Information Centre

Finding a dishwasher company that caters for your every need can be both time consuming and difficult. Aventus Group will provide you with the right advice, the correct machine for your needs and guarantee to be the lowest price available anywhere.

Our Information Centre contains useful information helping you understand how to begin your search for a new or replacement dishwasher. We look at various aspects of the dishwasher purchase to help you identify the correct type of washer for your business.

Why should you be buying a commercial dishwasher?

  • It is cheaper than washing by hand
  • It is faster than washing by hand
  • The dishwasher is more reliable than staff
  • A commercial dishwasher gives consistently sanitary results
  • Because drying by hand causes cross contamination
  • Whilst the dishwasher is washing the pots the staff can do something else

When you first switch on a dishwasher, what happens?

  • First it will fill the wash tank
  • Then heat the rinse boiler
  • Followed by heating the wash tank
  • It will then tell you it is ready to be operated

When the dishwasher is ready to be operated you can load the dishwasher

What happens during the wash and rinse process?

  • Select the desired wash cycle (if multiple cycles are available)
  • Press the start button (or turn the start switch)
  • The dishwasher washes by re-circulating the hot water in the wash tank (mixed with detergent) around the dishwasher at high speed for the duration of the wash cycle
  • At the end of the wash cycle the machine briefly pauses before rinsing the pots with the hot fresh water (mixed with rinse aid) from the rinse boiler for a short period
  • At the end of the cycle the dishwasher stops so you can unload the dishwasher
  • The dishwasher can be re loaded and operated again as soon as it has re-heated

How many plates can a dishwasher wash per hour?

Wash cycles per hour

  • Commercial dishwashers wash in an industry standard 500x500mm basket and wash 1 basket at a time.
  • Industry standard baskets hold 16-18 10” (250mm) diameter plates at a time
  • Assuming the dishwasher has a 2 minute wash cycle the maximum possible number of plates that can be washed is: 30(the number of 2 minute wash cycle in an hour) x 18(the number of plates that will fit in a basket). Therefore the “theoretical “maximum number of plates that can be washed in 1 hour is: 30x18 = 540 plates per hour, this figure does not take into account the time to load and unload the dishwasher or the time it takes to re-heat between washes.

It takes on average 15 seconds to take a clean basket of plates out of a commercial dishwasher and to load it with a fresh basket of soiled plates, therefore this reduces the maximum “theoretical” number of plates washed per hour to 468. This assumes that the dishwasher can re-heat fast enough to keep up.

Re-heat time & plates washed per hour

A commercial dishwasher has to re-heat the amount of fresh water it uses every wash (this is the water used in the final rinse). This is the figure the manufacturers quote in their literature as water used per wash, typically 2.5 – 3.5 litres per wash. For the sake of argument we will assume a typical commercial dishwasher uses 3 litres of water per wash and the water supply on a cold water fill is 10°C.

To heat 3 litres of water from 10°C to 85°C (the correct rinse temperature) in a commercial dishwasher with a maximum rinse boiler heating capacity of :

  • 3Kw will take 5 minutes 30 seconds - Maximum plates washed per hour = 180
  • 4Kw will take 3 minutes 55 seconds - Maximum plates washed per hour = 270
  • 5Kw will take 3 minutes 10 seconds - Maximum plates washed per hour = 324
  • 6Kw will take 2 minutes 35 seconds - Maximum plates washed per hour = 414

If you have a hand hot water supply of 50°C the heating times are:

  • 3Kw will take 2 minutes 25 seconds - Maximum plates washed per hour = 432
  • 4Kw will take 1 minutes 55 seconds - Maximum plates washed per hour = 558
  • 5Kw will take 1 minutes 30 seconds - Maximum plates washed per hour = 720
  • 6Kw will take 1 minutes 13 seconds - Maximum plates washed per hour = 882

For a single basket commercial dishwasher to be effective, a wash cycle of 2 minutes is recommended.

What are the costs of running a commercial dishwasher?

Most Commercial dishwasher manufacturers do not publish running costs and any values they do give are factory based and tested in laboratory conditions. We all know however that real life is quite different to laboratory conditions and this will reflect in running costs.

Example differences:

  • Water temperature can differ considerably depending on the source and time of year and given it takes 4.18 KiloJoules to heat one litre of water by one degree Celsius, this can make a significant difference over time.
  • Even a slight limescale build up on heating elements can radically affect their efficiency, meaning that the factory specified power consumption can be way off.
  • Not all chemicals are equal. Some are cheaper and weaker and require more volume. Some are stronger, require less volume but are more expensive.

The other issue is that all manufacturers measure differently and so apparently comparable figures are actually like comparing apples with pears. Trying to get to the bottom of this is difficult, time consuming and in our experience largely futile.

The more important question is. What are the Lifetime costs of a commercial dishwasher?

Lifetime costs include

  • Electricity - £0.0154 per unit (1kWh) for electricity (DECC, March 2017). Average small to medium businesses electricity costs can vary between £1000-£3000 per annum. Your dishwasher electric costs will represent a fraction of these costs.
  • Water costs are complex and depend a variety of factors – whether you have a meter or your costs are based on rateable value, sewerage charges, seasonal, alternative, seasonal, uninterruptible tariffs and so on. That said for small to medium businesses water bills are normally in the high £100’s or low £1000’s of pounds per annum. Your dishwasher water costs will represent a fraction of these costs given what other demands a typical organisation has on its water. Catering sinks for example are very wasteful of water.
  • Detergents – based on 50 covers and two services a day should cost around £250 per annum.
  • Breakdowns – If covered with a meaningful warranty then this will be minimal consideration in lifetime cost calculation. If however the machine warranty is short and only covers parts, the repair costs over the life of a commercial dishwasher could easily be equivalent to your entire business’s water bill for a year.
  • Machine longevity – If your machine only lasts 2-3 years or significantly less than 60,000 washes then this will be a big cost in your lifetime (expected) cost calculations. Contributing factors to longevity will include, the quality of the machine, how the machine is used and treated and the regularity of maintenance and service schedules.
  • Machine downtime – This can be an intangible cost in terms of general hassle, or tangible cost of employing personnel to wash up manually.

Many businesses think about consumable costs (water, electricity, detergents) in their calculations in order to be ‘greener’ and financially prudent. This is of course understandable however even with double digit % savings on utility or consumables these savings pale into insignificance if the machine has an inadequate warranty, leading to an expensive repair or replacement. So, based on our experience a machine with a meaningful warranty, service responsiveness and proven longevity will always be the logical choice when considering the holistic running costs of a commercial dishwasher.

Where can a commercial dishwasher be fitted?

Commercial dishwashers with a 500 x 500mm basket are generally the same size (give or take 5mm).

They are 600 x 600 x 850mm high (the same size as a domestic washing machine) and can be installed on the floor or below a standard work top.

Installing a commercial dishwasher on the floor (below a work top), means that either full dishwasher baskets (try picking up 20 plates at one time to see the weight, have to be lifted from low down and put on the work top, or you have to load or unload each basket plate by plate (this increases the time between washes).

Alternatively the dishwasher can be fitted onto a stand so that the open dishwasher door is at waist height, eliminating the lifting and bending from loading and unloading the dishwasher.

Do I need a water softener?

Commercial dishwashers must be supplied with a softened water supply to work correctly. We can advise you if you need to have a water softener in your area.

Water softeners for commercial dishwasher come in 5 varieties:

  1. Manual
  2. Integral
  3. Continuous
  4. Automatic cold
  5. Automatic hot

Manual water softener

A stainless steel cylinder about the size of a medium fire extinguisher with a water inlet and water outlet. Manual water softeners need to be manually re- generated 1-2 times a week dependent on you water hardness and the amount of washes you do in a week. For instructions on how to regenerate a manual water softener -

Manual water softeners are fitted near to the dishwasher or in a cupboard nearby and you will need regular access to them.

Integral or internal water softener

These look similar to the water softeners in domestic dishwashers and need to be topped up with salt regularly unlike domestic dishwashers, they do not operate automatically. On some machines you have to remember to operate the water softener by pressing a button. On a higher specification system, a light will come on telling you to operate the water softener.

Continuous water softener

They look and operate just like the water softeners in domestic dishwashers, all you have to do is keep them topped up with salt.

Automatic cold water softener

For use on a cold water supply. What you will see is a plastic box with timers and controls on it. The water softener is plugged into the mains and connects to the water and drainage supply. It’s operation is fully automatic, all you have to do is keep it full of salt. Automatic water softeners need to be installed next to the dishwasher, under the dishwasher stand or in an adjacent cupboard.

Automatic hot water softener

As above, but for use when the dishwasher is connected to a hot water supply.

All of the above water softeners work if they are used in the correct way and are specified correctly.

The manual water softener is the cheapest and will work in all water conditions. On the down side it takes the most looking after and a regular routine to maintain its performance.

The integral water softeners have very limited resin capacity and so are only suitable for moderately hard water areas and for low usage situations.

Continuous water softeners have the same low resin volume but as they operate continuously, they are suitable for moderate use in moderate water quality areas.

Automatic water softeners have the resin capacity and are capable of operating in all water quality areas and at high wash volumes but are the most expensive.

There is no substitute for a water softener when one is needed. Electrical scale inhibitors and hard water detergents cannot be used instead of a water softener.

Remember if it doesn’t use salt it is not a water softener.

What detergents do I use for a commercial dishwasher?

Commercial dishwashers use liquid commercial dishwashing detergent and commercial dishwasher rinse aid. The detergent removes grease and debris from the pots during the wash cycle and holds it in suspension until the rinse cycle. The fresh water rinse mixed with rinse aid rinses the plates clean, providing thermal disinfection and aids the drying process.

Dishwasher detergents and rinse aids to be effective, must be introduced into the dishwasher at the correct time and in the correct quantity. To be effective this process should be automatic. All commercial dishwashers and glass washers supplied by Dishwashers Direct , are fitted with automatic detergent and rinse aid dosing systems that automatically draw up the correct amount from 5 litre containers. The containers must be close to the dishwasher (maximum 1 metre).

You cannot use domestic dishwasher detergents or tablets in a commercial dishwasher.

Always use a quality detergent, your hygiene (and your reputation) rely on them. (Remember they only have 2-4 minutes of wash time to do the job). Dishwashers Direct supply Premium strength dishwashing consumables with free delivery nationwide.

What about the servicing and repair of a dishwasher?

Would you buy a car and not have it serviced? A commercial dishwasher is much the same as a car, the more it is used and the less well it is looked after, the more it will need service and repair. Dishwashers Direct can provide planned servicing or provide service on demand, the choice is yours. We have our own service engineers and extensive spare parts stocks to keep your machine working for the whole of its service life.

Commercial Warewasher Terms & Phrases

For a complete understanding of commercial warewashing terms and phrases click here

As you would expect from a specialist in ware washing with over 25 years of experience and worldwide sourcing we have the answers for your site. So, why not test us out and arrange a site visit from one of our experts.

Call us today 0115 9613 720

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