Ongoing problem with CH on a Valliant EcoTec Pro 28 system

[Chris_c81]

Hi all, thanks for reading.

My dad has rented this property for over 8 years and has had no end of trouble with the central heating at the property. The landlord has dragged his heels quite a bit and has been difficult at times to get him to sort the issues out. He's sent several engineers around over the years, had radiators reluctantly changed and eventually after much hassling agreed to pay for a power flush. That was done earlier this year if memory serves and things did seem to improve temporarily. Then the warmer weather came and the CH wasn't on again as much. As the colder weather has started to appear again now my dad has turned his heating back on and we're back to square one. The radiators seem to heat up at least part way, I'd say about a quarter to a half way horizontally (i.e. top or bottom half heats). He's always had one really problematic radiator (which a friend of his who has some experience, swears has been installed the wrong way round??) in the living room which just never seems to heat well at all. The system is controlled by a digital thermostat programmer (also by Valliant) on the wall in the dining room. I don't know if it's of relevance but there are 6 radiators in the house in total. He has no problem with the hot water. The programmer seems to be working fine, it does trigger the CH on and off at the specified times. I should also mention that the pressure in my opinion, seems to be too high. The needle basically sits at the max of the grey bar, just before the red section. If it's not around there, the radiators don't seem to heat at all. Yet my mum has the same boiler (or variant with timer built in) and the pressure is much lower.

My dad is 70 next year and he's not from an engineering background and isn't great with technology. So I've come here on his behalf hoping I can get some advice on any steps I can take to try and troubleshoot this problem once and for all.

A little about myself. I'm no plumber. I am however competent with a digital multimeter and digital Megger as I work on the railway as a signalling test engineer.

I would really appreciate your feedback on this. I look forward to receiving your responses.

Many thanks.

 

[fender]

Initially it sounds like the expansion vessel needs re-pressurising.
If you're not sure what to do you need to get someone in. You need to release the pressure from the heating side, and re-pressurise the vessel to circa 1 bar. Then refill to the pressure the manufacturers specify when the system is cold. You could be unlucky and the diaphragm in the pressure vessel has failed.
Does water come out of the rads if you open the bleed valve on them?

 

[Chris_c81]

Initially it sounds like the expansion vessel needs re-pressurising.
If you're not sure what to do you need to get someone in. You need to release the pressure from the heating side, and re-pressurise the vessel to circa 1 bar. Then refill to the pressure the manufacturers specify when the system is cold. You could be unlucky and the diaphragm in the pressure vessel has failed.
Does water come out of the rads if you open the bleed valve on them?

Hi Fender thanks for taking time to respond.

Definitely sounds like something he'd need to get someone in as you say. In answer to your question about bleed valves, yes water will drip from them when opened up with the key.

 

[fender]

No prob,

Just seems odd they are only hot at the bottom, but water comes out of the valves.

I'm sure someone will pop in who knows more than me..
If only the top heats - indicates sludge in the bottom, but lower half heating suggests air in the top half of the rads.

 

[Chris_c81]

No prob,

Just seems odd they are only hot at the bottom, but water comes out of the valves.

I'm sure someone will pop in who knows more than me..
If only the top heats - indicates sludge in the bottom, but lower half heating suggests air in the top half of the rads.

Yeah I can appreciate the sludge issue, but given it was power flushed recently, surely that's unlikely?

 

[fender]

Yep,

That was my thinking too, but if only the top is getting hot, to me anyway, it still indicates sludge in the bottom.

 

[simond]

Poor flow rate of water causes partial warming of radiators.

Vaillant ecoTECs have rubbish Zilmet expansion vessels, many don't stay airtight for even 4 years. I think they may have changed supplier very recently, as I've noticed the metalwork has changed slightly around the schraeder valve. Hope so.

 

[ScottishGasMan]

It sounds like it needs a compitent engineer to look at and test the system, seen plenty of "powerflushes" that made no difference to the system.

The pressure will not be the issue with regards to the radiators heating. Also if the pressure also sits that high when the system is cold then the expansion vessel cant be the issue, although a decent engineer would check and repressure it as required as part of his boiler checks.

The system may need balancing/flushing/repiping dependant on what the root cause is. First thing i would try is get a radiator that only partially heats, close the rad valves on the other radiators and run heating to see if the poor radiator heats up properly,

As said, normally cold at bottom is sludge and cold at top is air, but seen a few over the years where sludge in certain areas in the middle of the rad stops it heating at the top, and where flushing has cleared out the lower part of the rad only, gives the impression of air but you bleed it and only water comes out.