shower heater liters per min water flow questions

[sometimewoodworker]

3 hours ago, flipper2222222 said:

 

 

this is how Stiebel used to install them, , Look ok for you? 

No problem, though I’m not convinced the check valve is of any use. It can’t do any any harm that I can see and there is no special benefit to blocking the feed from 1 heater to the basin.

 

As I don’t think you need a bath-tub or basin feed you can simplify the layout by a lot IMNSHO.

[VocalNeal]

On 1/11/2022 at 3:31 PM, flipper2222222 said:

today I removed the external tap as you illustrated above and still only got 8 Liters in the test bucket. 

as you suggested the Frankenstein approach might be the only way?

 

do you think there is another internal restrictor in the heater?

The flexible pipes that connect the heater to the house may be the small ones. Slightly larger ones ca be found but how much more flow I don't know.

[VocalNeal]

 

The flow out of a water heater is a simple ???? input/output energy calculation.

 

No amount of pontification about plastic widgets will change the physics.

 

 

[Artisi]

3 hours ago, VocalNeal said:

 

The flow out of a water heater is a simple ???? input/output energy calculation.

 

No amount of pontification about plastic widgets will change the physics.

 

 

correct, you can assume the hydraulics from input to output have been considered based on a flow in versus "X" temperature out. Lower pressure in result in lower flow and the potential for a higher temperature rise, higher pressure in gives an increased flow rate and the potential for a lower temperature rise - however the temperature control knob assists in this regards - allowing you to increase or lower input power to the unit  for temperature control - BUT there is a point where a maximum flow rate is achieved irrespective  of the pressure applied or the pump is capable of supplying.

 

Head (pressure rise) loss from the pump to and thru' the unit and shower head increases as the square of the flowrate, standard 101 hydraulic calculation. 

 

so, let us assume that your 8 litres / minute requires a pressure of 10 metres head from the pump discharge to the shower outlet to overcome the height of the shower above the pump, the friction losses thru' your pipework and the friction loss thru' the heater and the shower head -- now expecting a flow of 16 litre / minute will require ------ 

 

 (Q2/ Q1)^2 X H 

  =  (8/4)^2 x10  = 40 metres.

 

what is the capability of the pump????

                

[flipper2222222]

49 minutes ago, Artisi said:

correct, you can assume the hydraulics from input to output have been considered based on a flow in versus "X" temperature out. Lower pressure in result in lower flow and the potential for a higher temperature rise, higher pressure in gives an increased flow rate and the potential for a lower temperature rise - however the temperature control knob assists in this regards - allowing you to increase or lower input power to the unit  for temperature control - BUT there is a point where a maximum flow rate is achieved irrespective  of the pressure applied or the pump is capable of supplying.

 

Head (pressure rise) loss from the pump to and thru' the unit and shower head increases as the square of the flowrate, standard 101 hydraulic calculation. 

 

so, let us assume that your 8 litres / minute requires a pressure of 10 metres head from the pump discharge to the shower outlet to overcome the height of the shower above the pump, the friction losses thru' your pipework and the friction loss thru' the heater and the shower head -- now expecting a flow of 16 litre / minute will require ------ 

 

 (Q2/ Q1)^2 X H 

  =  (8/4)^2 x10  = 40 metres.

 

what is the capability of the pump????

                

not sure of the exact capacity ( it is a grundfos scala 2 set at 3.5 bar) but I get 19 liters per minute out of the tap with nothing connected

8 liters when connected to the heater.

 

now I am thinking that I can split the output from the tap with at t-piece  one to to the heater one straight to the hand shower and then rejoin them together with another t-piece  at the hand shower , I would likely lose 50% of the heat but it still might be warm enough without the need from the second heater and I would get the full pressure from the tap , am I on the right track

[sandyf]

On 1/5/2022 at 11:10 AM, flipper2222222 said:

I am after more pressure rather than hot temperature, agreed doubling the flow might make the water not quite warm enough.

You will not get any more pressure, that is determined by the pump which operates in the range of the pressure switch. The flow is determined by the pressure and the cross sectional area of the pipework and with showers it will be the size of the pipe for the tank that will be the determining factor which is only about 1/4 inch. I think all heaters have a tank about the same size with just a different rated heater hence the flow being similar.

I think you are confusing pressure with water velocity and again that is down to area that the water must pass through. There are usually filters in the line that can be removed as they cause an obstruction but they are intended to prevent the shower head clogging up and that may have to be replaced more regularly.

Other ways to increase the water velocity are to reduce the size of the shower head or as I have done in the past, block off some of the holes in the one you have.

You could also adjust or fit a higher pressure switch on the pump but you would have to be careful with that.

Invariably problems like this cannot be resolved in one large step, more often a few small ones.

[sometimewoodworker]

2 hours ago, sandyf said:

You could also adjust or fit a higher pressure switch on the pump but you would have to be careful with that.

Flipper has no need of fitting a different pressure switch as his pump is able to be set all the way up to 5.5 bar from the current 3.5 bar, it takes seconds and is designed for user adjustment.

[sandyf]

21 hours ago, sometimewoodworker said:

Flipper has no need of fitting a different pressure switch as his pump is able to be set all the way up to 5.5 bar from the current 3.5 bar, it takes seconds and is designed for user adjustment.

Not familiar with the Grundfos pump but that seems a bit on the high side. I have several Mitsu and Hitachi and I think they are in the range 1.4 - 2 bar. The one on the house is a 200 model at I think 1.8 bar and that delivers about 20 litres/ minute at the taps.

With the higher pump pressure I do not see why there should be a problem and he may have to have a closer look at the pipework.

[sometimewoodworker]

1 hour ago, sandyf said:

Not familiar with the Grundfos pump but that seems a bit on the high side. I have several Mitsu and Hitachi and I think they are in the range 1.4 - 2 bar. The one on the house is a 200 model at I think 1.8 bar and that delivers about 20 litres/ minute at the taps.

With the higher pump pressure I do not see why there should be a problem and he may have to have a closer look at the pipework.

It is standard with his pump, FWIW I have the same one

[sometimewoodworker]

1 hour ago, sandyf said:

With the higher pump pressure I do not see why there should be a problem and he may have to have a closer look at the pipework.

It’s the water heater that restricts the flow, nothing to do with the pipe work.

[Artisi]

6 minutes ago, sometimewoodworker said:

It is standard with his pump, FWIW I have the same one

Any flowrate numbers with that info.?

[sometimewoodworker]

15 minutes ago, Artisi said:

Any flowrate numbers with that info.?

One, yes, though the pipes will restrict the final figure.

[Artisi]

Flipper: just had a quick look at the performance of your pump at 50 hz operating speed - your 19 litres per minute is optermistic. 

1. What is the height of the shower outlet above the pump centreline.

2. Can you fit a pressure gauge to the pump discharge of somewhere close, this could be the nearest tap at ground level - if yes, run the pump not connected to the heater /shower and then rerun the pump connected to the heater /shower taking pressure measurements for both-- this will tell you what's going on. 

[sometimewoodworker]

3 hours ago, Artisi said:

Flipper: just had a quick look at the performance of your pump at 50 hz operating speed - your 19 litres per minute is optermistic. 

Really??? The pump is rated for 3 cubic meters per hour. So 2.6 X greater than the 19 litres per minute. I think your math skills are rather lacking, aren’t they?

 

The problem has nothing to do with the pump and everything to do with the flow through the water heater.

 

Also with the same pump and an outlet about 25 metres from the pump it took 28.15 seconds to over fill a 5 gallon container 5 minutes ago. My results are probably a lot better than his due to the size of my pipes (32mm) and outlet ¾” 
 

And if you look at the original post he is already getting 16 litres per minute from the hand shower unit, so your suggested tests have no benefit that I can see.

[Artisi]

11 hours ago, sometimewoodworker said:

Really??? The pump is rated for 3 cubic meters per hour. So 2.6 X greater than the 19 litres per minute. I think your math skills are rather lacking, aren’t they?

 

The problem has nothing to do with the pump and everything to do with the flow through the water heater.

 

Also with the same pump and an outlet about 25 metres from the pump it took 28.15 seconds to over fill a 5 gallon container 5 minutes ago. My results are probably a lot better than his due to the size of my pipes (32mm) and outlet ¾” 
 

And if you look at the original post he is already getting 16 litres per minute from the hand shower unit, so your suggested tests have no benefit that I can see.

Thank you for your polite response to my comment re flowrate, seems I was thinking in GPM there as the OP was talking in LPM. 

You are correct in your comment re the restriction thru' the heater results in the reduced flow.

Would still be of interest to know the head at or near the pump discharge. 

[sometimewoodworker]

1 hour ago, Artisi said:

Would still be of interest to know the head at or near the pump discharge. 

Isn’t that information already in my posted page from the manual?

There is no suggestion that the pump is at all defective, & if it were it would be immediately replaced by Grundfos.

[Robin]

What ever pump you use, it cannot pump more than your mains will give it.  Here in village, the restriction is the water supply.  I have a normal 3.5KW shower sand never use it at more than 30% on the heater dial.  Simply cannot get enough flow, because of low input pressure. Village water supply is such a poor thing hat I would not use a pump as it would only cause negative pressure on incoming mains, and suck in God knows what pollution.  I have had a header tank installed for the whole house.  Tank about 3m above the level of all taps.  Give just about bearable shower flow.  before the header tank, flow at times was more like a trickle.

Like most things in Thailand.  now it just about works.  No idea what the supply water pressure is, but main pipe is only 3 in dia.,, so cause of all the problems is not enough water available.  Thai plumbing here is all PVC pipe with solvent joins, which will not stand much pressure.

[Artisi]

3 minutes ago, sometimewoodworker said:

Isn’t that information already in my posted page from the manual?

There is no suggestion that the pump is at all defective, & if it were it would be immediately replaced by Grundfos.

NO, the actual operating head imposed on the pump during operation is not listed, there is no vertical head, pipe length or pipe size given by the OP -  knowing the discharge pressure will give the losses up to the outlet point  - plus no one is suggesting there is any defect in the pump.

[sometimewoodworker]

2 hours ago, Robin said:

What ever pump you use, it cannot pump more than your mains will give it.

Well if you are not breaking the law, yes it absolutely can. As it is either illegal to pump from the mains or against your water supply contract.

 

2 hours ago, Robin said:

Simply cannot get enough flow, because of low input pressure. Village water supply is such a poor thing hat I would not use a pump as it would only cause negative pressure on incoming mains, and suck in God knows what pollution.  I have had a header tank installed for the whole house. 

You simply put the pump AFTER the header tank as all correctly formatted supplies do.

 

the allowed structure is your header/storage tank is feed from the village/mains supply and you pump from that tank.

[sometimewoodworker]

2 hours ago, Artisi said:

NO, the actual operating head imposed on the pump during operation is not listed, there is no vertical head, pipe length or pipe size given by the OP -  knowing the discharge pressure will give the losses up to the outlet point  - plus no one is suggesting there is any defect in the pump.

Is that really going to give any more relevant information than is in the first post?

The maximum flow is given.

The unrestricted flow at the heater is given.

The throughput of the hand shower is given.

The restricted throughput of the shower is given.

As the hand shower will pass double the output of the water heater QED a second heater in parallel to the first will increase the throughput of the hand shower, possibly not to its maximum but significantly more than the current amount. This is the required result.

 

 

FWIW

My unrestricted flow through a ½” supply is the same as flipper’s 

My flow through my 6,000W heater is 5% greater than his at 19 litres in 2 minutes so not significantly more.

 

It is extremely likely that these are close to the maximums available.

Pipe losses are thus ruled out (see my earlier posting as to why they cannot be a factor) as are all other possible things that can effect the result. 
 

I could increase my pump’s output pressure to see if it altered the results but see no benefit to doing that, and it is unlikely to make any difference.

[itsari]

On 1/3/2022 at 11:21 AM, sometimewoodworker said:

Your power cable can almost certainly allow for a a more powerful heater, however that will not increase the flow. You could however add a second heater and run that in parallel to the first one, though not the most elegant solution it is simple to implement and guaranteed to at least increase the flow by 50% at least quite possibly almost 100% more

I think that if you have two heaters on the one circuit there will be problems with supply on a 2.5mm wire 

[flipper2222222]

just to recap 

19 liters per min at the tap

16 liters at the shower head

8 liters per min when fitted to the heater

 

my latest thoughts was to take the suggestion from sometime wood worker of adding a second heater. but prior to doing this  just add 2 t-pieces one at the tap end and other at the shower head end

one line direct (8 liters per min approx ) and the other via the heater (8 liters per min approx) a total of 16 liters per min 

I would expect to lose 50% heat but would the direct water side not going to heater push through too much water and not let as much as the warm water from the heater therebby making the heat loss much more than 50%?

thanks for all the contributions 

[sandyf]

21 hours ago, sometimewoodworker said:

It is standard with his pump, FWIW I have the same one

What did you find difficult about the words "not familiar"

I have been here a long time and it looks like Mitsu and Hitachi are the most widely used.

[sandyf]

21 hours ago, sometimewoodworker said:

It’s the water heater that restricts the flow, nothing to do with the pipe work.

You are obviously choosing to ignore this statement.

"19 liters per min at the tap"

Remind us,  how does that compare to the nominal output.

[sandyf]

4 hours ago, Artisi said:

NO, the actual operating head imposed on the pump during operation is not listed, there is no vertical head, pipe length or pipe size given by the OP -  knowing the discharge pressure will give the losses up to the outlet point  - plus no one is suggesting there is any defect in the pump.

Exactly. There are a lot of variables that interact with  each other and you must never lose sight of the overall picture.

When I built my house in 2010 I only put an electric shower in the guest ensuite. Winters were quite short and not much of a problem to use that one for a couple of weeks. Last couple of years the winters have got longer and last year I was in 2 minds whether to fit another in the main ensuite, by the time I thought about it the winter was nearly over and didn't bother.

When I came back from the UK last Oct the overnight was so low needed the electric shower so it became one of my first jobs on return. Fitting the electric shower gave me a stronger shower than I had been getting from direct feed, the new shower head, although the same diameter had a lot less holes giving a higher water velocity. Hot water and a better shower, a real win-win for less than 2000 baht.

[Artisi]

39 minutes ago, sandyf said:

You are obviously choosing to ignore this statement.

"19 liters per min at the tap"

Remind us,  how does that compare to the nominal output.

Correct, without having the necessary info such as to height to the outlet (static head), length of pipe run, pipe diameter, how many bends / T junctions etc  its a bit like crystal ball gazing - however working backwards that is always hit-and-miss and without knowing how accurate the bucket flow measurement is, 19 lpm equals 1.14 m3h --- from the 50hz pump performance curve it indicates the discharge head is over 40 m head at the pump --- now that's a lot of static head and friction loss. 

Of course is the pump running at full speed, no blockages in the discharge or inlet pipe and the water supply can meet what is required. 

 

Probably enough confusion now, so I'll leave it to the experts from here on. 

[sandyf]

11 minutes ago, Artisi said:

Probably enough confusion now, so I'll leave it to the experts from here on. 

Quite, always plenty of them.

I was given a pump from my BiL that had been acquired as part of a debt repayment. Can't quite remember the make but well known European company, very powerful with 2HP motor and can deliver up to 100 litres /min via 1 inch outlet.

I was at a bit  of a loss what to do with it and then thought about a sprinkler system, what a nightmare I had. Couldn't get it to run, had 8 sprinkler heads and it just kept bursting the connections as it was unregulated. I decided then to put another line back into the supply tank and using that to relieve the back pressure managed to bring it under control. It was a tedious job then trying to balance all the sprinkler heads to get a reasonable spray pattern.

I have restructured the garden and haven't yet had the enthusiasm to set it up again.

[Artisi]

33 minutes ago, sandyf said:

Quite, always plenty of them.

I was given a pump from my BiL that had been acquired as part of a debt repayment. Can't quite remember the make but well known European company, very powerful with 2HP motor and can deliver up to 100 litres /min via 1 inch outlet.

I was at a bit  of a loss what to do with it and then thought about a sprinkler system, what a nightmare I had. Couldn't get it to run, had 8 sprinkler heads and it just kept bursting the connections as it was unregulated. I decided then to put another line back into the supply tank and using that to relieve the back pressure managed to bring it under control. It was a tedious job then trying to balance all the sprinkler heads to get a reasonable spray pattern.

I have restructured the garden and haven't yet had the enthusiasm to set it up again.

Looks like a Grundfos multi-stage, you could remove 1 or 2 impellers, flow will remain the same but the discharge pressure will reduce, more power efficient as you won't need to pump back to the tank, - - - but this is high jacking this thread, start another thread if you want to pursue it. 

[sandyf]

9 minutes ago, Artisi said:

Looks like a Grundfos multi-stage, you could remove 1 or 2 impellers, flow will remain the same but the discharge pressure will reduce, more power efficient as you won't need to pump back to the tank, - - - but this is high jacking this thread, start another thread if you want to pursue it. 

Bit of a turn up, I said I wasn't familiar with Grundfos.

Not worth the effort I got the hang of it just a question of putting in the effort. Good pump, had it many years now, also have a hose on it which I use regularly.

[sometimewoodworker]

3 hours ago, sandyf said:

You are obviously choosing to ignore this statement.

"19 liters per min at the tap"

Remind us,  how does that compare to the nominal output.

I am not ignoring that, it is the output available from a ½” outlet

 

The available flow with a ¾” outlet is virtually double.