Heating, Ventilation and Air Conditioning Products

Welcome back to our Product Spotlight series!

This week, we shine the spotlight on our final product of the series, our HVAC products, but we have our final challenge in store for you.

Test your knowledge and seize the opportunity to win a £30 gift card.

The quiz is waiting for you at the bottom of this post. Are you ready to take on the challenge?


When did we start to develop VTMS products? 

GTS began developing HVAC products in 1993.


What does HVAC stand for?

All-Electric Driver Cabin Heater HVAC Unit - Full product shot



Why did we develop HVAC products?

We initially developed our HVAC systems for Plaxton coach.

Originally, all of our air conditioning equipment and systems came from Thermo King.

Thermo king bus

Vehicle at the Falkirk ADL Facility in 1997

25 years ago, Grayson achieved a milestone by completing the first 100 air-conditioned vehicles using the Thermo King MRT Split unit. This unit was specifically designed as a bespoke configuration for ADL Falkirk.

Pavel Ikrath provided bus application support from Thermo King, with technical leadership by Stuart Hateley and installation support from Ian Hateley, all under the project leadership of Graham Hateley. The prototype was successfully installed on a vehicle at the Falkirk ADL Facility in 1997.

In 2010, we then developed our own air conditioning system for Alexander Dennis’ Enviro400 MMC being supplied to London, this was known as “Upper Deck Chill”

An Enviro400 is a double-decker bus – (you may recognise the West Midlands Platinum Travel buses around the Birmingham area).

Black National Express bus

West Midlands Platinum Travel buses


Our HVAC Products for Buses

A HVAC system for a diesel bus is made up of the following products:

  • Heater box – provides heat to the saloon for passenger comfort. The heater box is typically mounted under the seats or in the wheel arches.
  • Demister box – provides heat to clear the cab windscreen and for driver comfort. It is mounted below the windscreen in the dashboard.
  • Heat / Cool demister – provides heat and cool air to the windscreen and driver for increased comfort on hotter days.
  • Upper Deck Chill system – evaporator installed within the roof structure of a double deck bus to cool the top deck of a double deck bus. The condenser and fan assembly is fitted on the rear of the bus.
  • Boost Pump – Used in the heating circuit to flow hot water from the engine block around the demister and heater boxes

We manufactured our own air conditioning unit for the Enviro400 and used a Thermo King SR10E electric air conditioner for Enviro200 vehicles. The Enviro200 is a single-deck bus and has driver-only air conditioning. The Enviro400 bus has a driver and upper deck chill air conditioning system.

Some Enviro200 vehicles were supplied with full air conditioning for specific customer request, we used a Thermo King rooftop unit for these projects.


What are the key components of HVAC products?

Aluminium heater matrix: This is a heat exchanger that takes hot coolant and allows cool air to flow over it, producing warm air. It exchanges heat from the coolant to the cool air. Our standard heater matrix range was developed by Nathan Stephens and Ian Hateley.

Temperature sensor: This component measures the air temperature in the bus at various locations.

Blower: Blowers are used to move air through a heat exchanger and into the vehicle. The blower is available in single or twin scroll and can use a brushed or brushless motor. A traditional electric motor has wearable brushes made of carbon, while brushless electric motors do not have brushes, making the life of a brushless fan more dependent on the bearing life.

black blower component

Blower component

Water valve – controls the coolant flow through the heaters.

The below are only applicable to air-conditioning vehicles:

Compressor – compresses cold refrigerant gas to hot refrigerant gas in the refrigerant circuit.

Condenser – condenses hot refrigerant gas into warm liquid refrigerant.

Expansion valve – a refrigerant metering device – controls the refrigerant flow through the evaporator. It has a very small orifice forcing the refrigerant to expand rapidly when passing through the valve.

Evaporator – evaporates expanding warm liquid refrigerant into cold refrigerant gas before entering the compressor again. This heat exchanger provides cool air to passengers.



What application do we supply HVAC products to? 

Buses and Coaches

The biggest HVAC system supplied to date is the Plaxton Panorama double-deck coach. The coach has full AC on both decks (including the driver), as well as a 4-fan condenser and a dedicated fresh air conditioning unit.


image of blue mega bus


Test your Knowledge!

 Join us now on our Product Spotlight quizzes that will take you on a journey through the world of Grayson products.

But the best part? You’ll also have the chance to win a £30 gift card, simply for showing off your knowledge!

Are you up for the challenge? Take the seven multiple choice question quiz now and find out what you’re made of!

Simply just click the button to get started:

The deadline to complete the quiz is at 12 p.m. on 15/12/23.