| Author | Message | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 214 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
I intend to use a bladder-type pressure tank in my water system. Do I need to use a pressure switch to turn the pump off and on? I keep seeing illuminated water pump switches that are apparently designed to remind one to turn off the pump. That means that the pump will keep running until pressure reaches a predetermined point, I guess, but will the pump turn itself on at a predetermined low pressure? If so, will the pressure tank keep the pressure too high? I want to use the tank to eliminate the pulsing in the water flow. Is there a better way? Thanks Don | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 138 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
Your pressure tank only gets pressure from the pump, the job of the tank is to hold the built-up pressure for a longer period, so the pump wont run as often. all else is the same.>>>Dan | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 215 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
But! Will the pump pump against the head pressure in the tank? In other words, when will the pump cut in? Thanks Dan | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 139 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
the tank is charged with air pressure on one side of the diaphram (about 35 lbs.)the pump has a pressure senser, both high and low, air will compress, so when the pump comes up to normal preset pressure in the system the diaprham is preloaded. As you use water the air pressure depleats in the tank until the system pressure goes below the low preset point and the pump cuts back in, and the cycle repeats itself.>>>Dan | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 647 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Don, A bladder type tank is indeed what you should use. According to the manufacturer's instructions, the air pre-charge should be set at two pounds less than the pump cut in (start) pressure. With no water pressure, the diaphragm is pushed all the way to the bottom of the tank by the air pressure. As water pressure increases, the air above the diaphragm is compressed by the diaphragm moving upward, until the tank is about half full of water, and half full of higher pressure compressed air, with the diaphragm inbetween. How far up you push the diaphragm, and how much water you store in the tank, depends on how high the cut out (stop) pressure is set at. Most of us use a seperate switch to shut the pump off at night, as I will guarantee you it will decide to run at about 400am. Also good practice to turn it off when you leave, as then you don't return to a flood when something vibrates loose. Clear? George | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 368 Registered: 3-2007 Posted From: 71.55.230.210  Rating: N/A |
George; In working with large boilers and water heaters, I found a new style of bladder tank that is much smaller than normal and it does a beetter job than the larger ones. If you need more info I will get it for you all. Gomer | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 649 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Gomer, If you wouldn't mind, please do. In a boiler room, size of an ex tank isn't critical, but in an RV, wahoo! Thanks, George | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 580 Registered: 10-2006 Posted From: 69.19.14.30 Rating: N/A |
Depending on the water pump style , a bladder is REQUIRED 1 to have a place for expanding hot water to go as its created from cold. 2 Allow the pump to shut off "soft', the over run time between switch off and zero RPM would fracture many old PAR junk pumps. 3 The bigger the tank, the fewer cycles , off /on the pump will have to survive. Starting is hardest on the pump, stopping on a DC pressure switch. Bigger IS better , IF you can get it installed. FF | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 216 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
Thanks, all. I've installed over 100 tanks in houses that I built, but what I didn't know is that the rv water water pumps have their own pressure switch. That is a separate switch on house systems. My instruction sheet for the pump doesn't mention what makes the pump cut in or out; I assume a page is missing. | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 45 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
I don't have a bladder tank. Just run two water pumps in tandem. I run one for occasional use and kick both on for when showering. Can use shower and run sink at same time without difference. Both water pumps cut in and out almost at the same point. They have been completely trouble free for over 10 years. Good Luck, TomC | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1252 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
Camping World carry these. My coach has the two gallon one, although an older blue model.http://www.campingworld.com/shopping/item/shurflo-accumulator-tank/2290 | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 218 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
Does anyone use a check valve between the pump and pressure tank? (again, like a household system) | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 309 Registered: 8-2004 Posted From: 72.12.39.78  Rating: N/A |
Don Goldsmith wrote "Does anyone use a check valve between the pump and pressure tank? (again, like a household system)" What does that check valve do, Don? Stop water from flowing backwards towards the pump under pressure from the tank? | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 219 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
Yes, Bruce. It allows the pump start without the higher head pressure, and that prolongs the life of the motor on a household system. | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 311 Registered: 8-2004 Posted From: 72.12.39.78 Rating: N/A |
Thanks, Don. I'm guessing you mean on a not-city-water system -- i.e. where someone has their own well and pump. And it certainly sounds as if the check valve would work well (in household well systems and bus water systems). Thanks for that info. One will go in mine. | ||
| Brian Elfert (Belfert)
Registered Member Username: Belfert Post Number: 75 Registered: 7-2006 Posted From: 75.72.107.232 Rating: N/A |
I have a 4 or 6 gallon accumulator tank from a local Farm and Fleet type place that I bought for around $30. More capacity for less cost if you can spare the space. I placed it in a spot that wouldn't get used otherwise. | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 169 Registered: 1-2007 Posted From: 208.81.157.90 Rating: |
"Does anyone use a check valve between the pump and pressure tank? (again, like a household system)" If you have the typical RV water pump with the pressure switch built in, the pump is going to start at the same pressure every time, check valve or no. The only way I can see to "unload the pump" for easier start would be to relocate the pressure switch to the other side of a check valve and provide some sort of pressure relief to bleed the pressure from the output of the pump back to the tank. If it ain't broke...... But then I could be all wet. YUK YUK Don 4107 | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 584 Registered: 10-2006 Posted From: 69.19.14.24 Rating: |
"Does anyone use a check valve between the pump and pressure tank? (again, like a household system)" NO house check valves are used to keep heated water from going "back" into the cold supply as the water expands , the bladder should be after the check valve to allow the HW to expand. See above post. FF | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 224 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
I agree with Fred. Check valves are used at the pressure tank, while the bladder tank is normally found at the water heater (house system), way downstream. Since our bladder tanks would be close to the pump, I believe that check valves would be detrimental on an rv system. So, no check valve. | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 225 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
Don, does that mean that the system maintains pressure indefinitely? It seems then that a loss of pressure in a relatively short time would indicate that the pump may need overhauling soon. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 894 Registered: 12-2000 Posted From: 71.54.29.215 Rating: N/A |
Our ShurFlo pumps have a check valve built into them. Our bladder tank is after the pumps, so it can allow for expansion in place in the pressurized part of our water system. Jack | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 170 Registered: 1-2007 Posted From: 208.81.157.90 Rating: |
"Don, does that mean that the system maintains pressure indefinitely? It seems then that a loss of pressure in a relatively short time would indicate that the pump may need overhauling soon." If your pump is cycling and there is no leak anywhere then it is probably leaking back through the pump. To test, if you have a valve between the tank and pump, close it just after the pump turns off. That should stop flow back to the tank. If pressure does not drop then it was probably leaking back through the pump. I think that the reason that RVs and boats get away without a accumulator tank is that there is almost always some air trapped in the top of the hot water tank. It takes care of the expansion when the water is heated from cold and acts like an accumulator for the pump also. If there is no air cushion in your system just a couple drops of use or leaks causes the pump to 'thump'. As someone else said it always does it at O dark thirty when you are trying to sleep. Things that won't happen if you have an accumulator tank: The dreaded pump thump mentioned above which must be hard on the pump. The truly annoying on-off cycling of the pump when you have a facet turned on at a low flow. The pump turning on EVERY time you open a facet no matter how little water you use, as when someone steps on the toilet flush valve in the middle of the night.  You may not realize as quickly that you have a facet dripping or a minor leak somewhere. Remember, you can put the accumulator tank just about anywhere on the pressure side of the cold water system. On our boat, I tucked a two gallon tank into an otherwise unused spot under the head sink. Had problems with pump motors before the tank. Been 10 years since the tank. No more motor problems. Tank good. Good pumping Don 4107 | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 655 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Don just said it all! Fred and Brian's posts are absolutely correct, and should be followed also! If someone just HAS to put a check valve somewhere in a system, do it between the storage tank and the pump. Otherwise, if the pressure switch is built into the pump, and the check valve is between the expansion tank and the pressure switch, the switch doesn't have a clue. The expansion tank MUST see the water heater at all times. If using a seperate pressure switch, it should be right next to the expansion tank, to avoid the pump starting surge turning the switch right back off. G | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 586 Registered: 10-2006 Posted From: 66.82.9.56 Rating: N/A |
You may not realize as quickly that you have a facet dripping or a minor leak somewhere. As an offshore sailor this could be a killer. Simple solution Hard Mount the pump. Every one aboard can hear each and every cycle. Saves water too... FF | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 9 Registered: 11-2006 Posted From: 166.128.127.130 Rating: |
bladder tank goes on the cold side of pump.....check valve between wh cold inlet and pump or bladder tank to prevent hot water tank from acting as a storage tank and backflowing into cold system...bladder tank after wh will mean you have to flow that many gallons of hot water before you get any at faucet ...gg | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 599 Registered: 10-2006 Posted From: 66.82.9.80 Rating: N/A |
.check valve between wh cold inlet and pump This is a very good idea for folks that plumb camp water into the conversion. Yes there is a check valve in the fresh water pump, but if it fails city water may fill and pressurize the FW tank, something most are no longer designed for. THe extra check valve is GOOD! insurance. FF | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 663 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Don, I hate to jump on a newbie, but Ricky's post is confusing and not correct. The whole purpose of an expansion tank is to absorb the extra volume that is created when water is heated. If a check valve is installed between the cold inlet to the water heater, and the expansion tank, YOU DON'T HAVE A WORKING EXPANSION TANK ANYMORE, PLAIN AND SIMPLE. Nobody said anything about putting the bladder tank on the hot side, so I'm just lost... If the check valve prevents the pressure switch from seeing the expansion tank, then you get short cycles. The expansion tank acts as a "buffer, or shock absorber," as well as making a place for the expanding water to go when it is heated. Fred explained this VERY CLEARLY when he said "making a place for the water to go when making hot water out of cold." (Its in one of these closely related posts.) A properly plumbed system will have, in order: the plastic or metal storage tank, which can't be pressurized, a check valve, the pump(s), which probably have check valves, a tee for regulated shore inlet, tees for the cold faucets, the expansion tank, the water heater cold inlet, and the pressure switch. The pressure switch, if seperate from the pump, wants to be very near the bladder tank, so it isn't affected by the pump starting surge. Again, less short cycles. The hot side is self-explanatory. George | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 10 Registered: 11-2006 Posted From: 166.128.8.85 Rating: N/A |
sorry not a newbie....read all previous posts before commenting...a water hammer preventing expansion tank is really not needed too small a system..if you have to have one it goes on the hot side...if you expand enough water to fill and expansion tank you have to flush it with hot water to get hot water to the fixtures...a proper hot expansion is just a capped 1" riser off a t straight up off of the hot run...you have to have a check valve between wh cold inlet and supply other wise the hot water heater just becomes a pressurized supply for the entire system..just as a bladder or holding tank is meant to be... | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 666 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Ricky, Apparently you don't understand the difference between an expansion (bladder) tank, and a water heater. 1. Water expands when it is heated. 2. A liquid cannot be compressed. 3. A bladder tank has a rubber diaphragm in it, with an air precharge on top of it, the air pressure is set at the pump start pressure, so that when the pump starts, the tank is essentially empty. The pump works against the air above the diaphragm, WHICH IT CAN COMPRESS, and the diaphragm rises, storing water under pressure below it. WE ARE NOT TALKING ABOUT WATER HAMMER HERE, NEVER WERE, we're talking about water expanding when you heat it, AND a pressure switch needing to know what the pressure is in the system its controlling! (It can't do that with a check valve in the way.) Nobody pays any attention to this in a city water system house, (without a regulator or backflow preventer) as the expansion simply backs out the cold water line. The same thing happens in a house on a well, WITH A BLADDER TANK OUT IN THE YARD, the expansion simply backs out into the tank. By the way, the well pump has a check valve in it too. Now, we have a bus, with a water pump, which has a check valve in it, WHICH WON'T LET THE EXPANSION OUT, period. Remembering that you can't compress a liquid, the check valve won't let it back out the cold, the hot valves are closed, so things bulge, or the TP valve relieves at 150 psi. and dribbles water as it expands. Section 608.3 of the Uniform Plumbing Code reads "Any water system provided with a check valve, backflow preventer,...which does not have a bypass feature...SHALL be provided with an approved, listed, adequately sized pressure relief valve, or a means to control expansion. In addition to...an approved, listed expansion tank...designed for intermittent operation for thermal expansion control SHALL be installed whenever...or when ANY device is installed that prevents pressure relief through the building supply." (Page 52 of the 2000 UPC) You REALLY need to go back and read Jack Conrad's and Don Evan's posts on this subject now. Then read Fast Fred's post on the companion thread, specifically: "A place for the water to go when making hot out of cold." Then, if you still want to differ with all of us, and the UPC, at least we have tried to explain it. Water hammer was never mentioned here, until your last post immediately above, what we all were talking about was cold water expanding when heated, and short cycles of water pumps. The proper position of an expansion tank is on the INLET side of a water heater, so it is not exposed to hot water. IF and ex tank was installed on the hot side, it would push hot water back out the cold inlet of the water heater, into the cold side of the system, until the pressure dropped enough to start the pump! The second half of your second post is in direct contradiction of the UPC, and doesn't make sense! As information, straight out of table 6-6 of the UPC, the minimum required air chamber size for a 1/2 inch pipe run of less than 25 feet, is a 1/2 inch pipe 15 inches in length above the tee. (Page 57 of the 2000 Code) George | ||
| David Lower (Dave_l)
Registered Member Username: Dave_l Post Number: 111 Registered: 11-2007 Posted From: 67.58.201.10  Rating: N/A |
George can you post a basic rv plumbing diagram here, or can you direct me to where I could find one as I am planing on plumbing my coach next spring thanks. Dave L Thanks in advance! (Message edited by dave_l on December 15, 2008) | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 722 Registered: 7-2006 Posted From: 74.230.106.244  Rating: N/A |
I began camping with a typical motorhome. It used a typical RV propane hot water heater (with expansion room inside the tank itself). No bladder is used with an RV type heater, nor is there any need to use a separate expansion tank. When it's initially filled, it is never filled to the top of the tank. Perhaps that's where the confusion about "hot water systems" enters. For any RVer that's owned a typical commercially made camping vehicle, all the talk here about this "variation" and "need" for what's never been used before, is confusing. Soooo... It should be pointed out (IMNSHO), that the dialog regarding expansion tanks, only pertains to those that are using a standard home-type hot water heater, and -not- the typical recreational vehicle type hot water heater. There. Maybe that will reduce some of the arguments? | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 668 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Dave, I will, in three or four days, as I have 3 heating systems down right now, and it is snowing at the highest one. John, As usual, I appreciate your perspective. Just a couple of thoughts, however. A check valve on the inlet of an rv water heater won't help pump short cycles at all. Using an rv water heater for a buffer will put warm water back into the cold as the pressure decreases, and make it use more fuel heating the "cycle" water. How do you reply to someone who doesn't put ONE sentence in their entire post? (I can't refer to the 2nd sentence in the 1st paragraph, because there aren't any of them either.) Frustrating, G | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 319 Registered: 8-2004 Posted From: 68.84.6.177 Rating: N/A |
John writes: "the dialog regarding expansion tanks, only pertains to those that are using a standard home-type hot water heater, and -not- the typical recreational vehicle type hot water heater." Thanks for that John. As I mentioned above, I'm using an Atwood 10-gallon and I was puzzled about the need for all this valving and tankage. | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 172 Registered: 1-2007 Posted From: 208.81.157.90 Rating: N/A |
I don't know that anyone said you "need" a pressure/accumulator tank. The original question was not if but how to install one. Zillions of RVs and boats are out there without one. It is just one of those things you can do to make your rig work better and be more reliable. Somebody has to buy all those replacement water pumps to keep the volume up and the price down for the rest of us. If you "need" a reason, just ask yourself how many of the high end conversions/yachts have an accumulator tank as part of their freshwater system. I may not be able to run with the big boys but I can have a good reliable freshwater system for not many more bucks. Actually I will save a few by not replacing the pump as often. Don 4107 | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 239 Registered: 10-2003 Posted From: 66.165.176.60  Rating: N/A |
When I built my FW system I just used one of the small sureflow units and it does prevent a LOT of pump cycling. http://members.tccoa.com/timb/water.jpg | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 723 Registered: 7-2006 Posted From: 72.154.191.17 Rating: N/A |
Don - Re: "I think that the reason that RVs and boats get away without a accumulator tank is that there is almost always some air trapped in the top of the hot water tank." Exactly, Don! Many RVers don't read the paperwork when they buy an RV, and open the W/H relief valve, or a H/W faucet, as they re-energize the water system after a winter. Doing that allows too much water to fill the tank. Once too full, water will spit out of places not intended when the water's heated enough. The RV designed hot water tank, is it's own expansion tank. All of this is moot, though. The original question was regarding adding an accumulator tank to the cold water system, in an effort to stabilize the water pressure when the -pump- is supplying it. I guess it should be noted at this point, that ShurFlo now makes pumps that are self-regulating, doing away with the need for an accumulator tank. http://www.marineengineparts.com/shopsite_sc/store/html/page97.html Shurflo 4901-0211 "Extreme Series mart Sensor" 4.0 GPM Water Pump Is Shurflo Designed For Cruisers And Mid-Size Yachts. Multi-Fixture Capability. Micro-Controller Based Variable Speed Pump Precisely Monitors Your Syatems Water Pressure And Adjusts The Motor Speed. Providing "Just Like Home" Shower And Quiet Operation. 3-Year Limited Warranty.  (Message edited by john_mc9 on December 15, 2008) | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 11 Registered: 11-2006 Posted From: 166.128.83.73 Rating: N/A |
sorry that it won't work..but this is bus four,since '78..we have lived in this one full time since '02...If you are running a large 20 gal or more hot water system when the pump pressurizes the system the wh is just another storage tank until the pump comes on again...live in one a while and you will find out quick....use a regular rv wh and the volume is so low it doesn't matter...If you don't seperate wh from fresh system hope you like hot water in the warm months...always parked where its warm...GG04 | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 12 Registered: 11-2006 Posted From: 166.128.83.73 Rating: N/A |
Made me call an old friend and dig out an old lab book...In a 10 gallon system rise from 60F to 180F is 12.8oz or 1.6cup or in a 40psi system 1.0087psi rise....not rocket sience just a water system..and codes do not apply to rvs,some are still vented through a check valve in the wall.....have been around since we were all on Zanes board paying him $20 a year to chat and post...then along came BCM and Ian and everything got easier. All this has been done a hundred times before..just search....GG04 | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 669 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Ricky, I appreciate your doing the research on expansion. But please explain how the psi on a system has anything to do with pressure increase. Like it or not, you still can't compress a liquid, so to only increase pressure one pound in a system, will require a large expansion volume. "...and codes do not apply to rvs,..." I have a real problem with that, but never mind. Do us all a favor, and post in sentences and paragraphs, please. G | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 724 Registered: 7-2006 Posted From: 74.230.106.211 Rating: N/A |
An RV doesn't have to conform to the same "codes", electrical or otherwise, and of course, no-one needs a CDL to drive a rig that weighs over 10+ tons empty. Sure, we can get hurt by someone else's lack of common sense, or expertise...... but... Personally, I'd rather have it that way. "When we abandon liberty for safety, we deserve neither". | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 605 Registered: 10-2006 Posted From: 66.82.9.57 Rating: N/A |
An RV doesn't have to conform to the same "codes", electrical or otherwise, True enough BUT, A stop at an RV scrap yard , and the instalation of a used RVIA tag may help at some snotty places. FF | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 725 Registered: 7-2006 Posted From: 72.146.80.234 Rating: N/A |
HAR! With this economy, Fred, the "snotty places" are letting VW buses and pop-ups in.  | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 13 Registered: 11-2006 Posted From: 32.176.45.236 Rating: N/A |
No research involved just old working papers..Have been through the same discussion on these boards before...In a sealed system (like mine) with a 40# cut off on the 12volt water system from a dead cold system to a 180F will raise the system pressure to 41#....sorry I no longer have an employee to type my papers...English never made sense to me not in black and whites...all liquids will compress just not as you want..how do you think your 12volt pump will build 35-40# on your water system then cut off????? I used the 60 to 180 in a ten gal system as reference because it gives a 1% increase in volume and nearly in pressure...just simple physics..the expansion space you need in your system is nearly negelable..GG04 | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 232 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
All liquids will compress? I need to catch up on my reading... | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 672 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Don, When you figure this out, will you please let me know! (I think there is a saying about one's ability to lead a horse to a liquid, and then the inability to make it drink it?) In a post above, he says "...heating a 10 gal. system from 60 to 180 degrees produces 12.8 ounces of expansion..." THIS IS CORRECT, AND EXACTLY WHAT I AM TALKING ABOUT! BUT WHERE THE HECK DOES IT GO????? (If he has the air tank he is talking about in a later post, AND no check valve inbetween, the answer is obvious, he just doesn't know it.) Then we're going to have to deal with Ricky's post #12, of 12/16, reading "...and codes don't apply to rvs..." Well, there is a small matter of Article 551 of The National Electric Code, which reads "Recreational Vehicles and Recreational Parks." Its published by the National Fire Protection Association, funny thing. Section 551 starts on page 800 of the 2002 Edition Handbook, and continues through page 816, all single space printed, everything specific to RV wiring methods, generator and inverter installations and grounding, etc. Starting with Section 551.77, are the requirements for RV parks to provide proper standard locations and connections for rvs. If six posts doesn't equal a newbie, I'll apologize, right after Ricky explains how to compress a liquid, and codes don't apply! Sorry this is sarcastic, but I'm frustrated, I have tried to explain... George | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 727 Registered: 7-2006 Posted From: 70.157.211.128 Rating: N/A |
What the NEC said in 2002: "The specific requirements for low-voltage systems in Recreational Vehicles has been deleted Part II Low-Voltage Systems comprising 551.10(A) through (H) is deleted. The primary standard for the construction of Recreational Vehicles is NFPA 1192, Standard on Recreational Vehicles. The 2002 edition of this standard at 4.4 states that low-voltage installations, systems, and equipment shall comply with ANSI/RVIA 12V, Low-Voltage Systems in Conversion and Recreational Vehicles, and no longer references Part II of Article 551." Did they change back since 2002? oops, never mind. You referred to the park, not the rver. mia farrow (Message edited by john_mc9 on December 20, 2008) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 674 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
John, Wasn't she married to Woody Allen, or was that Mia Culpa? Now that I've stopped laughing, and recovered enough to type, all I can say is this. What I posted was straight out of my 2002 NEC Handbook, which is the Codes, AND explanations. As you say, Section 551 part II covers the low voltage systems in RV's. Mine starts out with "551.10 (A) Low-Voltage Circuits. Low voltage circuits furnished and installed by the recreational vehicle manufacturer, other than automotive vehicle circuits, or extensions thereof, are subject to this CODE. Circuits supplying lights subject to federal or state regulations shall comply with applicable government regulations and this CODE." I don't know whether or not it has been changed since, and as you note, only the low voltage requirements may have been changed. The rest of part II, and all of part III, which is the 120/240 VAC portion of the wiring is still in effect. All of this was posted simply as a reply to Ricky's post above reading "Codes don't apply to RV's..." After all of this, and I'm reasonably sure you are ROTFLYAO, he posts on the other thread running with this one, that he has "a 10 gallon tank with an air fitting on top...we don't charge it so the drawdown isn't as good..." This does explain why 12 ounces of expansion only raises his pressure one pound. KUTGW! George | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 728 Registered: 7-2006 Posted From: 74.230.106.107 Rating: |
Re: "Low voltage circuits furnished and installed by the recreational vehicle manufacturer, other than automotive vehicle circuits, or extensions thereof, are subject to this CODE." And thus: "The 2002 edition of this standard at 4.4 states that low-voltage installations, systems, and equipment shall comply with ANSI/RVIA 12V, Low-Voltage Systems in Conversion and Recreational Vehicles, and no longer references Part II of Article 551"  That aside (far aside, if we will), I think the point he was trying to make, was: The "codes" are designed for manufacturers and service providers, but the "end user" can do whatever turns his grove (as in apples/oranges). (it's kinda' like that tag on the side of a new mattress that "people" won't rip off, for fear of imprisonment!) I always felt that understanding the intent of the "code", is more important than knowing a "code" exists. For the average guy, making a recreational vehicle out of a sow's butt, is open to improvisation at it's worst. It's better to know that ground should not be bonded at anyplace other than the point of supply, and the reasons why (ala' fried tootsies), rather than hear "it ain't oughta' be done, or else". And I want to gleefully add (as long as I'm on a roll): That you George, are among the several on this board, that take great time to do your best to explain in great detail, why things should be done in a cohesive manner. Oh.... And... the reasons why a guy can get hurt if they aren't. But back to topic...... As far as this water pressure thing? I seriously can't understand the need for a "bladder tank", to maintain a decently stable amount of water pressure. The new pumps (link above), keep the pressure decently steady, without the addition of expensive added tanks, etc. The tanks will need maintenance; bladders rot, seals decay, and mold grows on rubber. Why, oh why, are so many, so hell bent on adding to the woes of owning a recreational vehicle. I always liked to keep things as simple as possible; a "vacation" shouldn't be spent repairing things installed for comfort. HEY.... Happy Holidays! | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 16 Registered: 11-2006 Posted From: 166.128.32.70 Rating: N/A |
was replying to pressure tank bladder required to relive hot water pressure...all supply systems are sealed..Your house or business has a check valve between public system and supply..if on a well a check valve between pump and tank..on your rv or bus a check valve between pump and system and between city water supply system.. if supply is to code another check valve or anti backflow between supply and your hose...If your water system is at pressure any increase in volume will increse pressure on the entire system.. . ... at low pressure and temp volume just replaces what is called free air...its how your pump can build pressure without a pressure tank....my total hot water system is 28 gal with heat set at 180 actual temp is 146 at cut off .never any leaks ...at least for the lsst ten years gg (Message edited by gg04 on December 26, 2008) | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 18 Registered: 11-2006 Posted From: 32.176.12.63 Rating: N/A |
George I appologize was misreading your posts..thought we were on bladder tanks..you did mention precharged expanssion tanks...sorry ...retired in 86 since change of code did not realize small affordable precharged were avaliable...gg |
