ASHRAE Journal - September 2009 - 46

water heaters and tempering valve. This became apparent after we added control to the recirculating pump that had been running continuously before the solar water heating system was installed. We had to have the maintenance staff manually dump solar-heated water several times to prevent a potential hazardous situation. The installing contractor returned and re-piped the tempering valve and added a check valve, after which we were able to make the tempering valve function properly in its safety role. To prevent future problems, additional temperature sensors were added to monitor the hot-water system. We also added a solenoid valve, so the automation Photo 1: The (four) flat plate collectors with the solar pump PV panel. system could automatically dump hot water to prevent overheating on light usage days. The dc pump pushed about 2 gpm (0.13 L/s) of city water on peak solar days, or 0.5 gpm (0.03 L/s) per panel, falling within the collector manufacturer’s guidelines. However, this would probably not be adequate once glycol was added to the system. When the glycol heat exchanger tanks were installed, we ran the system on city water for a few days to discover any problems before we pumped in glycol. The tanks were piped reverse-return for the glycol and domestic water sides, but we discovered that one tank heated to 155°F (68°C) during the time that the other tank only heated to 125°F (52°C). We had the contractor re-pipe the glycol heat exchangers, counting every elbow and tee to make sure each tank heat exchanger was exactly Figure 1: Solar energy data on the project’s live data Web site (www.utahashraesolar.tzo.com). balanced. The next day the two tanks were tracking within 0.5°F (0.3°C). If we had been using a higher head and flow acpowered pump, we could have corrected the problem by balancing with an isolation valve. This was not possible with the lowhead and low-flow photovoltaic-powered dc pump that we were using. Controls and Live Monitoring The original control sequence called for differential control: starting and stopping the solar pump based on the collector output and tank temperatures. However, with PV powered pumping, we started with the much simpler approach of the PV panel powering the pump whenever the sun was shining, with load-matched Figure 2: Live solar collection hourly Btu data log from the project Web site. flow during the collection period. Because the automation system was calculating and logging collected in the storage tanks. The data logs showed the daily solar hot-water Btu production, we shortly discovered that the Btu count decreasing, while the collector output temperature pump operated for several hours beyond the 8 hour (±4 hours was lower than the input. of solar noon) thermal collection period. This resulted in the We had temperature sensors on the collector output, input, flat plate collectors reradiating energy that had already been and the tank, so we programmed the automation system to 46 ASHRAE Journal 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
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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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