Hot water works fine the boiler kicks in and everything.

The boiler doesnt kick in for central heating at all no fault codes on screen etc.

Thermostats all set on high and still nothing. Other night I went in the loft and yanked the little lever on the honeywell mid position motorised valve and it would go back to auto but when I held it to 'manual open' the nearest radiator got half warmed. But after a few pulls of the lever the lever's resistance was gone!

I went to a plumbers merchant and they said its usually the little motor that needs replacing if there is no resistance. I opened mine today and there's many wires and am clueless. (I havnt bought the replacement motor as it cost £17 and wasn't sure if I definitely need that espeically as the refund policy was 'cant be used')!

My boiler is brand new bought it in Jan 2009 its a 38kw Vaillant powerful machine lol and usually heats the whole within 30mins! At the time of installation of 'the machine' (as I call it) I had the honeywell motorised valve but in. But to be honest, since the middle of April we havn't used heating and its been a good 5 months, so am assuming it might have seized up a little on the water side especially as water was being heated for about 2-3hours per day on seperate occasions whilst cenral heating was on the 'off' position on the programmer!

Any help would be appreciated, as I have tried to call gas engineers out but they don't like to attend small jobs as there's not much 'profit' in it for them as they say!

If you are confident...replace the valve...99% sure this is the problem..


Chances are the heating Guys will log on later and say 100%....

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I Know it says I'm On-line, but I might have just left myself logged in, whilst I'm out....

Be interesting to know what boiler it is and type of system etc.

Unless it's a combi 38kw, is for a 6-7 bed detached house, or a 2 up 2 down with no glass it the windows.

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How much do you wanna bet the primary flow and return are in 22mm Scruff

If all resistance is gone in the lever the valves seized, change the whole thing

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If the valve has seized inside 18 months there's a fault with the way it's all been chucked in.

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I was thinking to just replace the little motor and not the whole valve! In order to change the valve I'd have to drain down the whole system which am not sure how to do properly and therefore cannot do myself.

Its a Vaillant ecotec 438 not a combi its an open vent system I think. Sorry am a bit confused with the 2 up and 2 down / no glass statement? Clarify please?!

How large is the house, 38Kw is not your average town house.

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4 bed detached with double garage (boiler situated here and no radiators here), 2 extended rooms downstairs with flat roofs (no loft/roof insulation), 2 further rooms downstairs, kitchen, 4 bedrooms (1 again with flat roof), 1 bathroom, 1 wc, and 1 shower room. Majority of rooms have large double radiators except bathroom and kitchen and 1 of the extended rooms.

I mentioned flat roofs/no insulations because I believe that more heat is required to heat the room etc

Worcester Bosch and a few other sites recommend a similar sized boiler for my house type despite corgis oppose this (most likely they want you to have an underpowered boiler so it breaks down = more money for them)! I had this issue previously with a 40,000btu boiler and it completely died on me hence I got this 130,000btu machine installed!

Unfortunately Nadsta it doesn't work like that, and your reasoning is way of track, you could have had a much better and more reliable boiler than the one you have, for the same money.

Whilst 40,000 sounds to low, 135,000 is just plain silly, whereas I would guess 65-75,000 would have been a far better option, anyway that is immaterial now, we need to sort the boiler out and why the valve has gone defunct in such a short time.

Can you post a few pics showing the valve, pump and surrounding pipework.


Ps, they ain't Corgies them be gasesafe now.

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Sorry had no net access.

I called one guy out today and he wasnt willing to climb in the loft due to a sore back but said the head of the motor valve would need replacing. I spent countless hours today (broke one and exchanged it by the skin of my teeth) and finally put it in!

Even though I bought a whole valve I decided to only put in the top half as I do not know how to drain the system! Unfortunatley the issue still remains, however with the new top half of the valve central heating does come on by manually opening the valve ONLY when hot water is on as well! Central heating cannot come on by its self!

Now am thinking maybe its the bottom half of the valve that is stuck but I moved the little 'knob' whilst fitting the new head, and it moved freely!

Any suggestions?!

Have you wired it up correctly?

I would range rate the boiler down to 20Kw, using 'd0'.

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Yes I have, I bought another honeywell exactly same model, same wires (even checked pcb board markings etc).

Sorry mate but this low kw issue annoys the hell out of me. If one says to me you need a 16-20kw boiler, 24kw being max for your house then, then what do flats, and small terraced houses require? 5kw? 10kw?! (Minimum produced are 10kw for a small flat!)

When I bought this house in 2000 it had an old Glow Worm, one of them that sit on the floor which was roughly about 80-100k btu. The house heated up so quickly within 30-40 minutes including water!

That unfortunately conked out on me in 2003 (as it was like 30 odd years old) and I bought a Ravenheat via a gas man which was 16kw (54k btu) that lasted until 2005. Then came along a 20kw (68k btu) Ideal Classic, again via gas man, which lasted until 2009, again conked out!

In 2009, I finally learnt to do my own home work (top boiler manufacturers' websites to start off with) and met a few old plumbers/gas men who new the 'real deal form back in the days' and they recommend I should go for atleast a 100k btu boiler for the size of my house.

So, if someone paid me a million quid to downgrade my boiler its still not happening.

Fact:
New boilers are NOT 'economical' infact they are a waste of money. When a boiler breaks down, the poor engineers are absolutely cluless on whats gone wrong with it because they simply have too many gadgets in them (pcb's and what not)! An old cast iron boiler is much more efficient and are easily repairable (only consists of 5-6 parts!). There is no 'efficieny' its simply a marketing scam, if you think about it, gas prices rise throughout the year, so what are you really saving on?!

Sorry am not having a go at anyone, but quiet a few people said I have an oversized boiler! The logic simply is its got more 'power' in it and will not need to use that. i.e. a 1.0l car which max's 100mph is more likely to have its engine blown or breakdown (like my 2 underpowered boilers!), whereas a Ferrari which max's 200mph+ will not have a problem simply 'cruising' at 100mph...

So did you just replace the motor? or you replaced the powerhead?

Did you check to see if the valve was turning freely when the powerhead was off?

Was the valve in the correct postion when you put the powerhead back on?

Also is it possible to get someone else to get get the system to call for water then call for heating while you are in the loft and see what happens?

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sorry, just read you other post through, so it is moving freely

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Replaced the motor last week and no change, a gas man said today change the head or the whole unit and couldnt do the whole unit as I dont know how to drain down so just changed heead today. Yes it was in correct position. Someone helped me last week with old valve and it all worked just for water not heating.

Its been running for 2hours today with the water on (so rads aint piping hot but are ok'ish) I switched off water on the programmer and heating goes off as well. When I put both back on the heating and water contiue to work. Maybe cos the valve is left on manual open or the system needed the rads to work for a while as it was switched off for months?

I was thinking it might be the programmer but then rads work when I manual open... so am assuming it maywell be the bottom half of the valve! I googled this issue and honeywell valves apparently inflate or get squashy/squdigy when only using water for continuous period i.e. summer.