Worcester Bosch
Worcester Bosch Turbine Flow Switch 87170021320
Worcester Bosch 87170021320 turbine flow switch for Greenstar combi and system boilers, detecting DHW flow to trigger hot water demand.
At a glance
- Part type: Flow switch (turbine)
- Also known as 1019903
- This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.
Showing prices
£91.00
£75.83 ex. VAT · VAT at 20%
In stock
Cut-off passed — dispatches next working day
Not certain it's the right part? The technical team verifies fitment before dispatch — no charge, and it stops a second trip.Call the technical teamSend a technical question
Same-day dispatch
Ordered by 4pm Mon–Fri, 10:30am Sat.
30-day returns
Unused, in original packaging.
What it is
The Worcester Bosch 87170021320 is a turbine flow switch supplied for the manufacturer's Greenstar family of gas boilers. It sits in the domestic hot water circuit and uses a rotating turbine to detect water movement, sending a signal to the boiler control when a hot tap is opened. That signal starts the hot water sequence, so the switch plays a direct part in reliable DHW delivery.
Signs this part needs replacing
- No hot water at the taps while the central heating continues to run normally
- The boiler does not fire when a hot tap is opened
- Hot water is intermittent, or the temperature at the outlet fluctuates
- A flow switch or DHW fault code appears on the boiler display, sometimes with a lockout
- The turbine is found to be sticking, seized or not rotating when the DHW circuit is checked
Before you order
- Check the GC number and model on the appliance data badge against the compatibility list to confirm the correct application.
- Compare the number on the existing component with 87170021320 and the alternative numbers listed before ordering.
- This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.
Mechanical
| Part type | Motors |
|---|---|
| Length | 0.1mm |
| Width | 0.1mm |
| Depth | 0.1mm |
Compliance
| Manufacturer part number (MPN) | 87170021320 |
|---|---|
| GC number | H21-232 |
| Barcode / EAN | 4010009615743 |
| GPC classification | Household Boilers/Furnaces/Tank Water Heaters Replacement Parts/Accessories |
| Alternative numbers | WB87170021320, 1019903 |
| Make | Model / assembly | Reference | Years | Fitment |
|---|---|---|---|---|
| WORCESTER GREENSTAR 24 FSN-GB COMBI NG | 47-406-32 | 47-406-32 | — | — |
| WORCESTER GREENSTAR 25SI COMPACT LPG | 47-406-51 | 47-406-51 | — | — |
| WORCESTER GREENSTAR 25SI COMPACT NG | 47-406-50 | 47-406-50 | — | — |
| WORCESTER GREENSTAR 25Si ErP COMPACT LPG | 47-407-74 | 47-407-74 | — | — |
| WORCESTER GREENSTAR 25Si ErP COMPACT NG | 47-406-73 | 47-406-73 | — | — |
| WORCESTER GREENSTAR 28 CDI COMPACT LPG | 47-406-45 | 47-406-45 | — | — |
| WORCESTER GREENSTAR 28 CDI COMPACT NG | 47-406-44 | 47-406-44 | — | — |
| WORCESTER GREENSTAR 28 FSN-GB COMBI NG | 47-406-33 | 47-406-33 | — | — |
| WORCESTER GREENSTAR 28CDi ErP COMPACT LPG | 47-406-78 | 47-406-78 | — | — |
| WORCESTER GREENSTAR 28CDi ErP COMPACT NG | 47-406-77 | 47-406-77 | — | — |
Showing 10 of 50 compatible appliances.
Fitment listings are a guide, not a guarantee. Plant-room assemblies get modified on site more often than not. Send us the GC number off the data badge and a photo of the existing valve and we will confirm before anything is dispatched.
Documents & drawings
Everything we hold for this part. Where a document exists but we don't hold it, the technical team will source it from the manufacturer — usually the same working day.
manual
WORCESTER appliance manual — GREENSTAR 25SI COMPACT LPG (GC 47-406-51), GREENSTAR 25SI COMPACT NG (GC 47-406-50), GREENSTAR 30 SI COMPACT LPG (GC 47-406-53), GREENSTAR 30 SI COMPACT NG (GC 47-406-52)
manualmanualWORCESTER appliance manual — GREENSTAR 25Si ErP COMPACT LPG (GC 47-407-74), GREENSTAR 25Si ErP COMPACT NG (GC 47-406-73), GREENSTAR 28Si ErP COMPACT, GREENSTAR 30Si ErP COMPACT LPG (GC 47-406-76), GREENSTAR 30Si ErP COMPACT NG (GC 47-406-75)
manualmanualWORCESTER appliance manual — GREENSTAR 28 CDI COMPACT LPG (GC 47-406-45), GREENSTAR 28 CDI COMPACT NG (GC 47-406-44)
manualmanualWORCESTER appliance manual — GREENSTAR 28CDi ErP COMPACT LPG (GC 47-406-78), GREENSTAR 28CDi ErP COMPACT NG (GC 47-406-77), GREENSTAR 32CDi ErP COMPACT LPG (GC 47-406-80), GREENSTAR 32CDi ErP COMPACT NG (GC 47-406-79), GREENSTAR 36CDi ErP COMPACT LPG (GC 47-406-82), GREENSTAR 36CDi ErP COMPACT NG (GC 47-406-81)
manualmanualWORCESTER appliance manual — GREENSTAR 32CDI COMPACT LPG (GC 47-406-47), GREENSTAR 32CDI COMPACT NG (GC 47-406-46), GREENSTAR 36CDI COMPACT LPG (GC 47-406-49), GREENSTAR 36CDI COMPACT NG (GC 47-406-48)
manualmanualWORCESTER appliance manual — GREENSTAR HEATSLAVE II 12/18 ErP, GREENSTAR HEATSLAVE II 18/25 ErP, GREENSTAR HEATSLAVE II 25/32 ErP
manualmanualWORCESTER appliance manual — GREENSTAR HEATSLAVE II EXT 12/18 ErP, GREENSTAR HEATSLAVE II EXT 18/25 ErP, GREENSTAR HEATSLAVE II EXT 25/32 ErP
manualmanualWORCESTER appliance manual — GREENSTAR HIGHFLOW 440 (GC 47-311-82)
manualNo technical questions yet for this part.
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