New to Boating. New to Forum.
1984 53' Extended Deckhouse
Using 2 Cruisair systems onboard for heat. They seem to work fine individually. Both operate the same seawater pump when their compressors are running. Everything seems to be fine unless we try to operate them at the same time. If we do, after a while we realize we are getting cold and that the seawater pump is no longer working...the 20 amp fuse in the PR8X has blown.
I have put my hand on the pump after it has been running for hours and it is just warm - not at all hot.
I don't have a lot of experience with AC systems, but it seems that if a pump is running and another unit calls for that same pump to turn on, that there would not be a significant change in the power being consumed by the pump circuit.
What might be the cause of the fuse blowing? It has happened 3 times so far, but if we run only one unit at a time, we are going on more than two days now without a blown fuse.
Any thoughts? Any experience with this problem?
Thanks for any help!
Nick
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Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
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01-15-2019 11:05 PM #2
Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
Voltage drop from a second unit running.
As the voltage drops the pump gets browned out and blows a fuse.Scott
41C117 "Hattatude"
Port Canaveral Florida.
Marine Electronics and Electrical Products Distributor.
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Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
Welcome to the forum. I’ll take a guess because I’m not there in person. The fuses are old and weak. Try switching them out. If that’s it, it’s a cheap fix. Question, what power do you have going to the boat? 50/125/250?
SEVEN
1979 53' MY Hull #563
Antioch, California
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01-15-2019 11:26 PM #4Senior Member
- Join Date
- Jun 2018
- Posts
- 1,069
Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
Where is this fuse? The water pump has a breaker, no? Also, the controller only turns on the water pump once, that I am aware of, no matter how many AC units are turned on. I wasn't aware that it speeded it up as more units are turned on. As far as I can see, the pump feeds a manifold that then distributes the water to all of the units equally, regardless of whether they are running or not.
Prometheus
1978 53' MY Hull #529
Viera, FL
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Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
We have 240V to the boat.
The fuse is a 20amp SFE (slow-blow?) fuse that looks like the old automotive size/style fuses. Box was onboard when we arrived 2 weeks ago and appears to be new.
The fuse holder cap sticks out of the top of the PR8X box.
I assume that the pump would operate at a fixed speed no matter whether one or more units call for it to be operating. The pump feeds water to a manifold that supplies water to all the Cruisair units.
I must admit that I assume that there is a breaker for the pump, but I have not specifically looked for one (yet).
Nick
(in San Francisco...it is cold enough to want the heat to work!)
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01-16-2019 06:11 AM #6Senior Member
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- Jun 2018
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- 1,069
Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
I see. I haven't had to look at mine, but the PR8X is a set of relays that turn on the water pump if any AC unit is on, but the fuse in it supports the relays, not the pump. The pump is supported by a breaker in the helm. My guess is that the fault is in the PR8X, not the pump. Maybe one of the relays is bad, or the controller circuitry is bad and burning out the fuse. You could test which by turning on the other two AC units and seeing if that also burns out the fuse. But I don't think the water pump has anything to do with this issue.
https://citimarinestore.com/en/parts-displays-accessories/7230-cruisair-pr8x-pump-relay-115-230v.html#/1776-control_triggers_included-four_115v_triggers_115
I have the same box and might take a peek inside this weekend.Prometheus
1978 53' MY Hull #529
Viera, FL
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Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
I just spoke with a fellow at Dometic in product support for Cruisair.
He said that the problem is probably the fuse holder itself. He said that the spring in the fuse holder is weakened by heat over time and ends up not holding the fuse with enough pressure to maintain a good connection, building up heat and causing the fuse to blow. He said that they eventually eliminated the fuse from the design as the pump is protected by a breaker.
Perhaps this makes sense, as I was getting a brain cramp trying to figure out how we were blowing a 20 amp fuse in a circuit that is supposedly protected by a 15 amp breaker.
He suggested I just bypass the fuse holder and depend on the breaker to protect the circuit. I must admit that this makes me a little nervous. (I hate removing protection from a circuit where the wires are bundled up together with lots of other wires for other circuits...!)
Nick
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Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
Wouldn't eliminate the protection of the fuse. Just replace the fuse holder or do what we did, changed the fuse holder to a breaker, fit in the same hole.
CRICKET
1966 HAT50C101
Purchased 1985 12v71Ns
Repowered 1989 with 8v92TI
Repowered 2001 with 3406E
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Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
Cricket,
What was the source for your fuse-holder-replacement circuit breaker?
I do like that idea much better than just hard-wiring the fuse out of the system.
The fellow I spoke with at Dometic said that the fuse was originally a 10 amp fuse. What size breaker are you using?
Thanks!
Nick
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Re: Cruisair PR8X Pump Relay Fuse Blowing When 2 Units Operating
The boat is laid up for the winter and not close.
Not sure what size breaker, most likely whatever size fuse it originally came with.
Pretty sure it's like these.
https://www.bluesea.com/products/213...aker_-_15_AmpsCRICKET
1966 HAT50C101
Purchased 1985 12v71Ns
Repowered 1989 with 8v92TI
Repowered 2001 with 3406E