BPHE sub dimensioning

THE PROBLEM: BPHE sub dimensioning is a known and, unfortunately, a frequent sales technique used in this market.

There are companies which choose to sub dimension the BPHEs they offer with 25% to 35% to achieve a lower selling price.

This is our first installment in our “Watch out” series. Throughout this series of articles we’ll try to help you avoid mistakes and dishonest sales tactics when choosing your heat exchanger.

You can read here the other installments.

Why would some companies sub dimension BPHEs

Their reasoning is a simple one – it’s very unlikely that the customer will check the heat exchanger’s running parameters after its installation. So, in their reasoning changing the parameters in the data sheet it’s a risk worth taking – this will lead to a smaller BPHE which in turn leads to a better offer than those of their competitors.

Let’s see a practical example to better understand how some distributors profit from this practice.

Let’s take an application with a chiller and terminal circuits (convectors) that need to be intermediated by a BPHE.

The data used are these:

  • Heat load: 50 kW
  • Side 1 inlet/outlet water temperature: 7 °C / 12°C
  • Side 2 inlet/outlet water temperature: 13°C / 8°C
  • Side 1 flow rate: 8.586 m3/h
  • Side 2 flow rate: 8.591 m3/h
  • Maximum pressure drop on both sides: 50 kPa

In this case the selection software would indicate the B120T model with 105 plates. Read here its data sheet.

But if we raise on side 2 the inlet/outlet water temperature by just 0.5°C to 13.5°C / 8.5°C then the selection software would indicate the same B120T model, but with just 89 plates this time – with 16 plates less. Read here its data sheet.

This change by just 0.5°C leads to a BPHE that is approximately 15% smaller.

Also, you should consider the total heat transfer area – it decreases from 13.6 m2 to 11.5 m2. This means you will end up with a less efficient BPHE and an incorrectly designed one for your setup’s needs.

Most customers will not check the heat exchanger’s parameters. But even if they did they would most likely say that a difference of just 0.5°C is not one that would matter and that it’s not necessary for the heat exchanger’s parameters to be exactly the same as the ones written in the data sheet.

But believe us when we tell you that it’s wrong to think like this. Those 0.5°C lead to a sub dimensioned BPHE which in turn will lead to additional costs for electricity and to a premature chiller and pumps’ usage.

So don’t choose to overlook the heat exchanger’s data sheet parameters because in the end this will prove costly.

What are the risks for you, the customer

  1. Your applications will consume more electricity
  2. Your installations (boilers, chillers, pumps, etc.) will have a premature usage
  3. You will end up spending more money

So how can you be sure of your heat exchanger

It’s very simple actually – you need to ask for the heat exchanger to be AHRI certified and ask for the data sheet to be committed in contract.

AHRI is the biggest worldwide organization that certifies HVAC equipment. Their procedures are very strict – at any time they can pick equipment from the certified factories and test it in their laboratories. If the test data doesn’t match with the data sheet, then that producer will lose the certification. It’s that simple and catastrophic for the producer.

All our heat exchangers are verified and AHRI certified. You can read more about this here.

Key Takeaways

  • Be aware of the risks of BHPE sub dimensioning
  • BHPE sub dimensioning leads to increased expenses
  • Ask for the heat exchangers to be AHRI certified and ask for the data sheet to be committed in the contract

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“Watch out” articles

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