Help Worcester 280 RSF

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Help Worcester 280 RSF 12 October 2009, 11:02 PM

thewebweazel Joined 12 Oct 2009 1 posts

Problem: Boiler runs OK on CH mode. (Quick 5min test)
When drawing hot water down with the tap wide open boiler runs for 30-40 secs then shuts down, if the tap is left running the it fires back up again after 10 secs runs for 30 -40 secs and shuts down again, it carries on like that continuously until the tap is shut off. If the hot tap is opened only one third then the boiler will run until the tap is shut off.

What I have already done.
I have tested the water flow switch by shorting the flow switch input (x1) on the Honeywell 45,005,362-001 (ZAGAS127) Main Driver board Fault still present.

I have tested the Water diverter valve (ZAMAJ133) by starting the boiler in CH mode and then turning the hot water tap on, the toggle on the Water diverter valve moves from A to B (or the other way round) hot water runs for 40 secs and boiler shuts down. Fault is still present.

I have tested the overheat thermostat (ZAMAJ133) by removing it from the thermostat pocket. Fault is still present.

I have tested the Central Heating and Domestic Hot Water Sensor
(ZAMAJ197) swapped around. Fault is still present.

I have tested the Domestic Hot Water Sensor by leaving it connected to the Main Driver board but removing it from the Domestic Hot Water output pipe. Fault is still present.

I have tested the Central Heating Sensor by leaving it connected to the Main Driver board but removing it from the Gas to Water heat exchanger pipe. Fault disappears

Plan of action: It looks as if the water flow is restricted to the Gas to Water heat exchanger? And I’m considering flushing the central heating. Is this a wise course of action or have I missed something?

Many Thanks

Help Worcester 280 RSF 23 October 2009, 7:01 PM

MiketheBoilerman Joined 15 Sep 2009 4 posts

This is almost certainly contamination of the water-to-water heat exchanger. Most likely water scale but identical symptoms result from contamination with products of corrosion in the primary water side. I suggest either replacing the HE if it is still available as a spare part, or if not, flushing it with Kamco FX2 or Fernox DS9 acid descaling chemical using a powerflushing pump.

Hope that helps.

Cheers, Mike

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