Some of my radiators are cold - Is it sludge or pump?

[Elmo's_world]

Hi,

I started my CH up last weekend and all the rads upstairs heated up fully, but downstairs remanded cold. I tried bleeding all the rads, but no air in any of them. I then tried turning the upstairs rads off to see if the heat would come through downstairs. Eventually, the downstairs rads warmed, but only luke warm at best. I can hear the pump, and if I touch the flow or return pipes I can feel what I assume is the pump working. BTW Flow pipe is red hot and return is luke warm unless I feel the return right next to the pump where it is red hot also, but a few inches further away it soon cools. Also the flow pipes into the rads which heat fully are hot, but return pipes are hardy warm at all.

I'm thinking it is sludge so have added some X400 and plan to flush (manually, not power) the rads at the weekend. However, things seem to be getting worse! I have had system running constantly for a few days (to push the X400 around), now rads which had heated up only get luke warm, even upstairs. Downstairs is always cold even if I turn the upstairs rads off. Can sludge do this or is the pump on its way out and just not up to pumping the whole system anymore? Also would the X400 have goto into the rads which remained cold?

Now some details; I have a Baxi Combi 105e and the CH worked fine last year. I did have a drip fixed on the boiler a month ago, I think the engineer replaced the diaphragm on the flow switch. Most of the rads have a TRV, which I fitted a year ago, but I have loosened the collars so they are really loose. If you need more info let me know.

It would be great if anyone could guide me if they think it is sludge or the pump, or is it something else?

Thanks in advance.

Martin

 

[ChrisRoberts]

I'd check to make sure that the engineer didn't close any valves under the boiler 1st.

 

[Elmo's_world]

Thanks ChrisRoberts,

I've just checked and they all appear to be open, I.E. they are pointing forward. I just tried to turn them, and the return valve is quite stiff, but I did manage to hand turn them all (flow, water feed and return).

For info, when I got home today none of the rads were even warm, and I had left everything running all day.

If it is sludge, it must be causing quite a blockage, as the return is still coming back cool, and none of the heat is making it to the rads.

Martin

 

[Rob]

id be looking at pump or trvs

 

[ChrisR]

It need the pump to be working properly for the HW to be good. Is the temp/flow as it always was?

If there's a drain cock anywhere, let some water out. If you run it over something white like paper, it will give an idea about how clean it is. Though most of the bad stuff gets stuck in the rads of course.
Take a trv head right off. The pin in the valve should spring up and down.

 

[Elmo's_world]

Thanks ChrisR and rob884,

HW is the same as normal. CH boiler temp has been maxed out all night and is hardly ever going down. I think this is because there seems to be no real flow to take the hot water around the system. The flow pipe out of the boiler is red hot, but the return is cool. So the flow is not as it is normally at all.

I have drain cock off all the downstairs rads, so will draw some water off later on. When I took some water out to put the x400 in it seemed quite clear, though it was from the top of a rad which untill tonight had been getting hot, so probably not a good guide. The engineer who fixed the drip on the bioler told my wife that it may be worth flushing the system but I don't know why he thought this was needed. He wasn't offering to do it.

I have taken all the trvs off and all the pins move freely.

The pump seems to be making the same noise as it has always done (quite hum), and I can feel it on the nearby pipes, but does this mean it is still working? I think it is worth checking. Can I unscrew the large disk/screw on the front to check if its rotating?

Thanks once again for all your help.

Martin

 

[panda2006]

ihave exactly the same problem have replaced old knackered rads with doubles which have trvs but the heat is only getting to a few rads i know it is not my pump because i replaced that yesterday. could it be as my old rads were singles and i upgraded to doubles the pump needs to be bigger or could i be running the pump too fast????? desperate help needed!

 

[Elmo's_world]

I took the central screw off the pump this evening, as the casing was getting very hot. I could see it rotating when the HW and CH were on, so I think I can say that the pump is OK and it is looking like I have a massive blockage somewhere.
Would like to know if the pump running against the blockage has done it any lasting harm?

I'll try a manual flush of the CH system over the weekend...

 

[Martini]

If a particular radiator is not warming up the TRV valve may be stuck!
This happens over the summer as the heat has held the valve closed!
Remove the head and spray the pin on the valve with WD40. Pull it up and down with pliars to free it and it will be as good as new.

 

[Elmo's_world]

Thanks for the tip Martini.
unfortunetly all my rads are now not heating up - infact the only thing that is heating up is the flow pipe out of the boiler and the pump. Both of which are red hot.
I have now confirmed that the pump is still spinning, and am a bit concerened that it may have been damaged. Does anyone know if this would cause the pump problems?

Martin

 

[chrishutt]

Remove the head and spray the pin on the valve with WD40. Pull it up and down with pliars to free it and it will be as good as new.

Don't do this! The WD40 will achieve nothing, except perhaps damaging the seal. Pulling the pin may cause it to come out altogether, leaving you needing a new TRV. If you want to know the right way to free a stuck TRV look in the Wiki or FAQ topic.

Elmo, why don't you just flush the system and see how bad it is? Chances are it will need it, and it may solve your circulation problem. Guidance on manual flushing given in the Wiki or FAQ topic.