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View Full Version : 2 ACs, one pump - need switch relay?



akintosyali
03-18-2008, 04:40 PM
This is getting interesting. I got 2 16.7 oceanbreeze ACs with direct heat. I have one water pump. Factory says do not attach the same pump to both AC circuits unless I use a switch relay ($92).

a-for $20 more, I can just get another water pump
b-Why is this switch relay so expensive? Is there something I can but at radio shack for a lot less?

MikeP
03-18-2008, 04:46 PM
Our 53MY has one water pump for all four A/C units and they work fine. I don't know why you would have to have relays or separate pumps at all unless the single pump is too small. If so, why not just install a larger one? Then again, one would expect the manufacturer of your units to know what they are talking about.

akintosyali
03-18-2008, 05:12 PM
Yeah, I agree. i bought a Mach that has 1000 GPH. (per recommendations from the board). The service guy sais that if I hook both AC;s to the pumps, I will fry the circut board at the ACs..

Beckytek
03-18-2008, 07:05 PM
The circuit board is only capable of providing a small current flow. That is why you need the relay. The circuit board energizes the relay when your AC comes on. This allows the relay to apply the full large current flow to the pump motor. I don't think you will be able to get a relay like that from Radio Shack. They are available through Allied Electronics or other outlets. I would just buy the one that's recommended and forget about saving money. It's a boat! Ron

captbuddy
03-19-2008, 11:25 AM
On my 42 LRC 1981, I have 3 AC units and one pump. The power box contains 3 seperate power relays. The pump relay box contains 3 pump relays. Salon is 230 volt. The V-Berth and Master sate room is 115 volt. Just found out this past weekend the Salon has a time delay on the pump. You can turn the all the way on to run and nothing happens except the fan runs. When the compressor kicks on the pump starts running. Just turning the fan on this unit will not ativate the pump as soon as you turn it on. The difference in the 115 volt units you can activate the pump by just starting the fan. Got all three new pump relays for $100. Replaced them last weekend.
captbuddy

Pascal
03-19-2008, 12:53 PM
yep... need a relay box.

if you have room for a second pump, you can do that but you will need a separate sea cock and strainer... so unless you have an old unused thruhull already there, it's cheaper to get a relay

Trojan
03-20-2008, 05:42 PM
There probably using a switching transistor on the control board to turn on the pump. Adding the relay lets the two circuits isolate them. Limiting the current flow in each unit and preventing any back flow.

BILL