VDI 2035 heating system water

[JohnMo]

Anyone using VDI 2035 spec for heating water in an ASHP.

 

Been looking at it seems a smart way to go. No chemicals to turn into a muddy soup, good heat transfer etc. Monitor with a simple conductivity meter and pH meter to control to quality of the water going into and in the heating system 

 

By monitoring 

Conductivity (80 to 1550 microsiemens)

Ph 8.2 to 10

And Scale products below 300ppm

 

Any one using are there issues?

What if any fitters are you using

Do you top up via an Ion exchanger or just tap water (of suitable quality)?

[Dreadnaught]

In case anyone else is not familiar with "VDI 2035", as I wasn't, this is a good quick intro…

 

https://www.heatgeek.com/heating-water-treatment-explained-vdi-2035/

[Nick Laslett]

I just read the Heat Geek VDI explainer, I think it needs a TLDR section. 
 

I filled my UFH loops with water from my Harvey water softener. Not using any anti-freeze. A low temp ASHP based UFH system seems like it will suffer from very little corrosion. Not anticipating ever having to drain down the system and refill. 
 

All the pipework is barrier pipe, very little metal. Do the stainless steel manifolds corrode much or let air in?

[JohnMo]

2 hours ago, Nick Laslett said:

TLDR

What's that mean?

[billt]

Too long, didn't read or similar. (Wants the precis because people don't like lots of words.)

 

No inhibitor in my system so you could call it VDI 2035 if you wanted to be pretentious. I've long been sceptical of the value of chemical additions to a properly sealed system.

[Nick Laslett]

1 hour ago, JohnMo said:

What's that mean?

Sorry, it means “Too Long, Didn’t Read”. I felt the primer needed a good summary, before getting into the details. I read the whole thing, but I felt some people will struggle to maintain their interest to the end. . 

[sharpener]

56 minutes ago, Nick Laslett said:

I felt some people will struggle to maintain their interest to the end.

 

Some of it just plain wrong e.g. "It's not always necessarily worth testing the tap waters pH as this should always be between 7.2 and 7.4ish."

 

The statutory range for potable mains water in the UK is in fact pH 6.5 to 9.5 see e.g. this web page.

 

Vaillant say for their HPs (after a load of stuff about VDI 2035, at least they got the inequality in the first line of the table right)

 

 

My experience of Fernox F and Sentinel X100 is that they do prevent steel radiators from corroding (based on doing the "nail test" every couple of years).

 

Previous installer was proposing to fill system with "1x25litre SECON T Glycol", presumably it has some inhibitor action. New installer is proposing to fit anti-freeze valves, I have given in on this point, bigger fish to fry. Will ask if he intends to use inhibitor after he has flushed the system. Will also make sure he fills system with mains water as is noticeably more alkaline than the treated rainwater.

 

[JohnMo]

So been looking and it seems a good little project.

 

Everything labeled as VDI 2035 seems to come at a premium price, so been looking at alternatives to get very low conductivity water, with hopefully a suitable pH.

 

So have ordered

10" clear filter housing with 3/4" ports. With Hozelock fittings.

A refillable housing for DI resin media.

Purolite MB400IND Mixed Bed Indicator DI resin - which is 60% Anion/40% Cation.

 

The Anion increased percentage should strip out the CO2 to hopefully leave a slight alkaline water.

 

So idea is flush system with my hard water to get the glycol out. Then flush via the resin filter with low conductivity water.

 

Then leave in place connected via the fill and flush manifold for any top-up required. And use the garden hose connector to give top ups.

 

[JohnMo]

On 24/07/2024 at 13:06, Nick Laslett said:

Harvey water softener.

Doesn't that add to the conductivity. Not an issue for plastic pipe.

 

Stainless in the heat exchanger - with salts and 60 degs can lead to putting corrosion, which could be an issue. Could you also get bug growth?

[JohnMo]

On 24/07/2024 at 16:55, billt said:

VDI 2035 if you wanted to be pretentious

Not really pretentious, just a standard, bit like saying building regs xxxx.

[Nick Laslett]

3 minutes ago, JohnMo said:

Doesn't that add to the conductivity. Not an issue for plastic pipe.

 

Stainless in the heat exchanger - with salts and 60 degs can lead to putting corrosion, which could be an issue. Could you also get bug growth?

John, I’m not sure what you mean? Admittedly I only watched a few YouTube’s on filling UFH loops. They  just seemed to use the mains supply. Not sure if the output from the water softener is particularly salty. But the water here is very hard, so the lesser of 2 evils. For the ASHP, the choice seemed to be add antifreeze or antifreeze valves. My ASHP is only used for heating, DWH is a separate system, so temps should rarely hit 32°-34° in depths of winter. 

[JohnMo]

1 minute ago, Nick Laslett said:

John, I’m not sure what you mean? Admittedly I only watched a few YouTube’s on filling UFH loops. They  just seemed to use the mains supply. Not sure if the output from the water softener is particularly salty. But the water here is very hard, so the lesser of 2 evils. For the ASHP, the choice seemed to be add antifreeze or antifreeze valves. My ASHP is only used for heating, DWH is a separate system, so temps should rarely hit 32°-34° in depths of winter. 

If you are not doing DHW then maybe not an issue. But the heat geek text says

" salt based softened water. The different makeup of the water can mean the self-alkalization process settles above 10 which is not healthy for aluminium systems and can affect the warranty of boilers that have heat exchangers made of it." May be worth getting some litmus paper and testing where you are.

 

Industry has a big issue with most grades of stainless steel in saline environments when the temperature hits 60 degs and get what is called pitty corrosion. Basically for pin holes in the metal. Most likely the ASHP heat exchanger will be stainless.

[Nick Laslett]

43 minutes ago, JohnMo said:

If you are not doing DHW then maybe not an issue. But the heat geek text says

" salt based softened water. The different makeup of the water can mean the self-alkalization process settles above 10 which is not healthy for aluminium systems and can affect the warranty of boilers that have heat exchangers made of it." May be worth getting some litmus paper and testing where you are.

 

Industry has a big issue with most grades of stainless steel in saline environments when the temperature hits 60 degs and get what is called pitty corrosion. Basically for pin holes in the metal. Most likely the ASHP heat exchanger will be stainless.

The article is not as clear as it needs to be, in another paragraph it states:

 

Quote

If you do have system fill water that you've measured above 300 parts per million, you may decide to use a softener to fill the heating system.

I’m definitely in the 300+ region for hardness. They then go on the say:

 

Quote

Now that is fine, but you should be aware that these can increase the conductivity and you need to be careful that you don't allow it to go above 1500 micro siemens

Which is good, but in layman’s terms how easy is it to measure micro siemens? Not sure where that was covered in the article?

 

Found this guide on Google, which seems simple enough. 
 

https://sciencing.com/measure-conductivity-water-multimeter-8523350.html

 

Found my local water report, the micro siemens before softening was 800. 
 

According to this website, softening water with ion exchange does not increase its conductivity. Not sure if this is true, but…

 

https://www.heylneomeris.com/en/conductivity-measurement-water-hardness-measurement/

 

I was more alarmed by the “bug growth” statement. Is this a concern in a closed system?

 

Edited July 25 by Nick Laslett

[JohnMo]

4 minutes ago, Nick Laslett said:

how easy is it to measure micro siemens?

You need a gauge or tester. Will be looking for that next. Quick look looks like about £30.

[JohnMo]

So decided to install a permanent TDS and Conductivity meter and use Litmus Paper for pH. The one I got from Amazon read a range of pH from 6.2 to 9.0 in 0.4 steps, so should be just fine.

 

PH strips were £13 from Amazon

TDS and Conductivity meter £72 delivered from

https://www.osmotics.co.uk/lsm-100-commercial-grade-ec-tds-monitor.html?srsltid=AfmBOoqFcuTcWCe4eDl0kmA0H5AQqIF1z8Tk2OK6b2HGYpfNUt08T7Re

 

10" clear filter £25

Clear refillable resin insert £8

Some fittings £8

On 25/07/2024 at 16:34, JohnMo said:

Purolite MB400IND Mixed Bed Indicator DI resin

2x 1lt, £32.

 

Total spend around £170. I will have in-line monitoring also within that cost, instead of having to drain a sample and test; so I can keep on top of the system very easily. The parts will be used as a filler unit first, via a flushing point, then modified to make a top up unit at the top up point.

 

Total spend is around £70 cheaper than a cartridge top up unit from Viessmann Direct. And if I wanted a new cartridge they are around £140. Loose media is £16.

 

[sharpener]

Have been monitoring the acidity of my harvested rainwater for several years. Found litmus strips/pH test paper very unreliable and was advised against using them on low conductivity water by a helpful person at SWW technical support. Asked Camlab (reputable lab supplier) for advice but their test papers have very poor colour change.

 

Meters are not good either for occasional use as the probes need special looking after and periodic recalibration.

 

Ended up using these test drops, much more sensitive and economical to use, 1 drop is enough for strong colour changes, can now reliably and repeatably measure to 0.5 pH. (Have to do some tests tmrw so will check newly bought against 2 y.o. and report if there is any discrepancy.) Wouldn't buy any of the other overpriced "health" rubbish they sell though!

[JohnMo]

7 hours ago, sharpener said:

Meters are not good either for occasional use as the probes need special looking after and periodic recalibration.

I found that when I was looking.

 

7 hours ago, sharpener said:

Ended up using these test drops, much more sensitive and economical to use

Thanks for the drop info, have ordered a bottle.

[sharpener]

 

 

5 hours ago, JohnMo said:

Thanks for the drop info, have ordered a bottle.

 

IME the colour card is not quite accurate, pH 7.5 is a beautiful cyan colour not the pale blue shown on the card. 1 drop in 5ml is adequate strength. Swirl and then leave 1 min for colour to develop/stabilise.

 

Results are reassuringly stable, no detectable difference in colours between drops bought this month and two years ago, over the following range:

 

4.0 - Rice vinegar

6.3 - Rainwater supply from 5000 l tank (after bulk treatment with 900 g Juraperle and 100g magnesite, and then 100g sodium bicarbonate added per 1000 l drawn off)

6.6 - Rainwater supply via DHW tank (after cooling)

7.8 - Cold water from mains (SWW ex Avon Dam on Dartmoor after their treatment with alkali)

8.0 - Stock bicarbonate solution (100g in 2 litres)

 

[JohnMo]

On 23/07/2024 at 16:45, JohnMo said:

Conductivity (80 to 1550 microsiemens)

Ph 8.2 to 10

And Scale products below 300ppm

Got my meter today, similar size to a smart phone, so you don't need your glasses on the read the digits.

 

Just tested some tap water

Conductivity is 305 microsiemens

Scales produced (dissolved minerals) is 145 ppm.

 

 

So my tap water comes in fine. But higher than I would like, so will be treating it.

 

Ran tap water through the ion exchange resin, it seems to drop the dissolved minerals to about 45 ppm and half the conductivity to 150 microsiemens. A bit of playing with flow rates required to see how it changes. Have added a cheap hose pipe flow meter, then I can repeat a flow rate and also see the quantity of water I have, flushed out or added to system.

[JohnMo]

   

Basically started flushing yesterday by slowly pushing out the old heating water with demin (ion exchange) water at a rate of around 1L/min. The old stuff was brown and smelling very unhealthy. When I stopped last night is fully clear, but you could still smell the glycol.

 

System was left to circulate overnight. 

 

This morning. Moved to having the ASHP circulation pump on and slip steaming demin (ion exchange) water in, so 1 litre in 1 litre out, this morning and got the water to just better than tap water. 

 

Checking tap water and circulation water at the same time.

 

Tap

Dissolved solids 180ppm

Conductivity 380 microsiemens

Circulation water

Dissolved solids 166ppm

Conductivity 320.

 

Now have a side stream set up to push circulation water into the ion exchange filter, without adding new water. Aiming for below 150 ppm dissolved solids or below - currently at 166 compared to tap water of 180 ppm. 

 

Using a simple garden hose flow meter from B&Q.

 

One thing that surprised me was the effect on system flow rate. Nothing had been changed except the fluid pumped, it is now straight water. Prior to clearing the glycol mix from the system, it was circulating 1m³/h, this morning just below 1.3m³/h.

 

So a question 

Do I leave the flow rates high or adjust the UFH manifold rates down to bring overall rate down?

[JohnMo]

Did a final finish on the water yesterday and today, after leaving the water to circulate for a couple weeks.  Did the finish with a slip stream at 0.7L/min through the media. Let it run for about 7 hrs over two days.

 

Final ppm is 114

Final conductivity 236 microsiemen

Water looks really clear

 

The above was completed with one fill of Ion Exchange media and it processed around 850L of water. So from brown water with glycol in it, to clear fresh water.

 

On 27/07/2024 at 13:11, sharpener said:

colour card is not quite accurate, pH 7.5 is a beautiful cyan colour not the pale blue shown

 

This mine, none of the colours but looking more alkaline than acid.

[sharpener]

On 16/08/2024 at 12:48, JohnMo said:

This mine, none of the colours but looking more alkaline than acid.

 

Yes, that is what I meant, defo alkaline. If you titrate it carefully with say bicarbonate solution it will change into the sky blue colour they show for 8.0. Ditto wine vinegar, at neutral it will turn a proper green. Which is the basis for my thinking cyan is in the region of 7.5.

 

I had a fruitless exchange with Water for Health about this, couldn't get near anyone technical and gave up, however they are the only ppl I could find selling it in small qties. Tried searching online for other colour charts since this universal indicator mixture is fairly common, but found nothing better not even the Wikipedia article.

 

On 03/08/2024 at 20:49, JohnMo said:

One thing that surprised me was the effect on system flow rate. Nothing had been changed except the fluid pumped, it is now straight water. Prior to clearing the glycol mix from the system, it was circulating 1m³/h, this morning just below 1.3m³/h.

 

So a question 

Do I leave the flow rates high or adjust the UFH manifold rates down to bring overall rate down?

 

I would guess leave the flow rate as high as it goes for improved heat transfer provided flow is not noisy.

 

Meanwhile as you may have seen my 12kW Arotherm plus is operational. Total system capacity is 348 litres so installers put in 1.5 litres of Adey MC1+ inhibitor and 1.5 l of MC10+ biocide. They hadn't heard of VDI 2035 even though there is a paragraph in the Vaillant manual.

They also did a power flush with great fanfare, but the water looked pretty clean and passed the shiny nail test so the Fernox F1 put in many years ago was still working.

 

I would have preferred filling with glycol solution to fitting antifreeze valves but Hydratech didn't respond to my query as to when their product suitable for diluting to 5% was going to reach the market, and at 10% the cost of 35 litres would have been prohibitive.

[JohnMo]

18 hours ago, sharpener said:

would guess leave the flow rate as high as it goes for improved heat transfer provided flow is not noisy

The same conclusion I came to. Basically letting it run as fast as it wants in cooling mode and heat pump seems happy. UFH seems very quiet, advantage of no pumps in the house.

[sharpener]

7 hours ago, JohnMo said:

advantage of no pumps in the house

 

Have now got three (i) on the UFH manifold under stairs (ii) on the thermal store in utility room (iii) bronze destratification pump in loft off a bedroom. None of them make any noticeable noise. It seems to depend in rather unpredictable ways on siting and method of mounting so we are lucky.

 

(i) is an old Myson which came from a previous house where it was replaced in 2009 by (ii) a Wilo  because it was noisy but it is quiet here! I used it to replace a 1995 Grundfos which was terrible. Only the bronze pump was brand new (I suggested a Lowara but installer fitted an Archergas, he said they used to make the pumps that were branded Grundfos but lost the contract so now sell under their own name, don't know how true that is but the company was only registered in 2021).

 

Whole ASHP installation is very quiet except when there is flow through the automatic bypass, even that is not audible outside the util room. I was surprised that 16 litres/min flow in legacy 15mm pipe is not noisy - works out at 1.8 m/s which is rather higher than recommended.

Edited August 18 by sharpener

[ReedRichards]

1 hour ago, sharpener said:

....bronze destratification pump....

I have considered getting one of these but because the pump needs to be suitable for potable water it would seem to be prohibitively expensive.  Any thoughts?