASHRAE Journal - September 2009 - 92
ASHRAE Journal - September 2009 - Classified Advertising
ASHRAE Journal - September 2009 - 94
ASHRAE Journal - September 2009 - 95
ASHRAE Journal - September 2009 - Advertisers Index
ASHRAE Journal - September 2009 - Cover3
ASHRAE Journal - September 2009 - Cover4
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