Diamond H Controls of Norwich, England, built capillary thermostats for cookers and catering equipment — the brand now lives on through Heatrod Elements and Backer, who supply the current ET50 series to volume OEM customers. This page maps the Diamond H numbers our customers send us most often to their verified V.Crown equivalent. The overlap is a single function: every verified Diamond H capillary thermostat is a single-pole adjustable control, so every row below maps to the AG16-K.
How to read the original part number
Diamond H capillary parts carry a code such as ET50 or 40TH, and the range, capillary and bulb are properties of that code — read them from the rating label or the manufacturer datasheet rather than assuming them from the series. ET50 is the current low-profile control family; 40TH is its historical predecessor from the 1985 catalogue. ET51, ET52, ET54 and the 41TH / 42TH add auxiliary switches for a fan, a pilot light or a grill — the thermal control itself stays single-pole.
ET50 series — current single-pole controls
Low-profile liquid-filled capillary controls for modern cooking appliances, where control-compartment space is limited. Thermal contacts break on temperature rise. Capillary lengths and bulb sizes are made to order and are not published, so the mapping is by function and range.
| Original part | Original specification | V.Crown equivalent |
|---|---|---|
| Diamond H ET50 | Control · adjustable 45–320°C standard (45–110°C variant) · 1-pole · 16A resistive, 24–240V AC · capillary and bulb to order, not published | AG16-K |
| Diamond H ET51 | Control + integral single-pole auxiliary switch (oven fan and/or pilot light) · 45–320°C / 45–110°C · 1-pole thermal · 16A resistive; auxiliary 13A resistive | AG16-K |
| Diamond H ET52 | Control + single front-switch module (grill/oven combinations) · 45–320°C / 45–110°C · 1-pole thermal · 16A resistive; auxiliary 13A resistive | AG16-K |
| Diamond H ET54 | Control + integral switch + front-switch module · 45–320°C / 45–110°C · 1-pole thermal · 16A resistive; auxiliary 13A resistive | AG16-K |
The AG16-K covers the 50–400°C band at 16A/20A — see the AG16-K capillary control thermostat for the full specification, including capillary and bulb made to order.
40TH series — historical single-pole controls (1985 catalogue)
The predecessor of the ET50, from the 1985 Diamond H catalogue — smaller in all dimensions than the earlier Type 90TH, with a snap-action switch. Still fitted in legacy UK cookers, so customers still send these numbers in. The 40TH range is historical; the ET50 is the current series.
| Original part | Original specification | V.Crown equivalent |
|---|---|---|
| Diamond H 40TH | Control · adjustable 60–290°C standard (50–300°C to order) · 1-pole · 15A/250V AC · capillary min. 460mm · phial 243×4.6mm | AG16-K |
| Diamond H 41TH | Control + single-pole front auxiliary switch · 60–290°C · 1-pole thermal · 15A/250V AC; auxiliary 15A/250V AC · capillary min. 460mm · phial 243×4.6mm | AG16-K |
| Diamond H 42TH | Control + double-pole front auxiliary switch · 60–290°C · 1-pole thermal · 15A/250V AC; auxiliary 15A/250V AC · capillary min. 460mm · phial 243×4.6mm | AG16-K |
| Diamond H 44TH | Control · continental fixing (2 screws on 28mm centres, 6mm spindle) · 60–290°C · 1-pole · 15A/250V AC · capillary min. 460mm · phial 243×4.6mm | AG16-K |
The AG16-K covers the 50–400°C band at 16A/20A — see the AG16-K capillary control thermostat for the full specification.
Outside the scope of these tables
No verified Diamond H multi-pole capillary control, manual- or automatic-reset capillary safety limiter, millivolt gas control thermostat or capillary thermometer exists in any public source, so the AG32, AG16-S, VL-S, VL-Z, ARB-33 and AGT families have no Diamond H counterpart in these tables. The 4xER energy regulators (40ER–49ER) are bimetal duty-cycle power controllers with no capillary and no temperature sensing, and the 1100-series gas oven thermostats and GSD flame supervision devices are gas-valve hardware — none of them is mapped here. ET50 variants ordered below 50°C are outside the AG16-K envelope and are not listed.
Diamond H® is a trademark of Diamond H Controls Ltd. HengTherm parts are replacement equivalents manufactured by Guangzhou V.Crown Thermostat Co., Ltd.; we are not affiliated with Diamond H, and part numbers are used for cross-reference identification only. Verify the equivalent against the original specification before installation.
The five checks before you order
- Function and auxiliary switches — every Diamond H capillary thermostat in these tables is a single-pole adjustable control. The extra switches on the ET51, ET52, ET54, 41TH and 42TH switch a fan, a pilot light or a grill — they are auxiliary, not additional control poles, and they do not make the part a multi-pole control.
- Range — the original’s range must sit inside the equivalent’s range (AG16-K 50–400°C). The ET50 standard range is 45–320°C and the 40TH 60–290°C; the 45–110°C ET50 variant is covered from 50°C up. Variants ordered below 50°C do not correspond.
- Current and contacts — ET50 thermal contacts are 16A resistive; 40TH thermal contacts are 15A/250V AC. Check whether the original switches a resistive load within the AG16-K rating, and confirm the auxiliary-switch load separately — the 13A auxiliary rating is not part of the thermal control rating.
- Capillary length and bulb — 40TH capillary is 460mm minimum with a 243×4.6mm phial; ET50 capillary lengths and bulb sizes are made to order and are not published — quote them from the rating label or the order. Too short a capillary cannot reach the sensing pocket, and the bulb must fit the existing pocket.
- Mounting and spindle — the 40TH uses a single-hole bush fixing; the 44TH uses continental fixing with two screws on 28mm centres and a 6mm spindle. The replacement must fit the same panel cut-out and take the same knob — check the fixing and the spindle before ordering.
Send us the part number you are replacing — or a photo of its rating label — and we run all five checks in writing before quoting, so the equivalent arrives as a fit, not a project.
Certification: ask for numbers, then verify them
The AG16-K’s approvals are confirmed for the exact model before ordering. The original ET50 is built to EN 60730-2-9; when an alternative supplier quotes a safety device, ask for the file number — not a logo — and check it before the part goes into certified equipment.
Samples and trial orders
Free samples of the AG16-K are available for bench testing — you only cover the courier, and the freight is credited against your first order. Trial orders start from 200 pcs, with models mixed in one shipment, and mechanical customization (range, capillary length, bulb, dial printing) is developed free of charge. Send us the Diamond H number you currently buy and we will map it.
Related reading: Robertshaw Thermostat Cross-Reference: 5300-Series Controls & 5225-Series Hi-Limits · E.G.O. Thermostat Cross-Reference: 55-Series Controls & 56-Series Safety Limiters · Cotherm Thermostat Cross-Reference: GTL Controls & Safety Limiters · Tecasa Thermostat Cross-Reference: NT, VC and SP Capillary Thermostats · IMIT Thermostat Cross-Reference: TR2 Controls & LS1 / LS3 Safety Limiters · Campini Thermostat Cross-Reference: TY95 Controls & TY95H / TY95S Safety Limiters · Thermowatt Thermostat Cross-Reference: TCOD, TB / TBR Controls & SPC / TBST / TBSB Safety Limiters · How to Choose a Capillary Thermostat for Commercial Fryers and Ovens · Selco Thermostat Cross-Reference: CAP, SHQ / SJW Controls & CAP-MR Safety Limiters · Therm-O-Disc Thermostat Cross-Reference: 10H linear limit controls