navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address - following recent spam/hack attempts on the forum, all security is set to "high", and "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: [1] 2 3   Go Down
  Print  
Author Topic: ASHP setup with rads and UFH  (Read 9894 times)
flip
Newbie
*
Offline Offline

Posts: 21


« on: December 29, 2010, 02:07:22 PM »

I have a Delonghi AWR0031 MT 11.8Kw ASHP which feeds a 200 litre buffer tank which in turn feeds a ground floor with 5 zones on UFH and 1st floor and attic room with radiators.
It is currently setup to a return temp of 45 degC and I have a temp switch on the return flow of the buffer tank which will activate a grundfos pump when the temp is around 40 degC. Yes I know this is high for UFH but when I divert the water to the rads they are all but luke warm unless the ASHP is set up this way. The UFH downstairs makes the floor a comfortable 20 degC today and all the zones are off. The air source when this happens is off for a long period and thus saving us money.
For DHW we have solar and a immersion heater which comes on for 2 hours at night if needed to help raise water temp.
When I turn the rads on upstairs the pump then works harder and runs for longer periods.
I was wondering if anyone can advise on this setup, seems to be OK but I would really welcome some hints and tips.
Logged
Countrypaul
Hero Member
*****
Offline Offline

Posts: 1485


« Reply #1 on: December 29, 2010, 03:51:25 PM »

Is there just a single pump for both the UFH and the rads?
Does the water for the UFH go through a blending valve to use the returning water and thus minimise the use of fresh hot water from the store?

What you appear to describe is what some on here warn is the main problem with ASHPs, either you need UFH almost everywhere, or you need to get such hot water out of it that the COP ends up quite low.

When you use the immersion heater is this on E7?, do you run the ASHP on E7 when you can?

Paul
Logged
dhaslam
Hero Member
*****
Offline Offline

Posts: 6775



« Reply #2 on: December 29, 2010, 04:02:33 PM »

What you could do  is  have the  radiator circuit  use a higher take off point in the buffer tank and  use an immersion to boost only that section of the  tank in very cold weather.    This way you could keep the  output temperature  of the heat pump lower, particularly in cold weather,  when the heat pump would be  less efficient.    If the return from the radiators is at the bottom of the buffer tank  it would  increase  the underfloor  feed  temperature slightly.   Because upstairs radiators are  probably used mainly at night the immersion could use off peak electricity only.      

It is difficult to tell how much difference  to COP there is  when the output temperature  is higher.   The input air temperature makes an enormous difference.     I just set mine to the highest temperature  setting and let it  reach whatever temperature it can.   The electricity usage is the same  and a  higher temperature saves the immersion in the DHW cylinder.   When heating the buffer tank the first time  I   recorded the figures for the graph below.   Unfortunately   there was a heat dump from the  DHW cylinder in the afternoon, only a few kWh into the bottom of the tank,  but it upset  the  heat pump temperature control briefly.   What it shows is that once the ambient temperature is adequate there is virtually a straight line output  graph over quite a big  temperature range.


* HeatPump.jpg (69.83 KB, 1019x662 - viewed 863 times.)
Logged

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
flip
Newbie
*
Offline Offline

Posts: 21


« Reply #3 on: December 29, 2010, 04:19:26 PM »

Is there just a single pump for both the UFH and the rads? - no its one pump for the whole circuit

Does the water for the UFH go through a blending valve to use the returning water and thus minimise the use of fresh hot water from the store? not sure

When you use the immersion heater is this on E7?, do you run the ASHP on E7 when you can? not on eco 7

Logged
flip
Newbie
*
Offline Offline

Posts: 21


« Reply #4 on: December 29, 2010, 04:21:20 PM »

If I set the pump to its max return of 45 degC would this be achievable in the very cold winters?
Logged
dhaslam
Hero Member
*****
Offline Offline

Posts: 6775



« Reply #5 on: December 29, 2010, 04:52:46 PM »

45C  might be just about possible if the outside air is  -15C  for example.  That is a rise of 60C,  mine  will only do about  50C rise but it has  a relatively small air throughput so it just cannot find enough input heat to work with.      If you are using the  full output  capacity  the temperature setting doesn't matter, you just let it reach what temperature it can  but if you have a choice it is better to drop the temperature setting a bit in very cold weather and boost heat by other means.   Although an immersion may seem a little wasteful to boost the temperature,  it  won't add up to all that much extra cost over the average year.   I just turned my heat pump off for the last two weeks  but now the average temperature is  22 degrees higher than last week and it has the buffer tank up to 53C.     
Logged

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
knighty
Hero Member
*****
Offline Offline

Posts: 2792


« Reply #6 on: December 29, 2010, 11:35:56 PM »

as a short term test.... can you turn your down stairs heating up a bit ?

the under floor heating will be much more efficient than your radiators, so by increasing the downstairs temperature, you could hopefully let the heat rise to the upstairs naturally and help heat it ? (might not work as planned, but worth a go?)

the only way to make the pump work less, without making any physical changes to the system is to turn the water temperature down


the colder the water temperature the more efficient the heat pump is (at generating heat)

but colder water makes the radiators less efficient (at dumping the heat into your rooms)
Logged
flip
Newbie
*
Offline Offline

Posts: 21


« Reply #7 on: December 30, 2010, 10:42:19 AM »

Thanks for the advice, what I have done now is to put the heat pump to its max return temp of 45 degC. When the return hits a temp of 3 degC lower, in this case 42degC return the heat pump goes off. I have set the buffer to pump at around 40degC so at the moment the Grundfos pump will remain on all the time and ASHP will cycle, currently its off for 40min and on for 10min which is great (outside temp being 9degC now).

As for the UFH, I have left the hall stat fully open to heat rises and other 4 zones are set to 20 but have no call for water at this time.
We then put the rad upstairs on a timer to come on at night for 1 hour.

Seems to be working OK.
Main issue is when we get silly temps outside of -8degC etc.
I dont think the defrost cycle is correct, it starts to defrost at around -5degC and then goes into error, this is what messes it all up. The settings for this are only known by the company, not very user friendly pump!
Anyone know of Delonghi engineer settings for derfost?
Logged
dhaslam
Hero Member
*****
Offline Offline

Posts: 6775



« Reply #8 on: December 30, 2010, 12:20:34 PM »

It should need to defrost  when the ambient temperature is  above freezing,  the ice will build up due to  the cooling effect of the heat pump.     It is more likely that the intake being blocked by ice is causing the error. 
Logged

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
flip
Newbie
*
Offline Offline

Posts: 21


« Reply #9 on: January 01, 2011, 02:49:35 PM »

OK, I will contact supplier to see if they can change the settings.

I currently have Emmenti stats in each room controlling the UFH but find it a pain at night to turn them down in order not to waste heat. Does anyone of a stat that can be set to turn itself down at night, eg on timers etc, and can someone please give me a link to product.

thanks guys for your help so far
Logged
Baz
Hero Member
*****
Offline Offline

Posts: 1391


« Reply #10 on: January 01, 2011, 10:49:40 PM »

http://www.heatingcontrolsonline.co.uk/siemens-rdj10-programmable-room-thermostat-p-360.html
for example but a bit pricey for every room.
Do you want to turn them down or off? If they are plain 'stats that just go open circuit when hot enough you can just put a simple switch in series with the wires in a convenient place like at the boiler. That would give you a bank of switches for manual control. Starts to get more complex if you then want a timer to put them on/off but do-able with relays and a single timer.
Logged
flip
Newbie
*
Offline Offline

Posts: 21


« Reply #11 on: January 23, 2011, 10:02:27 PM »

I do not find the pump very efficent or capable during the cold temps of say minus 4 as it has been this week.
The default setting on my pump is a return flow of 45 degC and timer for upstairs rads to 8pm till 10pm. Think is when 8pm comes the pump struggles to warm the buffer tank up to make any differnence. To be honest I am thinking of getting rid of it, it may be eco friendly and all that but it simply don't work. Gas must be the better option surely?

The supplier says I could increase the return flow to as much as 55 degC, suppose this would at least make the rads warmer, but what effect does it have on UFH, it this temp too hot?
Any advice please or can anyone with a De-longhi pump give me feedback on theirs?
Logged
dhaslam
Hero Member
*****
Offline Offline

Posts: 6775



« Reply #12 on: January 23, 2011, 10:47:06 PM »

The idea of the buffer tank is that  you heat it before you need the heat,  normally this would be at night  in order to have heat in the morning.     The mixer valve on the UFH should mix the temperature down to  35C or whatever the setting is.  Of course you don't want to have to  heat  the water to 55C  and then have the mixing valve  reduce it by 20C   but  if the radiators need 55C then  you have to raise the setting.   In cold weather the heat pump probably won't  reach output temperatures above 40C.   

You need to have some way of boosting the temperature on occasions.   An immersion using off peak electricity  is  an option.   It would cut out on the thermostat if the heat pump reaches the target temperature.    In a normal winter  there is usually  only a total of a few weeks  with  below zero temperatures.
Logged

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
titan
Hero Member
*****
Offline Offline

Posts: 531


« Reply #13 on: January 23, 2011, 11:03:07 PM »

The most efficient way to run this system is to have low temperature rads to keep keep the ashp flow temperatures as low as possible. Oversized normal rads are a compromise , proper low temperature rads should work fine. Low flow temperatures are the answer to effective ashp operation.
Logged
baker
Sr. Member
****
Offline Offline

Posts: 320


« Reply #14 on: January 23, 2011, 11:59:22 PM »

Hi
sorry to hear of the problems
but it looks like a design problem
rads don't work  '@40c  as you now know
try fan coil rads  / java . go big
the defrost cycle is  temperature activated. and  timed to suit climate
could be a faulty sensor or reversion valve
does the heat pump auto re start after a set time?
is their any non return valves on Circe?
Logged
Pages: [1] 2 3   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!