View Full Version : Why do 'controls' baffle some engineers???

09-09-2014, 09:53 PM
Any supervisors/lead engineers here have their engineers blame controls for everything??? I'm now on the HVAC Side of things and it's all I seem to hear??? Is this common???

09-09-2014, 10:15 PM
It all depends on what is going wrong with the system.

Badly set up controls, or incorrect, can destroy the best laid plans.

Some problems can be created by control schemes designed by controls specialists who do not understand the medium that is being controlled.

09-09-2014, 10:25 PM
To me it seems nobody wants to touch any equipment that concerns controls, even testing voltages. Do any supervisors/lead engineers let there engineers pull this one?? Do we expect our engineers to be able to diagnose these issues?..

I have engineers who cannot diagnose a faulty contactor, and claim to need a 500 pound per day controls expert... And then tell me they do not get paid enough @28k PA!

What do other supervisors/lead engineers expect for this sort of cash??

monkey spanners
09-09-2014, 11:48 PM
I think they baffle them because they are not suited to trouble shooting at that level, maybe they are better working as install guys or possible some more training would help.

I can't imagine they would be able to find the fault but just not bother, but who knows.

10-09-2014, 04:29 AM
Control fault finding is a major part of our industry. A large proportion of service people, unfortunately are parts replacers until it fixes the problem.
Believe me most cannot read a wiring schematic, let alone understand the control logic.

10-09-2014, 02:07 PM
I suppose it all comes down to different backgrounds!

19-09-2014, 05:58 PM
I work in a country where most controls personnel do not understand the required control philosophy or logic. Im sure this is very common in most countries as most HVAC&R companies have gone the route of using specialist controls companies for their controls scope of work. I personally had to do an advanced diploma in automation and controls to demystify everything and I now do controls in house.

Rob White
19-09-2014, 09:24 PM

I have seen so many people who just want the answer without knowing how or why.

Some people just want to be told what the problem is, they either can't or
won't work out the problem for themselves.

Our industry is suffering from a component changing fix rather than a
proper diagnosis of the fault and a repair. Air conditioning started
with motherboards and inverter boards and then supermarkets with
scroll compressors.

The days when finding a hot cylinder head and then replacing valves or
pistons in commercials are few and far between and finding a dry joint
on a control board is exceptionally rare now. Its replace the board or replace
the compressor and the fault is repaired.

I don't truly know the solution because it is not just a UK thing it would seem.

Low profit margins, poor or no training, lack of loyalty to a company, unreasonable
expectations from the customer all add up I suppose and we have been like this for
the last 20 or so years.

It might seem a daft association but I feel the rot set in back in the 90's when they
started Sunday trading. 24 hours, 7 days a week does not let the engineer enough
time to run a fridge on test and because there is no money in the contract, your
not allowed to look at a system for 4 or 5 hours to diagnose the fault and do a proper
repair. It's easier to change a few components and just charge them to the customer.

Just my tuppence worth.



install monkey
19-09-2014, 09:35 PM
sparks are bad when it comes to controls and fault finding, i had a work retard (collegue) phone me 9 times today as he couldnt fathom out why a 24v contactor wasnt energised to enable a 240v solonoid valve- questioning me if i had it working when i modified the panel the week before! tried telling me it was damp filters causing the airflow switch to OPEN CIRCUIT!!! the airflow switch is only there to protect the heater bank,- i just left him to it- i know i'll have to nip to inverness in the next 2wks to sort it

19-09-2014, 09:58 PM
A lot of it down to apprentices been shoved out on the road as soon as their out of college . When i started it was fives years before you were even considered for a van. They dont get any quality time with senior engineers to pick up good working practices and avail of years of knowledge.

Glenn Moore
24-09-2014, 12:55 AM
All of the above are relevant points, but mainly its down to a lack of in depth training on new controller strategy that is coming from the refrigeration controls industry.
All new controllers now have multi functionality to try to squeeze the last watt of energy saving from their systems . Trouble is very few engineers have the knowledge to get these benefits from these controls because of the lack of in depth training. |All training is dedicated to getting the Fgas qualification , with very little on taking engineers to the next level on system knowledge, plant enhancement and building more energy efficient systems
Therefore a lot of the latest great controllers that are on the market are only used to their basic potential due to the lack of understanding of what these controllers can do.
With full networking of controllers in a system where individual controllers can talk to each other, this can lead to major energy savings by using variable speed on compressors to control the suction pressure to the system demand, Floating the condenser pressure with the ambient with variable speed condenser fans, cycling evaporator fans during the off cycle, eevs to run the evaporators with a lower stable superheat thereby fully utilising the evaporator surface, defrost on demand, load shedding and much much more,. Many of todays controllers have these functions and more besides but due to the lack of good quality training many of these functions are never set up in the controllers as their functions are not understood by the commisioning and later the service guys, but with more in depth training in the use of these controls the benefits to the industry and to the environment would far out weigh the waste of money that has been spent on the F Gas

24-09-2014, 10:10 PM
Those who don't know, are just those who don't care to know! Especially in these days of Internet and forums like this one.

07-02-2015, 08:51 PM
hi everyone

the issue for many is not in understanding controls rather the distinct lack of access to bms systems such as trend and the other makes no license or laptop no repair .!

tell me iam wrong !!!!!!

07-02-2015, 10:20 PM
hi everyone

the issue for many is not in understanding controls rather the distinct lack of access to bms systems such as trend and the other makes no license or laptop no repair .!

tell me iam wrong !!!!!!
You may have a point!
But your response timings suck!
Try posting your own up to date post!

02-03-2015, 11:03 PM
So I'm not the only one then.... It just seems pitiful sometimes that people can't open their minds to such resources such as this forum.

Thanks for the responses guys.

03-03-2015, 12:22 AM
Its the same the world over with controls being over developed to reduce running and manufacturing costs, and not enough detail to quality reliabilty, awareness of their capability, and instructions that are straight forward to follow.

What I've found is that an industry that has developed general EM controls from phial and bellows/bimetal thermostats, horse air humidistats, direct online, star delta, variable voltage trannies, resistance starters etc. To solid state analogue and digital electronics that require a signal from a processor to execute an instruction from a memory device that stores one or more programme. Suitable controls are not always not selected at the design stage, and incorrect replacement when being repaired.

Aslo makes such as LAE, Elliwell, Carel, and other brands are not standardised when it comes to programming and setting parameter values, or even accessing engineer level. I should imagine we've all come across single relay controllers on a system that requires 3 relays. No defrost selected, drip time, temp probes not set for defrost terminate, air off, evap fan off when on defrost, relays burnt out due to AC 3 rating not being considered, or generally over loaded because their spec has been overlooked at the design stage and replaced like for like. Or being over looked when replaced etc.

On many occasions I've come across condensate tank elements that are on all the time with no level switch or thermostat causing loading and ambience problems due to not being considered at design stage or as a quick fix with no return to fit replacement parts.

And also with regards to HVAC, the BMS engineers not allowing anyone but themselves allowing access or only limited access to the mainframe, because they think that the system requires a greater I Q than a service engineer. When as we all know the parameters are selected by English text or another language, and not the traditional boolean algebra, sub routine, or even ladder. They're much more user friendly these days even at higher access levels, with all the traditional stuff operating in the background. Which when fail, the BMS engineers usually consult with other controls engineers to remedy.