Hi. Thanks to reading the different posts on this forum I gained the confidence to have a go at the job myself. (I cringed at the idea of paying around £200 - £300 for the repair, seeing as I take care of just about every other type of DIY problem around the house. Anyway, I ordered a complete new inverter (Giannonie) valve, including 5 fibre washers from www.ezypart.co.uk tel. 0800-5877482. Cost: £56.00 incl. VAT plus £7.00 postage; quite reasonable compared to other quotes.
Started at 11am.and totally finished at 6am. Took longer than a heating engineer but I took my time and made sure that I did everything correctly..........I shut off the gas at the mains...(in my case in the garage), closed off the gas cock under the boiler housing and switched off the electrical supply at the wall feeding the boiler. I then closed the mains water feed in the kitchen and also the central heating flow and return cocks under the boiler.
Then, opened the hot and cold taps at the kitchen sink about a half turn. (Must be the ones lower than the boiler). Opened the safety valve to release pressure in the system. (In the super 90 this is a big orange knob just to the side of the pump). I opened the manual air vent slightly; this is on a pipe at the side coming out of the combustion chamber housing. (right side) and also made sure that the Automatic air vent above the air separator (small tank also on the right side) was open. Not sure whether these last two things were necessary but better to be safe than sorry. I turned the pump to the right (simply just hold body of pump and twist).
Now for the great extraction! This is a little bit fiddly because the valve is at the back but, considerably easier than you might at first think. I used two adjustable spanners (One reasonably large and one a bit smaller) as all my normal open ended are auto spanners. (None the correct size).
There are a few black electrical leads that cross in front of the valve; these can be carefully pushed down to give enough access, or a couple can be disconnected from their junction at a pipe on the right side. If you do disconnect make sure you write down which way around the terminals go. Once again I don’t think the polarity matters. but personally I think it’s best to put things back the way they come off. (if you’re not 100% sure that is).
Three of the nuts ‘broke’ very easily; however the biggest one at the bottom and the next biggest to the left that is joined to the heat exchanger were quite tight. DON’T simply put as much force as you can on the nut; you don’t want to break or rupture something else in the process! Use a spray or ‘PLUS GASS’ or ‘RUST OFF’ or WD 40’ and leave for a while. I gave it a few applications. This did the job.
You will find that there will be some water coming from the heat exchanger when the nut is opened but have a couple of old towels or rags in place to soak this up. Once the valve was off I cleaned the ends of the pipes of the old fibre washers, smoothed off with wire wool and thoroughly wiped with clean rag. I suppose I tend to over egg the pudding a bit but, I wound some PTFE tape around the threads on the valve and refitted to boiler.
DON’T, Over- tighten the nuts. It’s unnecessary. If you find a slight leak after re-filling the system you can always ‘bump’ the nut slightly. I re-fitted everything more or less in reverse order.
Before re-filling the system I turned the kitchen taps off (remember these were opened initially) and made sure that the drain cock at the pump was turned off as well as the safety valve. Also, once the pressure was up to one and a half bar. I turned the manual air vent off. Before turning on the gas and electricity I checked and re-checked that I hadn’t missed anything. Carefully checking for leaks (None….PHEW!!!!) …………With trepidation I turned on the hot tap…………………beautiful hot water and the thermostat up only two thirds. ………………………I’m now going to build an aeroplane…..a big one !!!!!!!!!
Steve.
STEVE, December 2007
