@derek-m 

What do you think of this plumbing software.

https://www.h2xengineering.com/free-trial/

Allegedly calculates Pressure drops , Temperatures , losses from a AutoCAD style front sheet.

If true, just up my street

ian

Posted by: @iantelescope

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@derek-m 

Yes Derek, I agree with you .......... I should have Designed my Heat Pump myself. 

 

External pipe Temperature Sensors?

The Only affordable sensors appear to be K type sensors which attach to the outside of the copper pipes.

This external temperature sensing can be inaccurate if not very inaccurate with the Temperature measurement being the Temperature of the copper , not the water!

 

Internal pipe Temperature Sensors?

These Sensors appear to be very accurate, judging by my experience with my German "Sharky".

Excellent but completely unaffordable.

 

How do you measure internal water Temperatures?

 

ian

The most accurate way to measure temperature would be to use a Resistance Temperature Detector (RTD) such as a PT100, which a fundamental resistance of 100 ohm at 0C. A RTD normally requires a transmitter to convert the resistance value to a 4-20mA or 0-10v dc output.

They are also available in different levels of accuracy.

The actual sensors come in a wide range of sizes and types, I would suggest that you have a look on this website:-

https://www.tcdirect.co.uk/Default.aspx?level=2&department_id=230

Posted by: @iantelescope

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@fazel 

Do you have an heat exchanger ?

Do you have a Buffer ?

First of all, it is not my system, it does not have a heat exchanger nor a buffer, it goes straight to the radiators or to the DHW.

You can watch the DIY installation video of the system here:

Posted by: @iantelescope

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@derek-m 

 

What do you think of this plumbing software.

https://www.h2xengineering.com/free-trial/

Allegedly calculates Pressure drops , Temperatures , losses from a AutoCAD style front sheet.

 

If true, just up my street

ian

 

Maybe you should suggest that your installer uses this system.

Posted by: @iantelescope

↑

 

External pipe Temperature Sensors?

The Only affordable sensors appear to be K type sensors which attach to the outside of the copper pipes.

This external temperature sensing can be inaccurate if not very inaccurate with the Temperature measurement being the Temperature of the copper , not the water!

 

Internal pipe Temperature Sensors?

These Sensors appear to be very accurate, judging by my experience with my German "Sharky".

Excellent but completely unaffordable.

 

How do you measure internal water Temperatures?

 

there's a lot going on in this thread but just want to say something on this specifically. This point is not correct IMO.

Affordable pipe (and room) temperature sensing exists for heating systems, and has been done, by many people who are into this monitoring  . there is LOADS about this on the openenergymonitor forum, there is no point duplicating the discussion here, please go read that forum or start reading their specs here https://docs.openenergymonitor.org/emontx4/other_sensors.html  

I myself have a large setup of DS18B20 sensors monitoring various pipe and room temps (using the easiest install method of taped external metal-to-metal contact to the pipe) and it works well and gives a very usable response time to changes in T, and a very usable accuracy. If you can be bothered to do the plumbing / soldering you can locate it inside a pocket for even better response.

DS18B20's cost about a pound each in 10 packs.

@iantelescope

How would I measure internal water temperature?

I would install a thermowell, into which I would install a suitable temperature sensor, making certain that it had good thermal contact. Depending on the level of accuracy required I would probably use a PT100 RTD.

You of course can use whatever method you wish, and agree or disagree to your hearts content.

@iancalderbank 

hi ian

DS18B20

I have , at the moment , several DS18B20 's attached to the Heat Pump.

These are excellent , but, no reliable pipe clamping system seems to be available.

Several DS18B20 can be used together ...................but each additional DS18B20 decreases the reliability.

DS198B20 's have been copied.

K Type Thermocouples

Clamps with K type thermocouples are readily available .

The K types are faster , but , suffer from voltage  offsets at the plugs/sockets.

Data loggers are available for multiple K Type Sensors.

The Copper problem.

With my system, built , such that all the Copper pipes are physically connected to a common copper mass, low frequencies , and DC Temperatures are often identical, with Higher frequencies, however,  accurate.

ian

@iantelescope like I said, ds18b20's work for me and hundreds of other people, there is umpteen pages on this in energy monitoring forums. I'm just objecting to your statement within this forum,  that "there isn't a usable inexpensive solution to pipe temperature monitoring". There IS. if you don't consider it good enough for your needs, that's a different statement.

clamping wise I use a bit of thermal paste for contact, and then tape it tight. ideally I believe one should use a minimally-stretchy metallic type tape,  but a load of winds of bog standard electrical tape does the job for me. there's people out  there who've soldered copper pockets to the outside that you can find howto video's of.

I do not understand what you are saying about copper mass , low frequencies and DC temperatures (what is a DC temperature?).

With the DS18B20 sensors in the right place and a device that polls the sensor sufficiently frequently and reliably, you can see the response to a change in flow temperature as the HP comes on, very quickly and clearly, in the primary and the distribution circuits and in individual radiators.

Posted by: @iancalderbank

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I'm just objecting to your statement within this forum,  that "there isn't a usable inexpensive solution to pipe temperature monitoring".

a £500-700 monitoring system is cheaper than years of paying £500-1000/year extra bills, on thousands of badly installed systems.

Ultimately one can buy it, set their system over 12 months the sell it on the forum, and so on.

Posted by: @derek-m

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The most accurate way to measure temperature would be to use a Resistance Temperature Detector (RTD) such as a PT100

I have been looking at these, but they are not easily integrated, so far as I can see, into a (and my) USB connected modbus wired system, because the USB port can only provide 5V, and PT100 analog to digital to modbus converters typically need 6V and more often than not more (eg 12V).

I've also tried to find some data on how well (or not...) an externally measured copper pipe temp correlates with the internal fluid temp (which itself perhaps isn't at a uniform temp, though possibly near enough so to be 'good enough'), but haven't found anything useful yet.   

Posted by: @iancalderbank

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@iantelescope like I said, ds18b20's work for me and hundreds of other people, there is umpteen pages on this in energy monitoring forums. I'm just objecting to your statement within this forum,  that "there isn't a usable inexpensive solution to pipe temperature monitoring". There IS. if you don't consider it good enough for your needs, that's a different statement.

clamping wise I use a bit of thermal paste for contact, and then tape it tight. ideally I believe one should use a minimally-stretchy metallic type tape,  but a load of winds of bog standard electrical tape does the job for me. there's people out  there who've soldered copper pockets to the outside that you can find howto video's of.

I do not understand what you are saying about copper mass , low frequencies and DC temperatures (what is a DC temperature?).

With the DS18B20 sensors in the right place and a device that polls the sensor sufficiently frequently and reliably, you can see the response to a change in flow temperature as the HP comes on, very quickly and clearly, in the primary and the distribution circuits and in individual radiators.

I have no doubt that DS18B20's work fine as you have described.

I suppose much depends upon what temperatures you wish to measure and what you intend to do with the data collected.

According to the specification, a DS18B20 has an accuracy of +/- 0.5C, so if the objective is to measure the DT between LWT and RWT on a heat pump, the measurement obtained could be between 4C and 6C for a normal 5C DT. If this obtained value is used in the thermal energy output calculation then the end result could be quite different from the truth.

Obviously these are the possible extremes, so it would be hoped that the end result would be closer to the truth.

To help minimise errors, both sensors should be tested together in water, preferably against a known standard, at approximately the temperature of final use. Any differences between the two readings should be noted, and allowances made when reading and possibly offset when used within calculations.

As you have already noted, when mounted externally any sensors should have good thermal contact and be well secured and insulated to minimise errors.

Posted by: @iancalderbank

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I myself have a large setup of DS18B20 sensors monitoring various pipe and room temps

We may have covered this before, if so apologies: how do you get the DS18B20 data into your monitoring system? I rather suspect the answer is going to involve ESP (electronic not ethereal variety) and HA which as you know I do not have the former, I want to keep things simple, and am not a fan of the latter.