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

For those who have outgrown the Memmert universal oven UN30 but do not yet wish to install a floor-standing cabinet, the Memmert universal oven UN55 is the obvious next size up: 53 litres’ internal volume with almost the same footprint, and still utilising natural convection rather than an active air turbine. 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 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 model, the Memmert UN55 universal oven deliberately does not feature an air turbine or a recirculation fan. Heat rises within the chamber purely by convection, without a fan stirring up dust or light sample particles. Consequently, the working 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 up to 99.9 °C and 0.5 °C from 100 °C onwards, 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 graphics display. The following can be set: temperature in Celsius or Fahrenheit, the position of the exhaust air damper, the programme duration, as well as the time zone and summer/winter time; the parameter for the 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 universal oven UN55

The interior measures 400 x 400 x 330 mm, whilst the external dimensions are 585 x 784 x 514 mm, meaning it has the same footprint as the UN30, but is slightly taller. The scope of delivery includes an electropolished stainless steel grid shelf, and 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 a 230 V (approx. 2,000 W) or 115 V (approx. 1,700 W) supply, in each case at 50/60 Hz.

Selection guide: choosing the right size from the UN series

The Memmert universal oven series with natural convection covers a range of internal volumes from 32 to 749 litres. When choosing the right size, the key factors, apart from the internal volume, are the footprint and the number of shelves required; not every larger model takes up 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, you will find them in the UN75 (74 litres, 6 shelves instead of 4, same footprint, just taller). All seven sizes can be found in our range of climate chambers and incubators.

Distinction: UN versus UF, and when to use which display

Within the Memmert family of heating and drying ovens, the most important purchasing decision is between natural convection (UN series) and forced air circulation (UF series). The UF models feature an electronically controlled air turbine, which actively distributes heat throughout the interior, thereby achieving shorter heating 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 universal oven UF55 with 53 litres. Anyone looking for an even more compact natural convection solution will find it in the Memmert universal oven UN30 with 32 litres. All standard models in the UN series, including the UN55, operate 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 according to DIN 12880

In addition to adjustable electronic temperature monitoring, the UN55 features a mechanical temperature limiter of protection class 1 according to DIN 12880, which switches off the heating when the temperature rises to 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 CE and EAC markings as well as a UL mark.

Installation, operation and disposal

For operation, a minimum distance of 15 cm from the wall and a minimum distance of 20 cm from the ceiling must be maintained; a minimum of 5 cm is sufficient on either side in relation to the wall or an adjacent unit. The unit may be installed 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 %, 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 agents. As an electrical appliance, the UN55 is subject to the German Electrical and Electronic Equipment Act (ElektroG) 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 universal oven UN55 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 laboratory glassware and medium-sized sample batches
• Vibration-free drying of samples and powders that are sensitive to dust or air
• Tempering, ageing and baking of material samples in routine operations
• Testing and curing in quality assurance
• A second unit alongside a UN30, as the sample volume increases

Investment rationale: Equipment tailored to the specific purpose

The scope of delivery for the UN55 includes 1 electropolished stainless steel grid shelf; the oven is designed to accommodate up to 4 shelves. Those who regularly run several batches in parallel should order additional grid shelves or perforated trays. A full-view 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 measurement 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 standards-based applications, calibration, IQ/OQ/PQ and maintenance services are available, including DAkkS calibration on request.

Frequently asked questions before making a purchase

Is natural convection sufficient for uniform drying?
For most routine applications, yes. For very densely loaded 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 any one time?
One grid shelf is included as standard; up to four shelves, 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 the 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 that the bench can safely support the load.

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

Can a glass door be fitted as a retrofit?
A fully transparent glass door is one of the common 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 feature 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 operation overnight?
The mechanical temperature limiter, of protection class 1 according to DIN 12880 switches the heater off at an excess temperature of approximately 20 °C and is designed for unattended operation.

Technical details

Scope of delivery

• 1x Memmert universal oven UN55
• Factory calibration certificate (calibration at 160 °C)
• Fully insulated stainless steel door with a 2-point locking system (compression door lock)
• 1x stainless steel grid shelf, electropolished

Regulatory information

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

Individual requirements and procurement service

Options available for the UN55 include full-view glass doors, interior lighting and a power socket, reinforced grid shelves and perforated trays, 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 acquisition. In addition, we arrange calibration, IQ/OQ/PQ and maintenance services, including DAkkS calibration on request. Do you require any of these accessories, a gas-tight version, or assistance in selecting the right universal oven for your application? Through our procurement service, we’d be happy to assist you with procurement and configuration.