Should I be able to make my Rads as hot at the bottom as the top?

Discussion in 'Plumbers' Talk' started by HarryCrumb, Sep 13, 2021.

  1. HarryCrumb

    HarryCrumb New Member

    Last week I fixed a radiator that wasn't getting hot. Problem was a 2m microbore tube packed full of silt. After fixing I also fitted a Fernox Omega TF1, and cleaner solution for one week. I flushed it out today and there wasn't much sludge, it was pretty clean.

    Now I'm trying to make all three of the ground floor radiators get hot along the bottom edge.

    The combi is on the 1st floor. The radiators on the 1st and 2nd floor seem to get equally hot on the top edge as they do on the bottom edge. On the ground floor the radiators are bigger, and I can't get them as hot along the bottom edge.

    The two that I can lift myself (1000mm x 600mm) I've had outside today, with a hose blasting water through and hitting them with a rubber mallet. There was a little bit of sludge but not much. The water seemed to be coming through strong.

    It's more noticeable on the 2000mm x 600mm but the middle lower part only gets warm, whereas the top edge gets piping hot.

    Am I expecting too much, or may I have incredibly persistent sludge?

    ...side question; a 2000mm x 300mm rad is £95. The x 600mm version is £440. Why is it such a hike up?
  2. Jimbo

    Jimbo Screwfix Select

    There will be a large temperature difference across the surface of large panel radiators. It’s really noticeable in systems with weather compensation and lower flow temperatures as a result. At 50*C flow the lower third of a 2600mm radiator I have will be only 35*C or so.
    HarryCrumb likes this.
  3. pppmacca43

    pppmacca43 Super Member

    I assume you are looking at the screwfix radiators? If so, that does seem very expensive tbh, u can get a stelrad double panel double convector radiator a lot cheaper than that. You can probably even get cheaper than the one I found if u look about.

    Attached Files:

    HarryCrumb likes this.
  4. HarryCrumb

    HarryCrumb New Member

    Thanks for the replies. I might have skewed my expectations by watching youtube videos where they look at the radiator through a thermal camera, and it looks equal heat, but they were probably looking at small radiators. If I can get hold of a reliable thermometer I'll take a look at the temperature differences and reassess.
  5. HarryCrumb

    HarryCrumb New Member

    I've got one lock shield that won't turn. It's different to all my other lock shields and I don't want to force it so thought it was worth checking here...

    Can anyone identify this? Thanks!

  6. dcox

    dcox Screwfix Select

    Looks like you just need a small spanner to turn the top of the valve clockwise to close.
    HarryCrumb likes this.
  7. FlyByNight

    FlyByNight Well-Known Member

    I would guess you have a solid lump of sludge in te radiator - cleaning solution may not clear it. Does it feel as though there is a hill inside - the ends are hot at teh bottom but the cold spot gets higher as you move across?

    Can I sggest you take one radiator off and take it outside, then start with a high flow rate hose. It may take a while but it will happen - trty it and see.
    HarryCrumb likes this.
  8. HarryCrumb

    HarryCrumb New Member

    On the 2000mm rad it does sort of feel like that, but it's not cold, just not nearly as hot as the top. I'm just experimenting with closing all the other rads, and the temp along the bottom edge is changing. The 3 rads that I thought might have sludge in are the ground floor rads. The combi is on the 1st floor (if that matters) and the rads on the 1st and 2nd floor all seem to get equally hot along top and bottom edge. But, they are smaller rads. I thought because heat wants to rise, maybe I need to force it downstairs.

    I've taken two out of the three outside and hosed them a couple of days ago, in several different positions and with a rubber mallet. The third rad is too big for me to lift, but I'll keep experimenting with the balance and I'll report back.
  9. HarryCrumb

    HarryCrumb New Member

    Got it moving now. It's the radiator at the top of the house and it was fully open.
  10. Baxi Boy

    Baxi Boy Active Member

    I have a 450x1400 type 22, this is never as hot at the base either,and it’s new after a system clean.Using a digital thermometer the top maybe 57 degrees,while the bottom is 45 degrees,I have just accepted this as normal,and found the same thing on smaller radiators to a lesser extent!
  11. FlyByNight

    FlyByNight Well-Known Member

    WHat is happening is that the sediment/sludge itself heats up from the water and will get quite warm, but not have enough heat energy to radiate much. If you left teh heating on for 48 hours you may well find that the cooler areas feel as though they are up to temperature.

    A few years back, I did my mothers house where rooms were not getting very warm and after 24/48 hours of heating rads felt hot all across, but the air was still chilly. I removed teh radiators, one by one, and flushed through with a hose, the amount of crud was unbelievable. When I put them back on, and set everything up, my mother "complained" - the house was like a sauna especially the upstairs bedroom as the original design and thremostat was not wonderful.
  12. Jimbo

    Jimbo Screwfix Select

    Only a fully pumped radiator (i.e. with a valve in the middle at the bottom) would be even. As radiator size increases the effect becomes more noticeable.
    Baxi Boy likes this.
  13. FlyByNight

    FlyByNight Well-Known Member

    I have just checked a 1400/1500 x450 radiator. Temperatures at mid point, Top 67-68 degrees, bottom 62 degrees.
  14. HarryCrumb

    HarryCrumb New Member

    Thanks for the measurements. I need to get hold of something that will measure the temp and I'll report back. The thing I've got only goes up to 40'something degrees, and is designed for armpit use, I think. I suppose if it ever read that high you'd be dead...
  15. FlyByNight

    FlyByNight Well-Known Member

    I bought a cheap IR thremometer gun from ebay. About £15. Accuracy - probably not too good, but when needed to look at relative temperatures, it is fine. You can check the gradient across a radiator left to right or top to bottom, floor temperatures, water &c.

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