Halstead Finest Gold, CH-OK, DHW burner cuts in and out ??

[DaveyD]

Hello,

I'm looking for a bit of help on the following problem...

The CH works 100%

The DHW works OK for about 30 seconds, then the flame goes out, then after another 30 secs it cuts back in. The cycle repeats.

Its a Halstead Finest Gold. I've been searching through the previous posts, but haven't any answers yet.

A steer in the right direction would be a great help.

Cheers, Dave

 

[ollski]

I would get a man in to check your gas modulation settings and sensor. If it were me I would link all three terminals on the air pressure switch to rule out a blockage in the fan venturii before taking out the hot water heat exchanger for a clean out.

 

[DaveyD]

Thanks ollski,

But wouldn't the venturii be OK if it works on CH and wouldn't that be the same for the gas modulation as well? (I'm not doubting you, just checking)

I have had the heat exchanger block up before and that caused the boiler to lock out, its not doing that, it relights Ok.

 

[transam]

If my memory serves me correctly , ther are 2 thermisters in this , boiler
there fore this would mean because u have correct modulation on C.H does not mean U have it on H.W , as it is controlled by different sensors .
both giving imfo' to a main control board , which than tells the modulater on gas valve what to do , it could be your plate exc' & if u have cleaned it before give a go ????

 

[Jerzed]

I have one of these boilers which started doing this after the system had been cleaned. The problem was sludge and residue clogging the plate heat exchanger. This is an easy fix.

Turn off the power and shut off the CH flow and return, also the cold water feed on the manifold. This isolates the main system and allows you to drain the boiler without draining the radiators.

Once dismantled you will find that the heat exchanger is easy to remove. It's held in place with two Allen screws. You only have to disconnect the right had side of the wide tube that runs under the exchanger. Pull the clip and CAREFULLY pry it clear, taking care not to bugger up any O-rings.

Reverse flush the exchanger. You'll be amazed how much crap gets into it. Fill the exchanger with kettle descaler and leave for half an hour to clean. Flush it through before refitting it. Make sure that all O-rings are in position before refitting or you'll get wet when you refill the boiler. Refit the push-fit tube and clip.

Open the cold water feed valve but not the heating valves yet. Fill boiler to about .75 bar checking for leaks. If satisfied, reassemble the casing and front panel.

THEN open both heating valves. Switch on power and let boiler cycle. The boiler should now work perfectly for both heating and hot water. If necessary bleed radiators and top up pressure to just under 1 bar.