Replacing standard hoods with enhanced weather protection hoods - LT31

LTEH211-230 and LTEH211-115 Installation Guide
Document code
M211276EN
Revision
E
Language
English
Product
LT31
Document type
Spare part manual
User guide
These instructions are for mounting enhanced weather protection hoods on both the receiver site and the transmitter site.
  • Ladder
  • Allen key, 3 mm and 4 mm
  • Spanner, 8 mm
  • Crosshead screwdriver
  1. Switch off the AC (mains) power in the interface unit.
  2. If the battery backup LTBB111 is installed, switch off the battery switch.
  3. To remove the white measurement head cover, open the 3 lock screws both on the right and left side of LT31.

    Use a ladder to access the lock screws.

    WARNING To avoid injuries and to avoid damaging the instrument, do not place a ladder or similar against the instrument.
  4. To remove the standard weather protection hood from the support unit, remove the 2 screws (hex socket head, size 3) at each rear end corner of the hood and remove the hood.
  5. Remove the 4 spacers from the support unit.
  6. To remove the measurement unit from the mast, disconnect the electrical connector from the measurement unit and loosen the 2 fastening screws (hex-socket, size 4) on the right side of the measurement unit.

    The fastening screws are accessible through the mast adapter of the support unit. Pull the measurement unit off the mast.

  7. Remove the old cover plate from the measurement unit and mount the delivered cover plate with the adapted air duct.
    Make sure that no dust, dirt, or moisture can enter the measurement unit enclosure while it is open. Vaisala recommends opening the measurement unit in a dry room.
  8. Close the measurement unit carefully. Pay attention to the position of the cover seal. Tighten the measurement unit cover screws firmly to prevent dust or moisture entering the measurement unit during operation in the field.
    Do not reinstall the measurement unit yet.
  9. To install the enhanced weather protection hood assembly, mount the hood and attach it firmly to the support unit with the 4 countersunk head screws included in the delivery.
  10. Route the heater connection cable inside the support unit towards the back of the support unit near the blower.
  11. To perform the electrical connection of the hood heater, open the small junction box located near the blower system to access the terminals.
    WARNING Death or serious injury may occur. Make sure the AC (mains) power is switched off.
  12. Insert the heater cable inside the support unit and through the cable feedthrough.
  13. Connect the wires.

    Tighten the cable feedthrough and close the junction box cover plate carefully.

  14. Align the support unit horizontally.

    Place the ladder behind the mast and check the orientation. Use the sight hole in the rear plate together with the sight pin.

    Make sure that the support unit is aligned exactly towards the opposite LT31 mast. The correct alignment helps avoiding any shadowing effect on the measurement light beam.
    You can loosen the 2 securing screws (hex socket, size 4) at the right side (operator's view) of the support unit mast adapter to make the entire support unit turnable. After alignment, tighten the screws firmly.
  15. Insert the measurement unit and re-establish the electrical connection.

    Plug the measurement unit on the mast top and secure with the 2 fastening screws on the right side accessible through the mast adapter of the support unit. Re-establish the electrical connection to the measurement unit and store the plug in the rear of the support unit beside the blower unit.

  16. Check the alignment of the measurement unit enclosure.

    Make sure that the measurement unit is parallel to the support unit (housing edges parallel to the outline of the support unit). The measurement unit must have a distance of approximately 8 mm (0.31 in) to all surrounding support unit parts.

    Loosen the fastening screws (hex-socket, size 4) on the right side of the measurement unit, which are accessible through the support unit mast adapter, and turn the measurement unit enclosure into a parallel position. Tighten the screws to secure the measurement unit position.

  17. To check the vertical alignment of the mast, place the ladder behind the mast and check the orientation of the support unit.

    Check the vertical alignment of the support unit with the sight hole in the rear plate and the sight hole in the horizontal plate inside the hood. Make sure the support unit is exactly towards the position of the opposite measurement head and you see the opposite measurement head through the sight hole in the horizontal plate. If you cannot see the opposite measurement head, correct the vertical alignment accordingly.

    Make sure the support unit is aligned exactly towards the opposite LT31 mast. The correct alignment is required to avoid any shadowing effect on the measurement light beam.
    Slightly loosen the 3 nuts that secure the mast base on the foundation screws and turn the foundation screw located towards the baseline to change the vertical orientation. Make sure the alignment is correct by looking through the support unit sight hole, and tighten the nuts.
    1
    Threaded frangible mounting rod
    2
    Nut M16 DIN 934 A2
    3
    Washer A17 DIN 125 A2
    4
    Washer A17 DIN 9021 A2
The weather protection hood is installed at the receiver site. To install the enhanced weather protection hood at the transmitter site, repeat this procedure.