Post edited 1:13 pm – February 4, 2011 by Steve Pooler

Hi Ed

Forgive the short reply here (I'm on my phone) but the short answer is 5 inch duct is simply not large enough for moving 16k worth of air….And the warmer the return air, the more that problem compounds.

Here is a link to a post with a longer description of what happens and if you have more questions please post back here in your thread…
http://marine-ac.com/forum/tro…..eat-cycle/

Steve~

If I choose AUTO sellection I noticed the dehumidify light allso come on should I run on this cycle in humid cold weather...

Though I have never used that FCF control…Humidity modes are typically for when you are away…They bring the system on in the cooling mode for a programmed amount of time, or for a set amount of temp drop (usually either 2-4-6 degrees) to remove humidity only….The system then stays off until it is time to dehumidify again…They are not meant for maintaining a given temp when aboard. 

I also noticed that there is a setting if you are running more than one ac unit  If I set thiis at setting of 30 which calculated to be 600 seconds…

This setting is usually called Time Delay…It's meant for when you have more than one system, and so that you can stage the starting of each unit after a power interruption such as shifting from shore to generator…You would set each system at a differing delay so that they don't all start at the same time when power is restored….This saves huge surges on your cord or generator….If you only have one system I would set it for 10 or 20 seconds…This will allow a refrigerator time to restart without the A/C coming on at the same time.

which is 10 minutes would this help If your recommendation is to add more output airflow should I increase the size of the one transition box and grill or add another one in line My options for vent location is very limited…

I think I would first do as your sales rep has suggested and remove the duct all together to verify that the unit will actually perform in heat mode…It would be best if you can rotate the blower so that no hot air is reflecting back on the unit from a bulkhead or cabinet…

If it won't heat the cabin to say 75 degrees, Then you are wasting time with ductwork until you get a unit that will operate in heat…But yes as I indicated…I don't see it working with 5" duct, but that's the way they spec it so they must get it to work…

Steve~ 

Ed D said:

Steve

 

Thank you so much I really appreciate the time taken to explain all of this to me Yesterday  I removed my ducting and attached a 1 ft lonf piece of 5" duct to divert the air away from the  unit

Ed

I'm just as curious about these Webasto units as anyone I'm sure since I have no experience with them…

Please keep us up to date  

Steve~

Post edited 11:07 pm – February 6, 2011 by Steve Pooler

Hi Ed~

Just curious…Where are you & your boat  ???

Ed~

This is an experienced guess of what is happening…Though without refrigerant gauges connected & a visual hands/eyes on the situation it really is only a guess….

It sounds from your description that the unit cycles 4 times before it trips the breaker, and that the amperage draw is rising as the cabin gets warmer…This cycling is likely from the High Pressure switch seeing pressures above it's cut off point…This is a normal situation for a unit that is either overcharged…that does not have enough air flow…or return air that is warmer than the system was designed to operate in…

I think we have eliminated that the cabin is too warm, or that it's blowing hot air back into the return…We also have eliminated the possibility of restricted duct (Though I still have issue with blower ring size being only 5") and being a new factory charged unit, the refrigerant should have been weighed in at the factory…Yes sometimes mistakes are made there, but it's not often I hope for Webasto.

Since you don't mention the control display showing any fault code/s…I can assume that either the high pressure switch is not connected into the control, or that the control must see more than 4 faults before it shuts the system down & displays a fault…Again I'm not familar with Webasto & the FCF digital control, but the systems I have seen in 20+ years will react similarly…More on that in a minute…

Your amperage draw figures seem very high for running load, so I'm also assumeing you are quoting start up amps ???

If you are in fact quoting run load amps…You must have an oversized breaker (which is not good & a definite fire hazzard) Not knowing the size wire, but I would guess that you should have a breaker rated for no more than 30 amps, and likely the wire is #12 AWG…So 20 amps would be it's continous breaker rating.

Back to possibilities/guesses….

When a unit is cycling on the High Pressure switch what happens is the pressure builds up to the switch rating…Usually 425psi for R-22/R417a units, and around 600psi for the newer 410a units…At which time it will interrupt to protect the unit…The compressor shuts off, and the pressure in the system starts to equalize pressure back thru the little capilary tube that sprays the refrigerant into the evaporator, thus lowering the "head" or high pressure….

Thing is, that the switches are usually made to automatically reset/reconnect before that pressure has completely equalized, and the compressor then tries to restart against that higher than normal head pressure which is very hard for it to do, and it draws much more amperage thus tripping the breaker…It's another form of protection if the breaker is sized correctly…This is if the switch is NOT connected to a digital control, but directly in-line with compressor power…

If the switch is connected to a digital control with fault protections, then the control interrupts power to the compressor when it sees the switch open, and then depending on the control software, is when the compressor is again sent power, and how many cycles it takes to show a fault on the display that lets you know what happened while you were away…The digital contols will usually energize the reversing valve to instantly equalize pressures befor sending power to the compressor so that it never trys to re-start against that extra load I mentioned earlier.

Your system seems to just trip the breaker…So either the switch is wired to the compressor, or the control does not hit the reversing valve before it starts the compressor, OR…..

Looking again at the pictures on the Webasto site it's hard to tell…But I can't see a High Pressure switch…I've seen bargain units in the past leave them out for cost reasons…In which case it becomes the Compressor overload's job to provide the protection…A compressor overload is supplied by the compressor manufactuer and is normally intended as a last line of protection…The overload senses heat…Either generated by high amperage draw, or by the compressor overheating…The unit could be cycling on the overload too…

As I'm typing this I see you have posted again so all of the above may be wasted…Or more than you wanted to know

I'll get out of this & read your new post…

Steve~