Another Central Heating Issue

[MMarve]

Hi all, I wonder if anybody would be able to give some pointers as to what possibly could be wrong with my central heating.

Valliant ecoTEC Plus 831 sealed central heating system
Thermostats controlled by Honeywell Evohome, kept in the living room with individual electric TRV heads in 3 bedrooms and the hallway.
For full disclosure, the boiler also supplies hot water to the kitchen tap and then also to a Megaflo Unvented hot water cylinder that is used to supply hot water to 2 bathrooms.

So the issue is that all of my radiators upstairs are getting luke warm and everything downstairs is staying stone cold. It did this for a few days back in October when the heating first started kicking in this year. At that time I tried shutting all of the radiators off and then turning one on but nothing I did made any difference until after a few days it started working all by itself again. Since then it has been fine, had its yearly service where the expansion vessel was changed, until yesterday when it is doing exactly the same again. I have been through the same routine of turning all of the radiators off but again, it doesn't make any difference.

So what could the problem be? Air lock? Pump on its way out? Sludge in the system? What do you think!?

 

[Gasguru]

I guess you have 2 motorised zone valves...one for the cylinder and one for the radiators.
Is the radiator zone valve responding when there's a demand? Does the boiler fire up in heating mode?

 

[MMarve]

I guess you have 2 motorised zone valves...one for the cylinder and one for the radiators.
Is the radiator zone valve responding when there's a demand? Does the boiler fire up in heating mode?

Thanks for coming back and apologies I could/should have given that extra info to start with.

So yes, 2 motorised zone valves, as you describe. The one for the radiators does respond, open up and the pipe is hot both sides of it so it's getting past there. So on that, you will work out that yes the boiler is firing up in heating mode, the outlet pipe from the boiler is red hot and the inlet pipe takes a loooooooooong time but does get almost as hot as well. So it seems the water is getting round someway, just not to all the radiators. The upstairs ones being lukewarm almost confuses me the most. If the hot water is getting to them, they should get hot hot...?

 

[Gasguru]

And with a cylinder demand does the cylinder zone valve open up and the pipes from the boiler heat up properly?

 

[MMarve]

Now that is a good question and one I don't think I am going to be able to answer for a day or so as I realised whilst rummaging around that I had the immersion switched on so the cylinder will have been getting all it needs from there I would think! I have switched it off now so if we're facing cold showers tomorrow morning, at least I'll know

 

[Gasguru]

That's an expensive mistake

 

[MMarve]

Quite! And I have no idea how long it has been on for, probably since we bought the house 3 years ago... I must admit it did confuse me how we had hot water immediately when returning from holidays when I have been sure I'd turned the timer for the hot water off! Let's see if I get a sudden drop in my electricity bill now

 

[shinds]

OMG!! This is spooky!! You have the exact same issues as me and you have the same boiler setup!!

Please try what I done?

Change the Hot Water schedule, so that it's not heating the water and Central Heating at the same time?

 

[MMarve]

Thanks Shinds, strange indeed! But I don't think I have been relying upon the boilder to heat my cylinder as I have inadvertantly had the immersion on the whole time...

@Gasguru I put the overide on for the cylinder for half an hour and certainly that zone valve seems to be working properly and the pipe in there got red hot.

 

[Gasguru]

Since the kitchen hot tap and cylinder circuit appear to be working you're pretty much ruled out the boiler....
And I guess the living room radiator is left open all the time to be controlled by the Evohome.

 

[MMarve]

Since the kitchen hot tap and cylinder circuit appear to be working you're pretty much ruled out the boiler....
And I guess the living room radiator is left open all the time to be controlled by the Evohome.

Correct.

So that is where I'm at. Something is causing it not to get round properly though. My thought was an airlock that cleared itself previously and has returned. But I don't know if that's likely or not, I'm just guessing.

I have my boiler man coming at some point but he's naturally very busy right now so not sure when he is going to squeeze me in yet. Until then, any other ideas or tricks to try would be appreiciated!

 

[shinds]

Do you have a Magna Clean? have you checked it?

 

[MMarve]

Do you have a Magna Clean? have you checked it?

Not as far as I'm aware or can see. I have a magnetic scale inhibitor on the coldwater inlet to the boiler but that's it. No mention of a Magnaclean being added in any of the commissioning paperwork for the boiler either.

 

[MMarve]

Just to update here, my plumber has been today and it looks like it is the diverter valve in the boiler. So I think this is what switches between demand for the hot tap and demand for the central heating.

The boiler is only 8 years old but in the last year its had a new PRV, new expansion vessel and now a new diverter valve. I would have probably been better off getting a new boiler!?

I'll confirm when its fitted and problem resolved.

 

[sxturbo]

Triggers broom.....

But in theory these components should last another 8 years