Wizard
SupporterAs I posted, I have not worked on cruise ships, but the problem of trying to balance such a system is not a "thermostat", but rather airflow dampers in the trunking outlet to each cabin. The systems that I have worked on usually have a central thermostat somewhere in the return airflow.Passengers would constantly adjust the thermostats never giving their cabin a real chance to stabilise.
If the system was built with individual evaporators for each cabin there would be a better chance of keeping it stable. This of course assuming it is a direct expansion system.
Swaggie
Seems an odd way of conditioning the air,as the amount of heating or cooling a full fresh air system is huge.Definitely not something that would suit a vessel,one would think.I presume they would use steam coils for heating.Or maybe these days they may use heat from the engines somehow.Originally Posted by DiscoMick
Cooling,one would think would be done by refrigeration,which would also dehumidify.
But anyway,I stand to be corrected.
Swaggie
That sort of system used to be common for offices as well,with re heat heaters for each zone.Mainly large DX plants,which are generally obsolete these days.Airflows balanced and fixed during commissioning.
But now they are generally more complicated,using chilled water with numerous VAV boxes(variable volume dampers),and re heaters.All electronically controlled for each office or a bank of offices along the same side of the building,on one VAV,as the heat load will be similar for that zone.Also utilising VSD’s on the main supply fans,working on duct pressures.
But then we still get the same issues,two people complaint about temps,one says it’s to hot,the other it’s to cold,in the same office.
Give me refrigeration any day
Cynical Moi?
You reckon that is bad. My learned colleagues can testify re the balancing problems It takes ages to physically go from Office to Office & adjust air & temps to suit the occupier. Bugger me dead the next week there is a change of staff & guess what? The previous conditions don't suit the new one so off you go again. They are not footing the bill, the Boss is.
Then you have the problems of Women's Menstrual Cycle & trying to obtain the best conditions to cope with hot flushes of the older staff etc.
You thought Air Cond was a piece of cake right?
YarnMaster
Hi,
New (ish) building, 1971.
My office was too cool, but tolerable.
A few weeks in, it was so cold a heater was needed.
Undid the thermostat cover and moved it up a tad,
Arrctic conditions prevailed.
Chap in the office next floor down was sweltering.
Turned out my thermostat controlled his office and his controlled mine.
Egg-nishner folk had crossed the lines!
Cheers
Swaggie
Common issue,seems many plants are never commissioned properly.
or modified and fiddled by others later in their life.
I could write a book about those sorts of stuff ups..........
I have even seen large DX plants,pipework crossed over,one was at the local golf course,it had been running for years,until one stage stopped on a fault.Then the **** hit the fan
Cynical Moi?
Common issue,seems many plants are never commissioned properly.
or modified and fiddled by others later in their life.
I could write a book about those sorts of stuff ups..........
I have even seen large DX plants,pipework crossed over,one was at the local golf course,it had been running for years,until one stage stopped on a fault.Then the **** hit the fan
Yeah as Paul said, not an uncommon problem especially when dealing with Multiple Fan Coils on different floors & offices with many coloured cables pulled through the building & Tradies not finishing the job they started but handed to someone else half way through.
Yes Paul, in conjunction with Rick I'm sure we could write a Book.
Suggested title could be "Global Monster ****ups in the HEVAC Industry" Unless you have another title in mind..
Notice that the link I posted referred to 'accommodation spaces' having total loss air and I said passengers were confined to cabins. I assume the public areas had a different system, as there were no doors between the public spaces on each deck. So they would only use the no recirculation system in the cabins, I assume
Swaggie
What it actually says is there is no recirculating of air on the vessel.
Then it goes on about the accomodation cabins.
So maybe there is no recirculating anywhere,which is surprising,but not saying they are incorrect.
Anyway the chance of the virus being passed around by an AC system is almost nonexistent.
ChatterBox
SubscriberIn my experience big ships are like hotels in that they mainly by law don’t have opening windows (portholes) to introduce a certain amount of fresh air (and humidity). So they run permanent extraction from the bathroom and the door will be cut short or have lower louvre to enable movement (extraction) from the room. The zone / floor / deck section will have a local AC unit with ducted supply of air con to the room/s it serves typically via a chilled water system (with pipe work immaculately insulated to avoid condensation) with the noisy chiller compressor system in the engine room or basement and pumps running the chilled water around to each unit. Local cabin temperature control (on fancy setups) is +/- a few degrees of the central system temp via a small heater element on the individual cabin supply. The ship’s engineer determines the master temperature.
Seperate to all that is a make up air unit/s that treats the outside air to inject a specified percentage 10-40% to the system to balance the extracted smelly air from the dunnies. Smelly extraction air from dunnies, galley and black water tank goes up the mast to the atmosphere. Everyone starts off wanting a lot of make up air till they hear the cost........
You need some fresh air and humidity to avoid people waking up with a super dry throat at night when sleeping (sound familiar?) as a 100% recirculated system will eventually dry the air out not to mention be stale and unfriendly (cheapy small boat systems are like this with individual cabin units and often no make up air). At night, with no sun on the window or wall and once all the hotel / boat doors are kept shut the air conditioning starts to work really well!!
The make up air unit has to achieve this comfortable level of humidity and unlike a hotel in a fixed environment needs to cope with both high humidity (Florida/ Asia / Kimberley / Caribbean) and low humidity (New Zealand / Canada) cruises. An enormous amount of water is removed in high humidity areas.
Make up air unit/s can be located in various deck cabinet locations drawing air in from outside and distributing to the cabin zone AC units.
This capability drives the size and cost of the units. The more make up air % the bigger the make up air unit the more electrical power the bigger generators, etc etc. All this creates a perfect war when the engineers say they need a bigger engine room and to delete a cabin or 3 to fit in the bigger plant and associated make up air throughout the boat. The engineers rarely get what they want in front of the sales guys so compromise is built in from day one.
I used to see customer specs stating the marine air conditioning system needed to cover -15 degrees to 50 degrees with 50-90% humidity assuming the different locations the boat would visit. The air conditioning contractor quotes would come back astronomical with an incredible plant size and power demand. Then I learnt something interesting........
You can’t have high temp and high humidity coincident at same time. Singapore has super high humidity in the day but the temp never more than low 30s. The Middle East may show very high humidity in the early morning but by midday at 45+ degrees the humidity burns off to lower levels. The range of temp and humidity extremes published do not happen at the same time. It’s a law of thermodynamics thing.
On this basis you can specify a more affordable system that will cope.
On top of this a boat needs a completely pinned, sealed and taped thermal insulation lining (seperate to A30 or A60 fireproofing insulation to fire risk areas) on the inside of the entire steel or aluminium structure between the structure and any air conditioned cabin or space. Without this in hot / humid areas the hull sweats causing an internal rain and enormous condensation / stink / mould / destruction/ rot issues. Having a sexy dark hull colour will greatly exacerbate the internal / external temp differential with the sun on it. When you next jump on a cheaply built ferry in Asian waters you will know what I mean as easy to save money on that insulation.
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