Worcester Bosch Danesmoor 15-19, rads not heating up

[jack]

This installation dates from 2006 and is in my parents house to heat 10-12 rads but not hot water which is done by the AGA.
They have the boiler turned on all the time and use the temperature dial to turn it on and off.
It has got the seven day timer, but that is beyond my parents usually.
So the pump is on constantly at the lowest speed; 1.
They don't usually have that many rads turned on, maybe only five and only turn the boiler on in the evenings in the summer.
But now it is cooler they tried to use it this weekend.

I had to re-pressurise the system and bled all rads.

The two rads furthest in the circuit from the boiler do not get warm quickly, the ones nearest the boiler heat up really well but the last two get just above cold, they may heat up up over time but the ones nearest get so hot I turn the boiler off.
I feel the feed pipe which goes upstairs getting hot quite quickly but the return takes a little longer to warm.

Any suggestions as to what the problem may be?

 

[Last Plumber]

When you say 2006 was that the boiler or whole installation?

The way you're describing it sounds like a one pipe system with a faulty pump or blockage !

Hard to say really.

Give us some more details on the heating system please

 

[Best]

Well it is poor circulation, but that could have several causes. At 2006, if entire installation, then system should be in good condition if inhibitor was added and all piped correctly. So hopefully not dirt, but that needs checked. (Just noticed you say it is sealed system, so it is more likely to be fine)
Pump at number 1 setting is perhaps too low. Try it at number 2 and see if furthest rads heat better. The fact you state the furthest rads are slow to heat suggests that it could be pump speed or first rads are stealing most of the heat.
The system might therefore need balanced properly, as the nearest rads are the easier route and need lockshield valves basically nearly off on closest rads, gradually opening more on next furthest from boiler etc until last are full open.
Or the pump is failing partly and needs replaced.
Do they get the boiler serviced each year? A sooty oil boiler, or if the burner has low output due to blocked nozzle, faulty oil pump etc, will mean it won't be able to build up the heat in the system well.

 

[SimonG]

Tweak the hot rads down. Turn the pump up.

 

[jack]

Thank you all for your help, I would not have known otherwise what to do.
The installation was a complete system install by a builder and myself using standard TRVs.
No inhibitor was used as it is a sealed system.
No idea what lockshields valves are but I am sure Google can help.
Edit: I am pretty sure lockshield valves are fitted on teh other end of the rads from the TRV, but more than likely not adjusted, just open.
The pump does not seem to be making any loud or unusual noises.
The boiler is serviced annually in January and has been since installation.
This problem may have been going on for some time as I don't check the system at all.
No shortage of heat in the system.

 

[Best]

Not surprised the system isn't balanced if you had a builder doing it.
The system also should have had inhibitor in it. Just because it is a sealed system, doesn't mean it doesn't corrode

 

[SimonG]

When in 2006?

 

[jack]

When in 2006?

The last week in September and the first week in October.

Not surprised the system isn't balanced if you had a builder doing it.
The system also should have had inhibitor in it. Just because it is a sealed system, doesn't mean it doesn't corrode.

So how do you get it into the system with a filling loop?
Pour it into a new rad?

 

[Dotty]

I should run cleaner through it first then flush it out before adding inhibitor if I were you.

 

[lame plumber]

I should run cleaner through it first then flush it out before adding inhibitor if I were you.

I would add that it would be better to have an expert carry out the flush and then balance the whole system correctly to make it work sensibly

 

[Dotty]

I would add that it would be better to have an expert carry out the flush and then balance the whole system correctly to make it work sensibly

Going by what we've been told so far, you think that's likely?

 

[lame plumber]

Going by what we've been told so far, you think that's likely?

Nope, but he isn't the only one on here tonight trying to diy and costing himself in the long term

 

[SimonG]

Condensing boiler then? Should be.

 

[jack]

Tweak the hot rads down. Turn the pump up.

I have done that and it improves the heating balance considerably.

Turned the boiler on to a dial position of 8 O' clock and the rads heated up nicely but the water got too hot so I turned the dial off to the 6 O' clock position and the boiler stopped.
No lock out lights.

So a thermostat it seems.

 

[Best]

Wouldn't be the thermostat. If they are faulty they just allow system to overheat.
Still should work if turned a little lower, albeit often still hotter than it should be at that setting

 

[PhoenixServices]

You said at the beginning that the hot water is off the aga not the boiler? So adjusting the boiler temperature won't effect the hot water temperature.