need to replacement my diverter valve - should i diy?

[emma_middlebrook]

Hi

Vaillant turbomax plus 824e, installed 2000.

The diverter valve seems to be stuck on central heating mode. If I turn on DHW, the boiler ignites, no cold water but the CH flow pipe gets hot. I also followed the boiler's manual - the spindle in the diverter valve moves (so it is trying to divert) i.e. everything 'in the chain' works except the last stage. From what I have read, this part seems to be one of the weak points of my particular model.

Replacing the part itself seems very easy so I went out and got a replacement! The initial steps seem OK: boiler off, electricity off, all valves closed.

My query is about releasing the water pressure and repressurising the system post-installation. I presume refilling the system is just opening all the valves, electricity on, boiler itself on, turning on all radiators, pressurise using the little key-operated thing underneath the boiler, bleed and check pressure until ok again. I have done something similar when the pressure was a bit low but not 'from scratch' if you see what I mean but from what I understand it's exactly the same principle. Is this right?

Here's the other thing: I have never drained a boiler before and, unfortunately, the manual has a picture (on page 32) but not the instructions that go with it! To drain, I hoped would be a case of shutting off all the valves on the pipes, then opening up another valve at the bottommost point of the boiler (i.e. like a car radiator!). I also see two pressure relief valves on the flow and return pipes of the central heating. Are both of these what I should be using?

I'll get someone in if anyone advises me to do so (for instance, I did read somewhere that said not to do this unless you have a bit of experience because e.g. the boiler's isolation sometimes leak) but I think, if I can make sure I have the releasing and repressurising steps clear, this seems to be one of the sensible DIY tasks that can be done with boilers.

Thanks for any help or advice,

Emma.

[Bob Minchin]

Hi Emma,

Before draining down etc, take the motor unit off your existing valve and see if you can move the valve manually. Quite often it is the motor unit that has failed. If the valve is OK then you might be lucky in that the new motor will fit the old valve.or you might have to return the new valve whole and get the right brand of replacement motor unit. You might not get this at a DIY shed but a prpoer plumbers merchant or heating specialist should be able to help you to find the right part.Take the old one along with you.

hth

Bob

[John Rumm]

It sounds like you should be able to just replace the motor rather than the whole valve. If that is the case then there will be no need to drain down.

Depending on how the boiler is plumbed you may find that you have stop valves on the central heating flow and return pipes (sometimes built into the point where the pipe connects to the boiler. If this is the case then you can shut these off, and turn off the mains water to isolate the valve again without needing a full drain down,

Have a look at the sealed system FAQ for details on refilling etc:

[Lee]

If you do a search through previous posts, there is some good advice on changing the valve in this particular boiler. I have done so myself and it was a very simple job; if you use the shutoff valves provided, then it's only necessary to drain the boiler itself. Though, as you point out, some have said that they may leak - though they didn't for me. Refilling is then just "topping up" and bleeding where necessary. I personally wouldn't turn the power back on until it's full of water and the shutoff valves are open though... :)

Lee

[Ed Sirett]

It seems to be a stock fault with the earlier T/max+s that have the turquoise knobs. The replacement unit seems to be reliable. The problem is the motor seems to fail to drive the valve properly - I don't even know if you could even get just a motor.

The flow and return pipes have isolators on them which operate by 1/4 of a turn and are screwdriver or allen key operated (4mm? AF). There are two little drain points on side of the flow and return isolators which you can fit a small rubber tube to or just put a bucket under.

After refilling turn both the isolators on, turn the gas off (1/4 turn with screwdriver) and put the heating on. The system will quieten down in about 30 seconds and you can then risk the gas back on.

Check the SealedCH FAQ for all the background info.

[emma_middlebrook]

Hi

Apologies for large delay in responding. Firstly, thanks to all who responded - would just like to say thanks and give some good news: I did it myself and there are no problems so far!

If it wasn't for this newsgroup, I wouldn't have had the confidence to have a try, even after diagnosing the problem and deciding it shouldn't be too bad to do given that the dodgy part was quite accessible.

I have to admit, I was quite nervous as I shut the whole thing off, drained the boiler, put the new part in and restarted!

Only one mistake really, before restarting I forgot to turn the flow back on and the boiler temperature reading shot right up to nearly 100 degrees after igniting! I presume this was because there was no water in there :-( I turned it off quickly and am hoping there wasn't any permanent damage.

After that scare, everything went well and I now have a properly working boiler again and nicely bled radiators etc. Saying that, it's still too mild to have the heating on (in London anyway), but at least I know it works fine!

Thanks to all respondents and this newsgroup - I feel like tackling all the other jobs I have now!

Cheers,

Emma.

[Ed Sirett]

You must have put the water back in first or the boiler would not have lit. I tend to be paranoid [1] that the boiler is going to melt down unless I get all the air out first, hence my recommendation to turn the gas off on the boiler until it's all quietened down.

[1] Born out of experience. Earlier this year I sprayed leak detector at a gas valve looking for a gas leak (on a Potterton ) The leak was elsewhere and got fixed. I left the customer, both he and I happy. Later the customer complains that his whole house has been plunged into darkness. Turns out that the whole house is protected by one 30mA RCD. The gas valve was now about 10k Ohms to earth after I had sprayed it. A hair dryer did not make things much better. Whining that the electrical installation was substandard would not have made it work so I lost £103 for a new gas valve.

Education is expensive but cheaper than ignorance.