Ämne: Normalt med pendlande tryck i köldbärarkrets (0.4-1.2bar)?

[fingalolsson]

Har en bergvärmepump (IVT Geo 512) som installerades i maj förra året. I höstas upptäckte jag att trycket låg på 0 bar i köldbärarkretsens expansionskärl, samt porlande ljud ute där slangen från hålet går in i huset. Pumpen hade inte larmat men jag kontaktade ändå servicetekniker som fyllde på med brinevätska. Detta var i december.

Har sedan dess kastat ett öga på manometern med jämna mellanrum och noterat att trycket varierar rätt mycket. När pumpen jobbar hårt tycks trycket sjunka, ibland kring 0.4 bar. När pumpen inte jobbar alls är trycket ofta betydligt högre, kring 1.2 bar eller så.

Jag skulle vilja veta om det här är väntat beteende. Vore även intressant att förstå vad som gör att trycket varierar.

[Roland]

Är expansionskärlet fyllt så pass mycket att det bara är en liten luftkudde i det kan det nog bli så. Det är flera hundra liter köldbärare i slingan. Temperaturändringar gör att köldbärarens volym ändras och därmed trycket i expansionskärlet.

[fingalolsson]

Är expansionskärlet fyllt så pass mycket att det bara är en liten luftkudde i det kan det nog bli så. Det är flera hundra liter köldbärare i slingan. Temperaturändringar gör att köldbärarens volym ändras och därmed trycket i expansionskärlet.

Okej, tacksam för svaret! Jag tolkar det som att det låter som ett fullt rimligt pendlande då!

[25fOCUS]

Att trycket åker lite jojo är normalt, var sitter manometern i förhållande till cirk-pumpen, sitter den före pumpen så skapas ett litet vacum som suger ner trycket. Den ska då sitta direkt på ett rör före pumpen . Åt andra hållet blir det om manometern sitter direkt efter pumpen. Kolla får du se.

[prpr]

Sorry for the English...
The fluctuation of the pressure with the temperature of the brine circuit is completely normal. This is due to natural expansion and contraction.
The only way to not have this pressure yo-yo is to fit a real fairly large expansion tank with a membrane, but there is not much point, because it works also fine without.

However, the sounds in the system are not normal, and this is because you have underpressure in the system.
The installation manual for your pump (and also for Bosch Compress 6000 series) states, that you must have 2.5-3 bar pressure in the system.
When the brine is cold and pump is working, it is good if you have at least 2 bar. But you have only 0.4 bar, this is why you can have sounds, also the efficiency of the brine pump can be lower at such low pressure.

Here is the cutout from the manual for your heat pump:


You need a simple filling tool with hose and hand pump, they can be rented, and you need to add some coolant (make sure you know which coolant is used, e.g. 30% ethanol or glycol or some other), or call the technician to do it. Probably not the best idea to put 2.5 bar after the brine has cooled, because in the summer you can have then over 3 bar pressure, but 0.4 is too low.

[fingalolsson]

Sorry for the English...
The fluctuation of the pressure with the temperature of the brine circuit is completely normal. This is due to natural expansion and contraction.
The only way to not have this pressure yo-yo is to fit a real fairly large expansion tank with a membrane, but there is not much point, because it works also fine without.

However, the sounds in the system are not normal, and this is because you have underpressure in the system.
The installation manual for your pump (and also for Bosch Compress 6000 series) states, that you must have 2.5-3 bar pressure in the system.
When the brine is cold and pump is working, it is good if you have at least 2 bar. But you have only 0.4 bar, this is why you can have sounds, also the efficiency of the brine pump can be lower at such low pressure.

Here is the cutout from the manual for your heat pump:


You need a simple filling tool with hose and hand pump, they can be rented, and you need to add some coolant (make sure you know which coolant is used, e.g. 30% ethanol or glycol or some other), or call the technician to do it. Probably not the best idea to put 2.5 bar after the brine has cooled, because in the summer you can have then over 3 bar pressure, but 0.4 is too low.

I haven't installed the pump myself, it was performer by an authorized IVT installer. I actually read about those pressure numbers (2.5-3 bar) also in the installation manual (of which I don't understand very much, I have to admit). But the pressure has never been *that* high, for sure. The technician set the red needle at about 0.75 bar. Not sure exactly what that means, I was expecting the pressure to be quite steady around that level but, as I said, it seems to fluctuate quite a lot (pressure goes down when pump activity goes up and vice versa, as it seems)

Could it depend on where the expansion tank is located? (mine is at about half the height of the pump)

I'd like to stress that there is no pouring sound now, that was before the brine "refill" when the pressure was close to zero bar. Everything *seems* to be working fine now (as far as I can tell with my very limited knowledge).

I'm just wondering what to expect in terms of pressure. Other posters seem to believe that my readings are normal, but now I'm a bit confused 🤔 😅

[prpr]

I simply show you what the manual says for your heat pump.
The manufacturer says that it is optimal to have 2.5-3 bar in the circuit. It does not depend on location of tank.

If you want to think about the details, then it depends a little about VP placement in relationship to the brine pipes, etc.
But I like to think that the manufacturer has a good reason why they recommend this amount of pressure in the KB circuit.

Will it work with 0.4 bar? Probably. But you have very little playing room there, maybe towards end of winter it can fall even lower.
Since you say it has been working for a year, then it is safe to assume all the air is out of the system, and it is not going to fall anymore at same temperature.
I just like to do how manufacturer is recommending, they are usually much smarter than the end user or the installer.

I have between 2.0 and 3.0 bar in mine, and everything is good. I have a Bosch Compress heatpump, this is ~same as IVT.

[fingalolsson]

I simply show you what the manual says for your heat pump.
The manufacturer says that it is optimal to have 2.5-3 bar in the circuit. It does not depend on location of tank.

If you want to think about the details, then it depends a little about VP placement in relationship to the brine pipes, etc.
But I like to think that the manufacturer has a good reason why they recommend this amount of pressure in the KB circuit.

Will it work with 0.4 bar? Probably. But you have very little playing room there, maybe towards end of winter it can fall even lower.
Since you say it has been working for a year, then it is safe to assume all the air is out of the system, and it is not going to fall anymore at same temperature.
I just like to do how manufacturer is recommending, they are usually much smarter than the end user or the installer.

I have between 2.0 and 3.0 bar in mine, and everything is good. I have a Bosch Compress heatpump, this is ~same as IVT.

Appreciate it. Thanks!

[fingalolsson]

Kontaktade en IVT service-tekniker som tyckte att rekommendationen i manualen på ett köldbärartryck kring 2-3 bar var satt "väl högt". I princip klarar de flesta pumpar att arbeta mot 0 tryck, men då finns det en större risk att luft kommer in i slingan (och försämrar flödet, om jag tolkade honom rätt).

Han berättade även att tidigare fanns en tryckvakt i systemet som såg till att trycket aldrig fick gå under 0.5 bar, men nu har IVT instruerat sina servicetekniker att montera bort den.

[25fOCUS]

Klart dom säger att koppla bort tryckvakten, dom flesta VP -anläggningar när KB börjar närma sig många minus så sjunker trycket väldigt mycket och då blir det larm på trycket och brukaren får kanske problem med att VP stoppar. I mina ögon en klar miss, vet inte om den går att justera ner under 0,5 bar som kan vara en vettig nivå på ett tryck.