I have a British Gas 330+ boiler (re-badged Glow-worm I believe) which is configured as a sealed system, installed in a four bed detached house we purchased a couple of years ago. We've had various issues with it (nothing too major) which has led me to getting quite a bit of information on it, which has made me concerned as to whether or not it's been installed correctly.
My main worry is around the size of the Expansion Vessel. The boiler has had the "integral sealed system kit" installed which from the information contained in the manual (see below) suggests is only rated to 18kW. The boiler is configured for 30kW, though can be changed via the control panel.
Am I right in saying that, if the pressure was too high in the system, the PRV would kick in to relieve the pressure? But would mean a drop in the level of water in the system leading to less pressure when not hot?
Section 5.14 of the install and service manual mentions around the sizing of the vessel. Allowing 10L per radiator (seems something a lot of websites say), with 15 radiators (and not including pipework runs) that the 150L multiplied by the 0.063 gives me 9.45L for the expansion vessel. Which is greater than the 7L vessel supplied in the kit.
I take it that this would need to either be replaced with an external expansion vessel of greater capacity? Or an additional expansion vessel added to the system, as it seems to suggest in section 5.19?
Apart from the PRV having to open, is it dangerous for the boiler to be configured to 30W with the current configuration?
Snippets from the manual: -
5.12 Sealed Water Systems
An integral sealed system kit, part no.0020051474 is available for models rated up to 18kW. The installation must comply with the appropriate requirements of the current issue of BS4814, BS5449, BS6759, BS6798 and BS7074 Part 1 and 2. See diagram 5.4 for a suggested layout.
5.14 Expansion Vessel
A diaphragm type expansion vessel, conforming to the current issue of BS4814 (see also BS7074 Part 1 and 2) must be connected at a point close to the inlet side of the circulating pump, see the diagrammatic layout, diagram 5.4. The expansion vessel volume depends on the total water system volume and the initial system design pressure. For
any system an accurate calculation of vessel size is given in the current issue of BS5449 and BS7074 Part 1. Example: For an initial design pressure of 0.7 bar, the minimum total vessel volume required is 0.063 x Total System Volume. NOTE: A higher initial design pressure requires a larger volume expansion vessel. Guidance on vessel sizing is also given in the current issue of BS5449 and BS7074 Part 1, for IE refer to the current edition of I.S.813 “Domestic Gas Installations”. The charge pressure must not be less than the static head of the system, that is, the height of the highest point of the system above the expansion vessel.
5.19 Sealed Systems
A sealed system kit is available to fit inside the case of the boiler. The kit is designed to operate up to a maximum output of 18kW. The kit contains an expansion vessel, electronic water pressure gauge and flexible pipe to be fitted in the boiler case. A pressure relief valve and auto air vent to be fitted to the system pipework.
The accessory is available as part no 0020051474, see diagram 5.6. NOTE: For systems greater than 18kW range rated an additional expansion vessel may be fitted or a proprietary kit installed matched to the size of the installed system. Ensure that the range rating of the appliance is indicated, see section 12.5 for details.
My main worry is around the size of the Expansion Vessel. The boiler has had the "integral sealed system kit" installed which from the information contained in the manual (see below) suggests is only rated to 18kW. The boiler is configured for 30kW, though can be changed via the control panel.
Am I right in saying that, if the pressure was too high in the system, the PRV would kick in to relieve the pressure? But would mean a drop in the level of water in the system leading to less pressure when not hot?
Section 5.14 of the install and service manual mentions around the sizing of the vessel. Allowing 10L per radiator (seems something a lot of websites say), with 15 radiators (and not including pipework runs) that the 150L multiplied by the 0.063 gives me 9.45L for the expansion vessel. Which is greater than the 7L vessel supplied in the kit.
I take it that this would need to either be replaced with an external expansion vessel of greater capacity? Or an additional expansion vessel added to the system, as it seems to suggest in section 5.19?
Apart from the PRV having to open, is it dangerous for the boiler to be configured to 30W with the current configuration?
Snippets from the manual: -
5.12 Sealed Water Systems
An integral sealed system kit, part no.0020051474 is available for models rated up to 18kW. The installation must comply with the appropriate requirements of the current issue of BS4814, BS5449, BS6759, BS6798 and BS7074 Part 1 and 2. See diagram 5.4 for a suggested layout.
5.14 Expansion Vessel
A diaphragm type expansion vessel, conforming to the current issue of BS4814 (see also BS7074 Part 1 and 2) must be connected at a point close to the inlet side of the circulating pump, see the diagrammatic layout, diagram 5.4. The expansion vessel volume depends on the total water system volume and the initial system design pressure. For
any system an accurate calculation of vessel size is given in the current issue of BS5449 and BS7074 Part 1. Example: For an initial design pressure of 0.7 bar, the minimum total vessel volume required is 0.063 x Total System Volume. NOTE: A higher initial design pressure requires a larger volume expansion vessel. Guidance on vessel sizing is also given in the current issue of BS5449 and BS7074 Part 1, for IE refer to the current edition of I.S.813 “Domestic Gas Installations”. The charge pressure must not be less than the static head of the system, that is, the height of the highest point of the system above the expansion vessel.
5.19 Sealed Systems
A sealed system kit is available to fit inside the case of the boiler. The kit is designed to operate up to a maximum output of 18kW. The kit contains an expansion vessel, electronic water pressure gauge and flexible pipe to be fitted in the boiler case. A pressure relief valve and auto air vent to be fitted to the system pipework.
The accessory is available as part no 0020051474, see diagram 5.6. NOTE: For systems greater than 18kW range rated an additional expansion vessel may be fitted or a proprietary kit installed matched to the size of the installed system. Ensure that the range rating of the appliance is indicated, see section 12.5 for details.