Draining down a Combi Boiler

Discussion in 'Plumbers' Talk' started by Sage, Jul 18, 2006.

  1. Sage

    Sage Member

    Hi guys.

    I have a Worcester Combi Boiler (Greenstar 40 HE) and I need to drain down the system to replace a number of TRVs, never drained down a combi before, can AKS please advise me of the procedure for draining down a combi please?
     
  2. tightenit

    tightenit New Member

    Morning Sage. Nice piece of boiler kit.Remember the system is sealed.
    <u>Isolate electrics to boiler</u>. Find drain off co*k for system (usually one inside boiler at the front). Might also be one under floor. Hosepipe on and open the plunger on it. Upstairs working down, open the rad air bleed valves until the system is empty. Without seeing the system it is also likely that as you lower the height of the water you will be left with some at the bottom of the downstairs radiator(s).
    My advice <u>before you drain</u> is to make sure that you know how to refill it again (via the filling loop). Bleed air from rads in usual way. I go low to high. Inhibitor replaced upon refill please.Quick one, lots of sheets under your rad valves when you remove them. Sometimes the gunk inside is like ink and can ruin carpets very easily!!
     
    Jodyq likes this.
  3. Sage

    Sage Member

    That&#146;s brilliant, many thanks for that info, must get the inhibitor before I start work, I had forgotten about that, cheers.

    I should have had all the TRVs installed at the time I had the boiler fitted,but alas ran out of funds :(

    I agree though it is a great boiler, I was unsure about combies at first, but took the advise of the guys on here and went for a Worcester, one of the few companies that manufactured a biggish boiler suitable for LPG, I have lashings of hot water for showers and baths and the CH is excellent very impressive & quick heat build up in the rads, very impressed thus far.


    Many thanks for taking the time to reply, Cheers.
     
    Jodyq likes this.
  4. tightenit

    tightenit New Member

    Pleasure to be of assistance Sage - we all learn from each other on this site. I think a couple of further points may help;

    Make haste slowly! Take your time on each and every TRV and make sure they're tight enough but not overtightened. Some valves are sound when the olives 'crack'.Overtightening is bad news.
    Repressurise your boiler to 1.5 bar (check this please!)
    Finally, unless you're confident about the valve replacements, it's not a bad idea to leave your hosepipe by the drainc*ck in case you need it.
     
  5. Dreadnaught Heating

    Dreadnaught Heating New Member

    I should have had all the TRVs installed at the time
    I had the boiler fitted,but alas ran out of funds
    :(
    Sage, if you have a room stat somewhere on the system, DO NOT put a TRv in that room the two will fight each other, leading to very short on/off times. - But I am sure you knew that already ............

    Patrick
     
  6. Sage

    Sage Member

    Thanks tightenit and PPH your advise was spot on, drained the system down yesterday, fitted half the rads (Flow & Return). no gunk from rads as the boiler fitter did a good job cleaning out the system prior to fitting the Worcester Combi, finished off today and repressurised the system and vented all the rads, powered her up and away she went.

    All went like a dream, many thanks guys, you were a great help.

    PS, got a great little return valve from Plumb Centre, it has little valve that allows you to drain down the rads without cracking open the unions, nice little valve, first time I have seen them around.

    Sage.
     

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