Complaint Forensics Analysis of Four-Channel Data Recorder to Improve Complex Domestic Hot Water

Buildera company can measure and monitor through the multi-channel data logger UX120-014M of Onset company, and carry out scientific calculation and analysis, and get the reason of hot water supply that has troubled users for many years.

conclusion of issue

Energy-conscious homeowners complain about not having enough hot water for morning and evening showers, especially during the warmer months. However, at other times of the day, on cold winter days, there is plenty of hot water approaching scalding above 120ºF. Occupants set the thermostat to the energy-saving setting recommended by the manufacturer, which remains unchanged after installation. Flushing the hot Water Tank and buildup, failed to significantly increase the hot water temperature on first use.

Before forensic analysis, homeowners suspected water heaters, replacements, including parts and labor repairs. To solve this mystery, Buildera performed a non-invasive, scientific analysis of hot water systems and thermostats using a battery-operated hysteresis four-channel temperature logger. To assist contractors, homeowners and property maintenance personnel, inspectors, and challenging hot water problems, this application note details troubleshooting methods, practical tips, and solutions.

Key Facts

key facts

Hot water temperature is inconsistent, especially on first use in the morning or evening

Hot water is more common during the warm (summer) months, but usually hotter during the colder (winter) months

Sequential showers (within 30-120 minutes), with plenty of hot water in the second shower and not in the first shower

Each shower has separate hot and cold water valves instead of the newer pressure equalizing or temperature limited mixing valves

2,500 square foot home built in 1994

Insulation of walls, ceilings, floors, and hot water pipes in compliance with California Title-24 energy standards during construction

Hot water point usage includes sinks in three bathrooms, kitchen and laundry room

The heater is a 12 year 50 gallon natural gas tank heater with dual sacrificial anodes

In the utility closet on the first floor, an external combustion air went into a tank

At the time of evaluation, the water heater was approximately 9 years old

Robert SHAW model r110rtsp thermostat set to 120ºF operating temperature

The first shower of the hot water heater is about 15 feet (5 meters)

Water supply is 3/4" inlet and outlet

System includes insulated 1/2" copper loop wire back to bottom of water heater, while homeowner previously disabled to save energy

Gas Heated Water Principles-Practical Review

Despite the increasing North American practice of adopting electric water heaters, natural gas and storage electric water heaters are controlled for most single-family, light commercial vehicle and multi-unit dwellings. Ease of operation and more efficient design deliver energy factors (EF) between 0.60 and above 0.90. For clarity, this application note focuses on the center flue of a traditional storage gas water heater, although many safety principles, including scalding prevention, also fall under the electrical and effective gas models.

Figure 2 shows a typical gas water heater thermostat with analog motion and a continuously variable setting dial, from vacation mode to hot (some manufacturers label the high end very hot). Within this scale, temperatures vary from the lower 60-80ºF to the higher 150-160ºF. Box manufacturers, the EPA (Environmental Protection Agency), and many municipalities recommend setting a target of 120ºF for energy efficiency and burn relief. However, OSHA, American Society of Plumbing Engineers (ASPE), Legionella and professionals recommend at least 140º water to kill harmful bacteria [1-3].

To reduce accidental burns and control your monthly bills, the most energy-efficient homeowners put their water heaters on the recommended 120ºF setting. Figure 3 illustrates the thermostat setting versus time for scalding healthy adults. Note that infants, children, and the elderly have thin skin or slower reaction times and are therefore more susceptible to irreversible burns, even at moderate temperature increases. Owners and maintenance personnel need to pay special attention to burn prevention et al. For example, an adult exposed to 140ºF water will experience irreversible second or third degree burns for five seconds. Obviously, water this hot is extremely dangerous and can cause serious injury to the most resilient of adults let alone children, disabled or elderly.

Thermostat differential control output water temperature

Many homeowners and uninformed contractors reasonably assume that the thermostat setting is an accurate proxy for the output water temperature. While it is true that higher thermostat settings yield higher average temperatures, it makes more sense when the average temperature varies widely.

Thermal differentiation is also known as thermal stacking—yields the thermal top of the sink bottom [4]. Sometimes, the temperature difference can be as high as 15 to 30 degrees. For hot water use tanks, inlet supply pressure forces cold water to the bottom of the tank through internal conduits. This directs the cold water close to the very good heating efficiency of the heating element. The heat rises to the top with more active hot water (and thus more heat), while the cooler feeds the bottom. Frequent bursts of hot water require such a faucet to be turned on and off several times, or a washing machine cycling—cause a sequence of cold water intrudes, shocking the thermostat for a secondary heat cycle.

Since most thermostats measure the temperature at the bottom of the tank, at the top when the water is already at the target temperature, this extra circulation causes the hot water temperature to spike even above the 120ºF thermostat setting. In addition, ANSI standard z21.10.1-2013 allows for a ±10ºF variation in thermostat accuracy, with field engineers reporting a wider range [5]. In extreme cases, guaranteed thermal stacking allows as much as 30 degrees above the target temperature setting. Therefore, even at a nominal setting of 120ºF, the water heater is capable of producing hotter than expected. This variability subjects occupants to the risk of severe and unpredictable burns, even with a nominal 120ºF thermostat setting.

cold shower syndrome

The opposite can also happen, with thermostat hysteresis and alternate heat losses that yield water temperatures considerably cooler than expected. Unlike pressure furnaces, where the air temperature is still a few degrees from the target temperature setting, the water heater thermostat has a wide hysteresis between travel on/off points. This range is as wide as 20-30 degrees loss for rapid cycling and excessive energy loss. This means that although the thermostat setting reads 120ºF, the actual tank water temperature may drop to 90-100ºF after a few hours of non-use overnight when the temperature is at its lowest. The tank water temperature will continue to decay until a loss of backup causes the temperature to drop below the minimum temperature trip point, or until a sudden demand for hot water causes an intrusion of cold water, signaling a new heating cycle to the thermostat.

A typical comfort shower range is 105 – 110ºF. Due to heat loss between the water heater and the shower head, there is a typical 2-5 degree temperature loss along the pipe. Therefore, to enjoy a shower at 108ºF, the lowest acceptable temperature at the water heater outlet should be at least 110-113ºF, assuming no cold water is mixed. Given the above discussion, it stands to reason that even if the temperature is set to 120ºF, the actual water temperature in the shower head could be as low as 90-95ºF—well below the acceptable temperature for a shower. No wonder many consumers complain about taking cold showers, ending up with their tanks or thermostats being defective.

Data for Forensic Analysis with Multi-Channel Loggers

Despite homeowners' preference for faulty water heaters, Buildera approached this survey without the potential issue of bias. Instead, an unbiased scientific approach guides all measurements and documentation using multi-channel temperature loggers. While simple fixes can be made to raise the dial temperature to see what's going on, this confuses potential cause and effect, as well as increases accidental burns.

Perform a reference temperature measurement

当Buildera第一次测试水温用沉浸式热电偶(侥幸®80 pk-22或类似)在各种水龙头,热水温度测量在113 – 113ºF,后在预计范围内占加热器和水龙头之间的热损失。为了清除管道内的温水,水可以自由流动,直到温度稳定在最大值附近。这表明,当时的基线测量,生产足够的热水的热水器能够满足淋浴。然而,这样的测量不够了解水温变化的负载和一天中不同的需求,更特别,为什么清晨淋浴温度远低于最低可接受水平。

考虑温度数据记录

评估整体温度模式,Buildera部署了Extech®SDL200 4-Channel温度计在图4的多通道能力和可移动SD记忆卡,简化数据导出到一个苹果®MacBook Air®。测试进行了为期两天的时间在5月25 – 27日2013使用各种优化k型热电偶测量任务。Buildera 温度记录器渠道分配如下表所示:

然而,在初始设置和验证,意想不到的温度补偿出现在所有热电偶频道。事后调查发现,就像许多数据记录器和采集系统,SDL200容易受到地面循环在测量热电偶保税制度。这是由于每个测量节点之间的小电压补偿和非隔离输入放大器。真正的微分仪表输入放大器隔离所有其他渠道,包括地面,帮助减少信道干扰和噪音都。

为了说明这一点,k型热电偶的热灵敏度41µV /°C。因此,即使只有100µV电压抵消由于地面电流的差异在一个有限阻抗引起错误的数度温度测量显示。测量热电偶之间的电压差与安捷伦(Keysight)U1273A DMM,几乎所有的测量误差可以看到传感器电压差异相关。虽然热,冷水管道已经粘合在一起,安装一个额外的重测量铜焊线测量点之间略有减少阻抗和抵消错误,但并不足以证明一个很好的实践。

减少测量误差,Buildera 重新安装除了一个热电偶使用薄绝缘层的聚酰亚胺薄膜®聚酰亚胺胶带。这一步电隔离每个热电偶接地和等电位连接的影响。薄带层没有实质性影响的目标表面温度测量精度,并消除所有地面传感器之间的循环。尽管非接地热电偶,热响应时间通常是由于传感器的机械隔离和放缓其住房。

与电脑公司开始合作,随后Builderaβ测试,最终将未来的实地测量的生产版本开始®流浪汉®ux120 – 014 m四热电偶数据记录器(图5),改进了测量精度,以及大大延长电池寿命适合扩展温度研究持续数周或数月。不管记录器的选择,用户需要总是为接地回路测试错误和电隔离每个测量节点,如果必要的。

热水出口温度Measurement-T[热]

一个Buildera ThermaDur™k型管夹表面热电偶如图6所示安装在3/4“热水出水口铜管,大约1”的热水器。在热电偶管绝缘被安装和重新安装热水出口测量环境温度影响降到最低。由于高导热性和快速响应时间的铜管,外管壁温度近似实际的水温,与独立Buildera验证水温测量来自源。

冷水入口温度Measurement-T(冷)

同样,Buildera安装第二个热电偶在3/4“冷水进口铜,大约12”的热水器。被小心地避免安装排气烟道附近的热电偶,这可能严重腐败的温度读数。测量的基本原理冷水供应确认传入的温度是低足以引发足够的冷水侵入后恒温器。

烟道温度Measurement-T(烟道)

Buildera部署侥幸®80 pk-11 k型尼龙搭扣®热电偶在烟道气体方法测量外部烟道温度。热水器上的热电偶放置通风烟道出口上方大约6”。这对恒温器激活测量提供了一个一致的代理。发射后,几乎瞬间烟道表面温度增加,上升到220ºF左右。到达高跳变点,恒温器关闭煤气阀门。烟道温度急剧下降,提供一个可靠指标的恒温器关闸。进行低通滤波和阈值的数据之前的数学导数烟道温度温度变化提供非常准确的标记的一步。相邻峰值之间的时间延迟表示加热循环的持续时间,而随后转化成二进制开/关情节与时间。

环境空气温度Measurement-T(环境)

Buildera坚持k型珠热电偶到附近的墙来测量周围的空气,这是有用的了解壁面影响温控器操作。

测量结果的讨论

恒温器4 – 6次/天骑了20到60分钟时间周期

环境空气温度在储藏室不同从60º-71ºF

期后停用,如五小时以上,热水温度衰减大约3º97ºF /小时-2.6º-103ºF度处的最小阈值触发自动调温器在第二天早上使用

早上第一次使用时,淋浴温度在95º-101ºF范围,远低于可接受的最低标准

足够侵入的冷水后,温控器开启,引发加热循环之间的温度上升3º-0.8ºF /分钟,期间According to需求复苏

温度是逐渐上升,持续20到60分钟

给出一个典型的淋浴时间8 – 10分钟,没有足够的热量上升在第一次淋浴提供一个令人满意的温度

如图9所示,在这样的时候,当第二个主人早上淋浴,有充足的热水由于早些时候恒温器激活

期间收集的数据是5月底,当环境气温相对温暖

According to热力学定律,是环境空气温度低得多(大差空气和水箱温度),如在冬季,热水器将失去在夜间热量更快,从而触发了自动调温器在清晨,首先喷头表现为什么冬天早上淋浴前是矛盾的温度比沐浴在温暖个月。

解决方案

带着取证知识,补救措施更明显。一个解决方案提高了恒温器的温度,这样低的跳变点至少足够热舒适的淋浴。使用图8为指导建立新的阈值,增加10ºF恒温器设置到130ºF将提高最低热水输出107 – 113º层更适合淋浴的温度。的确,后增加恒温器高跳变点到130ºF,房主经验丰富舒适的淋浴,甚至在第一次使用。然而,这个解决方案也提出了烫伤的风险由于较高的整体温度和叠加效应。

此外,这也提高24小时内消耗更多的能量,在实践中,水热后只需要在早上或没有热水消费已经过去了几个小时。热也可以减少水箱生活由于更高的热膨胀,以及加速矿藏和规模。在滚烫的风险和更高的能源需求日益增加的情况下,这个解决方案只是一个临时解决洗冷水澡的困境。

循环泵的救援

如前所述,该系统还包括一个1/2 “再循环线,格兰富泵。老板之前停用再循环系统因担心过早铜管侵蚀,增量循环消耗的能源损失,电力运行泵。

来缓解这些担忧,循环泵提供了实用的方法来触发的恒温器对能源消耗的影响可以忽略不计。不温不火的水回流管靠近环境空气温度在一夜之间,震惊了恒温器加热循环。在编程泵计时器,恒温器被重置回120ºF。自动激活泵几分钟5:30我迫使回流管冷却器水恒温器,从而重新加热水。的时候第一个主人早上淋浴,热水供应已经达到其目标120ºF极限。这提供了充足的热水至少两个背靠背的淋浴。

进一步的改善

然而，在最初的设置和验证，意外的温度偏移量出现在所有的热电偶通道。随后的调查显示，像许多数据记录仪和数据采集系统，该sdl200易受接地回路时测量热电偶在保税制度。这是由于每个测量节点和非隔离输入放大器之间的小电压偏移。真正的差分仪器仪表输入放大器是从所有其他渠道，包括地面隔离，有助于尽可能地减少信道干扰和地面引起的噪音。

为了说明这一点，K型热电偶有热灵敏度41µV /°C.因此，即使只有100µV电压偏移由于接地电流差在一个有限的阻抗引起的误差在几度显示的温度测量。安捷伦测量热电偶的电压之间的差异（Keysight）u1273a DMM，几乎所有的测量误差可以接地传感器的电压之间的差异相关。虽然热水和冷水管道已经粘合在一起，安装了一个额外的重测点之间的铜连接线测量点之间的阻抗和偏移量略有减少，但不足以证明一个很好的实践。

为了减少测量误差，buildera重新安装所有但一个热电偶用薄的绝缘层®Kapton聚酰亚胺胶带。这一步从接地和键合的影响中分离出每个热电偶。薄带层没有重大影响的目标表面的温度测量精度，并消除了所有的接地回路之间的传感器。虽然没有接地的热电偶，它们的热响应时间通常是慢由于传感器和它的外壳的机械隔离。

Buildera thermadur thermocouple in collaboration with ONSET, buildera subsequently tested the final exchange of future field measurements to the ONSET® HOBO® UX20-014M four-thermocouple data logger (Fig. 5), improved measurement accuracy, and extended battery life Study suitable temperatures for weeks or months. Regardless of the logger chosen, the user needs to test each measurement node for ground loop errors and galvanic isolation if necessary.

Hot water outlet temperature measurement [hot]

A Buildera Thermadur™ Type K Tube Clamp Surface Thermocouple as shown in Figure 6 is installed about 3/4" copper pipe hot water outlet, about 1" from the top of the water heater. Pipe insulation was removed and reinstalled thermocouples were installed at the hot water outlet to reduce the effect of ambient temperature on the measurements. Due to the fast response time of the high thermal conductivity copper pipe, the temperature on the outer surface of the pipe approximates the actual water temperature, this buildera independent water temperature measurement comes from source verification.

Cooling water inlet temperature measurement [cold]

Likewise, buildera installed a second thermocouple on the 3/4" cold water copper inlet, about 12" from the top of the water heater. Take care to avoid installing thermocouples near the exhaust stack, which could adversely affect temperature readings. The rationale for measuring hot and cold water supply is to determine if the incoming temperature is low enough to trigger the thermostat after a sufficient cold water shock.

in conclusion

UX120-014M four-channel temperature Recorder

Through scientific methodology and analysis using a multi-channel temperature Recorder, Buildera solves the frustration of over-cold showers that have plagued homeowners for many years. An improved understanding of temperature distribution over time yields rational solutions that balance the opposing needs of hot showers and energy efficiency. Increase the thermostat setting about 10ºF to 130ºF to ensure enough hot water year round. Another option for activating existing circulation lines in the morning. During the analysis, attention was paid to reducing bacterial growth and preventing scalding at the point of use. Other observations and improvements included temperature compensation at the output of the water heater mixing valve, plus anti-scalding devices at the point of use.