Rate of pressure loss

[ianmcd]

why do you think I said in #4 "at pressure 2 barg = 3 bara"?

I have no idea please tell me ?

 

[fixitflav]

I have no idea please tell me ?

Because it was relevant to the estimate I made. It shows I do know the difference between gauge (barg) and absolute pressure (bara).
BTW what would your estimate of volume for 0.1 bar pressure drop be?

 

[whenisayjump]

It's a rough guess based on the dial that's on the boiler, essentially shorthand for it's dropping a 'little bit' each day.

We have an external draincock that has a weep on one of the joins, the original question was to determine if that could be the reason for a small but noticeable daily loss of pressure.

 

[ianmcd]

It's a rough guess based on the dial that's on the boiler, essentially shorthand for it's dropping a 'little bit' each day.

We have an external draincock that has a weep on one of the joins, the original question was to determine if that could be the reason for a small but noticeable daily loss of pressure.

well start with sorting that

 

[ianmcd]

Because it was relevant to the estimate I made. It shows I do know the difference between gauge (barg) and absolute pressure (bara).
BTW what would your estimate of volume for 0.1 bar pressure drop be?

without knowing barometric pressure, system volume and system temperature at each measurement I wouldnt have a clue, was the pump running at first measurement and at second measurement,is it a fixed rate pump ? is it an ERP pump, what was demanded on the system was HW and all zones open when taken, the answer is I havent a clue and neither do you

 

[Gorners]

OP, why don’t you let some water out of a bleed vent into a measuring jug until you’ve lost approx. 0.1 bar. Might need someone at the boiler while you do it or a few trips back and forth. Only way you’re going to get a decent estimate on your own system with variables others have mentioned.

 

[fixitflav]

without knowing barometric pressure, system volume and system temperature at each measurement I wouldnt have a clue, was the pump running at first measurement and at second measurement,is it a fixed rate pump ? is it an ERP pump, what was demanded on the system was HW and all zones open when taken, the answer is I havent a clue and neither do you

You could try reading the OP's #18, I think we can give him credit for having the common sense to quote a typical figure over a few days, averaged over temperature variations. Do you really think variation in barometric pressure would make a significant difference? If the pressure vessel is close to the pump suction, as it should be, that fixes the minimum system pressure, and the pressure at the vessel connection varies very little whether or not the pump is running.
I do have a clue. I was trying to help the OP by making an estimate as requested, it could only be a rough one, as I said, and obviously based on some assumptions. If he wants to do a test as Gorners suggested, I'd be interested, and if my estimate is a long way out I'll admit I was wrong.

 

[ianmcd]

and the pressure at the vessel connection varies very little whether or not the pump is running.

What does the vessel have to do with it ? please explain why some boiler models need to see a pressure differential once the pump has been powered before they will allow the boiler to fire , if a boiler expansion vessel is correctly charged and the communication is clear then it will never affect anything to do with the system pressure, the primary water temp will, as will the pump

 

[fixitflav]

"

 

[fixitflav]

What does the vessel have to do with it ? please explain why some boiler models need to see a pressure differential once the pump has been powered before they will allow the boiler to fire

Certainly. Assuming the vessel connection is close to the pump suction, and is charged to say 1.5 barg, with cold system, that will be the pressure datum for the system. If the system pressure loss and hence the pump generated pressure are say 1 bar, when the pump starts the pressure at the suction stays at 1.5 barg. The pressure after the pump rises to 2.5 barg. The pressure falls round the system, back to 1.5 barg at the pump suction/vessel connection. There is a differential pressure across the boiler (and pump, and rads) any of which can be detected, if needed to allow boiler firing.
Of course, the pressure rises as the system heats up and the water expands. If checking to see whether top-up is needed, clearly it's best to read pressure over a few days, when it's in the same state each time, preferably cold.

if a boiler expansion vessel is correctly charged and the communication is clear then it will never affect anything to do with the system pressure, the primary water temp will, as will the pump

Sorry, I don't think that makes sense. Please reword it.

 

[fixitflav]

It's a rough guess based on the dial that's on the boiler, essentially shorthand for it's dropping a 'little bit' each day.

We have an external draincock that has a weep on one of the joins, the original question was to determine if that could be the reason for a small but noticeable daily loss of pressure.

Any developments on this?

 

[whenisayjump]

Any developments on this?

No not yet, the company that installed the boiler were supposed to be coming on Friday to fix the draincock... but that didn't happen

 

[fixitflav]

No not yet, the company that installed the boiler were supposed to be coming on Friday to fix the draincock... but that didn't happen

Did you do the Gorners test a la #21?