Memmert UN55 Universal Oven, compact heating and drying oven with natural convection, 53 litres, up to 300 °C

For those who have outgrown the Memmert UN30 universal cabinet but do not yet wish to install a floor-standing cabinet, the Memmert UN55 universal cabinet is the obvious next size up: 53 litres’ internal volume with almost the same footprint, and still utilising natural convection rather than an active fan. The temperature range extends from 20 to 300 °C, and the housing is made of textured stainless steel. As there is no active air circulation inside the chamber, the UN55 remains the first choice where vibration-free operation and low dust levels are more important than a particularly short heating-up time – for example, when drying samples laid out in the open or fine powders in slightly larger quantities than with the UN30.

Natural convection: greater volume, same operating principle

Like the smaller UN30, the Memmert UN55 universal oven deliberately does without an air turbine and a forced-air motor. Heat rises within the chamber purely by convection, without a fan stirring up dust or light sample particles. Consequently, the operating temperature range starts from at least 5 °C above room temperature up to 300 °C, whilst the forced-air models of the UF series only start from 10 °C above room temperature, but heat up more quickly thanks to forced air circulation. A Pt100 temperature sensor of DIN Class A in a 4-wire configuration ensures a setting accuracy of 0.1 °C from 0 to 99.9 °C and 0.5 °C from 100 °C upwards, regardless of the unit size within the series.

ControlCOCKPIT SingleDISPLAY and data acquisition

The UN55 is controlled via the ControlCOCKPIT SingleDISPLAY, an adaptive, multifunctional digital PID microprocessor controller with a high-resolution TFT colour graphic display. Settings include temperature in Celsius or Fahrenheit, the position of the exhaust air damper, the programme duration, as well as time zone and summer/winter time; the parameter for a recirculation fan speed is omitted due to the design. A digital countdown timer with target time can be set from 1 minute to 99 days; the SetpointWait function only starts the process time once the setpoint temperature has actually been reached. The data logger can be read out and managed via the Ethernet interface; a time-limited trial version of the AtmoCONTROL software is available for download.

Capacity and dimensions of the Memmert UN55 universal chamber

The interior measures 400 x 400 x 330 mm; the external dimensions are 585 x 784 x 514 mm, meaning it has the same footprint as the UN30 but is slightly taller. An electropolished stainless steel wire shelf is included; the cabinet can accommodate up to four shelves in total. The maximum load capacity is 80 kg for the entire unit and 20 kg per shelf. The interior consists of easy-to-clean stainless steel, reinforced by deep-drawn ribbing, with protected, integrated 4-sided all-round heating; the housing is made of textured stainless steel with a fully galvanised sheet steel rear panel. The UN55 is connected to 230 V (approx. 2,000 W) or 115 V (approx. 1,700 W), in each case at 50/60 Hz.

Selection guide: choosing the right size from the UN series

The Memmert universal cabinet series with natural convection covers a range of internal volumes from 32 to 749 litres. When selecting the appropriate size, the key factors – in addition to the internal volume – are the footprint and the number of shelves required; not every larger model requires more floor space than the next smaller one.

The UN55 is the obvious choice when the UN30 (32 litres) becomes too small for the volume of samples to be processed, but a significantly larger footprint is not yet available. If you need even more shelves whilst maintaining the same footprint, the UN75 (74 litres, 6 shelves instead of 4, same footprint, just taller) is the solution. All seven sizes can be found in the LT Laborhandel range of climate cabinets and incubators.

Differences: UN versus UF, and which display to choose

Within the Memmert range of heating and drying cabinets, the most important purchasing decision is between natural convection (UN series) and forced air circulation (UF series). The UF models feature an electronically controlled fan, which actively distributes heat throughout the interior, thereby achieving shorter heating-up times; however, this only applies from 10 °C above room temperature, rather than from 5 °C as with the UN55. For samples sensitive to dust or air movement – such as loose powders or fibres – natural convection remains the more suitable choice. A direct forced-air equivalent of a similar size is the Memmert UF160 universal cabinet with a capacity of 161 litres. Those looking for an even more compact natural convection solution will find it in the Memmert UN30 universal cabinet with a capacity of 32 litres. All standard models in the UN series, including the UN55, are equipped with the ControlCOCKPIT SingleDISPLAY; the TwinDISPLAY variant, featuring two displays and additional safety and logging functions, is reserved for Memmert’s ‘plus’ models and is not part of this series.

Safety in accordance with DIN 12880

In addition to adjustable electronic temperature monitoring, the UN55 features a mechanical temperature limiter of protection class 1 in accordance with DIN 12880, which switches off the heating when the temperature reaches approximately 20 °C above the maximum cabinet temperature. A self-diagnostic system assists with fault-finding, and three freely selectable temperature values can be calibrated. The unit bears the CE and EAC markings as well as a UL certification mark.

Installation, operation and disposal

For operation, a minimum distance of 15 cm from the wall and a maximum distance of 20 cm from the ceiling must be maintained; a minimum of 5 cm is sufficient on the sides relative to the wall or an adjacent unit. Installation is permitted at altitudes of up to 2,000 m above sea level at an ambient temperature of 5 °C to 40 °C and a relative humidity of no more than 80 per cent, non-condensing. Electrically, the UN55 is designed for overvoltage category II and pollution degree 2; it must only be transported in an upright position. The interior, made of easy-to-clean stainless steel, can be cleaned using standard laboratory cleaning products. As an electrical appliance, the UN55 is subject to the Electrical and Electronic Equipment Act at the end of its service life and must not be disposed of with household waste; see Regulatory Information below.

Typical applications

With an internal volume of 53 litres and natural convection, the Memmert UN55 universal cabinet is suitable for laboratories that require slightly more capacity than a standard benchtop unit but still wish to operate in a vibration-free environment.

• Drying of laboratory glassware and medium-sized sample batches
• Vibration-free drying of dust- or air-sensitive samples and powders
• Tempering, ageing and baking of material samples in routine operation
• Testing and curing in quality assurance
• As a secondary unit alongside a UN30, as the volume of samples increases

Investment rationale: Equipment tailored to the specific purpose

The UN55 is supplied with 1 electro-polished stainless steel wire mesh tray; the cabinet is designed to accommodate up to 4 trays. Those who regularly run several batches in parallel should order additional wire mesh shelves or perforated sheets. A fully transparent glass door is available as an option for visual inspection without opening the door – which reduces temperature fluctuations inside the chamber – as are interior lighting and an internal power socket for additional measuring equipment. Those wishing to use the data logger on a permanent basis, rather than just with the time-limited trial version, should add an AtmoCONTROL software licence and, if required, a USB-to-Ethernet adapter. For pharmaceutical or standard-compliant applications, calibration, IQ/OQ/PQ and maintenance services are available, including those accredited by DAkkS.

Frequently asked questions before purchase

Is natural convection sufficient for uniform drying?
For most routine applications, yes. For very densely packed batches with widely varying sample sizes, a forced-air model such as the UF160 distributes the heat more actively; for dust- or air-sensitive samples, the gentle natural convection of the UN55 is advantageous.

How many samples can fit into the UN55 at once?
One wire rack is included as standard; up to 4 trays, each with a maximum load of 20 kg, are possible, giving a total load capacity of up to 80 kg.

Can I place the UN55 on a laboratory bench?
Yes, with a net weight of around 57 kg and a footprint of 585 x 514 mm, the UN55 is designed for use on a laboratory bench, provided the bench can safely support the load.

What is the accuracy of the temperature control?
0.1 °C up to 99.9 °C and 0.5 °C from 100 °C onwards, as the UN55, like all models in the UN series, uses a DIN Class A Pt100 sensor with 4-wire technology.

Can a glass door be fitted as an aftermarket option?
A fully transparent glass door is one of the standard options for the UN55 and can be selected when placing your order.

How does the UN55 differ from the smaller UN30?
Both operate using natural convection and the same ControlCOCKPIT SingleDISPLAY; the UN55 offers greater capacity – 53 litres instead of 32 and 4 shelves instead of 3 – whilst occupying a similar footprint.

Is the UN55 suitable for continuous overnight operation?
The mechanical temperature limiter, which complies with Protection Class 1 according to DIN 12880, switches off the heating if the temperature rises by approximately 20 °C and is designed for unattended operation.

Technical details

Contents of delivery

• 1x Memmert UN55 universal cabinet
• Factory calibration certificate (calibration at 160 °C)
• Fully insulated stainless steel door with 2-point locking (compression door seal)
• 1x stainless steel grating, electropolished

Regulatory information

The Memmert UN55 universal cabinet is registered with the Stiftung Elektro-Altgeräte Register (Stiftung EAR) under WEEE registration number DE 66812464.

Customised requirements & procurement service

Options available for the UN55 include fully transparent glass doors, interior lighting and a power socket, reinforced grating and perforated panels, slide-in or floor-standing drip trays, as well as wall brackets, levelling feet and a stacking kit. A USB-to-Ethernet adapter and AtmoCONTROL software licences are available for data logging. In addition, we arrange calibration, IQ/OQ/PQ and maintenance services, including those accredited by DAkkS. Do you require any of these accessories, a gas-tight version or assistance in selecting the right universal cabinet for your application? Through our procurement service, LT Laborhandel will be happy to assist you with procurement and configuration.