Shurflo Pressure

[Badger]

Following on from my recent post regarding shurflo pumps. I eventually fitted a new Shurflo, changing from the original 15psi model to this new one rated at 30psi. Limekiln told me I would have to replace the PRV on the hot cylinder with a 3 Bar one, because it would probably be only a 2 Bar rated valve. However on inspection the original PRV is rated at 3.5 Bar, so I left that alone......is that OK ?. After fitting the new pump I then tried to check the pressure in the accumulator, but because of the position it is fitted in the locker (and the cheapie pressure gauge I was trying to use this proved almost impossible. The pump seems to be working fine, there is about a 10 second delay till the pump kicks in after turning on a tap. Similarly the pump runs on for about the same time after switching off a tap. If I experiment with different pressures in the accumulator could I get the pump and tap to work simultaneously, or am I being to fussy....Any thoughts gentlemen.

[alan_fincher]

Following on from my recent post regarding shurflo pumps. I eventually fitted a new Shurflo, changing from the original 15psi model to this new one rated at 30psi. Limekiln told me I would have to replace the PRV on the hot cylinder with a 3 Bar one, because it would probably be only a 2 Bar rated valve. However on inspection the original PRV is rated at 3.5 Bar, so I left that alone......is that OK ?. After fitting the new pump I then tried to check the pressure in the accumulator, but because of the position it is fitted in the locker (and the cheapie pressure gauge I was trying to use this proved almost impossible. The pump seems to be working fine, there is about a 10 second delay till the pump kicks in after turning on a tap. Similarly the pump runs on for about the same time after switching off a tap. If I experiment with different pressures in the accumulator could I get the pump and tap to work simultaneously, or am I being to fussy....Any thoughts gentlemen.

It's considered to be an advantage of an accumulator based system that the pump doesn't kick in immediately after a tap is opened.

 

If your accumulator is working properly, it can deliver the initial water until the pressure drops to the pumps cut in pressure, (usually around half the rated cut-out pressure of the pump, so perhaps 15 psi for a 30 psi pump).

 

Why an advantage ? - Because theoretically it allows small quantities of water to be drawn off, without noisy pump running, (eg visits to bathroom in the night).

 

Similarly it is not unusual, (in fact can be expected), for pump to run for a while after tap is closed.

 

However 10 seconds sounds a lot - do you know capacity of the accumulator ? Is it a very big one ?

 

You really do need to set the accumulator up with a pressure gauge, (pump off, taps open !), for optimal performance, though.

 

I don't remember the original thread, but a 15 psi pump sounds an odd beast - I've never seen one sold for boating use under 30 psi - did it actually indicate on it that it had such a low cut-out pressure ?

 

FWIW every bit of "advice" I have been handed out in either branch of Limekiln, (and they don't half spout a load of it!), has proved to be bo**ocks. The "advice" that you would need to change the PRV is about up to his usual standard! (The important thing is that the PRV can open and relieve pressure, before it exceeds the designed maximum working pressure of the calorifier - it's unlikely you will find a fitted one that would be opened by a 30 psi pump, and the 3.5 bar one sounds OK to protect a typical calorifier, but could still be used with a pump up to 45 psi cut-out pressure).

[Badger]

Thankyou for your swift and very informative reply. Firstly I do not know the size of the accumulator. Secondly , maybe the reason I could not set the pressure is because I was not trying to do it as you state. Do you mean cutting the power to the pump, and opening all taps and shower valve ? before trying to pressurize the accumulator ?.Thanks once again, I will on my next visit check out the size of the acc.

Badger

[alan_fincher]

Thankyou for your swift and very informative reply. Firstly I do not know the size of the accumulator. Secondly , maybe the reason I could not set the pressure is because I was not trying to do it as you state. Do you mean cutting the power to the pump, and opening all taps and shower valve ? before trying to pressurize the accumulator ?.Thanks once again, I will on my next visit check out the size of the acc.

Badger

Yes,

 

You "pre-charge" the accumulator with the water side unpressurised.

 

That means turning off the pump, and opening a tap, (one should suffice - you just want everything to be unpressurised as you are checking it, and setting it up).

 

If you use the search facility, there is loads on here about the optimum setting, but to be honest, it does not have to be quite as precise a science as some of the near scientific papers you will find some have written. .

 

If you pump it up more than the "cut-in" pressure of your pump though, (probably around 15 psi ?), you will not be using the full capacity of the accumulator.

[ditchcrawler]

Thankyou for your swift and very informative reply. Firstly I do not know the size of the accumulator. Secondly , maybe the reason I could not set the pressure is because I was not trying to do it as you state. Do you mean cutting the power to the pump, and opening all taps and shower valve ? before trying to pressurize the accumulator ?.Thanks once again, I will on my next visit check out the size of the acc.

Badger

From the information you have given, 10 sec there side etc. I would suggest that you don't worry about the set presser of the size of the accumulator, its doing what you want and what it should do. If its not broken, don't fix it. Just my opinion.

[Keeping Up]

From the information you have given, 10 sec there side etc. I would suggest that you don't worry about the set presser of the size of the accumulator, its doing what you want and what it should do. If its not broken, don't fix it. Just my opinion.

That's my opinion too.

 

Everything is doing what it should; it ain't broke, don't try and fix it.

[alan_fincher]

Yes,

 

That's actually good advice, and I withdraw my "you really ought to check it's correctly set up comments".

 

Provided the flow from a tap is strong, the accumulator being able to deliver 10 seconds of noise free water before the pump kicks in is actually pretty good.

 

As both Ditchcrawler & Allan said - if it ain't broke, don't fix it.....

Edited January 5, 2010 by alan_fincher

[Badger]

Yes,

 

That's actually good advice, and I withdraw my "you really ought to check it's correctly set up comments".

 

Provided the flow from a tap is strong, the accumulator being able to deliver 10 seconds of noise free water before the pump kicks in is actually pretty good.

 

As both Ditchcrawler & Allan said - if it ain't broke, don't fix it.....

Thanks to all, I have to agree the water flow pressure is good, and I am inclined to leave well alone. Happy new year to all, and thanks again.

 

Badger

[PaulJ]

Well Im envious-you just dont realise how much time Ive wasted buggaring about trying to get that 10 second pump free water LOL

[DHutch]

Limekiln told me I would have to replace the PRV on the hot cylinder with a 3 Bar one, because it would probably be only a 2 Bar rated valve. However on inspection the original PRV is rated at 3.5 Bar, so I left that alone......is that OK ?

I would be very happy with the setup, infact, far more happy than to be changing a 2bar prv to a 3bar one having upped the pump.

- The PRV is the protect the cylinder from over pressure as the water inside it expands when heated

- Hence the hesitation to fit and uprated prv to the tank. As long as the prv is above the cutout presure of the pump the system will work fine.

 

3.5 bar is 50psi

 

 

Daniel