Cruisair AC

[a64pilot]

Originally Posted by medsailor1

Thanks I understand all that but the sea water is around 19/20c which isn't that cold plus last time we used it the sea temp was colder and we got hot air out so much that you couldn't stand next to it for long .
So in this case it has nothing to do with the temp of the water .

Well I think you have sort of answered your own question then if I remember what it was, but if it used of get hot and doesn’t now somethings wrong. My little Webasto used to get warmer I think, but never really blew much heat.
I’d start with ensuring there is good water flow, low flow will result in lower heat, once your sure of that, try rapping the reversing valve with the plastic Handle of a screwdriver, they sometimes stick, can’t hurt to try.

[Auspicious]

Originally Posted by a64pilot

Actually believe it or not but my 16K Webasto gets stinking hot.
We have a cold snap coming tonight, I’ll try to remember to measure it tomorrow, but I bet it’s over 100F, with say a 70 intake air.
It does not have resistance heat.

Could you check sea water temp with your depth sounder please?

I don't think I get 100F air from my forced air Espar heater.

[Coolerking]

Keep in mind that it's the temp difference between the air going in the unit and the air coming out that will tell the story, a difference of between 15 and 20 degrees F is good.
As the air going in heats up, the air going out will follow.
If you think about the actual time the air spends passing through the coil, its easy to understand why it takes a bit to heat a boat in cold water.
The small units take the longest.
Keep in mind that you are also heating the copper tubing, the fan blades, enclosure, and the duct, all of this can add time to the heat cycle.
The fans are usually programmed reverse of what you have in cool mode, they start slow and speed up as the set point is reached.
They also all rely on the heat of compression to help build the heat in the circuit.
Good luck.

[a64pilot]

Originally Posted by Auspicious

Could you check sea water temp with your depth sounder please?



I don't think I get 100F air from my forced air Espar heater.

Speed log is out due to growth, USCGS says St John’s river temp is about 70f though, but I promise you even down to 50 something it still blows hot. I was wrong about the 100, I thought it would be higher and it is, now this register is the only one and it’s only about 2’ away from the unit and it’s insulated, so this is discharge temp.
Inlet air temp was 73F. This is a calibrated Fluke thermocouple, so I know it’s very accurate.

Air flow is not restricted

[DeepFrz]

Originally Posted by medsailor1

Thanks I understand all that but the sea water is around 19/20c which isn't that cold plus last time we used it the sea temp was colder and we got hot air out so much that you couldn't stand next to it for long .
So in this case it has nothing to do with the temp of the water .

Have you descaled the raw water passages of the HVAC system?

[GordMay]

Originally Posted by Coolerking

Keep in mind that it's the temp difference between the air going in the unit and the air coming out that will tell the story, a difference of between 15 and 20 degrees F is good...

By way of comparison, a residential forced air furnace data tag will usually give a maximum outlet air temperature (typically around 170°F), as well as a temperature rise (typically 40-70°F above the return air temperature).
This is the temperature degree rise measured by comparing incoming return air temperature to outgoing supply air temperature within about 2 meters of the furnace air handler.
Factory settings at the fan limit switch typically will be as follows
1. FAN ON: not let the fan turn on until temperature reaches 20°F above the FAN OFF - that's typically around 130°F
2. FAN OFF: the low off number is typically 90°F
3. FAN LIMIT OFF: the high limit is typically factory set at 200°F - a safety level to avoid overheating
A typical supply air temperature measured at a supply register of a forced air heating system is around 110 degF.

I don't know the typical characteristics of a water/air heat exchanger system. I would expect temperatures & Deltas to be lower for HEX unit.

[a64pilot]

I believe if you get a 20f Delta in temps for a heat pump, that’s considered great.
I can’t explain my 50 degree Delta.

[medsailor1]

For them who are interested the problem was a air lock in the return flow pipe , once I removed it and let it run for a bit , it soon heated up .

[Sailmonkey]

Originally Posted by medsailor1

For them who are interested the problem was a air lock in the return flow pipe , once I removed it and let it run for a bit , it soon heated up .

If you were airlocked, the unit would only run for a short time before shutting down for either high pressure or low pressure.

[lancelot9898]

Originally Posted by medsailor1

For them who are interested the problem was a air lock in the return flow pipe , once I removed it and let it run for a bit , it soon heated up .

Are you talking about a blockage in your air handling system? ( ie the return ducting)

Someone mentioned descaling the raw water tubing. Is there any suggestion as to how that should be done? I've descaled the HX to the Perkins engine by removing the heat exchanger tube bundle, putting it in muric acid and then rodded it. Interested in hearing some suggestions for the AC.

a64...I also have a Webasco unit (12,000 btu) and installed it last year. I had trouble getting the required coolant flow through the unit, but finally accomplished it. I do feel a good bit of heat coming out of the unit which was surprising since there is no resistive heating. A tech at Webasco told me that in winter I might be able to get more heat even when the water temperature drops below 40 degrees F if I throttle back on the coolant flow.
That was counter intuitive to what I was thinking ,but in heating mode lower coolant flow seems to be doing fine.

[Coolerking]

The system needs water to pull heat from, reduce it and you will get less heat, and the system will eventually fault on low pressure.
Be careful restricting the water flow in very cold water, you can do damage and even freeze the condenser and break it.
The tech most likley meant that by reducing the airflow through the coil the discharged air temp will rise.
Water flow through the condenser must remain the same in cool or heat mode.
3.5 gallons per minute per 12,000 btu.

[medsailor1]

Removing the return sea water pipe and used a bucket to catch the water , the water flow didn't seen right then there was a gasp of air and the water flow increased , I can only put this down to some kind of air lock , no obstructions came out of the pipe , no sooner I replace the pipe the AC heated up .

[a64pilot]

Originally Posted by medsailor1

Removing the return sea water pipe and used a bucket to catch the water , the water flow didn't seen right then there was a gasp of air and the water flow increased , I can only put this down to some kind of air lock , no obstructions came out of the pipe , no sooner I replace the pipe the AC heated up .

You hade some form of restriction, not a stoppage.
If a stoppage then the system would overpressurize and shut down due to overpressure.
However a water restriction results in lower performance as your pulling heat from the water, less water, less heat to pull. And as has been posted that can lead to a complete freeze up of the evaporator, and total blockage.
I’d guess you had a frozen partial blockage

[Coolerking]

What are the specs of the system we are talking about? Seawater pump model number?
Is the AC the only thing the seawater pump is supplying?
Look at the hoses from the unit to the overboard thru hull fitting.
Does the seawater discharge above the waterline?
If you cannot see/access the hoses then you might
get a one gallon bucket and see how long it takes to fill it, then do the same at the unit, you need 3.5 to 4 gallons a minute per 12k of ac.
Hoses should be 5/8" on anything smaller than 48k.
Pictures!

[Marinerefer]

Originally Posted by medsailor1

Our Cruisair AC unit works fine in cold but on heat it just blow Luke warm air ,
Has any one got any suggestion what the problem could be ?

What's the model or capacity on the nameplate?
Some lower capacity units really won't kick out too much heat, water temperature also has a big effect on how much heat is available to be drawn in by the system.