No hot water

[MtB]

33 minutes ago, WotEver said:

??

Surely adjusting the cut-out pressure IS changing the output pressure? Until it cuts out, all you have is flow, no?

:::waiting for someone to shout NO:::

 

Yes. Consider the flow as equivalent to current (in Amps) in an electrical circuit, and the water pressure as analogous to the voltage....

[Tony Brooks]

I agree with the other Tony (WotEver) but am not sure the OP means that.

If a pump is cycling when an outlet is open it is because the output volume of the pump is greater than flow rate from the outlet. Reducing the cut out presssure will to a degree reduce the flow rate from the outlet because of the resistance in the pipes but I doubt it would make much difference re cycling.

This topic seems to have got mixed up, at first I thought it was about no hot water but now the OP seems to suggest its more to do with cycling from the shower but not from taps. If that is the case the problem is likely to be with the shower. Does it have a restricter or strainer where the shower hose attaches to the head or mixer?

Has the shower head be de-scaled or has it been changed for a low water use one?

Are there strainers at the inlet to the mixer?

 

[philjw]

23 minutes ago, Tony Brooks said:

Has the shower head be de-scaled or has it been changed for a low water use one?

What is the flow like with the shower head removed from the hose?  Does it still cause the pump to cycle?

[WotEver]

1 hour ago, Tony Brooks said:

Reducing the cut out presssure will to a degree reduce the flow rate from the outlet because of the resistance in the pipes but I doubt it would make much difference re cycling.

No, but raising the cut-out pressure might reduce it, I’d have thought?

Yes, this thread has got confused. There again, I’m easily confused. 

[Tony Brooks]

11 hours ago, WotEver said:

No, but raising the cut-out pressure might reduce it, I’d have thought?

I can't work that one out.

Greater pressure at the pump end of the system will force more water past any restrictions so increase the volume  flowing. Reducing the cut out pressure gives less "push" to the water so output volume should reduce.

 

[WotEver]

27 minutes ago, Tony Brooks said:

I can't work that one out.

Greater pressure at the pump end of the system will force more water past any restrictions so increase the volume  flowing. Reducing the cut out pressure gives less "push" to the water so output volume should reduce.

Probably because I’m wrong...

My thinking is that the water pushing against the obstruction (like a partially blocked shower rose) raises the pressure in the pipes sufficiently to operate the pressure switch. Raising the threshold of the switch would make that less likely. Is my thinking wrong?

[Bricksh]

This pump has a bypass valve to help prevent pulsing, could some crud have got into the pumps bypass when the tank was shut off then reopened? Does the pump have a suction strainer?

[Tony Brooks]

7 minutes ago, WotEver said:

Probably because I’m wrong...

My thinking is that the water pushing against the obstruction (like a partially blocked shower rose) raises the pressure in the pipes sufficiently to operate the pressure switch. Raising the threshold of the switch would make that less likely. Is my thinking wrong?

I think we are talking about different things. I am talking about the volume flowing from any given outlet. I think that you are talking about the likelihood of the pressure reaching cut out pressure and causing the pump to cycle. I agree that raising the pressure will force more water from the outlet, the question is will this be enough to keep the pressure at the pump below the cut out pressure. I think the answer to that is unknown but it may in marginal cases - and this may or may not be a marginal case.

 

8 minutes ago, Bricksh said:

This pump has a bypass valve to help prevent pulsing, could some crud have got into the pumps bypass when the tank was shut off then reopened? Does the pump have a suction strainer?

If a bypass valve has crud in it the chances are that it is jammed open and this would reduce the output because water is leaking back to the inlet all the time the pump is running. That should reduce any tendency to cycle. I doubt crud would jamb such a valve closed and that would do as you suggest. If the said crud has soemhow manage to reduce the volume flowing back to the inlet then, yes it may explain the problem.

I can not see how a blocked suction strainer (or any restriction on the inlet) can cause a pump to cycle. If anything it would do the opposite because  the pump would not be receiving the volume of water it should.

 

A water pumps cycle because it is producing a greater volume than can flow from the outlet. That is the basic principle that we need to keep in mind. Messing with accumulator pressure can not alter that although it may alter the cycling frequency. As I said above in MY view messing with the cut out pressure is also unlikely to make a significant difference in the majority of cases. In the case of a bypass pump as Brickish suggests this one is then the flow volume we are talking about s a combination of the flow from the outlet plus the flow back through the bypass valve. Reducing either may cause cycling.

[MtB]

28 minutes ago, Tony Brooks said:

I can not see how a blocked suction strainer (or any restriction on the inlet) can cause a pump to cycle. If anything it would do the opposite because  the pump would not be receiving the volume of water it should.

 

My thoughts too. In fact I wonder if the tank isolation valve had been carefully adjusted 'part open' by the installers of the new pump to achieve just this effect, i.e. get rid of the cycling.

Then a week later for some reason the OP turned the tank valve OFF then fully back ON later without realising this fact, thereby introducing the fault. 

Try opening a hot tap that cycles, then progressively close down the tank outlet valve until the cycling stops. Sorted!

(Well, bodged  )

[Tony Brooks]

59 minutes ago, Mike the Boilerman said:

 

My thoughts too. In fact I wonder if the tank isolation valve had been carefully adjusted 'part open' by the installers of the new pump to achieve just this effect, i.e. get rid of the cycling.

Then a week later for some reason the OP turned the tank valve OFF then fully back ON later without realising this fact, thereby introducing the fault. 

Try opening a hot tap that cycles, then progressively close down the tank outlet valve until the cycling stops. Sorted!

(Well, bodged  )

That makes sense and also seems to fit what we know. Certainly worth a go as its a free "repair" if it works.

[WotEver]

1 hour ago, Mike the Boilerman said:

 

My thoughts too. In fact I wonder if the tank isolation valve had been carefully adjusted 'part open' by the installers of the new pump to achieve just this effect, i.e. get rid of the cycling.

Then a week later for some reason the OP turned the tank valve OFF then fully back ON later without realising this fact, thereby introducing the fault. 

Try opening a hot tap that cycles, then progressively close down the tank outlet valve until the cycling stops. Sorted!

(Well, bodged  )

Good bodge sir

[Bricksh]

1 hour ago, Tony Brooks said:

I can not see how a blocked suction strainer (or any restriction on the inlet) can cause a pump to cycle. If anything it would do the opposite because  the pump would not be receiving the volume of water it should.

I agree, I was just pondering if there were no strainer, it could be a source of crud into the pump. I do however think Mikes part open valve explanation makes a lot of sense, on the basis that it was OK before it was turned off and its not now.

[Tony Brooks]

5 minutes ago, Bricksh said:

I agree, I was just pondering if there were no strainer, it could be a source of crud into the pump. I do however think Mikes part open valve explanation makes a lot of sense, on the basis that it was OK before it was turned off and its not now.

That illustrates nicely how we get things resolved on here. We just bounce ideas off one another until some kind of consensus appears.

My reply to your post got Mike's brain working a certain way and that brought a potential solution.

[MtB]

8 minutes ago, Tony Brooks said:

My reply to your post got Mike's brain working a certain way at all and that brought a potential solution.

 

Corrected that for you Tony!

[Markinaboat]

9 hours ago, Mike the Boilerman said:

 

My thoughts too. In fact I wonder if the tank isolation valve had been carefully adjusted 'part open' by the installers of the new pump to achieve just this effect, i.e. get rid of the cycling.

Then a week later for some reason the OP turned the tank valve OFF then fully back ON later without realising this fact, thereby introducing the fault. 

Try opening a hot tap that cycles, then progressively close down the tank outlet valve until the cycling stops. Sorted!

(Well, bodged  )

Sorry guys n gals, not long moored up at Kings Langley. Home Tomorrow  thank god.

 

i would like to answer every post but will keep to the point. Firstly, there were two issues, number one being the cycling, number two hot water via the eber thingy. I then updated that the hot water was no longer a problem and focused on the cycling. Yes there is a strainer and it's clean. 

MTB and others brilliant theory of the main tank valve having been partially closed to disguise the issue does hold some water (pun intended). I gradually closed this a little and the cycling surely stopped. However, the pump noise/vibration increased significantly as if cavitating. During those first five days when all worked, we do not remember this awful noise so whilst the theory is correct and works, it would appear that a problem elsewhere still exists. 

On the upside, two other leaks accounting for the bilge water cured during the process where the shower drain hose had almost disconnected from the dump pump spigot and the main feed strainer had been overtightened and dripping as well as the pump outlet pipe at a itessure side isolating valve peeing out. Very professional eh? 

Thanks to all for contributing to this frustrating subject!

[ditchcrawler]

On 03/01/2018 at 20:07, philjw said:

What is the flow like with the shower head removed from the hose?  Does it still cause the pump to cycle?

My pump will cut in and out with just the shower being used, it doesn't pulsate because I have an accumulator so when the shower is opened the pressure slowly drops until the pump cuts in,the pump then runs re-pressurising the accumulator and supplying water to the shower until it reaches the cut out pressure

[Chewbacka]

9 hours ago, ditchcrawler said:

My pump will cut in and out with just the shower being used, it doesn't pulsate because I have an accumulator so when the shower is opened the pressure slowly drops until the pump cuts in,the pump then runs re-pressurising the accumulator and supplying water to the shower until it reaches the cut out pressure

I suspect you have a flow restriction, either a little water saving flow control on the shower mixer inlets or outlet, or possibly a kinked outlet pipe or blocked shower head.

Edited January 5, 2018 by Chewbacka

[Tony Brooks]

1 hour ago, Chewbacka said:

I suspect you have a flow restriction, either a little water saving flow control on the shower mixer inlets or outlet, or possibly a kinked outlet pipe or blocked shower head.

Knowing Brian I very much doubt that.

Personally I am fed up with people who seem to think that if they have a pump with a greater volume output than any outlet can pass the pump will not cycle.  It will, end of story, and I suspect Brian knows that, as I do, and accept such cycling as normal because its is. To cure it in most cases would need a lower output volume pump.

[ditchcrawler]

3 hours ago, Chewbacka said:

I suspect you have a flow restriction, either a little water saving flow control on the shower mixer inlets or outlet, or possibly a kinked outlet pipe or blocked shower head.

No its just the pump is capable of supplying more water than will flow through the shower.if it was the other way round the pressure would just continue to fall all the while the shower was running.

[Iain_S]

2 hours ago, ditchcrawler said:

No its just the pump is capable of supplying more water than will flow through the shower.if it was the other way round the pressure would just continue to fall all the while the shower was running.

.. until the flow through the shower reduced to pump flow rate.

[Chewbacka]

5 hours ago, Tony Brooks said:

Knowing Brian I very much doubt that.

Personally I am fed up with people who seem to think that if they have a pump with a greater volume output than any outlet can pass the pump will not cycle.  It will, end of story, and I suspect Brian knows that, as I do, and accept such cycling as normal because its is. To cure it in most cases would need a lower output volume pump.

Then he must have a much bigger pump them I have, as my parmax runs continuously whenever the shower or galley tap is full on.

[Markinaboat]

8 hours ago, Iain_S said:

.. until the flow through the shower reduced to pump flow rate.

So why did it work ok for five days?

[Bricksh]

10 hours ago, Markinaboat said:

So why did it work ok for five days?

I don't know the answer to that. Is it possible to measure the flow rate through the shower, just get a bucket and fill for a minute from the shower head then measure with a measuring jug. The minimum flow rate for the pump according to the leaflet I have attached is 2.5l/min. If the flow rate is less then the pump will switch on and off.

http://www.xylemflowcontrol.com/files/31x95_PAR_Max_1.9_and_2.9_Promo.pdf

[ditchcrawler]

32 minutes ago, Bricksh said:

I don't know the answer to that. Is it possible to measure the flow rate through the shower, just get a bucket and fill for a minute from the shower head then measure with a measuring jug. The minimum flow rate for the pump according to the leaflet I have attached is 2.5l/min. If the flow rate is less then the pump will switch on and off.

http://www.xylemflowcontrol.com/files/31x95_PAR_Max_1.9_and_2.9_Promo.pdf

Note that is the open flow rate, straight out of the pump, no pipe work

[MtB]

Going back to the beginning, it seems to me the only issue left is that the pump cycles on and off when the shower is being used. This is normal behaviour I suggest, and we are trying to chase down a non-problem.

My pump certainly cycles on and off when the shower is in use. Could the OP clarify please, does the shower actually work, or not? (Notwithstanding perfectly normal pump cycling).)