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Relay Switch & Contactor FAQs
Q&A on clicking chattering relay switches in Air Conditioners, Heat Pumps, Water Pumps, & other controls
- POST a QUESTION or COMMENT about contactor switch or relay switch noises in mechanical systems used in buildings or building air conditioners, heat pumps, water pumps or other equipment
Control relay switch chattering noise diagnosis and repair Q&A.
This article series discusses control relay switch chattering or rapid, repeated clicking noises, their cause, meaning, and repair. Relay switches are widely used to control equipment found in or on buildings including air conditioning system or heat pump compressor/condenser unit compressor motors, fans, and in an air handler the blower fan used in forced air heating and air conditioning systems.
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Clicking or chattering electrical relay switch FAQs
These questions and answers about clicking or chattering electrical control relays were posted originally at RELAY CONTROL SWITCHES - be sure to see the diagnosis and repair advice given there.
On 2018-05-07 by (mod) - every 30 seconds it tries to turn on
Sounds like excessive head pressure, maybe a stuck TEV
On 2018-05-07 by Compressor
I just installed a new compressor on a heat pump. The compressor was working fine then it stopped and won't turn on. About every 30 seconds it tries to turn on for a sec then nothing for 30 secs then tries again.
On 2018-01-10 by (mod) - A chattering relay is most likely failed or failing;
Mike
A chattering relay is most likely failed or failing; in an emergency a short term repair is, with power off, to try to clean the contacts but it's difficult. SOME techs can replace a relay; most replace the whole control.
This illustration https://inspectapedia.com/heat/Honeywell_R8182D_Internals.jpg shows the two relays in a typical aquastat, one for the burner and one for the circulator.
The L1 L2 are the power or LINE-IN terminals
The C1 C2 are the wires that control the circulator
Those are shown in the lower right of the illustration found at this article:
That image is discussed at https://inspectapedia.com/heat/Aquastats.php our article on AQUASTAT CONTROLS
That article includes links to PDF files that describe the installation and use of the aquastat.
Bottom line: you probably need a new relay or a new control.
On 2018-01-10 by Mike C - circulator relay trouble in Minnesota
@Paul,
I've got the same issue up here in northern Minnesota. So, I'm waiting for a response too. What image of the control system are you referring to in regard to the L1 L2 line and C1 C2 control?
On 2018-01-04 by Paul
I have a hot water boiler for radiators and the circulator pump only runs when the burner is on. I want to be able to manually over-ride the contactor/relay with an external switch to have the ciruclator run continuously during very cold outside temps. Can I simply add a typical single-pole light switch between the L1 L2 line in and the C1 C2 circulator control? If not, how else to do this?
On 2017-12-03 by (mod) - replace wet relays
FOR safety turn off electrical power to the pump, then ask your electrician to replace the wet switch. And of coirse, fix the leak.
On 2017-12-03 by Ronald Williams
My water pump leaked for along time where the pressure gauge is and then my water pressure just stopped period no water at all. I'm getting power but no water, wires are everywhere relay switch isn't connecting to turn pump on ethier. HELP.
On 2017-11-30 by (mod) -
Katherine, also see our discussion of clicking relays in the page bottom COMMENTS about clicking aquastats at AQUASTAT CONTROLS inspectapedia.com/heat/Aquastats.php
On 2017-11-26 by (mod) - when the air turns on I hear a continuous non stop clicking sound
That's doesn't sound normal to me. I would ask for an investigation in repair by the service technician
On 2017-11-12 by Katherine
An air conditioner repair man replaced the relay switch for a 24 VAC coil in the heating unit. Now whenever the air turns on I hear a continuous non stop clicking sound from the part. Is this normal or does it need to be fixed?
Thanks.
On 2017-01-29 by John - water pump won't come on
I installed new well pump pressure control switch. Yet now, when I turn off power, at circuit box, to well pump (to leave for periods of three weeks at a time) the pump will not come on upon my return and switching breaker "on". I have to crawl under house to flip lever on the new pressure control switch to "jump start" the well pump. I did not have to do this before installing new pump switch. What can I do to fix this?
On 2017-01-28 by Evaporator coil in air handler makes high speed chattering noise
Evaporator coil was installed in residential heat pump system 12/2015 and 12/2016 it began making high speed chattering noise. Tech cannot find the cause. Installed new thermostat, checked for foreign body in system which may cause valve to not close but none found,
Where do I find solution, only makes noise when system is set to heat cycle.
...
Continue reading at RELAY CONTROL SWITCHES - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see these
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- CAR / TRUCK AC PRESSURE SWITCH
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- CAUSES of CONTACTOR / RELAY CHATTER
- CONTACTOR REPAIR, CLEANING POINTS - temporary repair success
- AIR CONDITIONER / HEAT PUMP RELAY SWITCH CONTACTOR CHATTERING
- HEAT or ELECTRIC HEAT CONTACTOR SWITCH CHATTER
- WATER PUMP CONTROL SWITCH CHATTERING
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- WATER PUMP PRESSURE CONTROL SWITCH
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Citations & References
In addition to any citations in the article above, a full list is available on request.
- "Solid State Relays Common Precautions" [PDF], Omron Management Center of America
2895 Greenspoint Parkway, Suite 100, Hoffman Estates, IL 60169
TEL: 1-224-520-7650 FAX: 1-224-520-7680,
OMRON Electronics LLC (Omron Automation - Americas) 2895 Greenspoint Parkway, Suite 200, Hoffman Estates, IL 60169 TEL: 1-847-843-7900 FAX: 1-847-843-8568/7787
Omron Corporation has offices world wide, retrieved 2016/.08/03, original source: https://www.omron.com/ecb/products/pdf/precautions_ssr.pdf - Barrett, P. G., and P. A. Collins. "Troubleshooting low voltage controls." In Pulp and Paper Industry Technical Conference, 1992., Conference Record of 1992 Annual, pp. 103-107. IEEE, 1992.
Abstract:
Control components are a vital aspect of any industrial process. It is argued that costly shutdowns can be minimized or eliminated through a complete understanding of the control devices along with a conscientious maintenance program and troubleshooting procedure. The electromechanical design of various types of starters, contactors, and overload relays are analyzed in terms of operation, application maintenance and troubleshooting. Specific suggestions for troubleshooting procedures are offered for various problem scenarios. - Carfagno, S. P., and G. Erich Heberlein. "A Study of the Effect of Aging on the Operation of Switching Devices." IEEE Transactions on Power Apparatus and Systems 6 (1980): 2272-2280.
Abstract:
An experimental study was conducted to determine whether equipment aging affects the vulnerability of electric switching devices to malfunction caused by vibratory stresses in the range of seismic frequencies and acceleration amplitudes. The study included a vibration test before and after a program of accelerated aging designed to simulate forty years of service in areas outside the containment of a nuclear power generating station. Gamma irradiation, thermal aging, electrical/mechanical cycling and simulation of operating basis earth- quakes were included in the program of accelerated aging. Malfunction was defined as spurious opening or closing of contacts for times in excess of 1 ms during the vibration tests. - Elphick, Sean, Vic Smith, Vic Gosbell, Gerrard Drury, and Sarath Perera. "Voltage sag susceptibility of 230 V equipment." IET Generation, Transmission & Distribution 7, no. 6 (2013): 576-583.
- Feldbauer, B. "The design of contactors with regard to their industrial application." Electrical Engineers-Part II: Power Engineering, Journal of the Institution of 95, no. 46 (1948): 439-448.
Abstract:
Modern contactor design is reviewed and reference is made to the influence which various applications of contactor type control gear have had on design and development. After a general survey the special considerations appertaining to motor-control duty are examined in detail, having due regard to the extreme cases which frequently occur in practice. Arc control and contact developments are mentioned, and a short discussion of the oil-immersed contactor follows with particular reference to its use in chemical plants and for high voltage. Some special contactor designs are discussed, as well as the problems arising in connection with the control of electric furnaces. A short summary of the desirable features of contactor auxiliary switches concludes the paper. - Haines, Roger W., and Douglas C. Hittle. "Electric and Electronic Control Devices." In Control Systems for Heating, Ventilating, and Air Conditioning, pp. 42-67. Springer US, 1993.
- Herman, Stephen. Electric motor control. Cengage Learning, 2014.
- Knights, D. S. "Relays & Contacts." In Component Reliability, pp. 45-56. Macmillan Education UK, 1971.
- Kreveld, Phil. "Relays and Contractors: From Little Things Big Things Grow." Electrical Connection Winter Quarter 2008 (2008): 28.
- Lee, Yim-Shu, Hon-Chee So, and Martin HL Chow. "Design of AC voltage sag compensators." In Power Electronics and Motion Control Conference, 2009. IPEMC'09. IEEE 6th International, pp. 2587-2590. IEEE, 2009.
Abstract:
AC operated electronic equipment are vulnerable to momentary losses of AC voltage, which are known as voltage sags. Voltage sags are commonly caused by lightning, accidental short circuit, loose connection, starting of large motors (or air-conditioners) or abnormal use of the AC mains. In sensitive and critical applications, such as semiconductor material processing and medical operation, voltage sags may result in serious problems. In order to tackle this problem, the Semiconductor Equipment and Materials International (SEMI) defined, in 1996, a voltage sag immunity standard, known as SEMI F47-0200, for semiconductor processing equipment manufacturers to conform to. Equipment compliant to this standard must have the specified immunity characteristics against voltage sags without the use of batteries. Based on the experience learned, the standard was redefined, in 2006, as SEMI F47-0706. It is expected that new semiconductor processing equipment will be designed to be compliant to the new standard. It is also likely that the SEMI F47-0706 requirement will be extended to other application areas. This paper describes the design of voltage sag compensators which can be operated in conjunction with a piece of equipment for SEMI F47 compliance. The voltage sag compensators described can provide sine-wave AC backup power to enable electronic equipment to meet the SEMI F47-0706 standard and to tolerate 100% momentary loss of AC mains voltage. - National Electrical Code (NEC) for the U.S., Article 430 Air Conditioning and Refrigerating Equipment
- National Electrical Code (NEC) for the U.S., Article 440 Air Conditioning and Refrigerating Equipment
- Roberts, HC, BG Liptak, and WP Durden. "5.9 Relays." [PDF] (2006).
- Taylor, Carson W. "Concepts of undervoltage load shedding for voltage stability." IEEE Transactions on Power Delivery 7, no. 2 (1992): 480-488.
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- In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
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- Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
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