Cold radiators

[PragS]

Hi, have a Vaillant Eco Tecplus 624 system boiler with megaflow. Has 3 zones : one for room radiators, one for hot water and another for towel rads. Boiler has both internal and external expansion tanks attached. Complete system was installed 2 years ago.

Over last couple of days have found that downstairs radiators are luke warm or stone cold whereas upstairs the rads are giving off heat as normal. Up until 2 days ago, all rads were producing heat as normal.

This problem seems to happen when I have heating on (for room rads) at the same time as hot water or towel rads being on.

If only heating for the room rads is on, then all rads (upstairs and downstairs) are giving off heat as normal.

Also found that when heating and hot water are on, then upstairs hot water is not as hot as I expect it to be.

Any experts out there have any suggestions for possible problems? External pump was replaced about 4 months ago.

Have bled all rads - found a bit of air in the towel rads and topped up external expansion tank so that pressure is about 1.25 bars (just above red needle).

Have had BGas round as I have Homecare agreement but their engineer thinks that system may be clogged up and hence hot water not getting around everywhere when both heating and hot water are on at the same time.

He recommended Powerflush to remove blockages - would others agree with his conclusion or are there aspects of the system to consider, eg. zone valves, pump, heat exchanger?

Any suggestions/help would be most appreciated especially if Powerflush doesn't help.
Thanks.

 

[JohnD]

At two years old it should not need a powerflush unless for example it has been leaking and you keep topping it up with fresh water, or it was installed onto old radiators.

When you bleed it what colour is the water? Do you get gas out? Why did the pump need to be replaced when less than 2 years old?

Powerflushes cost hundreds of pounds. This might be why some companies recommend them a lot. It is also why, if you are the one paying the bills, it should not be the first thing you try.

If you have reason to believe it suffers from dirt and sediment, you could for £20 or so give it a DIY chemical clean with Sentinel X400 (which loosens sludge so that it is washed round by the circulating water). It is a very mild, non-acidic cleaner. You can see it is working if the circulating water quickly goes jet black with loosened sediment. You leave the system running as usual for 4 weeks then drain it out with the loosened particles, rinse and refill using inhibitor. Better still fit a Magnaclean at the same time which will cost an extra £100 for parts. If you believe it suffers from sludge and you don't want to do it yourself, ask around for a recommended independent boiler engineer who can do it for you.

However you have not yet said anything that proves sludge to be the problem. Do you remember what else the BG man said? Poor circulation? Pump working OK? Boiler and rads sized correctly? Did it work properly in the past? Boiler Flow temperature correct?

Incoming mains water is very cold at the moment so reheating the store will take quite a lot of power, which might be an issue if the boiler is small for the house. Do you use a lot of hot baths or powershowers? How long does it take before the water store is fully hot again, and does the CH then heat up again? Do you know who the installer was? Might be worth asking then to come back and see what's gone wrong.

If some of the rads are very hot and others are not, this is often due to poor balancing. You can detect this by turning off the hottest ones and seeing if the cool ones then heat up. Has anyone adjusted any of the lockshield valves recently, or taken rads off e.g. for decorating?

I am a householder not a pro.