Vaillant Ecotec 30 Pro heat problems

[Mike13]

As Title, we have a vaillant, diverter valve replaced febuary, started leaking again, so we ordered a repair kit to renovate the old one we still had.

Repaired diverter valve greased and fitted. the hot water works, but heating is very weak.
used a torch to inspect the solenoid rod (vaillant calls it a motor, but it is just a solenoid really), it is fully forward most of the time, and when we turn a hot water tap on the solenoid retracts and hot water delivered, tap turned off and after a delay the solenoid returns to radiator supply.

two days ago it was working fine, and we would get nicely warm radiators around the house, now they stay lukewarm all around the house.

Any ideas if there is an easy way to prove the central heating pump is ok?

We have a magnetic filter fitted, and there has only been a little trace of magnetite on the magnets in February and just now, water still clean, just colour from the inhibitor.

I have just checked, it is a grundfos pump, those are supposed to be reliable?

Also went round and tried bleeding the radiators, no air noted in any of them ( I did not need to bleed down the whole system, just dropped the pressure to zero, changed the diverter valve, checked the magnet trap, topped up the pot with some extra inhibitor to make up for lost water, then filled to pressure again, about 1.8 bar. Only a two storey house so do not need more.

 

[Mike13]

Well looking at the vaillant site I came across this gem:
"Firstly, if you have a combi boiler, it might accidentally be set to only heat water but not the central heating. This can happen if the boiler is set to this mode during the summer months when radiators do not need to be heated but is forgotten about. It may also be that the boiler is set to turn on at an unexpected time. Check the boiler display to see if this is the case."

But it gives no clues about the screens you have to go through to check if that is the case.
Anyone know where I check that setting?

I have water and radiator temps set up, and it was working up to when the diverter was changed ( it still worked, but needed regular topping up to stop the 75 error code.) But may have inadvertently turned heating off somehow? not sure but it is only thermosyphoning, no pumping at all in heating mode.

 

[Mike13]

I am starting to think it might be the pump failing, when I look into the hole in the middle of the grundfos pump I see a screw with a phillips head on it, is that meant to be rotating when the pump is meant to be running?
Mine appears to be stationary all the time.

 

[terryplumb]

If the boiler is firing up for central heating , and radiators are heating up to some degree,then you have a circulation issue.
Pump not working, or possibly full of air ,or there is a restriction preventing full flow.

 

[Mike13]

Well the system was working, just a leaky diverter valve, changed that, not finding any air, hot water is fine, it seems to try to run the radiators, but only the ones nearest and above that boiler get lukewarm. I am struggling to see what could cause a blockage? if the diverter rear face o-rings got misplaced it would leak buckets full of water, but it is bone dry, and I can see the diverter valve driving in or out as expected. I understand mostly how it all works, but do not know how to be certain if the pump has become stuck. It is about 4-5 years old.
Also with the pump, if I need to buy a new one I am hoping that the last portion of the designation is for the hose coupling only? mine is a UPM3 15-70 VH2004, but many are 25-70 or 15-75 in the middle numbers, I think those numbers are for the turndown and max capability, the ones for sale have various other letters and numbers at the end, are those for other pipework and arrangements? I am hoping I would be able to swap on the back bit from mine to any of those and it would fit? is that a good guess, or is it critical to get the right one?

If it was full of air then how do I make sure it is ok? I did hear air coming out of the grey knob on the top of the pump body at the back, and opening it up does not release any more air or anything. Is that correct, or is it expected to weep water when opened as far as possible.

 

[picasso]

The boiler would not run if the pump wasn't running, have you opened the valves fully on the flow and return ?

 

[Mike13]

they were never touched. hot water works, but boiler is pants, lukewarm for the closer rads.
The copper pipe above the pump is very hot when the taps are on, but cool when radiators are demanded, currently a daytime thermostat setting of 27 to guarantee a full time demand keeps the house at about 19-22 depending on time of day and room you are in.

 

[CBW]

Try removing the diverter head and manually moving the spindle, if this improves, could be diverter repair kit and would be beneficial to replace for whole diverter. Make sure you check the boiler for safety afterwards.

 

[Mike13]

I have peeked in and can see the diverter valve going in and out, I have also moved it manually and can feel it is loose, still visible silicone grease on the spindle and around the boss on the pushed in valve assembly.

"used a torch to inspect the solenoid rod (vaillant calls it a motor, but it is just a solenoid really), it is fully forward most of the time, and when we turn a hot water tap on the solenoid retracts and hot water delivered, tap turned off and after a delay the solenoid returns to radiator supply."

 

[Mike13]

Well I found a link that explained if you push in the screw in the middle of the motor (with power off) you can force turn the impeller, it moves freely enough while pushing the screw in.
So I think that leaves me with a faulty controller?
I have found comfort mode turned that on for a bit to see if it changed anything, but no change noted.
Found temp settings for hot water and for the radiator temps, have currently set the water temperature for radiators higher so that hopefully a bit more heat can get into the radiators round the house. BUT water temp for radiators is dropping to 35 or so on a regular basis, then boiler kicks in and it goes up to 60 or so then coasts down to 35 or so again.

Has anyone seen this behaviour and have any suggestions?

 

[Mike13]

well that was useful, called vaillant helpline, press top two buttons together, and it goes to an s.04 as expected when firing, but it then goes to an s.07, says that is a demand loss, but the controller lines and controller have not been touched at all. Not sure what to try next.
Any ideas

 

[Mike13]

Update, I have worked through all the thermostat wiring, and on the Vaillant connecter X1 on the main circuit board I have the "RT" line going live when heat is demanded, and going dead when I set the demand temperature lower than room temp.

There are no other connections between the thermostat (an anonymous old honeywell programmable with 4 different temps during the 24hrs that can be programmed for time and setpoint, I cannot work out what model it is), there are only two wires between the programmer and the rest of the boiler wiring.

So the demand temperature is responding and the thermostat is providing power, so why is it then going to S.07 all the time?

 

[Johntheo5]

S.07 is a status code, Pump Overrun, this should normally only be flagged if someting switches the boiler off. ie programmer, roomstat, etc., a hiccup in a wireless roomstat communication might cause this, if installed.
Can you monitor the flow/return temps, d.40&d.41 when it fires up?.

 

[Mike13]

It continuously cycles S.04, S.05, S.07, sometimes see S.97, water temps go up to about 60 then drop back to about 34 or so before starting again. pump seems to be free, and once I was turning the screw in the pump while the heating was running and ended up pressing a bit harder and it buzzed where the screw touched the rotating impeller.
I wouldnt know how to call up those d.xx numbers, a vaillant service person on the phone asked me for the codes and told me how to call up that info, but no more than that.

 

[Johntheo5]

If this is your model, go to page 17, Installer Level, and follow the instructions, you should be able to read d.40 and d.41 then I think, not familiar with these boilers but these codes are easily accessible I think.