HVAC Problem

[scarlet]

I'm hoping this is the right forum... I didn't see a forum for HVAC, and this seemed to be the best place.
I'm having a HVAC issue that I could use some advice on. All 3 of my AC's were serviced in August. (general maintenance, including topping off freon where necessary) The service man said that I needed to flush the AC in the master hull as it was freezing up, and he attributed that to "gunk" building up in the pipes. I flushed the system after his visit in August. It seemed to be running just fine.

Now that it is colder, I've been turning on the heat at night. Everything starts out fine. Nice hot air flowing out. Then after about 10 minutes or so, it stops blowing hot air. For reference, thermometer set to 70... room temp 66, and it stops heating...

The things I've checked are:

1. no obstruction in the thru-hull. Water is flowing in just fine.

2. pump is working

3. water is flowing out of the boat in a nice steady stream

4. Filter has been cleaned

5. heater is getting hot, and coil are condensing... until it stops heating

6. coils are NOT icing up

7. there is nothing obstructing the vents that would prevent room air from getting to the unit.

8. I've checked that the control panel is in the heat position... temp set properly... and fan is on

9. I also reflushed the AC just incase I didn't get all the gunk out the first time.

What more can I check? My instinct is that it may be a faulty control panel, but it seems to work fine on the cool setting.

One other point, I have seen an error message come up sporadically that indicates "high pressure" (error code HI/PS) That's what lead me to think that it might be an obstruction, or gunk still built up.

I have a Cruiseair AC with a Cruisair Q-Logic Direct Expansion Control System..

Anyone have any ideas what else I could check?

[Opie91]

Unfortunately a fair number of things could be causing the issue. The high pressure error code is a good clue. Does it show when the heat stops? What happens when you turn the temperature to maximum? Does it run longer or same thing?

It could be as simple as an over-service of the system. If it worked well before the service then I would definitely check for proper service.

It could be some type of obstruction in the pressurized system also. Even though it works cooling doesn't mean the heating function will operate.

You might want to try running it in cooling for a bit and then switch to heat and see if that helps or clears it up.

If you have multiple ac systems with the same size water pump run the one that works well, get a bucket and time how long it takes to fill it. Then try the same thing on the system that is giving you an issue. Sometimes the water flow looks good but it is not enough. (I suspect it is probably not this though).

Unfortunately you will probably need to get someone on the boat with a gauge set to see what is really happening.

[Coolerking]

Hi ps in cool mode is a condenser/ seawater issue.
Hi/ps in heat is an airflow, an overcharged refrigerant, or a loose wire on the switch itself.
What is the model number of the unit?

[Sailmonkey]

I’d venture to guess the tech slightly overcharged the unit that is shutting down.

[LittleWing77]

Wow this is an interesting thread.

While I'll never be one to have any HVAC units on my boat, thank you, Opie, CoolerKing, Samanta and SailMonkey for your informative answers!

It's one of those times that it's making me revel in the wealth of experience amongst Forum Members - which is so cool (or in this case, maybe I should say - so hot!) Hahaha

Gratefully,
LittleWing77