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Old 24-11-2014, 14:29   #1
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Water pump

Hi All. I have a sailboat and my fresh water system includes a jabsco automatic pump with max 40 psi and an accumulator tank. I recently installed an on demand tankless propane water heater in my shower. The problem is that it cuts out as the pressure drops. If the pump has just primed, it triggers ignition of the heater. As the pressure drops, the gas cuts off at some point.
Is there a way to reset the low pressure
cut- on point of the pump or increase the pressure at the accumulator?
Thanks,
Mike
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Old 24-11-2014, 16:39   #2
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Re: Water pump

I have a Shur flo pump and botht the tank and the pump have a means to adjust the required pressure but you need to look at the individual tanks to see them.
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Old 24-11-2014, 17:10   #3
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Re: Water pump

I hope you realize that kind of water heater does not meet code and is not allowed aboard boats. Better move on to plan B.
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Old 24-11-2014, 17:58   #4
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Re: Water pump

Most accumulators have a Schraeder valve. Add more pressure.
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Old 25-11-2014, 05:31   #5
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Re: Water pump

Greetings and welcome aboard the CF, Mike.
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Old 25-11-2014, 09:50   #6
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Re: Water pump

I found an adjustment screw for the pressure on one of my two pumps. In a short trial it seems to have done the trick. If not, I'll pump the accumulator slightly.
Thanks all for the suggestions.
Mike
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Old 25-11-2014, 09:59   #7
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Re: Water pump

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Originally Posted by CaptainSteven View Post
I hope you realize that kind of water heater does not meet code and is not allowed aboard boats. Better move on to plan B.
Sorry to disagree but depending on the brand and model there are certainly on demand, propane water heaters that are certified for marine use. The one I owned did require venting the exhaust overboard to meet the requirements.
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Old 25-11-2014, 09:59   #8
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Re: Water pump

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Originally Posted by mtenzer View Post
I found an adjustment screw for the pressure on one of my two pumps. In a short trial it seems to have done the trick. If not, I'll pump the accumulator slightly.
Thanks all for the suggestions.
Mike
I don't understand how adding air in the accumulator will affect the water pressure. All you'll end up doing is making less room for water by expanding the bladder, the pump decides what the pressure is.
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Old 25-11-2014, 10:11   #9
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Re: Water pump

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I don't understand how adding air in the accumulator will affect the water pressure. All you'll end up doing is making less room for water by expanding the bladder, the pump decides what the pressure is.
Agree. Pressure is pressure, whether air, water or combination unless you're getting air into the system shouldn't make any difference.
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Old 25-11-2014, 10:12   #10
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Re: Water pump

Quote:
Originally Posted by mtenzer View Post
I found an adjustment screw for the pressure on one of my two pumps. In a short trial it seems to have done the trick. If not, I'll pump the accumulator slightly.
Thanks all for the suggestions.
Mike
I think that as you raise the cut-in pressure on the pump you should increase pressure in the accum also. The 2 go hand in hand.
I'm surprised at the amount of unburned gas that comes out of some of those heaters on start up.
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Old 25-11-2014, 13:33   #11
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Re: Water pump

I'm surprised at the amount of unburned gas that comes out of some of those heaters on start up.[/QUOTE]



I have a pretty sensitive sniffer and I smell nothing as it ignites.
I'll add some pressure to the accumulator.
Thanks again,
Mike
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Old 29-11-2014, 16:38   #12
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Re: Water pump

Can I asked what brand of heater you have? I used to have a Bosch onboard and had a similar set up like you have. You can get different pressure switches which have a higher cut in setting. That will maintain the water pressure high enough for the on demand heater so the flame will stay on. You can check up what the minimum water pressure setting is for your heater. Then go and match the pump.
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Old 29-11-2014, 18:25   #13
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Re: Water pump

Ashore I have an on demand propane water heater. House is plumbed like a boat w a Shurflo pump and an accumulator tank. Its a bit of a balancing act getting some of these heaters to behave, they are picky about water pressure and flow, but upping the pressure in my system helped. I think its at 45 PSI now and the system works well.

Check the specs on your heater for water pressure and gas pressure specs...they are picky about both. Unfortunately the documentation is often poor so its a bit of trial and error to get it right.

Also check the details on your pump, some with internal pressure switches are actually fixed PSI and those adjustment screws may not do what you think.


...need that water heater now, DAMN its been cold on the Rio!
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Old 29-11-2014, 20:18   #14
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Re: Water pump

ShowerMate M-550 – Marine Tankless Water Heater - PrecisionTemp

Showermate.
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Old 01-12-2014, 14:05   #15
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Re: Water pump

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Originally Posted by Icarus View Post
Can I asked what brand of heater you have?
Sent from my HTC_PN071 using Cruisers Sailing Forum mobile app

I turned the screw and added a couple of pumps into the accumulator and Voila!!!! The pressure is noticeably higher and the heater remains on through the whole cycle. Thanks all for your help.
The unit is from a company called excel and I ordered from the dealer through ebay.

1 6 GPM Excel LPG Propane Ventfree Tankless Gas Water Heater No Flue Required | eBay

Thanks,
Mike
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