Built to perform

  • Features and benefits
  • Specifications
  • Literature
  • Case studies
  • BIM
  • Enquiry
  • Energy labelling

  • Up to 15 litres per minute satisfies the most demanding applications
  • Internal or external models available means flexible siting, especially where space is at a premium
  • Copper finned tube heat exchanger makes it low maintenance, reliable and robust
  • 5:1 fully modulating burner adjusts the burner to meet the desired water temperature with no stand-by heat loss
  • Flexible flueing options
  • Compact, light and robust construction so can be installed quickly, saving time on site
  • Factory fitted frost protection so can be installed externally and in areas without heating (external model only)
  • Up to 103% gross efficiency

View product specification

When clicked this will open the product specification in PDF format.



Natural Gas: WH42 WH56 WHX56 WHC56
Propane: LWH42 LWH56 LWHX56 N/A
Heat input (gross) kW 49 62.3 62.3 54
Heat output kW 42 55.8 55.8 55.8
Gross thermal-efficiency % 86% 90% 90% 103%
Standby heat loss mj/month N/A N/A N/A / 72 N/A
NOx emissions (0% 02) natural/propane ppm 52 / N/A 52 / N/A N/A / 72 60 / N/A
Gas data
Gas flow rate (natural gas) m3/h 5.1 6.5 6.5 5.1
Gas flow rate (propane) m3/h


2.5 2.5 N/A
Storage capacity Litre N/A N/A N/A N/A
Recovery rate at 50ºC rise Litre/hr 720 956 956 956
Recovery rate at 56ºC rise Litre/hr 642 854 854 854
Operating pressure (unvented) bar 3.5 3.5 3.5 3.5
Minimum working pressure bar 0.2 0.2 0.2 0.2
Maximum pressure bar 10 10 10 10
Depth mm 240 240 240 240
Width mm 450 450 450 465
Height mm 615 615 615 615
Diameter mm N/A N/A N/A N/A
Flue diameter mm 100 100 100 100
Fuse rating amp 10 10 10 10
Electrical power consumption max/min W 89/85 120/112 83 140
Noise level dBA 49 49 49 49
Weight full kg 30 30 31 30
Weight empty kg 29 29 30 29


Learn more about the FASTflo by downloading product literature. If you can’t find the literature you are looking for, or you have any questions, please contact your Area Sales Manager who will be able to help.

Find out more about the FASTflo by reading the case studies below.

New multi level BIM files coming soon for this product

The Andrews Water Heaters BIM library is being updated to comply with CIBSE PDT standards. If you require CIBSE compliant BIM files for this product, please fill out the form to receive new BIM files when they’re available and we will send them to you as soon as they’re ready. In the meantime, standard BIM files are available to download using the links below. If you can’t find the BIM file you require, or you have any questions, please contact your Area Sales Manager who will be able to help.

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FASTflo energy labels

Fastflo energy label WHX56 and LWHX56 updated 28/09/2015 (0.09MB) Fastflo energy label WHX42 and LWHX42 updated 28/09/2015 (0.09MB) Fastflo energy label WH56 and LWH56 updated 28/09/2015 (0.09MB)

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