Rads not getting hot

[shaunbh]

My boiler is an Ecotec plus (not sure on the number). Its been installed 2-3 years and generally I've had no problems to speak of. The pipework is microbore and I suspect this is where my problem lies.
I have 12 rads of varying ages and sizes. Since I've been here I've converted them all to TRV's - feed and return used to be on same valve.
3 or 4 rads get hot. These are backed off with the balance valve, bathroom rad has no valve and is the bypass. All other rads just get luke warm or stay cold. All TRV's are less than 3 years old.
The boiler is set to around 70. It fires when system calls for heat. Display increases but once it reaches 70ish, the boiler cuts out and starts its anti-cycling. After 2-3 minutes it fires again but then hits its temp and shuts down, continuing the cycle. The Pump continues to run.
This seems to have happened after draining down to replace the TRV in my daughter's room. This rad only gets slightly warm. Its flow pipe is hot but the return is not. While the rad was off, I flushed it through with a hoepipe. Also, there didn't seem like a great flow out of the return valve, but I have not compared this to any of the rads that get hot.
Could there be a blockage or airlock in this part of the system. If so, how do I remove it?
Any thoughts are much appreciated.
I do have a Magnaclean fitted and this was cleaned out at the end of last year when the boiler was serviced.

Shaun

 

[gigz]

Turn the boiler off and bleed all the rads starting downstairs. When thats done turn the heating on and give it time to heat up. Any rads that are cool/cold make sure the lockshields are open and close the trv's on the rads that are hot. This should get rid of any airlocks. Bear in mind that the air has to go somewhere so it will need bleeding again (usually only upstairs)

 

[dcawkwell]

You have a blockage or air lock.

There is very little circulation going on.

The boiler should fire and keep firing then modulate down but since the demand is slow low it has to cut off.

 

[shaunbh]

Thanks guys.
I was getting ready to answer that I had already bled all the rads (because I had) but I thought I would go round and check them all again first.
I got water out of all the rads, except 1. The smallest one upstairs that was getting warm, not one of the problem ones, which was pretty much full of air.
I have now switched the boiler back on and I'll let it heat and report back.

Shaun

 

[shaunbh]

Today, I turned off all TRV's of rads that get warm or hot, opened up just rads that stay cool, as was suggested. Bedroom rad is now luke warm, living room about the same. Neither are as hot as they should be considering they are fully open. I've bled all rads several times through out the day and got no air from any of them.
I also shut down ALL rads, just leaving bedroom on full, but it still only gets luke warm.
Last night, after getting air out of small rad, the boiler appeared to keep running for longer, but now it's back to its anti-cycling.

Do you think there is still air in the system? Is there a bleed valve any where else (not on the rads). I am not getting any air out of any rads.
Or could I have a blockage - there is a Magnaclean on the system. Would it do any harm if I ran the system with some sludge remover in it for a few days?

Shaun

 

[gigz]

Deffo sounds like a circulation issue if you're only leaving one rad open and its not getting hot. I would be checking pump or if there's a bypass open somewhere (could be under the floorboards). You could add some x400 and leave it in for up to 4weeks (won't do any harm) concentrating on the problem rads. If it is a build up of muck this may work. I would turn the boiler stat up a bit as well. Also bash the bottom of the rads (pref with a rubber mallet) to help loosen any debris. Good luck, failing all this it might need another flush.

 

[gigz]

On reading your OP again, when you fitted the trv's did you also change the lockshields ? Have you tried the bucket test on the lockshield side to see if its restricted ? Another avenue to consider.

 

[shaunbh]

Deffo sounds like a circulation issue if you're only leaving one rad open and its not getting hot. I would be checking pump or if there's a bypass open somewhere (could be under the floorboards). You could add some x400 and leave it in for up to 4weeks (won't do any harm) concentrating on the problem rads. If it is a build up of muck this may work. I would turn the boiler stat up a bit as well. Also bash the bottom of the rads (pref with a rubber mallet) to help loosen any debris. Good luck, failing all this it might need another flush.

I took the rad off the wall when I had it drained to replace the TRV? Flushed it through with a hose in the garden. When it still wasn't getting very hot, I swapped it with another, from another bedroom, of the same size that does get very. It made no difference.

All loskshields have been replaced when corresponding TRV has been replaced.

I did open TRV and lockshield after replacing them, just to see what flow there was. It wasn't exactly Niagra Falls, but then I haven't done the same with a rad that gets hot to compare the flow.

Shaun

 

[shaunbh]

Boiler still cycling. Adjusted temperature of boiler up, as suggested. A couple of rads getting very hot (backed off a little). Most others only getting moderately warm.
Added x400 into system today. Bled all rads for good measure.

I haven't actually checked if boiler still cycles if only calling for DHW and not CH. Is this worth trying? Would it point to any particular problem?

Shaun

 

[gigz]

Is it a sealed system (I took for granted it was) for some reason I thought combi .Has your system got a bypass fitted ?

 

[shaunbh]

No its not sealed, not a combi, but then I never specified, so you had to assume. The rad in the bathroom has no TRV so I assumed it is acting as a bypass. I suppose there could be a bypass somewhere else, but if so, I don't know its location

 

[gigz]

Do you have a three port valve or two two ports ? It's usually after the pump, tee'd off to after the valve/valves. Not all Y plans (3 port) have them fitted (some do) but there should be one if you have an S plan.(2 two ports)

 

[shaunbh]

Yea, I've got a 3 port valve that's been replaced in the last 3 or 4 years. It's a Honeywell. While system is calling for heat, there is no resistance on the lever, when it is not calling, then there is resistance and if I pull the lever over, it does return.

Shan

 

[shaunbh]

Just checked. The boiler is an Echotec Plus 418. If that makes any difference.

Shaun

 

[shaunbh]

Do you have a three port valve or two two ports ? It's usually after the pump, tee'd off to after the valve/valves. Not all Y plans (3 port) have them fitted (some do) but there should be one if you have an S plan.(2 two ports)

Okay, so I thought I would check the various states of the valve while the system is calling for heat and when it is'nt
Maybe somebody can tell me if it sounds as if its working correctly.
Tomorrow, I'll have a bit more time to look into which ports are getting hot when the controls call for heat, but in the mean time this is what I know:-

Does whether the lever on the back has any resistance or not correspond to the position of the valve? If not, then this doesn't help at all.

With no power at all, the leaver has no resistance (floppy)
Call for DHW only, the lever has resistance and returns to the centre if moved manually. Also, The boiler appears to work 'normally' in as much as it fires, heats up then modulates and continues running instead of continuously cycling. For how long, I'm not sure
CH only, the lever has no resistance -its floppy, just like it is with no power.
DHW & CH, the lever still has no resistance.

Shaun