--- title: "Combi Oven or Convection Oven: Steam, Water Lines and the Upkeep That Comes With Each" description: "How dry fan heat and controlled steam differ on the menu, the water pressure, quality and drain a combi needs, weekly and yearly upkeep for each, and which…" url: "https://commercialappliancerepair.center/guides/combi-oven-or-convection-oven/" date_modified: "2026-09-26" --- Choosing and comparing # Combi Oven or Convection Oven: Steam, Water Lines and the Upkeep That Comes With Each Choosing a combi oven or convection oven comes down to whether the menu needs controlled moisture. A convection oven bakes and roasts with fan-driven dry heat and asks for little beyond power or gas and a hood. A combi adds steam and humidity control, which demands water of a set quality, a vented drain, regular descaling and a yearly service visit. By [CommercialApplianceRepair.center technical team](https://commercialappliancerepair.center/authors/technical-team/) Published September 26, 2026 ## At a glance. Both ovens move hot air with a fan. The combi also makes steam and controls how much of it stays in the cabinet, and that single difference brings a water line, a drain, a descaling routine and a longer list of parts into the kitchen. Read the whole guide ### Rational iCombi Pro in steam mode 100 percent humidity, 86–266°F Convection mode runs up to 575°F with humidity set from 0 to 100 percent. ### Blodgett BCX combi water supply 40–50 PSI, cold water only With hardness of 35–180 ppm and chlorides under 25 ppm. ### Convection oven cook temperatures About 50°F lower than deck recipes Blodgett's starting point for its Zephaire convection ovens. ### ENERGY STAR convection ovens About 27 percent more efficient on average Certified combis also meet limits on water use. In this guide 1. How each oven cooks 2. What each oven needs from the building 3. Upkeep compared week by week 4. What each design tends to need repaired 5. Matching the oven to the operation 6. Questions ## How each oven cooks A convection oven blows heated air around the cabinet, which browns faster and more evenly than still air. Blodgett suggests starting about 50°F below a deck oven recipe and lowering further if edges finish before centers. Humidity comes only from the food, or from a pan of water set on the bottom rack, a trick Blodgett suggests for roasts. A combi oven adds a steam source and a controller that holds a set humidity. In Rational's iCombi Pro, steam mode runs at 100 percent humidity from 86 to 266°F, combi-steam mixes moist and dry heat from 86 to 572°F, and convection mode reaches 575°F. The oven removes excess moisture when the cabinet runs wetter than the setting. ### What controlled steam changes on the menu Steam lets one cabinet do the work of a steamer for vegetables, rice and seafood, hold roasts moist at lower temperatures, and rethermalize plated food without drying it. Kitchens that batch-cook proteins, run banquets or feed a hospital tray line lean on those modes every day; a bakery-cafe finishing pastries and cookies may never use them. Source: [Rational — iCombi Pro 20-1/1 and 20-2/1 original instructions for use (US)](https://hcms.rational-online.com/hcms/v1.7/entity/documents/155435/storage/MTU1NDM1LzAvbWFzdGVyLy8vMTAxNTcwMzIw/download/manual_original_instruction_icombi_pro_20-1_1,_20-2_1_english_usa.pdf) — Steam mode at 100 percent humidity from 86 to 266°F, combi-steam 86 to 572°F, convection 85 to 575°F; iCareSystem shows cleaning and care status in green, yellow and red and uses only Rational's cleaner and care tabs; service at least once per year.; [Blodgett — Zephaire G-ES convection oven installation, operation and maintenance manual](https://middleby-cdn.com/usermanuals/Blodgett_Zephaire-G-ES_ConvectionOven_Manual_1.pdf) — Cook temperatures generally 50°F lower than deck oven recipes; a sheet pan of water adds humidity for roasting; air intakes cleaned weekly; venting checked annually; no lubrication required. ## What each oven needs from the building A gas convection oven needs its gas supply, a circuit for the blower and controls, clearances, and a hood that meets local code. Blodgett also asks that the venting be checked every year for damage from moisture and corrosive flue gases. An electric model trades the gas line for a larger circuit. A combi needs all of that plus water and a drain. Blodgett's BCX manual calls for 40 to 50 PSI of cold water through a 3/4-inch connection, sets limits on dissolved solids, hardness, chlorides, silica, chlorine and chloramine, and wants an atmospheric vented drain that takes water up to 140°F. Plan the water treatment before the oven arrives, not after the first scale alarm. - Convection: power or gas, a hood, clearances, a level stand or stacking kit. - Combi: the same, plus a treated cold water line, a vented floor drain and, on many models, space for cleaning chemicals and a delime jug. - Both: a data plate that matches the voltage, phase and gas type at the spot. Source: [Blodgett — Zephaire G-ES convection oven installation, operation and maintenance manual](https://middleby-cdn.com/usermanuals/Blodgett_Zephaire-G-ES_ConvectionOven_Manual_1.pdf) — Cook temperatures generally 50°F lower than deck oven recipes; a sheet pan of water adds humidity for roasting; air intakes cleaned weekly; venting checked annually; no lubrication required.; [Blodgett — BCX and BX combi oven manual](https://middleby-cdn.com/usermanuals/Blodgett_BCX-BX_CombiOven_Manual_1.pdf) — Water at 40–50 PSI through a 3/4-inch cold connection with hardness 35–180 ppm and chlorides under 25 ppm; atmospheric vented drain, 140°F maximum; delime reminder after 30 hours of boiler operation; cycle about 45 minutes; boilerless BX-14 needs lime removed from the fan and heat source.; lime builds up inside the steam generator, reducing efficiency and damaging the boiler.; [ENERGY STAR — Commercial ovens](https://www.energystar.gov/products/commercial_ovens) — Certified gas and electric convection ovens are on average about 27 percent more energy efficient; certified combination ovens also meet water consumption limits. Close on the steam generator door of a combi oven standing open, the oven cool. ## Upkeep compared week by week Convection ovens ask for daily wiping, a soak for racks and the blower wheel when needed, and weekly cleaning of the air intakes; Blodgett names the blower motor, the rear cooling fan and the fan guard as the intakes that cool the controls. Beyond the yearly venting check, its manual lists no lubrication. Combis add a cleaning cycle and scale control. Rational's iCareSystem reads how dirty the cabinet is and how much scale sits in the steam generator, shows each as green, yellow or red, and runs with Rational's own cleaner and care tabs only. Alto-Shaam calls for the CT PROformance to be descaled monthly, and Rational asks for its iCombi Pro to be serviced at least once a year. ### Boiler or boilerless combi Some combis make steam in a separate generator; others spray water onto the fan and heating source. Blodgett's BCX with a steam generator reminds the crew to delime after 30 hours of boiler operation and runs the cycle automatically in about 45 minutes. Its boilerless BX-14 has no generator, but lime still builds on the fan and heat source and is sprayed off by hand, so neither design escapes hard water. Source: [Rational — iCombi Pro 20-1/1 and 20-2/1 original instructions for use (US)](https://hcms.rational-online.com/hcms/v1.7/entity/documents/155435/storage/MTU1NDM1LzAvbWFzdGVyLy8vMTAxNTcwMzIw/download/manual_original_instruction_icombi_pro_20-1_1,_20-2_1_english_usa.pdf) — Steam mode at 100 percent humidity from 86 to 266°F, combi-steam 86 to 572°F, convection 85 to 575°F; iCareSystem shows cleaning and care status in green, yellow and red and uses only Rational's cleaner and care tabs; service at least once per year.; [Blodgett — Zephaire G-ES convection oven installation, operation and maintenance manual](https://middleby-cdn.com/usermanuals/Blodgett_Zephaire-G-ES_ConvectionOven_Manual_1.pdf) — Cook temperatures generally 50°F lower than deck oven recipes; a sheet pan of water adds humidity for roasting; air intakes cleaned weekly; venting checked annually; no lubrication required.; [Alto-Shaam — Combitherm CT PROformance operator's manual (MN-35948), archived copy](https://web.archive.org/web/20220509173647/https://www.alto-shaam.com/en/media-library/widen-assets/technical-literature/operators-manual/operators-manual_combitherm_ctp_mn-35948-en-18-pdf.pdf) — On a monthly basis, decalcify or descale the oven; fats and solids coagulate in the drain and back water up into the oven; use the maker's own cleaner only. ## What each design tends to need repaired A convection oven's service list is short: blower motors and their bearings, door switches and hinges, igniters and gas valves on gas models, elements on electric ones, and thermostats or controls. A combi carries all of those plus parts that live in water, such as fill solenoids, level probes, the steam generator and its heating elements, drain pumps and valves, and the cleaning pump. That longer list is not a reason to avoid a combi; it is a reason to budget for water treatment and a yearly visit from the start. The makers' manuals keep returning to three risks: lime in the steam side, fats and solids clogging the drain until water backs up into the cabinet, and cleaning products the maker never approved. - Shared by both: blower motors, door switches and hinges, thermostats and controls, igniters and gas valves or heating elements. - Combi only: fill solenoids, water level probes, the steam generator and its elements, drain pumps and valves, the cleaning pump and the hand shower. Source: [Blodgett — BCX and BX combi oven manual](https://middleby-cdn.com/usermanuals/Blodgett_BCX-BX_CombiOven_Manual_1.pdf) — Water at 40–50 PSI through a 3/4-inch cold connection with hardness 35–180 ppm and chlorides under 25 ppm; atmospheric vented drain, 140°F maximum; delime reminder after 30 hours of boiler operation; cycle about 45 minutes; boilerless BX-14 needs lime removed from the fan and heat source.; lime builds up inside the steam generator, reducing efficiency and damaging the boiler.; [Alto-Shaam — Combitherm CT PROformance operator's manual (MN-35948), archived copy](https://web.archive.org/web/20220509173647/https://www.alto-shaam.com/en/media-library/widen-assets/technical-literature/operators-manual/operators-manual_combitherm_ctp_mn-35948-en-18-pdf.pdf) — On a monthly basis, decalcify or descale the oven; fats and solids coagulate in the drain and back water up into the oven; use the maker's own cleaner only. ## Matching the oven to the operation The right answer depends on how much of the menu uses moisture, the space under the hood, and whether the kitchen can keep up a descaling routine. ### When a combi earns its place Banquet and catering kitchens, schools and hospitals, hotels running several outlets, and restaurants replacing a steamer, a convection oven and a holding cabinet with one footprint all get daily use from steam and combi modes. ### When a convection oven is enough Bakeries, pizza-and-sandwich shops that only finish and bake, cafes with a short menu, and kitchens with no floor drain near the line are usually better served by a convection oven. A second convection oven is often a better buy than a combi that would spend most of its life in dry heat. ## Where to stop Book a visit before moving either oven or changing its gas type, circuit or water connection, and whenever a gas oven will not light, a combi shows a steam generator or water level alarm that the manual does not clear, or water leaks from under the cabinet. Staff should not open the rear or side panels, touch the gas train or reach behind the fan guard while the oven has power. Written by [CommercialApplianceRepair.center technical team](https://commercialappliancerepair.center/authors/technical-team/). Technicians who service restaurant, institutional and laundry equipment, working from site visits, service logs and makers' manuals. Sources: [Rational — iCombi Pro 20-1/1 and 20-2/1 original instructions for use (US)](https://hcms.rational-online.com/hcms/v1.7/entity/documents/155435/storage/MTU1NDM1LzAvbWFzdGVyLy8vMTAxNTcwMzIw/download/manual_original_instruction_icombi_pro_20-1_1,_20-2_1_english_usa.pdf) · [Blodgett — Zephaire G-ES convection oven installation, operation and maintenance manual](https://middleby-cdn.com/usermanuals/Blodgett_Zephaire-G-ES_ConvectionOven_Manual_1.pdf) · [Blodgett — BCX and BX combi oven manual](https://middleby-cdn.com/usermanuals/Blodgett_BCX-BX_CombiOven_Manual_1.pdf) · [Alto-Shaam — Combitherm CT PROformance operator's manual (MN-35948), archived copy](https://web.archive.org/web/20220509173647/https://www.alto-shaam.com/en/media-library/widen-assets/technical-literature/operators-manual/operators-manual_combitherm_ctp_mn-35948-en-18-pdf.pdf) · [ENERGY STAR — Commercial ovens](https://www.energystar.gov/products/commercial_ovens) For the heart of your home. ## Questions owners ask. ### Can a convection oven with a water spritzer stand in for a combi? Only partly. A spritzer injects a burst of water for crust and shine, but the oven cannot hold a set humidity, so it will not steam vegetables or hold proteins the way a combi does. ### Does a combi oven need a water softener? It needs whatever treatment brings your water inside the maker's limits. Some makers set minimum and maximum hardness, so a softener alone is not always the answer; a water test and the manual decide it. ### Which is cheaper to run day to day? A convection oven uses no water and fewer chemicals. ENERGY STAR certifies both kinds, and certified combis must also meet water use limits, so compare certified models of each. ### How long does a combi's descaling take out of service? It varies by model. Blodgett's automatic BCX cycle takes about 45 minutes, while a manual process on other units can take longer, so most kitchens run it after close. ## The problems behind it. Each has a page of its own: what it usually means and the causes in the order worth checking. [All 17 problems](https://commercialappliancerepair.center/problems/) Problem ### Combi Oven Steam Problem: Weak Steam, Scale or a Dry Cavity 6 causes, cheapest first Problem ### Commercial Convection Oven Baking Unevenly Across the Racks 6 causes, cheapest first Problem ### Pilot Won't Stay Lit on a Fryer, Griddle or Steamer on the Line 6 causes, cheapest first Problem ### Commercial Appliance Error Code on a Combi, Fryer, Dish Machine or Laundry Display 8 causes, cheapest first ## When it needs a technician. The repairs on the right are where this guide ends when the checks do not settle it. ### Commercial oven and combi oven repair Convection, combi and rapid-cook ovens, steamers and kettles: blowers, steam generators, probes, igniters and controllers. ### Commercial cooking line gas repair Griddles, charbroilers, restaurant ranges and hot tops: pilots, burners, orifices, valves and hoses, leak-checked after. ### Commercial appliance diagnostic visit One visit finding why a cooler, fryer, oven, dish machine or laundry machine stopped earning its keep. ## More in choosing and comparing. Gas or electric on the line, a combi or a convection oven, a door-type or a conveyor dish machine, leasing or buying, and when an aging commercial unit earns a repair and when it belongs on the replacement budget. [The whole section](https://commercialappliancerepair.center/guides/choosing-and-comparing/) Gas or electric, repair or replace, lease or buy ### Repair or Replace Commercial Equipment: The Failed Part, the Hours Lost and What a New Unit Asks Which failures are routine and which point to a new unit, how to weigh downtime and lead times, the EPA limits on cooling gas in new cold storage, utility savings and the paperwork to check first. Gas or electric, repair or replace, lease or buy ### A Service Contract or Call-by-Call Repair: Matching Coverage to the Equipment You Run What planned and full agreements buy, the yearly inspections fryer and combi makers already ask for, when paying per visit is enough, and the questions to settle in writing before you sign. Guides ### All 18 guides Six sections, by what you are trying to find out. --- **[Read on the site: Combi Oven or Convection Oven: Steam, Water Lines and the Upkeep That Comes With Each](https://commercialappliancerepair.center/guides/combi-oven-or-convection-oven/)** **[Book a visit with CommercialApplianceRepair.center](https://commercialappliancerepair.center/schedule/)**