Flow gauges for central heating pipe work

[Jones82]

Whilst installing a new heat only boiler today I thought why don't we have flow gauges, in litres per min, on the flow immediately after the pump and then on the return near the boiler?

This would allow us to see in real time the performance of the pump and the loss of flow around the system.

I've used a flow cup to measure water main performance and I've seen small gauges on underfloor heating pipe work but never seen one on flow and return pipe work.

 

[ShaunCorbs]

Commercial normally to limit flow but nothing to tell you actually the flow through the system

Eg

Balancing valve with flow meter

 

[chris watkins]

The flow from the pump & back to the boiler would be the same Jones82 as it is the primary circuit so only one flow gauge required (it would be a loss of pressure).
I know of heating engineers who are installing the Caleffi Balancing valves in domestic systems and by all accounts they work well, allowing the flow rate (amount of heat) to be accurately set & they aren't too expense.
However they don't give you real time flow rates as you have to pull the pin to allow water through the measuring / sight tube.

 

[Jones82]

Hmm interesting, I did halve think this. But thought the flow might be greater after the pump, on the positive side? Also the values would change as each radiator or zone closed and opened?

How about two pressure gauges, with a small range, 0-1 bar for example to measure how much the pump is pushing and how much pressure loss there is around the system.

It occurred to me that we use logical thinking a lot in plumbing rather than actual gauges. For example, its hot so its working!

Perhaps in the future the gauges will be digital.

Boilers take readings in order to regulate and modulate accordingly. So perhaps its just a case of putting these readings on a screen or an app.

It would be nice to see the performance of the system in real time, as zones opened and closed or even individual radiators.

 

[ShaunCorbs]

Hmm interesting, I did halve think this. But thought the flow might be greater after the pump, on the positive side? Also the values would change as each radiator or zone closed and opened?

How about two pressure gauges, with a small range, 0-1 bar for example to measure how much the pump is pushing and how much pressure loss there is around the system.

It occurred to me that we use logical thinking a lot in plumbing rather than actual gauges. For example, its hot so its working!

Perhaps in the future the gauges will be digital.

Boilers take readings in order to regulate and modulate accordingly. So perhaps its just a case of putting these readings on a screen or an app.

It would be nice to see the performance of the system in real time, as zones opened and closed or even individual radiators.

Have you been on the imi course if not it’s a great day I would recommend it

 

[John.g]

Hmm interesting, I did halve think this. But thought the flow might be greater after the pump, on the positive side? Also the values would change as each radiator or zone closed and opened?

How about two pressure gauges, with a small range, 0-1 bar for example to measure how much the pump is pushing and how much pressure loss there is around the system.

It occurred to me that we use logical thinking a lot in plumbing rather than actual gauges. For example, its hot so its working!

Perhaps in the future the gauges will be digital.

Boilers take readings in order to regulate and modulate accordingly. So perhaps its just a case of putting these readings on a screen or an app.

It would be nice to see the performance of the system in real time, as zones opened and closed or even individual radiators.

Hmm interesting, I did halve think this. But thought the flow might be greater after the pump, on the positive side? Also the values would change as each radiator or zone closed and opened?

How about two pressure gauges, with a small range, 0-1 bar for example to measure how much the pump is pushing and how much pressure loss there is around the system.

It occurred to me that we use logical thinking a lot in plumbing rather than actual gauges. For example, its hot so its working!

Perhaps in the future the gauges will be digital.

Boilers take readings in order to regulate and modulate accordingly. So perhaps its just a case of putting these readings on a screen or an app.

It would be nice to see the performance of the system in real time, as zones opened and closed or even individual radiators.

"Perhaps in the future the gauges will be digital."
The future is already here if you have certain models of Grundfos circ pumps..I think the Alpha 3 displays both the pump head and the flow rate which can be very handy. Practically all the replacement pumps now display the power in watts and the head and flow can then be derived from the pump curves, a bit messy but the info can be extracted if required.

 

[Rob Foster]

Whilst installing a new heat only boiler today I thought why don't we have flow gauges, in litres per min, on the flow immediately after the pump and then on the return near the boiler?

This would allow us to see in real time the performance of the pump and the loss of flow around the system.

I've used a flow cup to measure water main performance and I've seen small gauges on underfloor heating pipe work but never seen one on flow and return pipe work.

This is a great idea if you want help developing it UkPlumbing & Heating Innovation Centre .is a not for profit organisation in its embryo stage set up to help develop projects from conception thro to production and sales. Mike Clement and I set it up and we have backing assured ...let me know
Rob Foster aka centralheatking

 

[Rob Foster]

"Perhaps in the future the gauges will be digital."
The future is already here if you have certain models of Grundfos circ pumps..I think the Alpha 3 displays both the pump head and the flow rate which can be very handy. Practically all the replacement pumps now display the power in watts and the head and flow can then be derived from the pump curves, a bit messy but the info can be extracted if required.

loads of boilers already know this stuff in their little brains but dont tell anybody
Rob Foster

 

[doitmyself]

This would allow us to see in real time the performance of the pump and the loss of flow around the system.

There will be a loss of pressure around the system, due to the friction created by water flowing through the pipes. But the flow out of the pump must be the same as the flow into the pump. If it's not, where is the extra water coming from?

 

[Stu-B]

Something else to block up with sludg

 

[Rob Foster]

Something else to block up with sludg

However an inteligent pair of flow meters, cleverly sited, over time would be able to indicate sludge and debris build up esp when tied into the demands of the pump/s drawing more power to compensate...its a winner esp in the next generation of homes with mini BMS when the domestic system reports back ..to a monitor station ..already seen it a few months ago in North West England. Stuff like hive is so intermediate the next stage is automatic monitoring and reporting
and its a game changer and just around the corner.
Rob Foster aka centralheatking

 

[Rob Foster]

loads of boilers already know this stuff in their little brains but dont tell anybody
Rob Foster

Modern cars have a multiplug socket which the micknick connects to and then off he goes...this is potentially available in most modern boilers BUT guess what for the sake of a multi comnnector they dont...but rely on magical fault codes on an display...with secret sequences to stop mortals finding out whats wrong...a bit like masonic funny handshakes ...chking...this is not really my area of
centralheating component design but obviously I touch on it at
the odd meeting ...and listen it would be silly not to
Listen to everything !

 

[chris watkins]

Something else to block up with sludg

In 1980 I installed a complete heating system with Ideal W wall hung gas boiler for my Grandad & Nan, I took the revolutionary step of adding Fernox MB1. For the next 25 years I serviced it yearly & drew a sample from the drain offs it remained crystal clear if slightly yellow.
Look after your systems & forget about sludge!!!

 

[Jones82]

Thanks, just thinking out loud to be honest!

Its not "extra water" or "less water" but loss of pressure or flow.

For example

Imagine you had a pressure / flow gauge on your outside tap as soon as it comes out the wall. Then imagine you have one on the end of the hose pipe after its run 20m down the garden. Surely the gauges would read different values?

Now translate this to a heating system.

How do we know the flow or pressure of the system at the furthest radiator? We can measure temperature and balance the system accordingly but what if its an excessive run, or badly designed pipe work?

As plumbers we make alot of logical decisions and I just thought surely the technology exists to give us a clearer image of the heating system and how it works.

 

[doitmyself]

How do we know the flow or pressure of the system at the furthest radiator? We can measure temperature and balance the system accordingly but what if its an excessive run, or badly designed pipe work?

I don't see how measuring the flow and pressure will tell one anything about the run or pipework. If a pipe has to be run from A to B, common sense, or measurement, will tell one if a shorter run is possible; and there are tables available which give recommended pipe sizes, depending on the required flow.

In any case it's not the pressure at a particular point which is important, but the pressure difference between two points, e.g. either side of a radiator.

 

[John.g]

Granted, but I don't think any installer would mind having this sort of info available.

 

[Jones82]

Your looking at this from a design point of view doityourself. I'm looking at it from a maintenance point of view.

I often work on old heating systems where its impossible to see the original pipe runs. I've no idea what pipe they've used and where or how many fittings. Anything could be happening under a floor or buried in a wall.

And I did say two gauges, so i'd be looking at the difference between the two.

The house I was working on had 5 heating zones. So I'm thinking in theory a gauge after the pump and a gauge on the return near the boiler would read different readings as each zone opened and closed.

I'm still not sure if they would read pressure or flow though.... Also would the gauge on the return be better positioned at the furthest point of the system..? The pump gauge would likely remain fairly static at 10l min for example but the other gauge might read 8l if one zone was open or 5l if two zones were open.

That was a very loose example. But my point is we know we lose performance through frictional resistance, surely we can measure this?

 

[doitmyself]

John.g

Which device gives you that information?

It's interesting but only tells you what is happening at one point; and unless you have something to compare it with, e.g. calculations as to what should be expected, it's meaningless.

 

[Harvest Fields]

I like that idea. Patent it quick before @Rob Foster gets there.

 

[John.g]

John.g

Which device gives you that information?

It's interesting but only tells you what is happening at one point; and unless you have something to compare it with, e.g. calculations as to what should be expected, it's meaningless.

Searchbox "Grundfos Alpha 3 Pump settings for hydronic balancing".
If every circulating pump had a differential pressure gauge fitted (never happens) then just from this one gauge alone and access to the pump curves, one can tell a lot, as I stated above virtually all replacement circulating pumps now display as a minimum, the power in watts, and this can be used to derive the pump head/flow which surely can be useful if one cares to avail of it, it costs nothing as it comes with the replacement pump.

 

[chris watkins]

If you fitted flow gauges to the system they would read the same, if pressure then the one on the outlet of the pump would read what the pump head is being delivered and the one on the other end would be pump head less the frictional loss to that point.

 

[doitmyself]

The house I was working on had 5 heating zones. So I'm thinking in theory a gauge after the pump and a gauge on the return near the boiler would read different readings as each zone opened and closed.

I'm still not sure if they would read pressure or flow though.. Also would the gauge on the return be better positioned at the furthest point of the system..? The pump gauge would likely remain fairly static at 10l min for example but the other gauge might read 8l if one zone was open or 5l if two zones were open.

If there are two flow gauges, one each side of the pump, they must both read the same; but what it reads will depend on which zones are open. You can't have 10 litres leaving the pump but only 8 litres entering. Where have the two litres gone to, only to magically reappear at the pump?

Pressure gauges will show different readings; but this will depend on the pump setting.

But my point is we know we lose performance through frictional resistance, surely we can measure this?

The frictional resistance is much higher than needed because heating engineers do not understand how systems work. They have the idea, passed down from earlier generations, that the water has to be forced through the pipes, so the pump needs to be on the highest setting. This is incorrect. The pump only needs to be able to provide sufficient pressure to feed the index rad (the one with the greatest pressure loss). All other rads obtain their feed by having the correct pressure drop across the rad, i.e between flow and return Tees. (Water automatically flows from high pressure to low pressure.) Correct balancing will achieve this; and this involves more than "set all up stairs rads to fully open and downstairs to half open" or "TRVs do not need balancing as they are 'self-balancing'".

 

[Plumbthatin]

Good afternoon all,

What you are discussing here in essence is what is used in all modern commercial and industrial systems and to some degree in old systems too.

In years gone by old systems would use many manual gauges and controls which helped both during the commisioning process of a system and during fault finding and maintenance tasks. The gauges and controls would include

Pressure gauge - on primary flow from heating appliance(s)

Temperature gauge - on primary flow from heating appliance(s)

Pressure gauge - on primary return from heating appliance(s)

Temperature gauge - on primary return from heating appliance(s)

Temperature gauge - on each VT & CT circuit flow

Temperature gauge - on each VT & CT circuit flow

Pressure gauge - on each side of every pump

Wheel head Gate valves - used for isolation purposes only and should have been fitted fully open

Lock shield gate valve - used for isolation and balancing purposes, valves setting would be listed on a valve schedule as how many turns it should be closed and should be updated during the course of the systems lifetime whenever altered

There was of course many more gauges and valves placed around the system but the above In Essence was your initial controls for the system. In todays systems they have become much more complicated and now include temperature balancing valves, flow regulating valves, pressure independent control valves, double regulating valves to list but a few, each with there own specialised use and to be fitted where appropriately specified.

Progressing even further than this, most controls and system reporting are also incorporated electronically via system automation such as Building management systems. These use electronic signals provided to a computerised system (some mechanical versions exist in previous systems) via temperature probes, pressure probes, pressure differential switches, pump Information links, external weather sensors, internal temperature sensors, weather forecasting information to name a few. The closest domestic comparison to these is a weather compensation system I believe.

It’s a very in-depth subject and the above is just a short insight into what the commercial and industrial market currently utilises but I can imagine in coming years as we all look to optimise our systems that it may become much more common place to see the kind of devices incorporated into the domestic market.

I believe the main things holding back the domestic market from increased controls and system optimisation is the financial side as these items become exceptionally expensive especially when compared to the forecasted payback of such components.

 

[Jones82]

"If there are two flow gauges, one each side of the pump, they must both read the same; but what it reads will depend on which zones are open. You can't have 10 litres leaving the pump but only 8 litres entering. Where have the two litres gone to, only to magically reappear at the pump? "

But 10 litres is 10 l per min, so the water hasn't "disappeared" its just moving slower due to the restriction in the system?

For example some people get 20l per min from their kitchen tap, I only get 12l min due to my water main performance being worse than theirs.

So if there was a gauge at the pumping station it would read 20l min but my tap 10 miles away only 12l min?

 

[Jones82]

"The frictional resistance is much higher than needed because heating engineers do not understand how systems work. They have the idea, passed down from earlier generations, that the water has to be forced through the pipes, so the pump needs to be on the highest setting. This is incorrect. The pump only needs to be able to provide sufficient pressure to feed the index rad (the one with the greatest pressure loss). All other rads obtain their feed by having the correct pressure drop across the rad, i.e between flow and return Tees. (Water automatically flows from high pressure to low pressure.) Correct balancing will achieve this; and this involves more than "set all up stairs rads to fully open and downstairs to half open" or "TRVs do not need balancing as they are 'self-balancing'"."

"Heating engineers do not understand how systems work" is an inflammatory statement, I'd question your motives in making such a statement.

Its generalising, unhelpful and irrelevant.

I know how to balance a system, I was taught to obtain an 11 degree difference, now 20 degrees incidentally. But again the reality of domestic heating systems is they are often undersized, they are often tampered with and they are often poorly maintained.

Enter the humble heating engineer, trying to make a living, trying to make everyone happy and trying to solve the problem with out breaking the bank.

I do agree with one thing you said which is I was taught by old school plumbers who used a lot of rule of thumb, its hot so it works, its cold so turn the pump up.

This is all besides the point. Better information about the system would lead to better solutions and greater understanding, which is what this post is about.