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Author Topic: ASHP setup temperatures  (Read 5694 times)
chris wills
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« on: November 09, 2019, 05:13:35 PM »

Just wanted advice on best temp settings to have my ASHP on.

Currently I have the return temp on the unit set to 45 deg C, which goes into a buffer and the pump will switch it on at min temp of 43, to be circulated around the UFH downstairs and rads upstairs. 

As the weather gets colder the pump struggles to reach 45 return and so keeps running, this may be because I need to fill the buffer tank up.

Is 45 return too much?
Can I turn I down?
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Bodidly
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« Reply #1 on: November 09, 2019, 05:21:25 PM »

Hi Chris

I would have thought you want to run at the lowest temp possible for maximum COP. Not familiar with ASHPs but this is the case with our GSHP
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rogeriko
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« Reply #2 on: November 09, 2019, 05:29:52 PM »

Your electric bill must be humongous. You want the FLOW temperature set to about 32 or 35 degrees. Any more and you will win Scottish Powers customer of the year award.
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chris wills
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« Reply #3 on: November 09, 2019, 05:39:15 PM »

Thanks guys.
The manual says the flow temp is always 5 deg more than the return temp, so if I go for 35 should be ok?
I think any lower and rads will be too cold upstairs?
Shall I leave it on 24/7 too?
Currently on in the day only 06:30 until 22:30
« Last Edit: November 09, 2019, 05:40:56 PM by chris wills » Logged
Bodidly
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« Reply #4 on: November 09, 2019, 10:48:47 PM »

Again I can only comment for sure on GSHP but I would leave it on 24/7 and turn it down and down until you can't get enough heat into the room then turn it up a touch. Heat pumps will perform much better running for long periods at low temps. Our GSHP never has to heat over 30C to keep us warm but we do have UFH
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gnarly
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« Reply #5 on: November 10, 2019, 07:00:46 AM »

Leaving it on longer at a lower temperature will definitely save money.  Maybe you could try backing off the flow temp overnight if your controller has time/temp capability.

Also if you get economy 7 or a smart meter then electricity can be much cheaper overnight

In theory the flow/return temps should also depend on the outdoor temperature so they increase on the coldest days
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brackwell
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« Reply #6 on: November 10, 2019, 08:17:14 AM »

As Bodidly - on all the time and adjust temp down to suit is the most efficient/economical.

If you find the behaviour of one room is dictating the whole then changing the rad to a bigger one will bring benefits to the whole system. After all when a HP is fitted the rads have to be doubled in size.

Strictly speaking there is benefits in increasing the water temp as the outside air temp increases and vice versa.
So upping the temp of the water and the house temp in the warmer part of the day and reducing/swithcing it off under freezing conditions and using the house as thermal mass will produce economies,but you do need a house with thermal mass,good insulation and no draughts. So we are back to insulate and .....

Ken
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chris wills
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« Reply #7 on: November 10, 2019, 10:36:59 AM »

Thanks all. Sound advice.
Iíll give it a try.
Iíve put the return onto 40 for now and the flow to ufh comes on at 37.
My only worry is rads upstairs will not be so good.
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djs63
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« Reply #8 on: November 10, 2019, 02:45:06 PM »

We have a GSHP and radiators are lukewarm at best but the house is warm and comfortable. The radiators run at 40 C . So you could, should, probably will be OK,
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6 Kw Proven wind turbine, 15 Navitron evacuated solar hot water tube array and 1.8 Kw PV, grid connected (SMA inverters) and GSHP supplying radiators and UFH. Wood burning stove (Esse 300) and oil fired Rayburn. Rainwater harvesting 4000 litre tank underground. Nissan Leaf
chris wills
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« Reply #9 on: November 10, 2019, 04:01:15 PM »

Do you leave rads on 24/7 too?
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rogeriko
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« Reply #10 on: November 10, 2019, 09:04:26 PM »

Keep the flow down to 35 otherwise the ashp will keep defrosting which costs you money and worse still the COP of the heat pump will drop as it tries harder and harder to reach a higher temperature, this will cost you even more money. If the radiators are too cold then that is the fault of the installer and you must put fan assisted radiators, or install fans on top of your radiators. Fans make an incredible difference and cost nothing to run. We are talking computer fans here running slowly so they are silent. Radiators at 35 degrees will heat the room easily if the air is forced through them as opposed to natural convection will dosn't work at 35 degrees.



* radfan1.jpg (12.8 KB, 500x338 - viewed 212 times.)

* radfan2.jpg (49.4 KB, 1600x969 - viewed 200 times.)
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chris wills
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« Reply #11 on: November 11, 2019, 12:40:23 PM »

I've set the return to ASHP temp to 35 now and made the pump to circulate the water come on at minimum 34 degrees. Both UFH and first floor rads all on 24/7, lets see how much KW of energy I use and the verdict of the family for heat. If they are happy i'll go for 30 return maybe.
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Fionn
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« Reply #12 on: November 12, 2019, 09:33:13 AM »

Fans make an incredible difference and cost nothing to run. We are talking computer fans here running slowly so they are silent. Radiators at 35 degrees will heat the room easily if the air is forced through them as opposed to natural convection will dosn't work at 35 degrees.

Would you have a link to those fan shrouds or were they a DIY project?
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Tigger
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« Reply #13 on: November 12, 2019, 09:52:10 AM »

Have to agree with the Radfan, I got one for our living room (the model that sits under the rad and blows air up through it) and its made a great difference.  They're available from many outlets such as Lakeland, Amazon etc, just search for 'radfan'.

Ian.

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Fionn
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« Reply #14 on: November 12, 2019, 09:58:57 AM »

Thanks Ian, will have a look.

For the benefit of any other readers "Speedcomfort" is the key word for the under radiator version, their appearance is a bit tidier.

« Last Edit: November 12, 2019, 11:27:51 AM by Fionn » Logged

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