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New Calorifier & Expansion tank


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Hiya.

I have mentioned in a 'borrowed' thread, that I have recently had a new cauliflower and for the first time an expansion tank on the hot side of the water system.

What has been a continuing issue is that now when the hot water is run there is a period of high pressure and high flow of water, until the pressure has reduced and the pump kicks in. Switch off the hot water tap and the pump continues to run, building pressure in the system, for normally, or should I say unnormally, for up to 35 seconds. This never happened before the new addition. The cold water side acts as it has always, pump runs for 3-5 seconds after turning off the cold water tap.

Spoke to someone in a Chandlers and he suggested there's too much pressure in the expansion tank. I thought it was the opposite, ie. too little. Hey ho!

 

I have, just now looked into this, gone through various scenarios, let some air out of the tank, pumped some air back into the tank with no differences being evident. Done the same with pump off, released pressure in the pipes, etc.

 

The installation team that fitted the calorifier and the new expansion tank spent loads of time trying to correct this issue. The least pump run time achieved has been about 8-10 seconds time. This has gradually increased over time. I have operated the PRV on top of the calorifier as an indication that there isn't an air gap at the top of the calorifier. Water discharges over the side. No air gap?

 

Is this a simple fix as something obvious has been missed. Any suggestions. The fact that the cold side is still 'normal' suggests it's not a pump issue. 

 

Be nice chaps and chapesses

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Is the non return valve in the calorifier cold feed in at the bottom of the cylinder of sufficient bore size? It may be the same size as the pipework but horribly restrictive internally, many are.

Or is it bunged up with clag from draining the old cylinder?

It does suggest a restriction in the plumbing after the cold connection to the hot water system.

Edited by Boater Sam
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It sounds like there is a large air reservoir in the system.  If it is not the expansion tank, and it is not the calorifier itself, then is there anywhere else in the hot-side system where a large pocket could exist? Have you any other limbs or features on the system?

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56 minutes ago, Iain_S said:

Just to confirm : the expansion tank after the calorifier is set to pump cut out pressure, or just above?

 

 

What if it's below, or indeed above cut out pressure. I believe the sureflo cut out is about 20-25 psi.

18 minutes ago, system 4-50 said:

It sounds like there is a large air reservoir in the system.  If it is not the expansion tank, and it is not the calorifier itself, then is there anywhere else in the hot-side system where a large pocket could exist? Have you any other limbs or features on the system?

For me!, it's getting complicated.

 

The only large pocket I can think of is the ,also newly manufactured and installed skin cooling tanks. There are no air locks in those and they are happily doing there bit. As in most systems, the engine heats the calorifier. 

Edited by Nightwatch
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46 minutes ago, Boater Sam said:

Is the non return valve in the calorifier cold feed in at the bottom of the cylinder of sufficient bore size? It may be the same size as the pipework but horribly restrictive internally, many are.

Or is it bunged up with clag from draining the old cylinder?

It does suggest a restriction in the plumbing after the cold connection to the hot water system.

Non return valve! Do I have one? Where would I find one if I had one? There's 90% new pipework in and out of the Calorifier. I shell seek and may find.

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4 minutes ago, Nightwatch said:

Non return valve! Do I have one? Where would I find one if I had one? There's 90% new pipework in and out of the Calorifier. I shell seek and may find.

If it’s a Surecal cauliflower I believe they have them as part of the cold water inlet. 

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25 minutes ago, Nightwatch said:

What if it's (expansion tank pressure)below, or indeed above cut out pressure. I believe the sureflo cut out is about 20-25 psi.

(snip)

(my red)

It will have less capacity to contain the expanded, heated, water. If the pressure is low, it will act somewhat as an additional accumulator, which could explain some of the aditional pump running time after using a hot tap. The high pressure initially would be caused by the expansion of the hot water being heated.

 

If the expansion vessel pressure is OK, cause may be a restriction in water flow to the calorifier, most likely, as others have suggested, at a non return valve.

Edited by Iain_S
Typo
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1 hour ago, Iain_S said:

Just to confirm : the expansion tank after the calorifier is set to pump cut out pressure, or just above?

 

 

I think that is the problem, its a bit low.

7 minutes ago, Nightwatch said:

Is this a non return valve? Or just a 'T' piece.

IMG_1914.JPG

I now don't think it is. 

Looks like a T with a drain off to me

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2 minutes ago, ditchcrawler said:

I think that is the problem, its a bit low.

Looks like a T with a drain off to me

I agree. Looked at non return valves on line. I don't see one near my calorifier.

 

Are we saying, that the chap in the chandler was wrong to tell me that less pressure in the expansion tank is better. He did say set it at the pump pressure but slightly lower is better. Just looked at the pump. It indicates 40psi. Sounds a lot to me. Not sure my cheapy bike pump p, with a gauge, and me on the end of it, is/are man enough for the job to 40psi. When I checked the pressure this morning is was about 20 psi. Will that make a dramatic difference. Please remember you are advising me and not someone who knows what they're doing.?

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3 minutes ago, Nightwatch said:

I agree. Looked at non return valves on line. I don't see one near my calorifier.

 

Are we saying, that the chap in the chandler was wrong to tell me that less pressure in the expansion tank is better. He did say set it at the pump pressure but slightly lower is better. Just looked at the pump. It indicates 40psi. Sounds a lot to me. Not sure my cheapy bike pump p, with a gauge, and me on the end of it, is/are man enough for the job to 40psi. When I checked the pressure this morning is was about 20 psi. Will that make a dramatic difference. Please remember you are advising me and not someone who knows what they're doing.?

It will make it next to useless as an expansion vessel

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Okay. Just spent a good 15 minutes continuously pumping into the tank with my trusty bike pump. With Pump switched off and pressure in system released. Can't get above 20 psi. 

 

Self doubt setting in. 

 

Nightwatch, as far as I know, hasn't had an expansion tank before. What if it didn't have one again? ie. I isolate the new one?

Just now, system 4-50 said:

The non-return valve on my surecal calorifier was integral to a joint and wholely non-visible without dismantling.

So, if it's not 'up to the job', as I understand someone suggested earlier, I wouldn't know unless I dismantle.

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Without an expansion tank you will greatly reduce the fatigue life of the calorifier.  When I bought my surecal calorifier about 10 years ago they did warn me that there is no warranty for cracking if an expansion tank is not fitted.

 

Bike tires are often inflated to much high pressures than car tires, so a hand pump should be fine, but the expansion tank is quite a few litres so it will take a lot of pumping to increase the pressure even a little bit.  The expansion tank should be set to just above the pump cut-off pressure, say +3psi.  So if you have a 40psi water pump then 43psi is about right.

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12 minutes ago, Chewbacka said:

Without an expansion tank you will greatly reduce the fatigue life of the calorifier.  When I bought my surecal calorifier about 10 years ago they did warn me that there is no warranty for cracking if an expansion tank is not fitted.

 

Bike tires are often inflated to much high pressures than car tires, so a hand pump should be fine, but the expansion tank is quite a few litres so it will take a lot of pumping to increase the pressure even a little bit.  The expansion tank should be set to just above the pump cut-off pressure, say +3psi.  So if you have a 40psi water pump then 43psi is about right.

Thank you.  Think I need patience and possible a decent high volume pump. When we moved onboard five or more years ago I couldn't think of any reason why I would still need my car foot pump. My loss, my sons gain. Hindsight eh!

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Just now, Nightwatch said:

Thank you.  Think I need patience and possible a decent high volume pump. When we moved onboard five or more years ago I couldn't think of any reason why I would still need my car foot pump. My loss, my sons gain. Hindsight eh!

I have sent u a PM old boy.

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22 minutes ago, Nightwatch said:

Thank you.  Think I need patience and possible a decent high volume pump. When we moved onboard five or more years ago I couldn't think of any reason why I would still need my car foot pump. My loss, my sons gain. Hindsight eh!

I needed a new foot pump, but ended up the a little 12v air compressor from Sainsbury’s petrol station ‘on offer’.  Less effort and much cheaper than a foot pump, even came with a gauge - reads high when pumping, but turn off the pump, let a little air out and tighten up again and it reads fine.  Set up both my calorifier and accumulator with it.  Though it is slow, especially above about 20psi.

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Right oh, here we go. 

 

Got the pump. To summarise. My water pump indicates 40psi.

 

Am I correct to pump my expansion tank (hot) to 43 psi or there abouts. 

 

Also, am I correct to pump the accumulator tank (cold) to 35 psi?

 

 

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MExpansion tank to 40 psi.  That way the system pressure should not rise much above 40 psi.  If you go to 43 psi you gain nothing and lose some expansion capability.  Pressurise the expansion tank with the pump off and the taps open till the water stops.

 

Accumulator tank should be pumped up to the pump cut in pressure, again to get the maximum additional usable volume.

Pump up to 15 psi or so with no pressure in the water pipes.  Run the pump till it cuts out. Turn on a tap slowly and switch the pump and tap off as soon as the pump runs.  Measure the pressure in the accumulator.  Then open the taps and pump the accumulator up to the measured pressure.  Switch the pump on and the taps off.

Job done.

 

N

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All done. Chuffed to bits. Both cold and hot water runs okay and the pump runs for approximately 4-5 seconds after tap turned off.

 

The power lead on the tyre pump was, believe it or not about a foot short. So after another walk to Midland Chandlers for some 12v cable and a bit of wiring genius all works. Amazing.

 

Thanks so much for everyone's patience and advice. I really ought to have more confidence in myself. Always used to have when I was a whizz kid in management.

 

 

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37 minutes ago, Nightwatch said:

All done. Chuffed to bits. Both cold and hot water runs okay and the pump runs for approximately 4-5 seconds after tap turned off.

 

The power lead on the tyre pump was, believe it or not about a foot short. So after another walk to Midland Chandlers for some 12v cable and a bit of wiring genius all works. Amazing.

 

Thanks so much for everyone's patience and advice. I really ought to have more confidence in myself. Always used to have when I was a whizz kid in management.

 

 

I think that is an age thing, I often feel the same and use to run offshore installations 

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