Is it ok to use this tester for the 20a power outlet (not gfci)?

A Very good question, since the device name starts with GFCI. Answer is YES, because despite the name, the device is mainly a regular outlet tester, checking cross wiring, missing wiring, and reporting voltages, all worthwhile tests for non-GFCI outlet. Also works with 15amp & 30amp with adapter. Thanks for the question.

Most of the outlets in the basement where i'm living say >6.00 when i test them. are they wired wrong? is it safe to use the outlets?

It is not safe to use those outlets. If an outlet is good, the green light on the tester should illuminate, and the display should register a voltage close to 120 volts.

Is this accurate enough to measure with some confidence which is the most upstream receptacle in a circuit for choosing gfci location?

Resolution accuracy inadequate for that task. Displayed digits determines resolution. In this case, meter accuracy will not be and can not be better than +/- 1 volt because digital resolution is always +/- 1 in the least significant digit. Example: If measuring a true, standardised 120 volts, meter might display 119V (-1), 120V or 121V (+1) if calibrated/adjusted correctly. You've got the right idea, but this meter displays only 2-1/2 digits (120V). You will need a meter with 3-1/2 (120.0V) digits displayed. Worst case resolution at 120 volts will then be ~0.1V (100 mV). You need to see those millivolts differences. Get one with stated accuracy and preferably calibrated. Cheers!

What will happen if you press the gfci test on a non gfci? will it do nothing. or will it trip the breaker in the panel, and i have to flip the switch

The amber lights on the tester will blink, nothing will trip.

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Klein Tools RT250 GFCI Outlet Tester with LCD Display, Electric Voltage Tester for Standard 3-Wire 120V Electrical Receptacles,Green/Red

Klein Tools RT250 GFCI Outlet Tester with LCD Display, Electric Voltage Tester for Standard 3-Wire 120V Electrical Receptacles,Green/Red

Product ID: 557085750

Details

Brand
KLEIN TOOLS
Colour
Multi
Item Weight
118 g
Power Source
Corded
Style
Receptacle

⚡Detects wiring faults incl. open neutral/ground

📊Backlit LCD voltage & trip time readout

🛡️CAT II 135V safety rating for reliable testing

฿5412

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Description

⚡ Test Smarter, Work Safer — Never Miss a Beat with Klein Tools RT250!

AUTO HOLD CONVENIENCE - Locks readings for those hard-to-reach outlets—no guesswork needed
BRIGHT LED INDICATORS - Green/red LEDs provide immediate visual wiring status confirmation
ADVANCED FAULT DETECTION - Pinpoints open neutral, open ground & common wiring errors effortlessly
CRYSTAL CLEAR LCD DISPLAY - Instant voltage & GFCI trip time insights at a glance
PROFESSIONAL GRADE SAFETY - CAT II 135V rating ensures trusted performance on every job site

The Klein Tools RT250 is a professional-grade GFCI outlet tester designed for North American 3-wire 120V receptacles. Featuring a large backlit LCD that displays voltage and GFCI trip time, it detects common wiring faults including open neutral and open ground with patented technology. Equipped with bright LED indicators and an auto-hold function, it ensures accurate, convenient testing. Rated CAT II 135V for safety, this compact, lightweight tester is trusted by professionals for reliable electrical diagnostics.

Specifications

ASIN	B08QW7K1JJ
Best Sellers Rank	#388,545 in Home Improvement ( See Top 100 in Home Improvement ) #582 in Multi Testers
Brand Name	KLEIN TOOLS
Colour	Multi
Customer Reviews	4.8 4.8 out of 5 stars (10,989)
Global Trade Identification Number	00092644693212
Included Components	2 x 1.5V AAA Alkaline Batteries and Manual
Item Dimensions	11.5 x 2.9 x 5.1 Centimeters
Item Length	4.5 Inches
Item Type Name	Klein Tools RT250 GFCI Receptacle Tester with LCD Display, for Standard 3-Wire 120V Electrical Outlets
Item Weight	118 g
Item Width	2 Inches
Manufacturer	Klein Tools
Maximum Operating Voltage	120 Volts
Measurement Type	Voltage Tester
Minimum Operating Voltage	120 Volts
Model Number	RT250
Number of Items	1
Part Number	RT250
Power Source Type	Corded Electric
Specification Met	CSA
Style Name	Receptacle Tester
UPC	092644693212
Unit Count	1 Count
Upper Temperature Rating	60 Degrees Celsius

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Our prices include the product cost, international shipping, import duties, customs clearance, and local delivery charges. We handle all customs and import procedures, ensuring there are no hidden fees upon delivery. PRO members receive additional benefits including free shipping.

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฿5412

Duties & taxes included

In stock

Sold byAmazon ThailandDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Thailand.

Secure transaction

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TrustScore 4.5 | 7,300+ reviews

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