Doorbell Transformer Sizing: 16V, 24V and VA Explained
Volts set what your chime needs; VA sets how much it can power. How to size a doorbell transformer for one chime, two chimes or a video doorbell.
DIY doorbell repairs
Use this guide to narrow the problem before you replace parts. Most wired and wireless doorbell issues come back to the push button, transformer, chime, receiver, or a basic compatibility mismatch.
On This Page
- Volts and VA are two different things
- Is there such a thing as a 10V doorbell transformer?
- Transformer sizes at a glance
- How to size your transformer
- 1. Read what the chime needs
- 2. Count what is on the circuit
- 3. Check the wire run
- 4. Check how it mounts
- Signs your transformer is too small
- Kits that include a transformer
- Safety
- Frequently asked questions
- Can I use a bigger VA transformer than I need?
- Can one transformer run two chimes?
- Where is my doorbell transformer?
- Which transformer for a tri-volt system?
Related Categories And Products
Quick answer: match the voltage to what your chime and button call for, which for most wired doorbells is 16V. Then choose enough VA (capacity) for everything on the circuit: about 10VA for one chime and a plain button, 15VA for one chime on a long wire run or two chimes, and 30VA for a video doorbell or several chimes. A "10" on a transformer label almost always means 10VA, not 10 volts.
Volts and VA are two different things
- Voltage (V) is the electrical pressure the transformer supplies. Your chime is designed for a specific voltage, and the transformer should match it. Most residential wired chimes on our site run on 16V. The Craftmade CL4000, CH1000, CH2000 and the recessed ICH1725-BNK pages all call for 16V.
- VA (volt-amperes) is capacity: how much load the transformer can carry at that voltage before it runs hot or the voltage sags. Two transformers can both be 16V and still be very different sizes.
More VA never fixes the wrong voltage. If a device calls for 16V, stay at 16V. If a device calls for a range, such as 16-24V, stay inside that range.
Is there such a thing as a 10V doorbell transformer?
Not among the transformers we carry. Labels like "16V 10VA" are often read as "10V," but the 10 is the VA rating. If your old transformer says 10, look again for the second number. The voltage options you will see are:
- 16V: the standard for most wired chimes.
- 8V, 16V or 24V: a tri-volt transformer like the Carlon DH910, which can be wired for any of the three.
If your old transformer is a Carlon or Thomas & Betts DH905, it is the 16V 10VA equivalent of the IQ America DT-1610A below.
Transformer sizes at a glance
| Transformer | Output | Capacity | What the product page says it is for |
|---|---|---|---|
| Craftmade T1610 | 16V AC | 10VA | Single chime, up to 50 ft of wire, indoor use |
| IQ America DT-1610A | 16V AC | 10VA | One standard wired chime; mounts to a junction box knockout |
| Craftmade T1615 | 16V AC | 15VA | One chime on a long wire run, or two chimes; mounts to a junction box |
| Craftmade T1630 | 16V AC | 30VA | Multi-chime systems and video doorbells |
| Carlon DH910 | 8V, 16V or 24V | 10VA at 8V and 16V; 20VA at 24V | Up to two low-voltage devices |
How to size your transformer
1. Read what the chime needs
Check the chime's label or product page for its voltage. The CL4000 page, for example, says it "runs on a 16V transformer, which is sold separately." The ICH1730-GV page says it is compatible with 16V wired doorbell transformers.
2. Count what is on the circuit
- One chime and an unlit button, normal wire run: 16V 10VA, such as the T1610 or DT-1610A.
- One chime on a long run, or lighted buttons: step up to 16V 15VA. The T1615 page notes that "two lighted buttons on a 10VA transformer leave very little left over."
- Two chimes: 16V 15VA (T1615), or 16V 30VA (T1630) if you also have lighted buttons or a long run.
- A video doorbell: 16V 30VA. The T1615 page says to "step up to the Craftmade T1630" for a video doorbell, and the T1630 page lists video doorbells from brands such as Ring, Nest, Lorex, Arlo and Eufy. Always check the video doorbell maker's own voltage and VA requirements as well.
3. Check the wire run
Longer runs of thin doorbell wire lose voltage along the way. The T1610 page lists a 50-foot maximum. The T1615 and T1630 are listed for runs over 50 ft.
4. Check how it mounts
The T1615 mounts to an electrical junction box and runs on 120V, 60Hz input. The DT-1610A has a lock-nut clamp for standard junction box knockouts. The DH910 has a clamp-on mount. All three connect to household line voltage on the input side.
Signs your transformer is too small
- The chime rings weakly, or only part of the tone plays.
- A lighted button glows dimly or flickers.
- A video doorbell drops offline, reboots, or will not charge.
- The transformer hums loudly or feels hot.
Any of these can point to an undersized transformer, though loose wiring and a worn chime cause similar symptoms. See wired chime not ringing after a video doorbell for the video doorbell case.
Kits that include a transformer
If you are replacing the whole system, a kit takes the guesswork out. The Carlon CK225 includes a DH110 chime, two lighted buttons and a 16-volt, 10VA transformer. The Craftmade CK1002-W includes two CH1000 chimes, two lighted buttons and a matching transformer. If you later add a video doorbell to either one, check the transformer against the video doorbell's requirement.
Safety
The doorbell side of a transformer is low voltage, but the input side connects to 120V household power. Turn off the breaker before you touch the transformer, and if you are not comfortable working in a junction box, have an electrician do the swap.
Frequently asked questions
Can I use a bigger VA transformer than I need?
Yes, as long as the voltage matches. Extra VA is spare capacity, not extra voltage.
Can one transformer run two chimes?
Yes, if it has enough VA. The T1615 is rated for two chimes, the T1630 for up to three, and the DH910 for up to two low-voltage devices.
Where is my doorbell transformer?
Often near the electrical panel, in a basement or attic, or on a junction box near the furnace. Our guide I can't find my doorbell transformer walks through where to look.
Which transformer for a tri-volt system?
Use the voltage the chime calls for. The DH910 offers 8V and 16V at 10VA, and 24V at 20VA.
Shop every option in the doorbell transformers collection. For more on tri-volt models, read the guide to tri-volt doorbell transformers.