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Thread: Switched to evohome & caused damage to boiler?

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  1. #1
    Automated Home Sr Member
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    Jan 2018
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    Default Switched to evohome & caused damage to boiler?

    I have recently switched all my TRVs to HR92s; I also swapped out my hive relay/controller for a BDR91 and it was easy as that - evohomed!

    FYI, I have a Worcester Greenstar 30si, and I have decommissioned a Hive system (with dumb TRVs) to install the above kit. But the main radiator (which was in the same room as the hive thermostat, and didn't have a TRV) was almost always on, as long as any one of the other radiators was on.

    So: I thought I was being clever by adding a TRV valve to the main radiator (I did this by simply de-pressurising the system using a bleed valve, using pipe-freezing spray, etc.).

    However, I started to think about it, and I got worried... What happens if all the TRVs are off (at 0%), and (due to sync delay) the boiler is still providing/pumping to the CH? Is it pumping against a closed system? If so, can I damage my system?

    For now, I have put a TRV on a small radiator at set it to 5/5... But do I need to call a plumber and put in some plumbing to cope with the above scenario?

  2. #2
    Automated Home Guru
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    Default

    You need to have a bypass valve installed if you have HR92s on all the radiators. Do you have one?

  3. #3
    Automated Home Ninja Dan_Robinson's Avatar
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    Just leave the bathrooms uncontrolled.

    Or get a plumber in to fit an auto by-pass.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  4. #4
    Automated Home Sr Member
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    Default

    Thanks for the advice.

    Quote Originally Posted by chrisgare View Post
    You need to have a bypass valve installed if you have HR92s on all the radiators. Do you have one?
    I thought so. I do not have a bypass valve installed (all I can see is a MagnaClean, and a silver cricket-ball-sized thing which I assume is some sort of expansion vessel).

    Quote Originally Posted by Dan_Robinson View Post
    Just leave the bathrooms uncontrolled. Or get a plumber in to fit an auto by-pass.
    For now, I've left a radiator in the main room uncontrolled. But I want to put in an external thermometer, so I may get both done, along with the upcoming service.

  5. #5
    Automated Home Legend
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    Default

    Some boilers have internal bypass valves too. So check that

  6. #6
    Automated Home Sr Member
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    Default

    Apparently, it has got one! I guess this is why I didn't do any (apparent) damage.

    However, the manual says: The boiler is equipped with an internal bypass. The internal bypass is not intended to be a substitute for an external system bypass. An external automatic bypass should be used if the system flow can be significantly adjusted or stopped by zone valves and thermostatic radiator valves (TRV).

    I guess it'll pay to have an automatic bypass fitted so I don't end up needing a new boiler?

  7. #7
    Automated Home Ninja
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    Aug 2016
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    Default

    Bear in mind that ABVs don't play well with pumps that adjust their pressure/flow rate based on the pressure in the system (proportional pumps).

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