Boiler Help Needed

Discussion in 'Plumbers' Talk' started by ZTribe, Nov 23, 2020.

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  1. ZTribe

    ZTribe New Member

    We moved into our house in mid-July this year. The boiler we inherited is a Potterton Suprima and is located in the loft.

    As soon as we moved in we noticed that when the hot water was on the radiators were getting hot and so called our heating engineer to fix this and service the boiler at the same time - he changed a motorised valve. This was done at the end August / September and all seemed well for a while. Mid September we woke up one night to blasting hot radiators despite the room stat as low as poss and the controller / time clock in the off position. We had to isolate the boiler on fuse box to finally get the boiler off as house was like sauna.

    All then seemed OK for a few days then it happened again, and again, and again etc etc

    So far we have had the heating engineer back and the following have been changed;

    Both motorised valves - the hotwater one has now been changed twice in case the first one was faulty

    Controller / time clock (Honeywell) - downstairs

    We though the issue was solved when the HE realised the frost stat was set to 10degrees and turned it down to 5 but then it happened again so we then changed -

    Frost stat - Honeywell - we have had this set to 3.5 (lowest) and 5 to test but makes no difference

    There is no pipe stat associated with the frost stat (which from copious research online I think we need) but really it should make no difference as we put the sensor from a weather station next to the boiler / frost stat to monitor the temp in loft and even after a very cold night the lowest it got to was 9 degrees.

    It happened again last night at 1.40am, the boiler and pump are above our bedroom and so woke me almost immediately. I checked the loft temp and the reading was 12degrees so it cannot be the frost stat?!

    Anyone have any other ideas? We have called our heating engineer back but I think he's starting to get fed up with us ......
     
  2. MGW

    MGW Screwfix Select

    I have had this with a wireless thermostat loosing the RF link, More expensive types fail safe, but some cheaper ones if the base misses the signal to turn off, then it just keeps heating, so turning thermostat up, and back down would turn it off.

    So what thermostat is fitted?

    In the main we have two thermostats, one on wall and one end of radiator seems odd for both to fail.
     
    ZTribe likes this.
  3. nigel willson

    nigel willson Screwfix Select

    You need to get an electrician round who’s competent with ch systems to check it out
     
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  4. ZTribe

    ZTribe New Member

    Hi - it's not wireless, it is a Honeywell mechanical thermostat.
     
  5. ZTribe

    ZTribe New Member

    I think that's where we are headed but just wanted to check that we are not missing something completely obvious!
     
  6. Mike83

    Mike83 Screwfix Select

    If it’s happening at night and not during the day then it does seem like the frost stat.
    A frost stat simply won’t do what it’s designed to do if there’s not a pipe stat.
    If the heating zone valve is motored open when the issue arises then this can only come from the programmer or frost stat.
     
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  7. ZTribe

    ZTribe New Member

    Thank you for the reply.

    If we temporarily remove the frost stat from the circuit presumably that would determine whether it was indeed the frost stat or the programmer?
     
  8. Mike83

    Mike83 Screwfix Select

    Unlikely it’s the programmer as the feed from it goes through the room stat.
    If the room stat is turned down then can’t see power reaching the zone valve.
     
  9. quasar9

    quasar9 Screwfix Select

    Clutching at straws here ! Some Boilers have in internal frost stat and tend to have internal pumps or have control of the pump. However, when boiler fires under command of its own frost stat, the valves are normally closed so will use the bypass valve to stop itself from freezing. Room stats too have a built in frost stat that works in parallel to main stat but will only work if the programmer has enabled the stat. My vaillant is in loft and it’s internal frost stat will fire the boiler and run the pump for short periods regardless of what other stats are doing.
     
  10. Mike83

    Mike83 Screwfix Select

    Suprima is heat only.
    It will have no built in frost stat.
    Combis and system boilers tend to have built in frost protection but this will just cycle round the boiler through its internal bypass or external bypass if fitted.
     
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  11. ZTribe

    ZTribe New Member

    I had ruled out any internal frost protection. I found the Suprima boiler manual online and checked that, it mentions that external frost protection should be fitted.

    Apologies for the repeated questions, I have absolutely no experience / understanding of electrics or heating.

    Am I right in thinking;
    1. If we remove the frost stat from the circuit and the CH doesn't come on we can assume the frost stat is at fault / over sensitive.
    2. If that is the case we could fit a pipe stat to stop the heating blasting out all night and cooking us while we sleep.
    NB - I won't be removing the frost stat (as stated no understanding of electrics) my partner will, he has an understanding of electrics.
     
    Last edited: Nov 23, 2020
  12. Mike83

    Mike83 Screwfix Select

    1. Yes
    2. Yes
     
  13. Mike83

    Mike83 Screwfix Select

    You don’t need to completely remove it.
    Simply disconnect a wire.
     
  14. ZTribe

    ZTribe New Member

    As I said I have no understanding of electrics :D

    Thanks for your help.
     
  15. Mike83

    Mike83 Screwfix Select

    Keep an eye on the weather.
    Try avoid disconnecting it on the coldest nights.
     
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  16. MGW

    MGW Screwfix Select

    You say getting too hot, so forgetting the electric how? You set temperature on TRV head 61dmtMm13BL.jpg and it should not exceed that temperature unless the valve is stuck or not matched to head, with the head shown that would raise a fault code, but with any head if it over heads some thing wrong with radiator setting.

    A faulty wall thermostat may cause boiler to cycle, but should not cause over heating.
     
  17. ZTribe

    ZTribe New Member

    Thanks for your reply and question;

    A few (3) radiators in the house do not have TRV's - in the bathroom and ensuite (which are both towel rail rads) and the kitchen. I believe fitting new TRV valves requires draining down the system so not something we want to do unless totally necessary and / or we need to.

    The TRV's heads have broken off 2 rads - in the lounge and the upstairs landing so these can't be set to specific temperature and these just get super hot. I believe these are easy enough to replace - they need Pegler Terrier TRV sensor heads which I have found for sale online but they seem fairly pricey and TBH having moved into the house only 4 months ago whilst replacing these is on the to do list it's not top priority. When the CH is working the room stat turns these off at a reasonable temp and so it's not usually an issue.

    Another rad in a bedroom has a Drayton TRV but it seems faulty, either it's off when set on * or 1 but anything higher than 1 is full blast. Again on the to do list to replace.

    Finally I like to sleep in a cold bedroom so either we have to switch down / off TRV's in bedroom before going to bed and then switch them on again the next day (so room doesn't get too cold) on the off chance that the frost stat might kick the boiler on overnight and set the heating going.

    In an ideal world I'd have programmable digital TRV's on each radiator, zoned heating for upstairs and downstairs, a Nest (or similar) thermostat I can control from my phone wherever I am and a condensing boiler which wouldn't be in the flipping loft but we are where we are............... :rolleyes:
     

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