PED Responsabilities

[MemphisKing]

Hi,

First time on here so hopeful for some help.

I am the UK Sales Manager for a coil supplier based in Italy.

We have supplied 4 condenser coils 2-OFF 'V' unit chillers. The enquiry from our client was as below:

The operating conditions are:

Refrigerant: R407c
Air Temp: 30C
Condensing Temp: 50C (Dew Point)
Heat Rejected: 90kw
Air Flow: 7.5m3/s

We have designed the coils around these conditions, the selection shows a condensing pressure of 19.83 bar (a) and a maximim allowable pressure of 21 bar. This is in line with PED 97/23/CE Classification Class 1.

The selection was approved by the client.

The client is now rejecting the coils as he says the condensing pressure will be higher at start up when the water is above 12C. Also the coils will get dirty again rasing the condensing temp and pressure.

I believe we could only design the coil around the information supplied, it is down to the system designer to advised higher pressures etc.

Am I right?

[multisync]

Those are operating design conditions to allow for the correct KW duty rating. They are not to be interpreted as safety related regulations

The safety margin would be the responsibility of the manufacturer to ensure they designed a coil with a suitable safety margin -usually 1.5 max operating pressure.

I can't believe any coil manufacturer who designs refrigeration coils would allow a 1 bar safety margin. I suspect you would lose in court for failing to provide a coil with sufficient safety factor recognised within the industry

However you could always offer a free PRV as way of compensation ;-)

[Thermatech]

The chiller will have a high pressure safety switch.
If somthing happens like fan motor failure the chiller could run up to high pressure & stop on the HP switch.

So at the minimum the contractor would want the coils to be factory pressure strenght tested for the HP switch pressure + safety margin & provided with cirtification.

Does EN378 come into play in this case ?

[mad fridgie]

I think there is difference between maximum working pressure and burst pressure. I am not familar at all with your standard, but it may have pre-determined ratio between running pressure and burst pressure.
For example your tubing may have aburst pressure of 84bar, the ratio may be 4 to 1 so you maximum working pressure is 21Bar. You need to check.
Did the client forward the specs in writing? did you quote in writing showing all these details, did your client place an order based upon your quote. If yes to all then, clearly he is in the wrong.
Going back to the enquiry, did the client express a need for fouling factors to be included?
Practically if the burst pressure is well above 21bar, then the industry standard is to ignore startup senerios as far design performance, but ensuring protection of refrigeration machines. (in this case one option is to slow evap water flow rate)

[al]

High pressure trip point on a similar York chiller would be 25.7B, PRV would probably open at 27 to 29B.

Max condensing temperature i thought was to be taken at 43c, could be wrong on this?

So design pressure would be 407c at 43c multiplied by 1.3, as an end user i would place this with the factory, EN378 combined with the PED should dictate all your designs?

Could you not retest the coils to see if they meet the required criteria, if they do then the customer can't reject them on this basis.

Al

[Brian_UK]

High pressure trip point on a similar York chiller would be 25.7B, PRV would probably open at 27 to 29B.

Max condensing temperature i thought was to be taken at 43c, could be wrong on this?

Al

I think it is supposed to be 55°C.

[al]

i stand corrected!!

al

[El Padre]

I am quite surprised, as has already been stated we are required to pressure test to 55 degrees C under EN378, surely its the same in Italy. I would expect the factory test to exceed that.

Cheers