Originally posted by Heavysledz
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Accumulator - Where do I install it?
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2017 Ford F-350 DRW, '19 315RLTSPlus
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Cate&Rob (and forum members),
How often is "regularly"?
I'm referencing page 2 of the accumulator's instructions under the Pre-Charge Pressure Adjustment heading where this is written:The accumulator tank is pre-charged at 10 psi (0.7 bar). If your pump's electric pump cut-in pressure is significantly different, you may adjust the tank pressure to better suit your particular installation. To increase air pressure in tank, shut pump off, open a faucet to relieve system pressure, and adjust precharged pressure using ordinary tire gauge and tire pump at valve in end of tank. Pressure should be checked regularly. (Emphasis is mine.)
That requirement requires some ease of access to this accumulator, too. Do all accumulators have this requirement or did I just buy a dud?
Full manual attached.
Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
2017 Ford F-350 DRW, '19 315RLTSPlus
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Cate&Rob (and forum members),
The manual states to set the pre-charge pressure setting 3 psi below water pump switch cut in pressure. The pump I plan on using has a re-start pressure of 41 psi +- 5 psi (cutoff is 55 psi). So that's a re-start range of 36 to 46 psi
A couple of questions:
1) What do you recommend for the accumulator pre-charge pressure? 33 psi? (3 below the lowest possible value) 38 psi? (3 below the nominal re-start pressure?) Or something else (and why)?
2) Once the value of the pre-charge is established, what value should I set the city water inlet pressure regulator so it works with the accumulator? (The only "job" of the accumulator in this scenario is to absorb the expansion pressure due to hot water in the lines.)
Howard
P.S. It's 3 am and I'm thinking about stuff like this...why, I don't know.
Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
2017 Ford F-350 DRW, '19 315RLTSPlus
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I set the accumulator pressure above the pump cutout pressure since its only function is to absorb water heater expansion. That is still a tolerable pressure for the water system to rise to during water expansion and the bladder will spend most of it time at rest. Then there is no interplay with normal operating pressures. If the set pressure is too low the pump or city pressure will force the accumulator full with little space left to absorb water heater expansion.Ted
2021 Reflection 310RLS
2020 F350 PS,CC,LB,SRW
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Originally posted by TedS View PostI set the accumulator pressure above the pump cutout pressure since its only function is to absorb water heater expansion. That is still a tolerable pressure for the water system to rise to during water expansion and the bladder will spend most of it time at rest. Then there is no interplay with normal operating pressures. If the set pressure is too low the pump or city pressure will force the accumulator full with little space left to absorb water heater expansion.Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
2017 Ford F-350 DRW, '19 315RLTSPlus
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Howard,
If you have a gauge in the system, cycle several appliances and see what your pump cut in pressure is at. Air up your accumulator to 3psi below the cut in pressure (with no pressure on the system). You want the accumulator to store energy from 3psi below cut it to the cutout pressure so the pump does not run so often. Think of this device as a spring that can store energy.
Jim
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howson TedS Guest
Hi Howard,
Ted & Jim are both right . . . for different applications. In your situation, the small tank is intended to absorb volume increase from heating, so I would set the air pressure 3 psi above pump cut out pressure as Ted advises. What Jim describes is for a larger tank intended to accumulate water within the pressure range of the pump. In this case, I would set the air pressure 3 psi below the pump cut in pressure so that the tank supplies the pressurized water to the system until the pump comes back on, but you would want the pump to come on before supply from the accumulator tank is exhausted.
Unless I detect a water pressure problem, I typically check tank air pressure once or twice a year (done with zero water pressure in the system) and if there is more than a couple of psi reduction that would mean that there is an air leak somewhere. I suppose that some air permeates through the rubber diaphragm . . . but, it is typically not much.
​​​​​​​RobCate & Rob
(with Border Collies Molly & Angel + Kitties Hazel & Elsie)
2015 Reflection 303RLS
2022 F350 Diesel CC SB SRW Lariat
Bayham, Ontario, Canada
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Originally posted by Cate&Rob View PostThe accumulator that you have chosen will help to mitigate the pressure rise due to water heating..
Originally posted by Cate&Rob View PostThe tank is just not large enough.
Started by verifying water pressure before the Nautilus Panel connection (coming from a house exterior hose faucet) and at the Nautilus Panel.
Turned on water heater (WH). It took almost exactly an hour for the water to heat to maximum. (I could tell by watching the power draw--when the power dropped the water was at maximum temperature.) The gauge on the Nautilus had wrapped around and was off-scale high.
I did one final test by running the hot water in the camper for ~10 seconds and the gauge on the Nautilus went back to the nominal water pressure level (the same as before the WH was turned on).
With Accumulator (Step Two)
Preset the accumulator to 58 psi and installed at the cold water inlet, just past the Nautilus Panel check valve.
Drained WH and refilled with water from the hose ("cold"). Ensured all the air was out of the lines, so I was again starting from a known baseline, exactly the same condition as the first test except now with the accumulator.
Fired up the WH and went inside for lunch. Came out about 30 minutes later and the meter on the Nautilus Panel was again off-scale high. So...big fat failure. This small accumulator did nothing to address the increase in system pressure due to the water temperature rise. Any idea what I did wrong (if anything)?
In retrospect I can see one mistake. It should have worked as installed, but when the white selector valve on the Nautilus is turned to use the pump (water from fresh tank) it would have isolated the accumulator. <sigh>
Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
2017 Ford F-350 DRW, '19 315RLTSPlus
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Howard,
I would not worry about the pressure rise from the hot water tank since the plumbing is more than capable to handle that. The accumulator is used to stop pump pulsations and to reduce cycling. Set the air pressure to 2 psi below cut in pressure and its all good.
Also one blip of a hot water faucet will normalize the pressure. Some folks will talk about their relief valve purging on the first heating cycle where this is normal due to initial expansion from heating.
Jim
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Originally posted by MidwestCamper View PostHoward,
I would not worry about the pressure rise from the hot water tank since the plumbing is more than capable to handle that. The accumulator is used to stop pump pulsations and to reduce cycling. Set the air pressure to 2 psi below cut in pressure and its all good.
Also one blip of a hot water faucet will normalize the pressure.
Jim
Bottom line: I don't like what I'm seeing, Jim. The pex can handle it no problem, but I'm leery of having failures at connections at some point with the pressures I am witnessing.
Does my home's system have the same pressure rise as I'm witnessing on the camper? If so, could that be the reason for the accumulator tank over my home's water heater?
Have I mentioned lately that I hate plumbing?
Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
2017 Ford F-350 DRW, '19 315RLTSPlus
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LOL! I hate plumbing too since you touch one thing and you end up replacing so much more. At least in the home that is.
You raise a good point on the flex hose. My Imagine has no flex hose on the hot water tank and from what I've seen its only on my pump inlet and outlets. Pex at the hot water tank and a check valve at the pump outlet would be helpful as long as it does not reduce flow. Or a higher capacity braided hose as long as its made for potable water.
https://www.mcmaster.com/braided-wat...tube-fittings/
https://www.duraflexinc.com/heat-pum...assemblies.php
JimLast edited by Guest; 04-13-2021, 03:12 PM.
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The water pressure can rise to the water heater relief valve setting which is 150 psi. The rv water system is nominally built for about 100 psi. PEX by itself is rated to 480 psi at 73F; it should hold the overpressure.
The white valve should point to the right for all uses except for drawing from external water source. That means the city water inlet is connected to pump inlet.Last edited by TedS; 04-13-2021, 03:15 PM.Ted
2021 Reflection 310RLS
2020 F350 PS,CC,LB,SRW
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We could also assume the flexible hose that's in our rigs is the lowest cost hose that's available. I'll blip my faucet on the first heating of the hot water tank and will also install the accumulator.
Interesting video on the deliberate air pocket on suburban hot water tanks.
https://www.youtube.com/watch?v=JYSEaw1XRmQ&t=117s
JimLast edited by Guest; 04-13-2021, 03:28 PM.
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