Noninvasive flow measurement

[Beelbeebub]

I was having a think and one of the issues with retro fitting HPs is "oh you need to replace all your pipes for bigger ones" 

 

This is apart from upgrading the radiators. That can be relatively simple, in some cases a straight swap from a singkenoanelnradnti a double or even triple finned rad. Pretty quick and easy. 

 

But if you have to start ripping floors up etc it gets costly and disruptive quickly. 

 

The key thing is the flow rate. If the pump can push the required flow at a velocity that doesn't cause problems you're fine. 

 

So, when a plumber comes to a job it would be great if they  know what the pipework is capable of flowing at the moment, it might be enough. 

 

Which is where non invasive flow measurement comes in....

 

The kit is as low as a few hundred £ (though can be more). 

 

Plumber could come in, stick the boiler pump on full power and measure the system flow at various points to see if any pipes need replacing. 

 

Anyone aware of this happening? 

[TonyT]

What about one of these, let you see existing flow rates, play with pumps etc 

 

 https://midsummerwholesale.co.uk/buy/renewable-heat-accessories/taconova-tacosetter-inline-100-DN-20

 

 

[Beelbeebub]

7 minutes ago, TonyT said:

What about one of these, let you see existing flow rates, play with pumps etc 

 

 https://midsummerwholesale.co.uk/buy/renewable-heat-accessories/taconova-tacosetter-inline-100-DN-20

 

 

Yeah, but you'd have to cut into the circuit with all that entails. And would only give a single point measurement. 

 

For example you could tell you had enough flow in the system but maybe the flow to upstairs was too low. 

 

If this could be fitted to any exposed pipe you could go from rad to rad and measure the actual flow availible to each rad. Might only take half an hour to survey a house and say "yeah this pipework is fine" which could cut a load of work out of the job. 

 

I did see clamp on no invasive heat meters. These would be really good if it integrated with some room and outdoor sensors. 

 

You could basically measure the actual heat demand of the house over a few days and if you got enough temp variance about automatically generated a demand curve. 

[TonyT]

Ah get it, can you post a link to a heat meter you were describing just interested 

[JohnMo]

What you need is a strap on ultrasonic flow meter.

 

Or you could just use a look up table, like on heat geek. From the heat loss calculations you will know what each section of the heating system needs to supply in kW. Use the look up table to manipulate the flow rates and dT if required.  Maybe small sections of a header will need up sizing.

[sharpener]

Not quite an integrated heat meter but a useful intro here.

 

I used to work for the firm that developed the first u/s gas meters. You have to make assumptions about the flow profile across the pipe, I don't exactly know how they do it.

[Beelbeebub]

Just now, JohnMo said:

What you need is a strap on ultrasonic flow meter.

 

Or you could just use a look up table, like on heat geek. From the heat loss calculations you will know what each section of the heating system needs to supply in kW. Use the look up table to manipulate the flow rates and dT if required.  Maybe small sections of a header will need up sizing.

Yes that's exactly what I'm talking about. 

 

You could use the table but that only gives you a rough estimate. 

 

You might have 28mm pipes heading out of the boiler, but they drop down to 15mm in some boxing before meandering about all over the place.

 

Or, as has happened to me on a boiler system, you think the issue is the pipes are 15mm but it turns out it's actaukky 22 all the way to just before it pops up above the floor and you're fine. 

 

Measuring the actual flow has to be the gold standard. 

[Beelbeebub]

2 minutes ago, sharpener said:

Not quite an integrated heat meter but a useful intro here.

 

I used to work for the firm that developed the first u/s gas meters. You have to make assumptions about the flow profile across the pipe, I don't exactly know how they do it.

Yeah, something like that and i'm sure there is all sorts of clever magic going on under the hood. 

 

If they could make a £100-200 unit, maybe some bt sensors that link to your smartphone like the bt temperature clamps, so you could just clip it on and hey presto you've got the flow..... That would be really useful. Be great for tuning the emmiter output too. 

 

[JohnMo]

Your ok with 15mm in a lot of cases, I have a 2 port UFH manifold fed from the main header in 15mm Hep2O, approximately 6m each way. Zero issues with flow rate.

[Beelbeebub]

6 minutes ago, JohnMo said:

Your ok with 15mm in a lot of cases, I have a 2 port UFH manifold fed from the main header in 15mm Hep2O, approximately 6m each way. Zero issues with flow rate.

I'm sure it is in a lot of cases.  But there is the persistent assumption that you need at least 28mm thought your 1 bed flat to go with a couple of 2000x800 triple fin rads per room (not to mention a 150l buffer to go with your 18kw heatpump). 

 

Being able to stick a gizmo on the flow pipe of your booker and go "yup plenty of flow, no need to rip UK the floor or repwmce any pipes" would be a big time saver and eliminate a potential cause of poor performance. 

[JohnMo]

As posted by yourself

15mm fine for a 2 to 3 of kW.  I am also stuffing 6kW (0.96m3/h) through about 10-12m of 22mm Hep2O, but that needs the assistance of a second pump in the return line. So various ways around an issue.

 

8 minutes ago, Beelbeebub said:

But there is the persistent assumption that you need at least 28mm thought your 1 bed flat to go with a couple of 2000x800 triple fin rads per room

We all know that mentality will continue, given a magic bullet or not. 

 

10 minutes ago, Beelbeebub said:

not to mention a 150l buffer to go with your 18kw heatpump

That may be required the way most people seem to want a zillion zones all over the house.

 

Sticking a gismo on a random pipe is sh**e in sh**e out. It doesn't tell you much about how the water is being distributed, is it just opening a bypass valve, funnelling through a big section of pipe and then short cutting past most the system.

[markocosic]

Metering is my day job.

 

 

Clamp on meters are naff and fairly spendy. Micronics U1000 is the benchmark. Retail £1000 apiece.

 

 

Inline meters in small sizes are cheap as chips and easy enough to cut into an existing system if you're serious. Consider it part of the survey. Replace with a spool piece (spacer) if you decide not to go ahead with a heat pump install.

 

A DN20 meter (130 mm x G1" body) is £130.

A DN25 meter (260 mm x G 1 1/4" body is £175.

 

Meter unions go from 1" flat face couplings to a 3/4" male thread. (pair with 3/4" female to 22 mm compressions) Or from 1 1/4" to 1" male thread. (pair with 1" female to 22 mm or 28 mm compressions)

 

Use selective isolation to work out what the flowrates in branches are. Start with everything on. (so that pipes are showing full pressure drop) Then isolate one radiator. The difference in flow is what that radiator was flowing. Then turn it on again and isolate something else etc.

 

 

I wouldn't bother personally. Guestimate based on what you know about what you have. If the primaries are short you'll be ok.

 

 

Piping a 6 kW (old school fixed speed ground source) heat pump into 22 mm copper then a 200 litre volumiser (tank in series) then 1" manifolds to 16 mm MLCP to some rads is a job for me for the next couple of weeks. 🙂

[Gus Potter]

4 minutes ago, Beelbeebub said:

Measuring the actual flow has to be the gold standard. 

 

1 hour ago, Beelbeebub said:

This is apart from upgrading the radiators. That can be relatively simple, in some cases a straight swap from a singkenoanelnradnti a double or even triple finned rad. Pretty quick and easy. 

 

But if you have to start ripping floors up etc it gets costly and disruptive quickly. 

A few random thoughts from me.

 

If you are upgrading to a heat pump than that it some serious expenditure. I would want to make sure that my existing pipes supplying the rads are clean as I can get them so that means a good flushing... which is kind of what you are thinking about.. making sure the pipework is able to support the heat pump system.

 

What if you start by flushing your existing system and where the flush water comes out attaching a filter ( magnetic) so you can see how much crap is in the system. You can use the mag filter later on anyway. This is good for the sole not least.

 

Next if you get a hose pipe and run that off the mains water supply to where the outlet of the pump is going to be then you can measure the flow rate that comes out the hose with a bucket. You could do this with three rates of flows out the hose. Call this the inlet hose... the idea is you calibrate the flow rate out of the hose. You could just use a gate valve and say.. one turn open gives me x litres per sec.. two turns y flow rate. Just check what pressure variation the waterboard supply at.. could be pretty constant if you do it the same time each day.

 

Next isolate all the rads (which you are going to change anyway?) apart from one.

 

Put a pressure gauge on the flow just after the existing pump (flow side) so you know the pressure just after the water from the hose enters the system. Buy gauges that you are going to use later.

 

Attach another hose to the return side close to say where the return for the boiler is and run that into another bucket outside. Attach a pressure gauge here to just where the water comes out the return side so you don't capture the losses in the exit hose.

 

Now turn on the hose and measure the flow rate and pressure on exit. I have to go back to my Hydraulics for the equations but if you know the inlet pressure and the exit and flow pressure you can calculate the losses in the loop you are examining.

 

Do this for the three different inlet hose flow rates you have calibrated the hose for. In terms of flow what goes in has to come out the other end so I think from memory you have three variables and from that you can calculate the losses in the loop you are looking at..the losses gives you the head loss in the loop which you need to size the pumps etc. If you do this with the three different flow rates from the inlet hose it lets you then see how the different inlet pressure = pump head which impacts on the performance of the loop.

 

Now you know about your existing system with the rads you have. If you swap out all the rads then the short bit between the rad inlet and outlet should not make much difference.. its the pipes that you need to know about and if you change the type of TRVs at the rads. But if you swap all the TRVs for the same type it just shifts all the loop resistances by the same amount.. which you can adjust when you put in your the Heat pump system.

 

The next bit is the hard bit maths wise. You now know the loop resistance of each loop when all the other rads are turned off.

 

Go back and turn them all on and repeat the above but with all the rads open. This will give you the head loss for the whole heating system.

 

If you then compare the losses for each loop (with all the other rads off) then you should be able to see if you have problem loops. Then you can work out what to do about that.

 

But you also now know what the head losses are when all the rads are open.. so now you can start to design your heat pump system based on this is the worst it is going to be. You are going for larger rads and so on.

 

The upside!

 

1/ You'll need or need to learn some basic plumbing skills. But if you do this then you will be well set when you come to look at the plumbers work, have a sensible discussion and keep costs down.

 

2/ You will get a huge amount of enjoyment playing about with it, even if it's just a case of cleaning crap out the existing system.. you'll save some money for good use later and learn enough so the plumber does not take the mickey out of you.

 

3/ You may find that you don't need a HP at all and can splash out on other things..

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Beelbeebub]

All fair points, especially splicing in an inline mechanical meter then shitting various rads. 

 

My musing was more a simple first take device. Before any major work is done, to aid with the quote process.

 

If the pipe work needs lots of upgrades it will.add to cost and upheaval and might male the job less attractive. Better to find out before install starts! 

[Gus Potter]

3 minutes ago, Beelbeebub said:

My musing was more a simple first take device. Before any major work is done, to aid with the quote process.

By all means give that a go.

 

Much will depend on you enthusiasm for getting stuck into this bit of your project and if you have the time to play about with it.

 

In the last post I mentioned doing calculations etc. But if you want to just check that your loops to each rads work ok ish then you could just do the first part with the hose thing.. that at least will let you identify any really bad loops if there are any.

 

The heat pump thing is a big outlay.

 

How are you on diy plumbing?

 

if you want post some photos of the boiler pipework you have and folk will chip in as to how you can break into the pipework easily using DIY plumbing fittings.

 

Oh I forgot to mention. If you are flushing the system to investigate make sure you top up the inhibitor to keep things ok in the short term.

 

 

 

 

[sharpener]

If you have got a working (boiler) system to begin with you can learn a lot by comparing how long it takes the individual rads and their return pipes to heat up.

 

Ideally they should all take about the same amount of time, then the flow rate is proportional to the volume of each rad which if they are of similar construction will be directly related to the heat output rating.

[Gus Potter]

54 minutes ago, sharpener said:

If you have got a working (boiler) system to begin with you can learn a lot by comparing how long it takes the individual rads and their return pipes to heat up.

 

Ideally they should all take about the same amount of time, then the flow rate is proportional to the volume of each rad which if they are of similar construction will be directly related to the heat output rating.

Yes that would work I think to help you identify the loops that are not performing... which is what we would do normally.. we just walk round the house and put out hand on the radiators.. and go.. hey.. that radiator is not working that well.

 

But if I was going for a 10k plus heat pump I would want to know more about my existing pipework so I don't get shafted by the installer.

 

 

 

[Beelbeebub]

10 hours ago, Beelbeebub said:

All fair points, especially splicing in an inline mechanical meter then shitting various rads. 

That should be shutting various rads..... 👀😁

[markocosic]

On 31/08/2023 at 11:09, Beelbeebub said:

That should be shutting various rads..... 👀😁

 

And an ultrasonic meter not a clockwork meter; for performance at low starting flow rates.