Coldwater Accumulators - 1 not filling

[Skiddaw]

Hi,

First post, just joined in the hope someone may kindly be able to help with the problem as per the thread title. I will explain the setup:

On non mains water into holding tank then fed into house, into 2 accumulators via a Mainsboost charger. Been working fine for many years. During recent cold weather the external pipes/tank froze. This happens quite often due to being in an area which has very cold weather. Once defrosted everything normally kicks back in working. This time we received an error on the mainsboost charger saying it had failed. It had indeed failed and has now been replaced. So onto the issue, following the charger replacement, only 1 of the accumulators is filling. Plumber has checked everything he thinks and ST (Stuart Turner) tech help have been very helpful but to no avail.

Having tested the diaphragm in the vessel which is not filling, there is no water coming out of the schrader valve so the presumption is it is fine. All inlet valves are open to the vessel.

There has been lots of mentions of the vessel pressure. Today the readings for the 2 vessels were 0.95 bar for the one filling and 1.2 for the other one. The suggestion was to set the pressure to be the same for both which we have done. The mains pressure reading is 1.5 bar, so am I right in thinking the differential will mean the pressure on the vessels needs to be lower?

On setting the pressure on both vessels to 0.95bar and restarting the charger the same thing happened, only 1 vessel filled. If we shut off the inlet valve to the vessel which is filling and only leave the other one open, still no water goes into it. The charge continues running until the auto 180min cutout kicks in.

I really am hoping someone can help. Is there anything else, obvious or not, which is likely? We are in a very rural area and finding plumbers who can help is proving difficult. ST do not have any technicians anywhere in the county.

Many thanks in advance.

 

[Skiddaw]

Actually you said it only takes 15 mins to fill both together so the charger is pumping ~ 25 LPM.

If no pressure gauge anywhere its quite easy to see if its charging or not, just check the pressure at the air end (assuming you have a pressure gauge) it will be exactly the same as the water side.

We see the pressure on the charger which normally gets to just below 3 bar, the mains pressure gauge also increases accordingly to normally the same, is that what you mean?

 

[John.g]

Yes, this pressure should (normally) reflect the pressure in the accumulator(s), it will only read the correct pressure for the "bad" one if the other is isolated from it, the only other reason I can think of is that the diaphragm is stuck or jammed up against the water end but the pump should then cut out almost immediately on its pressure switch, taking the air end pressure will reveal a lot.

 

[Skiddaw]

Yes, this pressure should (normally) reflect the pressure in the accumulator(s), it will only read the correct pressure for the "bad" one if the other is isolated from it, the only other reason I can think of is that the diaphragm is stuck or jammed up against the water end but the pump should then cut out almost immediately on its pressure switch, taking the air end pressure will reveal a lot.

Yes, even with my very limited knowledge, the fact the pump does not cut out has confused me. When I closed the inlet valve for the one which is filling to try to "force" the other one to fill and it didn't I expected the charger to shut off, it obviously didn't.

I am not sure what you mean by taking the air end pressure. My plan is to change the pressure on each vessel again in the morning after emptying and try again. I will update the thread once done, nothing more to do tonight other than sleep!

Thanks for everyone's help.

 

[ShaunCorbs]

It’s trying to charge your whole system to 3.5 bar or what ever the charge pump is set too hence it never got there and erred out

 

[John.g]

What I mean by checking the air end is simply taking the air pressure which you read anyway when changing air pressures, if its still at the pre charge pressure then obviously no water in the other end.

 

[Skiddaw]

Morning. Thanks again for the posts yesterday.

This morning husband drained down the system. The vessel pressure were both 1.0 bar. We only have a small bike pump so struggled to get the pressure up on either vessel, in fact could not increase it at all.

Made sure there was no air in the system (air coming out of taps) and switched everything back on. Only one vessel filled again exactly as before.

Drained the system again once switched back on ensured the isolation valve to the vessel which was filling was closed. Once again the other vessel did not fill.

Final time have drained the system again and am now currently seeing if both vessels fill, I am not expecting any difference with only one filling.

If the vessel pressure is wrong (should be higher (or lower) than the current 1.0bar) why would one tank fill with that pressure setting?

Once again sorry if stupid questions which may have been answered before.

Thanks in advance for any further assistance.

 

[John.g]

Where are you measuring the 1 bar pressure?

 

[Skiddaw]

Where are you measuring the 1 bar pressure?

The Schrader valve on each of the vessels.

 

[John.g]

That's great, what is the pressure on the fully charged accumulator as measured at its schrader valve?

 

[Skiddaw]

That's great, what is the pressure on the fully charged accumulator as measured at its schrader valve?

Do you mean when full? If so I cannot tell you that currently as waiting for them (or it) to fill again.

 

[John.g]

You certainly can as the pressure will start to rise immediately water starts to enter the accumulator, it will start at your precharge pressure and then rise eventually to its final pressure...exactly the same as the water side pressure.

 

[Skiddaw]

You certainly can as the pressure will start to rise immediately water starts to enter the accumulator, it will start at your precharge pressure and then rise eventually to its final pressure...exactly the same as the water side pressure.

Thank you and apologies for not knowing I could check the pressure whilst filling.

A slight different outcome currently, valves open in both vessels, after approx 15 mins, neither vessel seem to be filling at all or at their normal speed. Husband closed the valve to the vessel which has not been filling, immediately the other started filling. It is not full but current pressure is 1.75 bar. I have also checked the pressure on the other one which is also showing the same.

Is it worth draining down again and starting again, leaving both the vessels to fill for longer ( a bit annoyed husband closed the valve to the one which has not been filling!).

 

[John.g]

I wouldn't drain down again, you have pre pressurised to 1 bar which is perfectly acceptable and they are both filling so see what the final pressures are.
I am just wondering if that charging pump is variable speed controlled and some problem with this, have you any info on it?.

 

[Skiddaw]

Only one vessel is filling exactly as before.

An update, charger still running, one vessel filling, the other isn't. Pressure on both vessels 2.1 bar.

The charger has a number of settings, but speed control is not one of them. I have all the documentation for the charger so can provide answers if need be.

Another question from me, if the pressure increasing on both vessels but water only going into 1, could I be looking at something as simple as a failure of the inlet valve? Even when open is actually closed?

Thanks as always.

I wouldn't drain down again, you have pre pressurised to 1 bar which is perfectly acceptable and they are both filling so see what the final pressures are.
I am just wondering if that charging pump is variable speed controlled and some problem with this, have you any info on it?.

 

[snowhead]

Only one vessel is filling exactly as before.

An update, charger still running, one vessel filling, the other isn't. Pressure on both vessels 2.1 bar.



Another question from me, if the pressure increasing on both vessels but water only going into 1, could I be looking at something as simple as a failure of the inlet valve? Even when open is actually closed?

If the vessels start out at the same pressure empty, then during the fill cycle they both increase pressure by the same amount, that would suggest they are both filling (with something) equally.
When you say 1 vessel is not filling, how are you determining that?

 

[Skiddaw]

If the vessels start out at the same pressure empty, then during the fill cycle they both increase pressure by the same amount, that would suggest they are both filling equally.
When you say 1 vessel is not filling, how are you determining that?

Highly technically (!), by tapping the side of the vessels, empty is hollow sounding, full does not sound hollow. An empty vessel also can be very gently rocked (we never do this!) a full one is much heavier and cannot be rocked if tried.

Prior to the charger change, when both vessels were full, the charger would switch off, from empty this would normally take no more than 20 mins. Currently the charger will run for a full 180mins before the auto cutout kicks in. I am presuming this is happening to try an fill the vessel which is not filling?

 

[Skiddaw]

Ok, another update which dare I say it a bit more positive, the first vessel now does seem to have some water in it (I think), the pressure readings are 2.3bar on both vessels - the same pressure showing on the charger.

Shall I let the charger just run, could it just be taking longer to fill them both than normal because they have both not been full for a while?

Thank you again for everyone's help.

 

[John.g]

Take it that you are taking pressures from both schrader valves, to increase the pressure from 2.3 to 2.8 bar will only require 72 litres, say 3 minutes, is the charging pump supplying the system normally as well, if so if the demand is close to the pump flow capacity of ~ 25 LPM then it could take hours to fill the accumulators.

 

[Skiddaw]

Yes both valves. So the hours to fill, because they were both very empty? Normally the charger does not run for any more than 20 mins when filling them both from empty. Apologies probably the same questions, I just trying to get my head around what may be happening having only changed one part of the system (the charger).

At least if both vessels are now filling it is more positive. I am hoping they will fill completly, the charger switch off and then as we use water in the house the charger kicks in as and when needed which is how it has always worked. The charger would only kick in if the demand was high.

This is the charger.

https://www.stuart-turner.co.uk/contentfiles/Mainsboost-Wall-Mounted-MBC-12-DS.pdf

 

[John.g]

The charger kicking in depends on its cut in pressure so if its set slightly lower than the (dynamic) mains pressure then will only cut in when both accumulators are empty. To fill both accumulators from 1.0 bar (empty) to 2.8 bar requires 426 litres of water so if the pump output is 25 LPM then 17 minutes to re charge, Still doesn't explain though why the pump was running continuously, the only logical explanation is that the demand was > 25 LPM or whatever the pump is rated at.
Have you any idea of the pump output or a link to it, for interest.

 

[Skiddaw]

The charger kicking in depends on its cut in pressure so if its set slightly lower than the (dynamic) mains pressure then will only cut in when both accumulators are empty. To fill both accumulators from 1.0 bar (empty) to 2.8 bar requires 426 litres of water so if the pump output is 25 LPM then 17 minutes to re charge, Still doesn't explain though why the pump was running continuously, the only logical explanation is that the demand was > 25 LPM or whatever the pump is rated at.
Have you any idea of the pump output or a link to it, for interest.

I have put a link to the charger on a previous post, I have the documentation here for it too, I am looking for the output but not finding anything currently. There are a number of settings for the charger which I can detail here and what they are set to?

Your calculations (thank you) seem to equate to the time the vessels used to take to fill prior to the charger change. So although further forward something still is not right. I have just checked again, everything still at 2.3bar, the vessels appear to be full (as far as I can tell) but the charger still running.

 

[Skiddaw]

The settings which can be changed on the charger are with current settings:

Set Point - 3 bar
Diff Pressure - 0.5 bar
Low Pressure - 0.2 bar
High Pressure - 4.5 bar
Pump Run Timer - 180 mins

The remainder are to do with the alarm settings

 

[John.g]

A set point of 3 bar with a diff. press of 0.5 bar would indicate to me that it cuts in at 2.5 bar and cuts out at 3 bar. I don't know what the low and high pressure settings refer to.
The pump data as you said gives no flow rate but the power consumption of 398 watts should by my calc give 20/25 LPM.

I think you have a problem with the new charger, could be something as simple as a bit of dirt under a non return vave, I don't think there was/is anything wrong on the accumulator side, I would get back on to your plumber & stuart turner. In the mean time you might consider reducing the setpoint to say 2.1/2.2 bar and then the pump shouldn't run continuously even though it is rated as such.

Only other thing I can think of is that it is pumping back through the mains due to a faulty NR valve (if) installed somewhere in your system (not the pump).

 

[Skiddaw]

A set point of 3 bar with a diff. press of 0.5 bar would indicate to me that it cuts in at 2.5 bar and cuts out at 3 bar. I don't know what the low and high pressure settings refer to.
The pump data as you said gives no flow rate but the power consumption of 398 watts should by my calc give 20/25 LPM.

I think you have a problem with the new charger, could be something as simple as a bit of dirt under a non return vave, I don't think there was/is anything wrong on the accumulator side, I would get back on to your plumber & stuart turner. In the mean time you might consider reducing the setpoint to say 2.1/2.2 bar and then the pump shouldn't run continuously even though it is rated as such.

The low and high pressure settings are the failsafe settings.

I have switched the charge off with the pressure at 2.3 bar as nothing more seemed to be happening, there is no doubt now both vessels are full.

Without sounding like I know too much, which I certainly do not, when I typed out the settings of the charger I wondered if I need to lower the 3 bar setting, you have kindly already answered. I will lower the setting now as you say which will at least allow me to use the system as planned and leave the charger switched on without constantly running.

I will speak to everyone tomorrow as you said and will come back and update, in the meantime thank you to you and everyone else for all your help, it is very much appreciated.

 

[John.g]

Very good, just to say it "cant" be any problem with a NRV in the mains as that is what is being boosted! so possibly NRV in the pump itself.