Halstead Finest not so fine

[Packstrapper]

When i turn on the hot water the boiler ignites and the water gets hot as you would expect ,but as it reaches temperature the boiler switches off and then reignites .this is continuous until tap is turned off.I have done the following:
swapped over c/h and h/w thermistors and even took the h/w one out and plugged the hole .but still the same.

Stripped and cleaned primary and secendary exchagers and diverter.Replaced seals etc.

Checked switches on divertervalve and nither drop out even when bioler stops.

Checked fan vaccum switch although usually goes into fault if this fails.

Could this be a board fault or have i missed something?Please help! i dont want to spend £250 on a board unless i have to and my local plumbers dont have a clue!

 

[scatmanjohn]

How is the heating?

Usually its the fan venturi that needs cleaning.

 

[ChrisR]

Ever had one only do that when hot though?

P - email (in profile) me if you need a new board

 

[Agile]

Its quite common for venturi problems to only manifest themselves when on full power ( DHW ) and the boiler is hot ( Greater volume from expanded hot flue gasses ).

Tony

 

[Packstrapper]

Thanks for your reply .The heating seems fine and runs continuously with no apparent problems .I'll clean the venturi tonight .Thanks again.

 

[fluke]

Did you get anywhere with this? I'm having a similar problem.

Called a Halstead reccommended engineer who said it needed a powerflush (the system is only six years old!! surely not!) and quoted me £650 and then "probably" another £250 or so for a new heat exchanger!! All diagnosed over the phone. I had a whole system installed for that in my last house, incluing rads etc., and okay i know prices go up but blimey! And he still wasn't sure that would fix it (how could he be?)

So, any information you can offer will be gratefully received.

Much thanking!

 

[Agile]

I am not very impressed by that fault finding.

There are several problems which could cause your fault. fan, venturi, gas valve settings, pcb, dirt etc.

To decide which applies in your case a competent engineer would need to do a few tests on it.

Powerflushing is usually about £300 to £350. Heat exchangers can be cleaned if someone knows how to do it.

Tony Glazier

 

[fluke]

No, i wasn't impressed either and told him not to bother. I thought getting a Halstead recommended guy would be the best way but i see how wrong i was (especially after reading some of the comments here!)

The problem isn't a major one, and only occurs when the water is on full flow. if you reduce the flow slightly it seems to be fine. I can live with it for now (until it gets worse i suppose) and have a look round here in case it's something i can clean or replace myself.

Otherwise i'll look around for a better engineer!
(Any recommendations in the cambridge/peterborough area? (UK that is))

 

[Biggles..]

try the tubes between fan and airpressure switch. give them a good blow through slightest bit of dirt causes this fault. Have come across this before and is also the remedy advised on BG database for faults.

 

[Agile]

If you need it fixed properly then "the good looking plumber" is based in Cambridge, I dont go much on his looks but I am sure he can sort out your fault. You may have seen him on the Test the Nation program last year as a "plumber".

Generally the manufacturer's recommended service engineer is the best bet because you can always complain to them if anything goes badly wrong.

Tony