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  1. Whoops

    glycol leak in closed-loop cooling system

    "... could be diffusing/evaporating through tubing elements which are all plastic." Is it oxygen barrier tube? Oxygen will permeate through the walls of non-barrier tube. The dissolved oxygen will react with hot glycol, producing acidic compounds. I don't know how hot it has to be, whether...
  2. Whoops

    cold draw

    Cold draw refers to thermal expansion bellows on heating pipework. The bellows is installed cold and is usually stretched on tightening the bolts. Cold draw is usually 50%; the bellows never has to expand by 100%, but is under tension for 50% and in compression for 50%.
  3. Whoops

    ASTM A-120 GALVANIZED CHILLED WATER PIPE

    Anti-freeze and galvanizing do not mix. I think the corrosion inhibitors in most anti-freeze mixtures react with the zinc. Anything over 1 1/2" (I think) is usually welded here (UK). ABS is commonly used now for chilled water systems.
  4. Whoops

    heat temperature require to generate ammonia refrigeration

    I think he means ammonia absorption refrigeration, in which the ammonia is regenerated by heat, a propane flame in caravan fridges. http://en.wikipedia.org/wiki/Absorption_refrigeration I think it's about 120 degC, but I'm sure someone who knows about it will be along shortly with the right...
  5. Whoops

    Discharge Humidity Sensor Saturated

    Sounds like it may be working normally. If the CHW coil is there to de-humidify the air then, when it cools the air, some of the moisture will condense and the air stream off the coil will be saturated, 100% Rh or thereabouts. If it's reheated then the moisture content (in gms per kg of air)...
  6. Whoops

    Holiday Party

    "Fact or Crap"? Questions about Thomas Crapper seem appropriate. Lots of material here. http://www.thomas-crapper.com/history04.htm He did exist but did not invent the flushing toilet, as many people believe.
  7. Whoops

    Electrical conductivity of 50% glycol with inhibitors

    How about a secondary heat exchanger, i.e primary steam/water heats intermediate water. Intemediate water is pumped to a secondary heat exchanger where it heats the glycol. No chance of glycol contamination. The secondary circuit would need a pump, expansion vessel & pressure relief valve,but no...
  8. Whoops

    Humidification and Dew point control

    For that flow-rate air, a BMS system would be very advisable. You'd use standard temp and Rh sensors and the BMS outstation would be configured to calculate the dew point from the Rh input. Vaisala do dew-point sensors, I believ but they're very expensive; I've never had cause to use them. The...
  9. Whoops

    Reuse of RO water in the Cooling Tower

    The last DI water plant I dealt with had a softener, a RO machine and then a de-ionization plant. If it's like this, the RO reject stream would contain more TDS than the feed, but these would be mainly sodium salts. The dissolved sodium salts should remain in solution, despite the cooling tower...
  10. Whoops

    HEPA Filter Gel Seal Failure

    Thanks for the feedback, it's uncommon. I find it surprising & worrying that 60% of the new 'tested' HEPAS were faulty and some of the new HEPA housings. The moral is to test after installation or it probably won't work as intended. The only time I've seen something similar was due to damaged...
  11. Whoops

    Heat recovery coils

    They probably used to be the most common means of ventilation heat recovery. You now see cross-flow plate heat exchangers and thermal wheels doing the same function. Heat recovery coils are typically 4 or 6 row coils with a lot of fins per inch of tube and are expensive. I think the price of...
  12. Whoops

    HEPA Filter Gel Seal Failure

    I think I'd be looking at the filter housings, the knife seal may be distorted. I believe the HEPA filters are individually tested but I've been dropped in it several times by the contractors procuring cheapo, non-approved plant. The filter housings may have been pressure tested, but this may...
  13. Whoops

    HEPA Filter Gel Seal Failure

    "Has anyone else had this problem?" No, not me. Are you sure it's the gel seal that is letting-by? Is the knife edge continuously welded to the HEPA filter housing? Are the HEPA filter housings new, or is this a new batch of HEPA filters? Have the terminal housings passed the DOP tests with a...
  14. Whoops

    Burst heating coil

    "I need to know for sure if at low load 40 degC water is normal..." I regret I can't prove this, it's beyond my maths, which was fairly shaky when it was in regular use. The low water return temperature does seem to be predictable from the Q = U x A x LMTD equation. U and A are constants. Q...
  15. Whoops

    WLHP w/ Condensing Boiler

    I would have thought that the building's heat distribution system would be piped on a primary circuit, with the heat generators (WLHP and boiler) on a secondary circuits. The WLHP would probably be working as the lead boiler. You should have the design heat load required by the heat...
  16. Whoops

    Burst heating coil

    "The coil supplier is using the low water temp in his defence..." He may be, but it seems to be a very feeble defence. It's a red herring; it is not relevant to the defect. You need to ask them to explain how a low return temperature could possibly cause a pin hole in their coil. If they can...
  17. Whoops

    Burst heating coil

    Whilst the thermodynamics of the coil and the LMTD equation are very interesting, I don't see that they have any relevance to why the coil burst unless, of course, it froze. If it had frozen, there'd probably be an axial split in one or more of the tubes near the return, not a pin-hole leak in...
  18. Whoops

    Code Quest.: Chillers and Boiler in Same Room?

    One relevant British Standard is; BS 4434:- Safety aspects in the design, construction and installation of refrigerating appliances and systems (No longer current but cited in the Building Regulations) The pertinent clauses are; 3.2 Machinery Rooms serve for accommodating refrigeration...
  19. Whoops

    Code Quest.: Chillers and Boiler in Same Room?

    I think there is, or was, a mention in a British Standard in the UK. I can't recall the details, something to do with toxic fumes if refrigerant was drawn into a boiler & burnt.
  20. Whoops

    How do you convert a 5 ton roof top unit into a generator?

    The little Black Box with three wires connected to the compressor will usually invalidate any remaining manufacturer's warranty. How did I find that out? Don't ask!

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