Central heating...now I'm confused.

[pilgrim1]

Hi folks,
I'm really confused by the behaviour of three of my radiators. I’ve very much appreciate your thoughts on this one.

Some facts first: - The house I live in is three floored. The system is open vented and the boiler and pump are on the middle floor. The system (as it was when I bought the house) is a mixture of 8mm microbore and some arbitrary 15mm that someone has put on two of the radiators on the lower floor. The radiators are split across the floors as follows :-

Top floor: - 4 rads
Middle floor: - 4 rads
Lower floor: - 5 rads.

The middle and lower floors are fed from manifolds from the middle floor and I presume (there are not enough connections on the manifolds to service all the radiators) there is a separate manifold for the top radiators.

I recently drained the system down to fit a new radiator downstairs, once refilled I find that one of the radiators upstairs no longer functions. Assuming it had filled with debris I drained and refilled the system, this seemed to cure the problem, however a few days later, this and one other radiator no longer heat up at all.

The odd parts (for me at least) are as follows:-

* These two radiators worked perfectly for days, without issue then stop dead.

* One of the radiators at the top of the house seems to fill up with air for a few days. It is not until I remove the air from this radiator that the other two stop working!

* These two radiators stay stone cold, as if they are totally isolated from the rest of the system, the feed pipe is stone cold.

* Perhaps just me being paranoid, however since I drained the system down, when I listen to the pump it sounds more like a water fall than a pump. I don’t recall it sounding like this before.

The only thing I can think is that the pump is not pushing the water through; however it seems to work fine prior to the full bleeding of the system.

The thoughts of the forum experts would be much appreciated here, before I have to start ripping up carpets and floorboards to see what’s going on?

Regards

ChrisC.

 

[Slugbabydotcom]

Try this for a start
Close off one end of every rad except one that does not work.
Keeping one rad open all the time work your way around all the problem rads
This will send all of the force of the pump to the problem pipes which I suspect are airlocked.
Remember when you bleed rads to do it with the system turned off.

* These two radiators worked perfectly for days, without issue then stop dead.

Possible ingress of air have you turned up your pump speed? It could be pulling air in through the vent or as I have occasionally seen through the pump itself

 

[pilgrim1]

Hi Slugbaby,
many thanks for the reply, your expertise is much appreciated. This is driving me mad. In response....

Try this for a start
Close off one end of every rad except one that does not work.

I'll give this a try this evening and see how it goes.

*
Remember when you bleed rads to do it with the system turned off.

I always make sure I do, normally it heat the system for a while, turn it off wait for the pump to stop and then bleed the rads.

Possible ingress of air have you turned up your pump speed?

No, but I think since I've drained the system I've let a lot of gunk out, I don't think has been drained for the past ten years! As I mentioned in my post the area around the pump sounds like a waterfall now, which it didn't before.

It could be pulling air in through the vent or as I have occasionally seen through the pump itself

I suspect you are correct, ever since I moved into the house I've been amazed at how much air I've found in the top rad. It seems to need bleeding every two weeks or so.

I'll try this and post to let you know how I get on. Once again many thanks for the reply.

Regards

ChrisC.

 

[pilgrim1]

Hi Slugbaby,
OK tried this approach, when all the other rads are off the two dead ones individually warm up. Tried bleeding each one off and that found very little air in any of them. I'll test tommorw morning and see if these two work as part of the whole. Not sure where to go from there if they do not.

My thanks once more.

ChrisC.

 

[meldrew's_mate]

No, but I think since I've drained the system I've let a lot of gunk out, I don't think has been drained for the past ten years! As I mentioned in my post the area around the pump sounds like a waterfall now, which it didn't before....

....ever since I moved into the house I've been amazed at how much air I've found in the top rad. It seems to need bleeding every two weeks or so.

Remove, dismantle, and clean the pump. This should make it work for about 20 minutes before more gunge gets sucked in to block the impellor.

Flush the system with a good product (Fernox/Sentinel etc) following their instructions. Don't rush, do a proper job! Finally add corrosion inhibitor to prevent the sludge and gas formation which now blights your pump and rads.

 

[Slugbabydotcom]

Not sure where to go from there if they do not

Cross that bridge if you come to it.

meldrews mate picked up on a valid point there about the gunge and flushing the system.
Pumping gunge makes a pumps life harder and shorter so depending on how you get on schedule in a system flush sometime soon or sooner.

Heres a question that may be relevant:- Have you adjusted the pump speed ?
Sometimes conditions are such that 'air vent sucking' can occur at speed 3 and not at speed 2. So it is possible that in your efforts to clear an airlock to these rads by turning the pump up you have created another problem

 

[pilgrim1]

Hello folks, sorry about the delay, short notice work trips

To bring you up to speed, I tried Slugbaby's suggestions and the results were a bit mixed a first. I followed the procedure and it worked with each individual radiator. However when I put the whole thing back on the entire top floor was stone cold

I decided this evening to try again as I got home early. This time it seemed to work. All the radiators are now streaming hot and free of air Just in time, it's freezing here tonight. My humble thanks to you all for that.

meldrews mate picked up on a valid point there about the gunge and flushing the system.
Pumping gunge makes a pumps life harder and shorter so depending on how you get on schedule in a system flush sometime soon or sooner.

I had planned to do this, however when it get's a little warmer. Also after asking some questions here first. All the radiators bar 2 are what I belive to be 8mm twin entry lance types. None of them are thermostatic, which basically means freeze or boil, depending on where you are in the home, so I plan to replace the lot which I considered would be a good time to clean it all out. The problem I have is, I can’t seem to find any to replace them with, also I'm not sure what products would be best.

Heres a question that may be relevant:- Have you adjusted the pump speed ?

No Slugbaby, I’ve not messed with the pump. If it works, don’t fix it, that's my motto. Until I drained the system out to fit the pain in the butt radiator in my bathroom, everything was fine, bar the top radiator upstairs, which was always full of some air.

So yet again the forum has come to my rescue, I can not thank you all enough for your help. It really is very much appreciated.

Regards

ChrisC

 

[Slugbabydotcom]

All the radiators bar 2 are what I belive to be 8mm twin entry lance types. None of them are thermostatic, which basically means freeze or boil, depending on where you are in the home, so I plan to replace the lot icon_sad.gif which I considered would be a good time to clean it all out. The problem I have is, I can’t seem to find any to replace them with, also I'm not sure what products would be best.

Twin entry rad valves are confined to history now as they were a load of poo!!


Replacing them with TRV and lockshields involves removing the blanking plug from the opposite end of the rad. You will have to beg steal or borrow a rad valve tool with a square peg end to get them out

 

[bathjobby]

Pilgrim1, when you get around to it go have a look at my post here //www.diynot.com/forums/viewtopic.php?t=22082&highlight=outside+tap+flush on a simple method for flushing your system through using mains cold water pressure.

 

[pilgrim1]

Twin entry rad valves are confined to history now as they were a load of poo!!

The plumber here seems to have been very keen on them I presume someone felt they were better/more attractive at some point.

Replacing them with TRV and lockshields involves removing the blanking plug from the opposite end of the rad. You will have to beg steal or borrow a rad valve tool with a square peg end to get them out

I suspect I'll end up just replacing the rads and the valves, the ones we have are ancient and a random collection of types and have many random layers of peeling paint, I've hit a couple with the paint remover and re-done them, however somehow they just never look the same. I'd like to sack all the microbore, however it runs around the three floors like a octopus It would involve ripping up, well everywhere. Some of the pipes are even embedded in the wall plaster Until I managed to get hold of a Bosch D-Tect scanner, putting up a picture on the bottom floor of the home was an....interesting experience!

I'll be doing this in the summer of next year most likley, so I'll in the forum then I'm sure

Once again Slugbaby you have been of invaluable assistance. I can't thank you enough.

Regards

ChrisC.

 

[pilgrim1]

Pilgrim1, when you get around to it go have a look at my post here //www.diynot.com/forums/viewtopic.php?t=22082&highlight=outside+tap+flush on a simple method for flushing your system through using mains cold water pressure.

Excellent bathjobby, my thanks. I look forward to reading it. I tried to from work today and it was just a broken link When I finally got ome it works fine.

I thank you for taking the time to post it's much appreciated.

Regards

ChrisC.