Mcquay Cond press high alarm

**sinnedobi** · 11-19-2012, 03:03 PM

I am working on some mcquay heat pumps but in one of them i am having a problem from some days. In cooling mode all is ok they newer got problems they are air cooled . One of them is having problems in heating mode and give ' Cond press high' alarm . This is a 2 circuit model i have switch off 1 circuit and run the other 1 and the error was the same. I have checked the circulation water pumps and they are ok water flow is ok. Both compressors run for 10 minutes but when they try to increase stage and speed compressor discharge goes 78-80 degrees celcius and compresor suction line temp is about 11 degrees. Water enter 42 degress in condenser and leave 44. It is near to stop for set point temp 45 but nothing it goes in alarm.

I think maybe is a problem with the transducer but the problem happened with both compressors is possible they use only 1 transducer on condenser?

Sorry for my bad english, Can anyone help?

**fitzyfitta** · 11-19-2012, 07:13 PM

I'll be the first to let you know that if you would like help, you need to convert your temperatures to fahrenheit.

**sinnedobi** · 11-20-2012, 05:22 AM

Originally Posted by fitzyfitta

I'll be the first to let you know that if you would like help, you need to convert your temperatures to fahrenheit.

I am working on some mcquay heat pumps AWS model but in one of them i am having a problem from some days. In cooling mode all is ok they newer got problems they are air cooled . One of them is having problems in heating mode and give ' Cond press high' alarm . This is a 2 circuit model i have switch off 1 circuit and run the other 1 and the error was the same. I have checked the circulation water pumps and they are ok water flow is ok. Both compressors run for 10 minutes but when they try to increase stage and speed compressor discharge goes 176 Fahrenheit and compresor suction line temp is about 51.8 fahrenheit. Water enter 107.6 fahrenheit in condenser and leave 111.2. It is near to stop for set point temp 113 but nothing it goes in alarm.

I think maybe is a problem with the transducer but the problem happened with both compressors is possible they use only 1 transducer on condenser?

Sorry for my bad english, Can anyone help?

**valdelocc** · 11-19-2012, 08:08 PM

sounds like an airflow issue, check for closed dampers

**sinnedobi** · 11-20-2012, 05:24 AM

Originally Posted by valdelocc

sounds like an airflow issue, check for closed dampers

Sorry valdelocc wich dampers it has not damper for air is in the roof, this is not an AHU

**valdelocc** · 11-20-2012, 06:58 AM

Originally Posted by sinnedobi

Sorry valdelocc wich dampers it has not damper for air is in the roof, this is not an AHU

typically here in the USA we are used to HP having ductwork attached to the discharge side of the blower, what kind of heat pumps you are working on? water to water? mini-splits?

**sinnedobi** · 11-20-2012, 07:17 AM

i am working on mcquay McEnergy HPI Extension Air to water heat pumps R134a like this http://www.mcquayeurope.com/en/index/prodotti/4/5

**sinnedobi** · 11-20-2012, 09:47 AM

Originally Posted by sinnedobi

i am working on mcquay McEnergy HPI Extension Air to water heat pumps R134a like this http://www.mcquayeurope.com/en/index/prodotti/4/5

At 45 % of load after 5 minutes of normal work Hp is 20 bar condenser pressure is 18 bar and when compressor increase stage it goes in alarm for high preassure alarm on board and Cond Press High on BMS software. Sometimes intervent the mechanical preassure switch wich means that the preassure is real and not a problem of any probe who read wrong values.

I don`t remember Low pressure

**Nuclrchiller** · 11-20-2012, 09:58 AM

I would verify proper water flow when in heating mode.

**sinnedobi** · 11-20-2012, 10:11 AM

Originally Posted by Nuclrchiller

I would verify proper water flow when in heating mode.

already done that the pipes of water are the same in cooling too but this happened only in heat mode also i have 2.5 bar on supply and return of pipes water

**Nuclrchiller** · 11-20-2012, 10:29 AM

Originally Posted by sinnedobi

...also i have 2.5 bar on supply and return of pipes water

The same pressure on the supply and return water indicates no flow. Make sure you use one gauge, moved back and forth between supply and return. This will eliminate the possibility of gauge error.

**sinnedobi** · 11-20-2012, 01:54 PM

Originally Posted by Nuclrchiller

The same pressure on the supply and return water indicates no flow. Make sure you use one gauge, moved back and forth between supply and return. This will eliminate the possibility of gauge error.

sorry 2.5 bar on supply and 2.0 bar on return. problem happen only when temperature is 42-43 near to setpoint of 45 degrees celcius

**sinnedobi** · 11-20-2012, 01:54 PM

Originally Posted by Nuclrchiller

The same pressure on the supply and return water indicates no flow. Make sure you use one gauge, moved back and forth between supply and return. This will eliminate the possibility of gauge error.

sorry 2.5 bar on supply and 2.0 bar on return. problem happen only when temperature is 42-43 near to setpoint of 45 degrees celcius