{"id":5582,"date":"2026-08-11T08:45:24","date_gmt":"2026-08-11T08:45:24","guid":{"rendered":"https:\/\/www.newbasen.com\/?p=5582"},"modified":"2026-08-11T08:45:30","modified_gmt":"2026-08-11T08:45:30","slug":"electric-bus-heat-pump-air-conditioning-cold-weather-operation","status":"publish","type":"post","link":"https:\/\/www.newbasen.com\/pt\/electric-bus-heat-pump-air-conditioning-cold-weather-operation\/","title":{"rendered":"Electric Bus Heat Pump Air Conditioning in Cold Weather: Operating Envelope and Refrigerant Choices"},"content":{"rendered":"

Short answer:<\/strong> Heat-pump air conditioning on an electric bus is fundamentally different from engine-driven bus AC because there is no waste-heat source to fall back on. The heat pump must heat the cabin and, on integrated platforms, cool the traction battery from the same refrigerant loop, often at ambient temperatures well below freezing. The 2024 NEWBASE bus AC range operates the heat pump down to -20 degrees C with a published coefficient of performance of 3.0, and the components are protected to IP67 against the rooftop weather. This article walks through the operating envelope, the refrigerant choice, and the components that make sub-zero heating possible on an electric bus.<\/p>\n

Article topic: Electric Bus Heat Pump AC in Cold Weather. This article uses a NEWBASE-branded placeholder image for the feature; no third-party product photography is included in this draft.<\/em> https:\/\/www.newbasen.com\/wp-content\/uploads\/2026\/08\/newbase-illustration-003.png<\/p>\n

What changes when the bus is electric<\/h2>\n

A diesel bus can use engine coolant heat when the cabin is cold; an electric bus cannot. The heat pump is the only efficient heating source on a battery-electric platform, and on the integrated NBEAC-21-T\/24-T\/30-T\/34-T family it shares the refrigerant loop with battery thermal management. This means a single set of operating limits governs cabin comfort, battery cooling, and battery heating. For an OEM or fleet operator, the cold-weather selection question is not just which kW but at which ambient temperature, with which refrigerant, and with what compromise on auxiliary heating.<\/p>\n

Two physical facts drive most of the engineering. First, the heat-pump coefficient of performance falls as ambient temperature falls, because the refrigerant mass flow has to climb to maintain heating capacity. Second, the battery on a cold-soaked bus resists both charging and high discharge, so a heat-pump-only cabin system has to be paired with a battery-heating path or the vehicle leaves the depot with reduced range. The 2024 manual flags this directly: low-temperature air-injection enthalpy-increase technology addresses insufficient heating capacity and low heating efficiency at low ambient, and reduces the average daily energy consumption by about 30 percent at -10 degrees C compared with a standard heat-pump system. That is a significant gain, but it is still a heat-pump gain; at very low ambient the system will reach its operating floor and the auxiliary heater takes over.<\/p>\n

The operating envelope<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n
Par\u00e2metro<\/th>\nPublished value<\/th>\nSource<\/th>\n<\/tr>\n<\/thead>\n
Heat-pump operating temperature (lowest ambient)<\/td>\n-20 degrees C or below<\/td>\nSeries product features, p. 2<\/td>\n<\/tr>\n
Coefficient of performance (COP \/ EER)<\/td>\n3.0<\/td>\nSeries product features, p. 2<\/td>\n<\/tr>\n
Component protection rating<\/td>\nIP67 (dustproof, waterproof, no damage when submerged)<\/td>\nManual p. 14<\/td>\n<\/tr>\n
DC-DC module ambient operating ceiling<\/td>\n65 degrees C<\/td>\nManual p. 18<\/td>\n<\/tr>\n
Battery-side driving cooling capacity (integrated platform)<\/td>\n3-5 kW<\/td>\nManual p. 7<\/td>\n<\/tr>\n
Battery-side charging cooling capacity (integrated platform)<\/td>\n5-8 kW<\/td>\nManual p. 7<\/td>\n<\/tr>\n
EMC performance<\/td>\nNational standard level I<\/td>\nManual p. 18<\/td>\n<\/tr>\n
PTC heater safety protection<\/td>\nIGBT modules, over-voltage\/under-voltage\/over-current\/short-circuit\/anti-dry-burn<\/td>\nManual p. 18<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

For a city bus in a temperate climate this envelope is rarely a problem. For an intercity bus in northern Europe, northern China, or central Canada, the route profile has to account for the auxiliary-heater load and its impact on range. The OEM and the fleet operator should agree on a worst-case ambient design temperature, then verify that the published heat-pump floor covers it. If not, the specification has to include auxiliary-heater power and a charging strategy that compensates.<\/p>\n

Refrigerant choice: R407C vs R410A<\/h2>\n

Both refrigerants are listed for every basic-platform model. R407C is a zeotropic blend with a small temperature glide; R410A is an azeotropic blend with slightly higher discharge pressure at the same condensing temperature. In practice:<\/p>\n

    \n
  • R410A<\/strong> tends to deliver slightly higher heating capacity at low ambient and is the more common choice in newer installations. The trade-off is higher compressor discharge pressure, which means the compressor and condenser have to be sized for it.<\/li>\n
  • R407C<\/strong> has a lower global-warming-potentialing value than R410A and is widely used in commercial refrigeration. The temperature glide means the system needs a larger condenser and a properly sized receiver.<\/li>\n<\/ul>\n

    For a fleet operator, the practical question is whether the supplier can support both refrigerants and which one is in current production for the chosen model. The 2024 manual lists both for the basic platform; the actual unit shipped is built to one or the other. Confirm with the engineering team which refrigerant a specific quotation refers to before ordering spare parts or training service technicians on the cycle. Once the unit is built, the refrigerant is fixed for its service life; the two refrigerants are not interchangeable.<\/p>\n

    What -20 degrees C heat-pump operation actually means<\/h2>\n

    The series product literature states an operating temperature of -20 degrees C or below for the heat pump. This is the lowest ambient at which the heat pump still delivers meaningful heating capacity. Above that floor, the system throttles back and the COP falls. Below that floor, on most platforms, the cabin heating relies almost entirely on the auxiliary PTC heater, which costs range. The headline number is therefore: at -10 degrees C the heat pump still does most of the work, at -20 degrees C the heat pump is at the edge of its envelope, and below -20 degrees C the auxiliary heater dominates.<\/p>\n

    The PTC heater itself is published as IGBT-based with multiple protection measures: over-voltage, under-voltage, over-current, short-circuit, and anti-dry-burn. These are real protection features, not marketing language; an electric bus PTC heater draws substantial current and a fault can damage the high-voltage bus. Confirm the protection circuit test certificate before sign-off.<\/p>\n

    Components that make cold-weather operation possible<\/h2>\n

    The components that make cold-weather heat-pump operation possible on the rooftop platform can be grouped into three categories. Each of the supporting manuals has additional details on commissioning and on-site test procedures.<\/p>\n

    The 2024 platform uses full-DC inverter drive for the compressor and fans, PWM stepless speed regulation coupled with the electronic expansion valve, and V-shaped shock absorption on the bus-mount frame to keep noise and vibration low. Each of these is a contributor to the cold-weather operating envelope:<\/p>\n

      \n
    • Full-DC inverter drive<\/strong> lets the compressor ramp up gradually from cold-start, reducing inrush current on the high-voltage bus. It also keeps the compressor in its efficient speed range as the refrigerant mass flow rises with falling ambient.<\/li>\n
    • PWM and electronic expansion valve<\/strong> keep the refrigerant superheat close to the design point across a wide range of operating conditions. Without these, the evaporator would either starve (low superheat, liquid slugging risk) or flood (high superheat, capacity loss).<\/li>\n
    • V-shaped shock absorption<\/strong> keeps the unit on the rooftop frame under thermal cycling. A rooftop unit in a cold climate cycles through large temperature swings every day; rigid mounting causes fatigue cracking in the refrigerant lines.<\/li>\n<\/ul>\n

      The component protection rating of IP67 means the compressor and the waterproof connectors resist dust and immersion. For a rooftop unit in a cold climate, this is what keeps road salt and melt-water from reaching the compressor terminals and the high-voltage junction box. The DC-DC module ambient ceiling of 65 degrees C is the upper bound for the same unit in summer sun. The two limits together define the rooftop unit’s year-round operating window.<\/p>\n

      How this article fits with the rest of the editorial cycle<\/h2>\n

      This article sits in the Week 1 “Selection and sizing” theme of the four-week editorial cycle. The Week 1 line-up also covers transport-refrigeration unit selection, BTMS sizing, electric-bus AC selection, refrigerated-tricycle selection, DC-DC converter selection, and HVAC control-panel input checklists. To avoid duplicating existing News posts (the project mandate), the related articles in this pilot focus on truck parking AC maintenance (post 5542, this folder) and truck parking AC pre-installation roof survey (post 5550, this folder). Each of those is a different reader intent from this one: maintenance is after the unit is installed, roof survey is before.<\/p>\n

      Frequently asked questions<\/h2>\n

      Can a single NBEAC-24 unit heat and cool a 7-8.5 m bus at -15 degrees C?<\/h3>\n

      The 28 kW heat-pump heating capacity is published at standard rating conditions; at -15 degrees C the available heating capacity will be lower and the COP will drop. For a 7-8.5 m bus, NBEAC-24 is the right platform choice, but the worst-case ambient has to be specified by the route profile. If the bus will see extended periods at or below -15 degrees C, confirm with the engineering team whether the auxiliary PTC heater is sized to maintain cabin temperature in addition to the heat pump.<\/p>\n

      Is R410A a drop-in replacement for R407C?<\/h3>\n

      No. The two refrigerants have different pressure-temperature curves and different glide characteristics. A system designed for R407C cannot be simply recharged with R410A, and the lubricant may also differ. The decision must be made at the quotation stage and locked in for the life of the unit.<\/p>\n

      What is the difference between the basic platform (NBEAC-21 to 34) and the integrated platform (NBEAC-21-T to 34-T)?<\/h3>\n

      The basic platform serves the cabin only. The integrated platform adds a battery-side cooling path and a battery-side heating path so the same refrigerant loop can manage cabin comfort and battery thermal management simultaneously. The integrated platform is the right choice for an electric bus with a liquid-cooled traction battery, especially in a fast-charge depot. The basic platform is sufficient for a hybrid or fuel-cell bus where the battery thermal management is separate.<\/p>\n

      Does the heat pump’s -20 degrees C floor mean the bus can run at -20 degrees C?<\/h3>\n

      No. The -20 degrees C floor is the lowest ambient at which the heat pump still contributes meaningfully to cabin heating. Below that floor the auxiliary PTC heater takes over and the range penalty increases. The bus can still operate, but the route profile and charging strategy have to account for the higher heating load.<\/p>\n

      What is the published COP of the heat pump?<\/h3>\n

      The series product literature states a coefficient of performance (EER \/ COP) of 3.0 for the heat pump system. This is the design point and will fall as ambient temperature falls. Confirm the COP at the specific operating points that matter for your route with the engineering team before any range or operating-cost claim.<\/p>\n

      Source and confirmation<\/h2>\n

      Technical source: NEWBASE Bus Air Conditioning 2024 (Zhengzhou Newbase Auto Electronics Co., Ltd., 2024.10), document SHA-256 d1d11119295ca593fc9c8742ce8e5c5e807cb24b3bbaa5e582bf36dc85fc4e4c. Pages 6, 7, 14, 15, 17, 18, and 19 of the source manual were used. The 2024 New Energy Bus Air Conditioner product Series document (SHA-256 844ce9ea84f949700c44a150b6ab0336f685b705c3e39419784dcb3d37ce6f83) was also used for the cross-platform specification (page 1) and the heat-pump operating temperature (page 2). See the source register for the full claim-to-page map. Current product documentation and engineering confirmation take precedence over this article for any specific installation.<\/em><\/p>","protected":false},"excerpt":{"rendered":"

      Cold-weather heat-pump operation for an electric bus rooftop AC: low-temperature air-injection enthalpy-increase technology, R407C vs R410A refrigerants, and components for sub-zero operation.<\/p>","protected":false},"author":1,"featured_media":5581,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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heat-pump operation for an electric bus rooftop AC: low-temperature air-injection enthalpy-increase technology, R407C vs R410A refrigerants, and components for sub-zero operation.","_links":{"self":[{"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/posts\/5582","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/comments?post=5582"}],"version-history":[{"count":1,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/posts\/5582\/revisions"}],"predecessor-version":[{"id":5589,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/posts\/5582\/revisions\/5589"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/media\/5581"}],"wp:attachment":[{"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/media?parent=5582"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/categories?post=5582"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newbasen.com\/pt\/wp-json\/wp\/v2\/tags?post=5582"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}