No hot water but at a loss as to why

[flotmangooner]

Hello
Hoping for some advice on a problem I have

I can't get the hot water to work - if I select HW mode on the programmer, the motorised valve can be heard and the boiler fires up but then about five seconds later it goes off again . The central heating side works fine so I don't think it's a problem with the boiler itself.
I had an engineer come out Friday afternoon who thought it was the motorised valve that had gone wrong so he replaced that but the problem remained. After much fiddling he now thinks it must be the programmer and is coming back tomorrow with a new one.
One thing I will say is that , before the HW stopped working, we hadn't been able to run the HW and CH at the same time - it was a case of one or the other (I assumed something had gone wrong with the motorised valve but it didn't really bother me because we just worked around heating the water up and having the heating on)
My boiler is about 5 years old and is a Vaillant ecotec plus 618 and the programmer is a Honeywell ST9400C.

If anyone has any suggestions as to what the problem might be I would really appreciate your thoughts...

 

[townfanjon]

I would be looking at the wiring and the cylinder stat first.

 

[gassafe]

Seems like a random fault with the symptoms you've described, my first thought was 3 port, it could be a programmer but then if the boiler is cutting out after 5 seconds it could be a boiler fault...

Let the engineer do his job... Seems your all too ready to lose confidence in him already... Maybe ask him to bring his crystal ball with him

 

[jtsplumbing]

Is this a open vent system or sealed pressurised ? when valve opens can you feel hot water going to cylinder ? are there any other valves on pipe work on flow & return to cylinder that may have been turned off, its possible there is a blockage on the return from cylinder, make sure that these pipes are clear.

 

[flotmangooner]

Is this a open vent system or sealed pressurised ? when valve opens can you feel hot water going to cylinder ? are there any other valves on pipe work on flow & return to cylinder that may have been turned off, its possible there is a blockage on the return from cylinder, make sure that these pipes are clear.

Hi
I think it's a pressurised system.
Nothing is happening when I put the hot water on but I don't know if this is because I have had the immersion heater on and the water is up to temperature?
I don't think there are any other valves on the pipework and even if there are no one would have turned them off. I am just wary about having the controller replaced if this isn't the problem as these are £100 and the motorised valve has already been replaced at £70 when it wasn't faulty

 

[flotmangooner]

Here are some photos of the pipework leading to the motorised valve and also the hot water cylinder

 

[ShaunCorbs]

gravity set up

but pressurized heating side

 

[gassafe]

Maybe a blocked coil in the cylinder...

 

[Robert Tyrrell]

Let the water in the cylinder cool down, or just try this immediately after you've had a bath/shower:

Check the temperature of the pipe leading from the 3port valve to the cylinder. Do this at the cylinder end and not the valve end.
Turn the boiler on to heat the water check that [it's] firing correctly and leave for 5 minutes.
Check the temperature of the pipe again.
Now check the temperature of the pipe leading back from the cylinder to the valve. It should be nearly as hot but not quite.

If the first pipe gets really hot but the second is cold then you've probably got a blockage in the cylinder coil as suggested by gassafe.

If this isn't the case then ask your engineer, very politely, (Some are more experienced than others and politeness goes a long way) to check the cylinder stat and the wiring to the 3 port valve. He/She could also check to make sure that the valve isn't stuck in the manual setting.
I've actually had this on a new valve that I fitted last year and I had to replace it. Once I had it all worked perfectly and I haven't had any complaints from the customer - just more work as I was the only person that figured it out

 

[joni os]

Are you getting water at the air vent.

 

[Tonycane]

Change plenty of these timer clocks, when you select heating/hot water you hear a click from the programmer, if you don't it's fubard.

 

[jtsplumbing]

Check ports on valve 'A' heating - 'B' hot water valve could be faulty, or problem with wiring something is sending power back to fire boiler

 

[kris]

Many engineers will come across this, this is when guys change or replace stuff without using a multimeter
And they charge the customer for there mistake , cost of a motorized valve when nothing wrong with the original....
Id be using my multimeter to see where power is going (in the junction box)when the clock is switched on and see where the power disappears from when the boiler goes off, this tells you if it's the clock, the mv or the stay, or it will at least tell you what it isn't, ,
Is your system Y plan or S plan do you have 2 2 port zone valves or 1 3 port valve?

 

[village idiot]

)
Is your system Y plan or S plan do you have 2 2 port zone valves or 1 3 port valve?

Kris I think his pictures suggests it's 3port

 

[flotmangooner]

Thanks for the comments guys.

I am really confused because the boiler won't fire up when I put the HW on the programmer yet when I just checked the pipe in the airing cupboard that leads into the top of the cylinder it was scorching hot.
How can that be?
I have had the immersion heater on but would this make the pipe into the top of the cylinder hot?.

 

[ShaunCorbs]

Thanks for the comments guys.

I am really confused because the boiler won't fire up when I put the HW on the programmer yet when I just checked the pipe in the airing cupboard that leads into the top of the cylinder it was scorching hot.
How can that be?
I have had the immersion heater on but would this make the pipe into the top of the cylinder hot?.

top pipe on the cylinder (dead top center) is your hot water to your taps

 

[flotmangooner]

top pipe on the cylinder (dead top center) is your hot water to your taps

OK thanks, that explains why it's very hot then. Is the middle pipe the one that comes from the 3port?

 

[ShaunCorbs]

OK thanks, that explains why it's very hot then. Is the middle pipe the one that comes from the 3port?

the middle pipe is from your pump if its piped right

 

[flotmangooner]

Let the water in the cylinder cool down, or just try this immediately after you've had a bath/shower:

Check the temperature of the pipe leading from the 3port valve to the cylinder. Do this at the cylinder end and not the valve end.
Turn the boiler on to heat the water check that [it's] firing correctly and leave for 5 minutes.
Check the temperature of the pipe again.
Now check the temperature of the pipe leading back from the cylinder to the valve. It should be nearly as hot but not quite.

If the first pipe gets really hot but the second is cold then you've probably got a blockage in the cylinder coil as suggested by gassafe.

Thanks for this - I am clueless on which pipes lead where. Is it the bottom or the middle pipe leading into the cylinder that comes from the 3port and which one leads back to the 3port?

 

[ShaunCorbs]

Thanks for this - I am clueless on which pipes lead where. Is it the bottom or the middle pipe leading into the cylinder that comes from the 3port and which one leads back to the 3port?

[video=youtube;vFCOmg3GiZQ]https://www.youtube.com/watch?v=vFCOmg3GiZQ[/video]

might help but ignore the wiring

 

[Tonycane]

This sorted yet?