Adjusting cut in pressure on a Shurflo pump

[Trilby Tim]

We have a Shurflo water pump like this one. Is it possible/advisable to raise the cut in pressure on the pump. We have a accumulator tank in the system, and it seems to work well in most respects. Open the tap and get a steady stream of water as the pressure in the accumulator is used up. The problem is that the pump waits until the stream has died away to a dribble before it cuts in and starts pumping. It's particularly annoying if you only have the tap open a bit as then the flow dies almost to nothing and you have to wait quite a while for the pump to kick in. Either that or you open the tap further and then get sprayed with water when it does suddenly kick in! It would be better if it cut in earlier, can I adjust this, and would there be any disadvantages to watch for? I don't need to change the high pressure cut out, just the low pressure cut in.

[Phil Ambrose]

We have a Shurflo water pump like this one. Is it possible/advisable to raise the cut in pressure on the pump. We have a accumulator tank in the system, and it seems to work well in most respects. Open the tap and get a steady stream of water as the pressure in the accumulator is used up. The problem is that the pump waits until the stream has died away to a dribble before it cuts in and starts pumping. It's particularly annoying if you only have the tap open a bit as then the flow dies almost to nothing and you have to wait quite a while for the pump to kick in. Either that or you open the tap further and then get sprayed with water when it does suddenly kick in! It would be better if it cut in earlier, can I adjust this, and would there be any disadvantages to watch for? I don't need to change the high pressure cut out, just the low pressure cut in.

 

Not sure if it is possible with this pump, some pumps can be adjusted but if you increase the running pressure you may find that you P.R.V. on calorifier will kick in or dribble.

 

Phil

[Trilby Tim]

Not sure if it is possible with this pump, some pumps can be adjusted but if you increase the running pressure you may find that you P.R.V. on calorifier will kick in or dribble.

 

Phil

No, I don't want to increase the running pressure, I just want it to keep the pressure more constant.

[alan_fincher]

It sounds like it could be your accumulator that needs the adjustment, rather than tinkering with the default pressure settings on the pump.

 

Have you checked it, and do you know it is correct.

 

I'd not touch the pump until I knew the accumulator was as it should be.

[mayalld]

It sounds like it could be your accumulator that needs the adjustment, rather than tinkering with the default pressure settings on the pump.

 

Have you checked it, and do you know it is correct.

 

I'd not touch the pump until I knew the accumulator was as it should be.

 

Agreed.

 

The system is working just like a system with no accumulator. It probably needs tha accumulator pumping up.

[pirate paul]

We have a Shurflo water pump like this one. Is it possible/advisable to raise the cut in pressure on the pump. We have a accumulator tank in the system, and it seems to work well in most respects. Open the tap and get a steady stream of water as the pressure in the accumulator is used up. The problem is that the pump waits until the stream has died away to a dribble before it cuts in and starts pumping. It's particularly annoying if you only have the tap open a bit as then the flow dies almost to nothing and you have to wait quite a while for the pump to kick in. Either that or you open the tap further and then get sprayed with water when it does suddenly kick in! It would be better if it cut in earlier, can I adjust this, and would there be any disadvantages to watch for? I don't need to change the high pressure cut out, just the low pressure cut in.

I have got one of these works no prob, may be the prob is the hight of water in the pipe,ie how high is the tap from the pipe.

[nb Innisfree]

Accumulators are there to prevent pump cycling which you don't have, so that would indicate it's not a prob with accumulator pressure, sounds to me you have diagnosed correctly, i.e. too low a cut in pressure.

[PhilR]

Accumulators are there to prevent pump cycling which you don't have, so that would indicate it's not a prob with accumulator pressure, sounds to me you have diagnosed correctly, i.e. too low a cut in pressure.

 

I agree it sounds like the pump. Is this an intermittent fault? I have had two micro-switches pack in. Does a clout with a rubber hammer start the pump working?

[pirate paul]

I have got one of these works no prob, may be the prob is the hight of water in the pipe,ie how high is the tap from the pipe.

Looks like mine any way, mine is operated by a diaphram (naff at spelling tried several combinations) which triggers a switch, the reduction in pressure, when the tap is opened, causes a movement of the diaphram, which triggers the switch.

 

Your prob could be back pressure, the hight of the tap, different thicknesses of pipe, the elasticity of the pipe, something along those lines.

[alan_fincher]

Accumulators are there to prevent pump cycling which you don't have, so that would indicate it's not a prob with accumulator pressure, sounds to me you have diagnosed correctly, i.e. too low a cut in pressure.

 

I agree it sounds like the pump. Is this an intermittent fault? I have had two micro-switches pack in. Does a clout with a rubber hammer start the pump working?

 

Yes, I have now read OP again - I'm not sure how I managed to get the wrong impression in the first place, as it's clearly enough written.

 

I've changed my mind - it does sound like the pump, but I also think it may be faulty, rather than just needing a tweak.....

 

I must learn to read first.

I must learn to read first.

I must learn to read first.

I must...............................................

[Greybeard]

QUOTE (chris w @ May 5 2009, 02:16 AM)

Make sure, when you are measuring the pressure of the accumulator, that the water pump is turned off (electrically) and that you have opened a tap to drain the accumulator. Now measure the accumulator pressure and pump up or release pressure as necessary to get around 12-15psi.

 

If you measure the accumulator pressure with water in the accumulator, the pressure you obtain will be the pump's cut-off pressure (typically about 30psi).

 

Chris

 

This was some advice given to me by chris w which I passed on to a couple who were having exactly the same problem as this.

 

Has you accumulator got a valve on it that resembles a tyre valve? (can't remember exact name of them)

 

If yes the bladder may need pumping up to the pressure shown above. (as mayalld has also mentioned)

 

The couple I mentioned used a foot pump with a pressure guage and it worked a treat.

 

It may be worth a quick check before adjusting / condemming the pump.

 

GB

[pirate paul]

Looks like mine any way, mine is operated by a diaphram (naff at spelling tried several combinations) which triggers a switch, the reduction in pressure, when the tap is opened, causes a movement of the diaphram, which triggers the switch.

 

Your prob could be back pressure, the hight of the tap, different thicknesses of pipe, the elasticity of the pipe, something along those lines.

Idont understand the accu stuff bat low no time, air in pipes.

[smileypete]

We have a Shurflo water pump like this one. Is it possible/advisable to raise the cut in pressure on the pump. We have a accumulator tank in the system, and it seems to work well in most respects. Open the tap and get a steady stream of water as the pressure in the accumulator is used up. The problem is that the pump waits until the stream has died away to a dribble before it cuts in and starts pumping. It's particularly annoying if you only have the tap open a bit as then the flow dies almost to nothing and you have to wait quite a while for the pump to kick in. Either that or you open the tap further and then get sprayed with water when it does suddenly kick in! It would be better if it cut in earlier, can I adjust this, and would there be any disadvantages to watch for? I don't need to change the high pressure cut out, just the low pressure cut in.

Sounds like it would be best to take a step back, actually measure the cut in and cut out pressures, and check the accumulator is pressurised properly.

 

cheers,

Pete.

[Iain_S]

We have a Shurflo water pump like this one. Is it possible/advisable to raise the cut in pressure on the pump. We have a accumulator tank in the system, and it seems to work well in most respects. Open the tap and get a steady stream of water as the pressure in the accumulator is used up. The problem is that the pump waits until the stream has died away to a dribble before it cuts in and starts pumping. It's particularly annoying if you only have the tap open a bit as then the flow dies almost to nothing and you have to wait quite a while for the pump to kick in. Either that or you open the tap further and then get sprayed with water when it does suddenly kick in! It would be better if it cut in earlier, can I adjust this, and would there be any disadvantages to watch for? I don't need to change the high pressure cut out, just the low pressure cut in.

 

The pressure switch is operated by movement of a diaphram which is fed through a small hole in the pump casing. If this hole gets partially blocked, it gives the above symptoms. I have enlarged the hole on mine somewhat, with a 3mm drill IIRC, which steadied the pump pressure considerably.

Iain

[blackrose]

I have a Shurflo Aqua King (looks like the same model as Tim's) 20psi cut in - 30psi cut out. My accumulator is set to 17psi and I have a hot water expansion tank on my calorifier that's set to 33psi. (According to previous discussions on the forum these are the correct pressures). The pressure of both tanks was set with the pump switched off and taps open so there was no pressure in the system.

I have exactly the same problem with the water flow as Tim describes.

 

The pressure switch is operated by movement of a diaphram which is fed through a small hole in the pump casing. If this hole gets partially blocked, it gives the above symptoms. I have enlarged the hole on mine somewhat, with a 3mm drill IIRC, which steadied the pump pressure considerably.

Iain

Where is this hole exactly? I know there's an adjustment screw on the head of the pump in the centre of the pressure switch. I think this adjusts cut in pressure, but it seems to make no difference to the problem.

Edited September 5, 2009 by blackrose

[nb Innisfree]

I think there is some confusion here, cut in and cut out pressures are controlled by pressure switch, they have nothing to do with accumulator settings. An accumulator is there purely to stop rapid cycling by delaying the drop, and rise, in pressure

[blackrose]

I think there is some confusion here, cut in and cut out pressures are controlled by pressure switch, they have nothing to do with accumulator settings. An accumulator is there purely to stop rapid cycling by delaying the drop, and rise, in pressure

There's no confusion - at least there wasn't until you posted!

Accumulator tanks should be set a few psi below the pump's cut in pressure, so in that respect they are related.

[tosher]

We have a Shurflo water pump like this one. Is it possible/advisable to raise the cut in pressure on the pump. We have a accumulator tank in the system, and it seems to work well in most respects. Open the tap and get a steady stream of water as the pressure in the accumulator is used up. The problem is that the pump waits until the stream has died away to a dribble before it cuts in and starts pumping. It's particularly annoying if you only have the tap open a bit as then the flow dies almost to nothing and you have to wait quite a while for the pump to kick in. Either that or you open the tap further and then get sprayed with water when it does suddenly kick in! It would be better if it cut in earlier, can I adjust this, and would there be any disadvantages to watch for? I don't need to change the high pressure cut out, just the low pressure cut in.

 

 

Call Shureflo LTD. Tel 01293 424000 Get it straight from the horses mouth. tosher

[nb Innisfree]

There's no confusion - at least there wasn't until you posted!

Accumulator tanks should be set a few psi below the pump's cut in pressure, so in that respect they are related.

 

I was referring to (possible) confusion created by suggestion that low cut-in pressure could be addressed by adjusting accumulator which of course it can't

 

Hope that's clearer, tho I doubt it!

[blackrose]

I was referring to (possible) confusion created by suggestion that low cut-in pressure could be addressed by adjusting accumulator which of course it can't

 

Hope that's clearer, tho I doubt it!

Ah, ok I'm with you now.

[alan_fincher]

I think there is some confusion here, cut in and cut out pressures are controlled by pressure switch, they have nothing to do with accumulator settings. An accumulator is there purely to stop rapid cycling by delaying the drop, and rise, in pressure

I think one needs to be a bit careful with "nothing to do with", as there should be an interrelationship between accumulator pre-charge and the cut in setting of the pump's pressure switch.

 

It seems to be generally agreed that your accumulator needs to be pre-charged to a few psi below the cut-in pressure of the pump for things to work in an optimal way. (E.g. pump with cut-out at 30 psi, and cut-in at 20 psi - set accumulator pre-charge to say 17 psi)

 

As I think we have now agreed in this case, the pump pressure switch seems more likely to be the source of difficulties than how the accumulator is pre-charged, but Smiley Pete is surely correct that the whole set-up should be checked.

 

Don't forget that accumulator pre-charge can only be set with the pump turned off, and taps open to relieve the pressure. Whilst that may sound like teaching grandmother to suck eggs, a surprising number of people don't seem to actually know that, and try setting with the system pressurised.

 

Finally, people have in the past suggested over-riding the inbuilt pressure switch on the pump, with a better quality independent one - something we have not had to resort to.

[nb Innisfree]

I think one needs to be a bit careful with "nothing to do with", as there should be an interrelationship between accumulator pre-charge and the cut in setting of the pump's pressure switch.

 

Point taken I need to be a bit more careful with my P's and Q's

[mudslide]

Not sure if it is possible with this pump, some pumps can be adjusted but if you increase the running pressure you may find that you P.R.V. on calorifier will kick in or dribble.

 

Phil

I recently replaced my pump with the same model . I don't have an accumulator and since replacement the calorifier is dribbling. It's not a real problem , just annoying . I was wondering if it is easy to cure . I don't want the calorifier to blow when it heats up so I'm not keen to play with the release valve on it.

Is the pump adjustable ?

[Paul Evans]

I recently replaced my pump with the same model . I don't have an accumulator and since replacement the calorifier is dribbling. It's not a real problem , just annoying . I was wondering if it is easy to cure . I don't want the calorifier to blow when it heats up so I'm not keen to play with the release valve on it.

Is the pump adjustable ?

You should be able to adjust the cut-in/cut-out pressure on the pump - have a look at the instructions that came with the pump for details. It sounds as though the cut-out pressure setting is slightly higher than the setting on the PRV on the calorifier. If you reduce the cut-out pressure setting on the pump the dribble should stop.

[nb Innisfree]

I recently replaced my pump with the same model . I don't have an accumulator and since replacement the calorifier is dribbling. It's not a real problem , just annoying . I was wondering if it is easy to cure . I don't want the calorifier to blow when it heats up so I'm not keen to play with the release valve on it.

Is the pump adjustable ?

 

In your setup, (assuming you have no expansion vessel) as a result of hydraulic pressure, the slightest expansion of water will lift the PRV off it's seating. An acumulator or expansion vessel will give water somewhere to expand into.

Edited September 5, 2009 by nb Innisfree