replacing new style buck boosts aqua hot 400

[nelsonwill]

We have the parts to replace the buck boosters on our aqua hot 400. These new ones are different than the original ones and of course came with no installation directions.
Does anyone have any information that would assist us or walk us through installing these two parts?
We are in a remote area and of course on a holiday weekend with no hot water.
Any help or moral support would be appreciated.

Nelson Williams
8065840069.

[voltdoc]

On my 2013 they were plug in modules. The connectors were green and had a small screw on each end. Loosen the screws and remove the connector.

Hard to believe they would send you new modules that didn't use the same connector. Then again...

Link to photo of AH buck/boost in a 375LP (lower right). The second buck/boost has been removed in this photo. https://photos.app.goo.gl/YIUJYrYekjpyNrFH3

[royals1212]

If you did not get new nylatch plastic fasteners to hold the boards on you can use small zip ties

[Chuck1957]

What is the purpose of the buck boosters and how do they affect the Aqua hot when not functioning correctly

[voltdoc]

Originally Posted by Chuck1957

What is the purpose of the buck boosters and how do they affect the Aqua hot when not functioning correctly

It's a voltage regulator, keeps the voltage at an exact value for sensitive electronics. If the incoming supply voltage is more than 12.0 volts (normally it will be) it "bucks" it back to 12.0. If the incoming voltage drops below 12.0 volts it "boosts" it up.

The problem with these on the Aquahot is they tend to burn up. I went thru three of them on my 2013 with a 375LP. There were two of these on the 375. Usually you can tell when they fail by the smell of burnt epoxy.

When they burn up they cease to function and some aspect of the AH will stop working. In my case it was always the one that powered the burner, so the burner wouldn't fire.

When the buck/boost fries it usually shorts out and blows the 20A power feed fuse inside the AH. One time I think it also took out the 30A fuse in the fuse compartment forward of the left front tire.

If it fries, the only way to fix it is to replace it.

[Chuck1957]

Originally Posted by voltdoc

It's a voltage regulator, keeps the voltage at an exact value for sensitive electronics. If the incoming supply voltage is more than 12.0 volts (normally it will be) it "bucks" it back to 12.0. If the incoming voltage drops below 12.0 volts it "boosts" it up.



The problem with these on the Aquahot is they tend to burn up. I went thru three of them on my 2013 with a 375LP. There were two of these on the 375. Usually you can tell when they fail by the smell of burnt epoxy.



When they burn up they cease to function and some aspect of the AH will stop working. In my case it was always the one that powered the burner, so the burner wouldn't fire.



When the buck/boost fries it usually shorts out and blows the 20A power feed fuse inside the AH. One time I think it also took out the 30A fuse in the fuse compartment forward of the left front tire.



If it fries, the only way to fix it is to replace it.

Are the 2 units exactly the same?

[voltdoc]

Originally Posted by Chuck1957

Are the 2 units exactly the same?

Yes, at least they were on my 375LP

[royals1212]

Same on the 400lp as well

[Chuck1957]

Thanks

[xtechgeek]

Originally Posted by voltdoc

It's a voltage regulator, keeps the voltage at an exact value for sensitive electronics. If the incoming supply voltage is more than 12.0 volts (normally it will be) it "bucks" it back to 12.0. If the incoming voltage drops below 12.0 volts it "boosts" it up.

The problem with these on the Aquahot is they tend to burn up. I went thru three of them on my 2013 with a 375LP. There were two of these on the 375. Usually you can tell when they fail by the smell of burnt epoxy.

When they burn up they cease to function and some aspect of the AH will stop working. In my case it was always the one that powered the burner, so the burner wouldn't fire.

When the buck/boost fries it usually shorts out and blows the 20A power feed fuse inside the AH. One time I think it also took out the 30A fuse in the fuse compartment forward of the left front tire.

If it fries, the only way to fix it is to replace it.

I'm in the power electronics industry, and what you described is typically due to inadequate cooling of the power device. This can usually be remedied by either providing a better heatsink and/or cooling fan.

If you crack the device open, any small pin-hole in the power semiconductor is typically an over-voltage event, whereas a large burn area, melted area, or chunk missing is usually due to excessive current / heat build up.

So, it may help to mount on a heatsink with the fins running vertical and at least 2" above and below the heatsink clear for airflow.

Regards, Cory

[voltdoc]

Originally Posted by xtechgeek

I'm in the power electronics industry, and what you described is typically due to inadequate cooling of the power device. This can usually be remedied by either providing a better heatsink and/or cooling fan.

If you crack the device open, any small pin-hole in the power semiconductor is typically an over-voltage event, whereas a large burn area, melted area, or chunk missing is usually due to excessive current / heat build up.

So, it may help to mount on a heatsink with the fins running vertical and at least 2" above and below the heatsink clear for airflow.

Regards, Cory

Sounds good Cory thanks for that, but I once had an Aquahot tech tell me that an Aquahot engineer had a nightmare one night them came into work and built what he dreamt, they called that the 375LP.

See the photo link in post #2, the buck modules are mounted to the steel case so should get a little heat sinking from that, but the whole thing is potted so the heat transfer can't be very good. It also has some ventilation from the open air grill on the floor of the AH case.

Also note the exposed control board above the buck module, it gets wet when you drive in wet weather and covered with road grime due to the unbaffled ventilation grill under the coach.

If the same engineering design principals (or lack thereof) were applied to the buck module I don't know if there is any help for it.

Hopefully the 400LP is a design improvement and it sounds like there is a new design for the buck module.