Qualified Gas/Vaillant Combi boiler knowledge required

Legacy_user

Hi,
I had a Vaillant combi boiler fitted in 1996 (three bed semi one bathroom 6 single large rad’s and two small single rad’s) It is in an upstairs cupboard on the gable-end with a vertical flue. Never, ever any problems until last year 2014, no heating or hot water so we opted for the 'One off repair' by a gas company and they replaced 'Fan Control P.C.B.' on 28.01.2014. Heating has been turned off all summer but on again in November. We have no problems with the hot water however recently the heating just comes on and off as it pleases sometimes nothing for five hours then it comes on. Does anyone know why? How much to fix?

1) I turn the heating on by pressing the switch which has tap and radiator icons on a few seconds later it fires up further and the heating comes on. The water is always fine yet the heating knocks off after an hour or so and won’t come back on for four or five hours

2) We have to top it up with the water tap every two weeks to between number 1 and 2 (always on the green section)and we don’t let it onto the red section on the gage.

3) I think I can prompt it to come on by running the hot water tap downstairs for about 4 min’s until boiling hot, this seems to make it come on however it could be my imagination.

4) When the heating is on but someone uses the upstairs shower it goes off and probably won’t come on for about four hours- just when it pleases.Even when it comes on it knocks off without the use of the shower etc.

5) Since the repair the timer doesn’t work, so all the tappets are placed outwards. I have the switch slid down to 'on' permanently, and just switch it off at the aforementioned switch in the evenings when we go to bed.
It must be costing a fortune at the moment.

If I get a new boiler will the ' VAILLANT ECOTEC EXCLUSIVE 838 COMBINATION BOILER 10002669' be OK for my home. I do hope to add a loft conversion with an on suite in the near future-3years time. Vaillant boasts that it will suit 4 bed 2 bath home. It has seven years parts cover if fitted by a Vaillant fitter.

British gas offer £400 of a new boiler until Feb 2015 but only covers it for two years, I think!

Who should I get to supply and fit or just supply then fit?

Thank you in advance.