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Author Topic: ASHP setup with rads and UFH  (Read 9847 times)
cornishben
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« Reply #15 on: January 24, 2011, 08:09:21 AM »

ben taking notes...
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flip
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« Reply #16 on: January 24, 2011, 12:07:10 PM »

In answer to some of your questions:

1. The pump will restart after 3 error codes automatically and then go off and require a manual restart, waiting for a response from supplier as to settings issue again. Problem here is that when we are in bed there is no way to tell if its on or off and results in a cold morning.
2. I understand that rads do not work good at 40 degC, but at the moment the buffer is set to pump water at 42 degC but when upstairs valves are open the heat pump struggles to get to this and keep the rads constant, this is why I wanted to boost the heat pump to at least try and get some hot water in there. With a return temp setting of 55 the pump will output 60, yes the ufh will regulate down to 45 but i think no other choice. I just can't believe I would need to consider a further booster to get the heat in there on a machine that cost around 4800 plus the 200 litre buffer and all the rest totals in around 6K plus labour.
3. If I were to set the timer on the buffer tank to be off through the night, so no flow out to UFH, only ASHP on, filling up buffer with hot water, I guess this would work, but is this not going to use lots of energy in the morning warming up the slab all over again? May be an option though. Scenario and suggested way forward:

a. set ASHP to 50 degC return temp to the buffer.
b. buffer timer to switch off grunfos pump at midnight and on at 5am to warm house in morning
c. remains on for rest of day until midnight cycle again
d. rads on at 8pm till 10pm upstairs

Is this the best way forward ignoring the defrost for now?
ANYONE WANT TO BUY IT? I'M GOING GAS, NOT SUITABLE FOR MY HOUSE ME THINKS. BUYER COLLECTS. WARRANTY RUNS OUT IN FEB. (2 YR OLD) OFFERS PLEASE.
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baker
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« Reply #17 on: January 24, 2011, 03:09:39 PM »

 HI
it looks like the buffer is the problem
if it can run down when the heat pump it on
what is the designed rest peroid for the heat pump
the buffed is designed for this peroid only
if the heat pump needs a manual restart
its not the start up secquence
maybe high limit /low pressure in sequence sensors
what part of the country are you in
i am sure it can be sorted / do you have the error codes and manual
send me email
john.eco4@gmail.com
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flip
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« Reply #18 on: January 24, 2011, 06:47:11 PM »

The heat pump has a 3deg rest period, the time will change dependant on outside temp and other factors such as usage of hot water in buffer tank etc.
I have currentlly set the heat pump to work on a 50deg return temp, it goes into standby when it gets to this and comes back on at 47deg. However when it comes back on the temp does drop to around 46degC and then continues to go up again to 50degC.

The buffer has a temp switch on it clamped to the return pipe and I have set it to come on no less than 46degC so that my rads will get a good flow of hot water into them. Going to see how it goes but temps here in S.Wales at the mo are around 5 degC as I type this so defrost not so much an issue and i await contact from heat pump manufacturer to change these settings.

Will also try tonight timer to switch off the pump from the buffer and restart in morning at 5am to give us heat when we go to work.

Worth a try I guess.

ANYONE HAVE A DELONGHI ASHP??
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dhaslam
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« Reply #19 on: January 24, 2011, 09:35:26 PM »

You could start the pumparlier and  also start heating earlier  and try to get all the heating into the  off peak electricity rate.    As you say the floors, once warm, will keep downstairs warm all day and of course any sun through the windows will add to that.     To some extent heat from downstairs will filter upstairs  during the day.   

I try to have all underfloor circuits off by mid morning but the buffer tank can manage that with the pump off.   However since my heat pump only outputs 2-3kW   I have to also use it for a few hours in the afternoon, which is much more expensive,  so it costs two euro per day instead of one.    However by next winter most of the underfloor heat should come from the seasonal store.
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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
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« Reply #20 on: January 25, 2011, 07:31:51 AM »

What is the ideal pumping condition?
I currently have it set to:

1. ASHP on a return of 50degC to the buffer, goes off and back on at 47degC
2. Buffer pump switches on at 46degC

New timer settings are:
1. buffer tank pump on at 5am till 9am
2. again at 1pm till 10pm

Not sure if this is the way to go but trying it out.
Any comments?

I am not on Eco7 electric as does not work out for me to be worth it.
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baker
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« Reply #21 on: January 25, 2011, 08:30:40 PM »

if you cannot use economy 7  and have natural gas
fit a combi will work out better
your heat pump is designed for underfloor heating to run on eco7
for a home 200sqm approx
if you fit a combi and do the rads and dhw
hope this helps
regards
john
 
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flip
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« Reply #22 on: January 25, 2011, 10:05:05 PM »

I have come to the conclusion that the ASHP will not heat my rads.
Tonight I turned off the UFH and turned on the rads to the first floor 8 in total.
Set ASHP to set point of 46 Deg C into the buffer and let rip.

As soon as the ASHP got to its max at 46 and turned to standby I watched it until it got to 44 and then activated buffer pump to send water to rads. At 43 the ASHP switched on as expected but failed in a 2 hour period to get to 46 again. Why is this, the temp outside is 7 deg C so the ASHP should be able to perform enough to get the temp to the rads only.

Are my buffer settings inadequate, what I am doing wrong here, or is the ASHP a load of shoit?
Getting frustrated now, lots of money spent here and wasted.
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dhaslam
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« Reply #23 on: January 25, 2011, 10:13:30 PM »

It is very hard to tell how much heat the  radiators are using.    The only way to check the  output of the  heat pump is to  cool the buffer tank,  turn off the radiators and underfloor heating  and then see how many degrise rise  per hour it can achieve.   
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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
Baz
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« Reply #24 on: January 25, 2011, 11:46:44 PM »

Went back to the beginning and see the pump is 11.8kw. You never said how big the place is but 2kw would boil most rooms after a few hours so that power must be enough for quite a few rooms, or it isn't giving anywhere near the output. What's the electricity consumption in eg the 2 hour period you mention?
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flip
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« Reply #25 on: January 26, 2011, 10:18:26 AM »

when the pump is running output on the electric meter shows around 3Kw. Yes its a 11.8Kw machine, but it does DHW also but I do not use this function.
I agree it should be able to supply a couple of rads.
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dhaslam
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« Reply #26 on: January 26, 2011, 10:36:59 AM »

The actual  output in cold weather is probably closer to  6  kW.    It should be able to raise the temperature of the buffer tank  by about 25C per hour with no heat drawn off.      It it isn't able to achieve 6 kW output, or close to it,  then there is something wrong.       
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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
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« Reply #27 on: January 26, 2011, 11:43:46 AM »

yes it will raise the temp of the buffer quite easily with no heat output to rooms when the pump is off. this is what i have done:

1. switched off the buffer pump
2. let the ASHP get to the set point or return temp of 45 deg C it then goes off
3. it then begins to drop slowly to a 3 deg hysteris and when reaches 42 deg C it starts up again, I switch the buffer on when it gets to 44 deg C
4. As buffer begins to pump water into house the ASHP drops to 41 and can not get back up to 45 again

Please see my system below:


* Presentation1 (20110126114124).pdf (61.79 KB - downloaded 248 times.)
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dhaslam
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« Reply #28 on: January 26, 2011, 12:10:16 PM »

The time taken to  gain 3C  may not be a very precise  measurement because  it is only going to be  around ten minutes and  the full tank may not be heated by  3C.   You need to leave the heat pump off long enough to drop the temperature down  below 30C and then see how long it takes to come back up.      The reason why the  heat pump struggles around  44C is because  it's output reduces as  temperature  rises and also the output of the radiators goes up.   
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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
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« Reply #29 on: January 26, 2011, 12:35:15 PM »

what setting would you recommend i put the buffer pump onto?
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