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Author Topic: Danfoss (Thermia) Heat Pump Engineer Needed  (Read 1215 times)
andyhanson
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« on: February 09, 2018, 12:06:16 PM »

Hi All,

We've had a Thermia DHP-L heat pump installed since 2010 and it's been faultless until recently.  We've had several Low Pressure Alarms and I've done all the normal checks with the brine circuit and tested the circulation pumps.  The heat pump is running normally most of the time but is producing low pressure alarms on an irregular basis. 

Anyway I would like to have someone look at the system and ascertain what's causing this but am having real problems locating an engineer in my area (Gloucestershire).  It was originally installed by Danfoss but they've handed across servicing to a company in Ireland.  I've contacted them who gave me a couple of contacts here.  One was too far away and the other has made two appointments and missed both!  He's now not answering his phone Angry.

Does anyone have any contacts for a suitable engineer in our area?

Thanks for any pointers.  Smiley
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knighty
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« Reply #1 on: February 09, 2018, 04:41:25 PM »

low pressure normally means the system needs a bit more gas in, it's a normal maintenance job


any refrigeration engineer will be able to do that for you, just search for local refrigeration engineers, phone a few different ones and see who sounds like they know what they're talking about

or phone a refrigeration supplies place and ask them for a recommendation ?
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andyhanson
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« Reply #2 on: February 09, 2018, 05:19:28 PM »

Ok that sounds like a good plan.

Out of interest why isnít the alarm constant if itís low in refrigerant?  We had an entire week with no alarms then another one. Also the alarms are produced when the heat pump is neither producing heat or hot water. I would have thought a low pressure alarm would only trigger when the heat pump is actively working??
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Westie
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« Reply #3 on: February 09, 2018, 06:10:13 PM »

Ok that sounds like a good plan.

Out of interest why isnít the alarm constant if itís low in refrigerant?  We had an entire week with no alarms then another one. Also the alarms are produced when the heat pump is neither producing heat or hot water. I would have thought a low pressure alarm would only trigger when the heat pump is actively working??

Its possible that you are low on refrigerant and hovering on the threshold of the alarm triggering, ambient temp could then affect the pressure, or, alternatively,  maybe the pressure sensor itself is simply failing....

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andyhanson
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« Reply #4 on: February 09, 2018, 06:39:45 PM »

That makes sense. Will see what we can arrange after the weekend.

Many thanks.
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rogeriko
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« Reply #5 on: February 09, 2018, 08:33:46 PM »

A low pressure fault is not related to the pressure in the brine circuit, it's a pressure sensor on the refrigerant circuit tripping out because the circuit is getting too cold, ie, the liquid cannot boil and turn to gas. This can occur for a variety of reasons but usually in older systems its because the ground is frozen after years of use. What are the brine temperatures flow and return?
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andyhanson
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« Reply #6 on: February 09, 2018, 09:23:25 PM »

Ok understood. Only the manual states that a low pressure alarm is related to the brine circuit. That's the only reason I looked at that first. However having studied the diagram of the components I can see that the low pressure switch is on the refrigerant circuit.

The brine in and out temperatures are around 5 and 2 respectively at the minute.
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rogeriko
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« Reply #7 on: February 09, 2018, 09:36:20 PM »

Is there any air in the brine cicuit, any bubbling noises from the pipework. Is the brine pump on full power and the brine cicuit pressure should be about 1 bar. The temperatures are good.
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andyhanson
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« Reply #8 on: February 09, 2018, 09:42:40 PM »

No air that I can tell with no bubbling noises. The pump is running fine and hasn't changed from what I can tell. The brine circuit in the DHP-L is unpressurised. There's no pressure in the circuit at all. I know some systems are pressurised but this one isn't.
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knighty
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« Reply #9 on: February 10, 2018, 02:38:08 PM »

it's pretty normal for big fridges/freezers to need a gas top up now and again.. there can be a leak so small you couldn't find a bubble if you dumped the whole system under water... but the leak is there... over a few year, hot/cold cycles, starts/stops etc. a bit leaks out


unfortunately... the gas that's in it is probably a fortune to buy now, so fingers crossed you don't need much!


(the 404A in my freezers at work has gone from £8/kg to ££75/kg)
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andyhanson
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« Reply #10 on: February 10, 2018, 02:53:44 PM »

That sounds entirely plausible and is probably the cause.

Have an appointment booked for tomorrow afternoon so will update when I know more.

Thanks again.
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andyhanson
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« Reply #11 on: February 12, 2018, 10:47:57 AM »

So to update after engineers visit.

Lots of tests run and pressures measured on refrigerant circuit. Heat pump running perfectly. No evidence of any leaks and brine circuit also tested without any problems. Low pressure switch also tested and working perfectly.

Has concluded it has to be a faulty control board. Due to the sporadic nature of the alarms it can't be anything else especially after all the tests carried out so will replace control board and that should cure the problem.

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