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johnjo
johnjo

Posted: Thu Nov 27, 2008 10:34pm

Post Subject: Expansion tank replacement

Hi Tony, the bladder in our 5lt 'CIMM' expansion tank appears to have failed, pumped it up to 25psi checked with a gauge, left it for 5mins didn't open any taps or run anything connected and re-checked and was down to around 5psi, repeated this several times with the same result. It's fitted directly after a Whale low pressure [pressure not stated] water pump which is connected directly to the feed from the cold water storage tank. My 1st question is, can I replace with one of a higher capacity, I am looking at one of 26lts 600mm [valve to pipe connection]x 300mm round, [it can be used as an accumulator or expansion tank], and what would be the benefits if any. 2nd question, can this be fitted horizontally i.e. valve on the same level as the pipe connection or must it be vertical, i.e. valve at the top, as it will be fitted under the bed so height would be a problem. If it is possible to lay it horizontally will this have any adverse effect on its operation or the diaphragm. Regards John P.S. I now know how calorifier is spelt, not chlorifier as in my previous postings.

Tony-B
Tony-B

Posted: Fri Nov 28, 2008 9:51am

Post Subject: Expansion tank replacement

Dear John, I trust you have already tries the "spit on valve" test to make sure its not the valve that is leaking. If not then do so and they are normally ordinary car tyre valve inserts. A diaphragm type accumulator can be fitted in any position - including upside down so feel free to lay it on its side. Accumulators and expansion vessels are the same thing but pressurised differently and may also be fitted at a different place in the system. Yours is definitely an accumulator UNLESS there is no non-return valve in the cold feed to the calorifier. If there's not a PRV it is probably doing a bit of both jobs, but its of little consequence. Fitting a larger accumulator will lengthen the pump's cycling frequency so it pulses less while a tap is open. It is unlikely to stop pulsing whilst the shower is in use. When you fit it pressurise it to about 10psi and then turn the pump on. When the pump cuts out measure the air pressure with a car's tyre pressure gauge. This will show the pump's cut out pressure. Turn the pump off and open the taps, pressurise the air to about half the pump's cut out pressure. Tony Brooks

johnjo
johnjo

Posted: Fri Nov 28, 2008 10:56am

Post Subject: Expansion tank replacement

No I haven't tested the valve, will do next time on board. There is nothing between pump and tank i.e. valve of any sort, just a pressure switch, tap side. The reason this apparent problem came to light is that our Paloma gas heater keeps cutting out. On advice, to test, I removed the water valve, lit the pilot and manually pushed the plunger on the gas valve in, this ignited the main burner and kept it running for as long as I held it in, about 5-6secs, couldn't hold it longer as there was obviously no water in the heat exchanger. Re-assembled & re-lit. Turned on hot water tap, main burner lights for 2secs goes out for 12secs relights, goes out and so on in a regular pattern. We assumed this was caused by a drop in water pressure and the fact that the tank was not holding pressure seemed to hold this therory up. The boat is new to us, only had it a month, bought through a third party, he wanted a residential mooring for a wide beam, ours was on one, he bought it and sold it on to us, so history a bit sparse. However the she has obviously been looked after but some things have been affected by lack of use over the past 8 months prior to us buying her. I intend getting in a registered gas fitter/plumber to check the system but could see no point until I made sure all other parts of the water system are working correctly, hence the possible purchase of a new PRESSURE tank. If the existing one is Ok and is being used as an accumulator, where in the system would you fit an expansion and an accumulator. Would one be better used for hot or cold and what sort & where would you place NRV's [none-return valves]. Also what are RTV's, not Radiator Thermostatic Valves or are they, I seem to find a lot of reference to them in forums, and what are they used for when fitted within the water system. If I'm asking too much for you to reply here, I won't take offence. Kind regards John

Tony-B
Tony-B

Posted: Sat Nov 29, 2008 8:59am

Post Subject: Expansion tank replacement

Dear John I think there may be a misunderstanding about the non return valve. The one I am talking about MAY (not will) be fitted at the cold water inlet to the calorifier but, not between the tank and pump. As you now say you have gas water heating you might not have a calorifier. A MESSAGE TO ALL READERS - unfortunately this is an example of a reader withholding vital information about the problem because it now seems this has little to do with accumulators/expansion tanks and a lot to do with instant gas water heaters. John, the water heater turns on as a result of pressure differences across a diaphragm and as long as the pump is producing enough pressure and the water pipes are large enough an accumulator will have nothing to do with the problem. First of all remove the cold water INLET to the heater. It is usually behind the diaphragm chamber. You may well find a small conical strainer inside the union that is blocked with rust and dirt. You may also find that the water pipes in the heat exchanger have furred up over the years. If you can get the whole heat exchanger disconnected from the diaphragm chamber and removed pour some hot kettle descaler and water into the heat exchanger. When the fizzing stops empty it out and repeat. I do not know where RTV came from, I only used PRV (which should have been NRV - my mistake). Please do not over complicate this. By all means sort out the loss of air pressure and pressurise it as I described but you do not need any from of accumulator of expansion vessel for the system to work. If you do not have one it will only make the pressure relief valve on any calorifier open for a few seconds as the water inside heats up, the pump run occasionally in the night and the normal pump cycling to be at a faster rate than it would be with an accumulator fitted. Please sort out the gas water heater before you do anything else. Tony Brooks

johnjo
johnjo

Posted: Sat Nov 29, 2008 11:06am

Post Subject: Expansion tank replacement

Tony, many thanks for the info on the Paloma. My apologies for not having related the full picture, I had been given the impression, by others, that the problem with the Paloma was all to do with lack of water pressure caused by a failure or lack of pressure within the expansion/accumulators. The system consists of a chlorifier with twin coils, one for the engine and one for a M/F with back boiler plus the Paloma. I'll try all that you have advised when next on the boat. Again many thanks. Regards John

Tony-B
Tony-B

Posted: Mon Dec 01, 2008 9:52am

Post Subject: Expansion tank replacement

John, please be aware that if you do not have a separate "gas hot water" taps you run the risk of boiling water coming from the taps if the water heater is left on when the calorifier is in use. At one time I think the BSS may have failed this (now they are more concerned with third parties rather than the boater so you are free to scald yourself). Once you sort out the heater you may find the pump is cutting out a too low a pressure (measure it at the accumulator as described in my last post). If that is so the gas burner may well shut down as before the pump cuts back in and the come back on as the pressure rises. If this happens try adjusting the pressure switch on the pump or fitting a separate pressure switch. However there is a faint chance the pump output volume is reduced for some reason like one or more pumping chambers being faulty. All the above are rare. Once you get the heater working expect the gas flames to go up and down with pump pressure. This is where the accumulator will help to maintain the pressure and reduce the frequency of the pressure pulses but you may not be able to stop this entirely. From memory there is a restrictor that screws into the side of the diaphragm chamber on some instant gas heaters. I have known these to block. Sorry I can not remember if the Paloma uses one or where it is. Tony Brooks

Tony-B
Tony-B

Posted: Tue Dec 02, 2008 12:18pm

Post Subject: Expansion tank replacement

Just seen your post elsewhere so follow the link give for Paloma info & you will find you do have that restrictor I was talking about. Cheers TB

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