I wish I was around Derek all the time to do just this but work takes me away for too long at a time. Increasing 2103 what will this achieve anything? And 04 at 0c? when it's -2c outside.

Everything seemed OK until it became cold now I feel like we have gone backwards for me then to be out of the country on Monday till next year.

This is why I find it so frustrating is that weather is so up and down and damp as of late. I honestly thought we were doing the right thing when the house was designed and someone would commission the unit and we'd be on our way. How utterly wrong we have been.

4 folk I know have ashp's. All of them have hassle

If anyone asks me what's your thoughts on an ashp I tell them keep your boiler for as long as possible. Same with the cars, they will have to pull me out kicking and screaming or that the tax will ruin us to be forced in an EV.

Posted by: @roamingbull

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I wish I was around Derek all the time to do just this but work takes me away for too long at a time. Increasing 2103 what will this achieve anything? And 04 at 0c? when it's -2c outside.

Everything seemed OK until it became cold now I feel like we have gone backwards for me then to be out of the country on Monday till next year.

This is why I find it so frustrating is that weather is so up and down and damp as of late. I honestly thought we were doing the right thing when the house was designed and someone would commission the unit and we'd be on our way. How utterly wrong we have been.

4 folk I know have ashp's. All of them have hassle

If anyone asks me what's your thoughts on an ashp I tell them keep your boiler for as long as possible. Same with the cars, they will have to pull me out kicking and screaming or that the tax will ruin us to be forced in an EV.

 

 

 

Setting the WC curve at 50C LWT @ 0C OAT, could produce the same slope as 55C LWT @ -5C OAT, the difference being that in the first instance the LWT will be limited at 50C at temperatures below 0C, in the latter situation the LWT would be limited at 55C at temperatures below -5C.

There is no reason why your wife, partner or a friend could not make the adjustments, the important thing is to only adjust one parameter at a time and don't go mad.

But I was under the impression that the higher the 2102 setting the higher the costs ?

My wife isn’t interested. And obviously I will be getting earache whilst away if it’s cold. 
It was miserably cold in the house tonight in which I stated we’d walk to the pub and get warm. And that’s where we are now. 

The system works well when it’s warmer. Says it all really  

Posted by: @roamingbull

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But I was under the impression that the higher the 2102 setting the higher the costs ?

My wife isn’t interested. And obviously I will be getting earache whilst away if it’s cold. 
It was miserably cold in the house tonight in which I stated we’d walk to the pub and get warm. And that’s where we are now. 

The system works well when it’s warmer. Says it all really  

 

You would need to provide the full details of your system for a correct appraisal to be made. It could be that your system has not been correctly designed, installed and/or commissioned.

Posted by: @derek-m

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Posted by: @roamingbull

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But I was under the impression that the higher the 2102 setting the higher the costs ?

My wife isn’t interested. And obviously I will be getting earache whilst away if it’s cold. 
It was miserably cold in the house tonight in which I stated we’d walk to the pub and get warm. And that’s where we are now. 

The system works well when it’s warmer. Says it all really  

 

You would need to provide the full details of your system for a correct appraisal to be made. It could be that your system has not been correctly designed, installed and/or commissioned.

 The system was designed by MainCor if I remember rightly.Plumber from building co. had to go on a course before he was allowed to install the system.Grant tech came to commission the system  

Had the Elite heat geek around earlier in the year.He carried out an audit and he was happy with the installation but not the control/set up side which adjustments were made.

I thought as of a few weeks back this nightmare was over as it seemed to be keeping the house at 21c. Cold snap arrived and I feel as if we’ve gone back to square one after 3 years. 
I don’t have the system set up that it shows me all the graphs etc as shown on the forum. 

It’s coming to the point that the large project we went through and the ongoing hurdles we have is not worth it.We have spent large amounts of money to get our dream to us thinking it’s ok. Ok is not good enough for me so we have spoken about moving after only a few years  

This Ashp issue doesn’t help.

Posted by: @mikefl

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@mab Sadly, lower temps aren't helping me at all - entered the night at -7C and left at -2C.

I tried dropping target LWT yesterday (the theory being that if I could hit that LWT, HP would modulate down, and "less energy required" = "less energy taken from air" = "fewer defrosts") but that didn't help, as I still didn't hit the target overnight. Running thru the night I just about maintained 18C downstairs, and 16C upstairs, but I'm needing extra heating to feel comfortable.

Defrost every 40 or so mins. It's the recovery from defrost which is the issue I feel. I'm wondering if stopping the secondary pump during a defrost cycle would help, as I'm circulating the cooling LWT which might be cooling the radiators faster than they'd be losing heat to the rooms? It might not be a simple yes/no answer though.

-- Attachment is not available --

@mikefl

Well, looking at your chart and comparing with my own observations it does look as if it's performing better at -7 than at -3:-

at -7 lwt and rwt rise to a point, then perhaps it's starting to ice a bit and only holds lwt constant until de-icing kicks in; whereas at -3 it looks as though it's icing up solidly and the lwt starts to drop before the de-iceing starts. This suggests that if we get properly cold dry weather, the de-icing finction will do it's job with a small loss in performance.

Of course,  that doesn't help us work out what to do in our cold damp winters 🙁 , although the 1st thing is to work out what temp/conditions are a problem for the hp to minimise wasting power. Then if possible, see if we can find a workaround.

One of my friends is renovating their house and was asking about ASHPs i have pointed out that they work very well in milder weather but can be proplematic near 0c: following discussion with the plumber, he's having an ASHP but there will also be an oil fired boiler plumbed into the heating system. That way, he can enjoy the benefits of the ASHP and PV for most of the year, and only pay for oil when the ASHP is not cost-effective. (Quite how the decision to switch to oil and back will be made is tbd). He does have to pay to install both however.

I did have a similar thought about dropping lwt to reduce icing (I'm operating with UFH and my WC targets LWT at about 29 or 30c at 0c), but the HP still insists on tunning flat out to reach target temp post defrost and unless i just run the HP 24hrs day i doubt it would heat the house at a lower setpoint.

I suspect that stopping the 2ndary pump (how?) wouldn't help much as your emmitters will still be losing heat - although it's difficult to know how much heat the HP pulls out to do it's defrost (it would help if it didn't wait til the HX and its ice pack were down to -20c before trying to warm it up!).

A lot has been posted here by others since i was last here that i still have to read to catch up...

Hi there, apologies for hijacking the thread but I’ve found it very relevant to an issue we have, and also useful in trying to get clued up before the pump manufacturer visits. 

We had a Grant Aerona 6kW installed in summer and it’s been a wonder until a few days ago when it started taking hours to go from 18C to 19C. It made us check flow temps (not done it before) - outbound was only in the 30s, return only a few degrees less (system reached 45C during commissioning and return was about 6-8C less). 

The installer (who’s been great) came out to troubleshoot but couldn’t see a fault. It’s almost a text book install as the heat loss was done by an independent specialist (3.4kW), the house is a well insulated new-build with u-value 3.5, all rads oversized with TRVs (all open), bathroom rail no TRV,  pump on outside wall with <10m pipe run into indoor plant room via loft where there’s a buffer tank. The only thing we’re not too keen on is the Hive thermostat which seems overcomplicated and glitchy, particularly the room temp reading. However, we don’t have enough tech knowledge to know if this can be affecting something as fundamental as a flow temp.

The installer explained the troubleshooting but we’re not techie enough to repeat it properly so it will sound a bit ‘Janet and John’. He tried to increase flow temps for heating and DHW by using weather compensation and fixed temp, also varying the target flow temp out (45C, 50C, etc.) and the variance with the flow coming back. There are three (?) speeds on the pump, tried those. There was more, but didn't grasp it.

He spoke to Grant and seemed to get some numpty questions (heard the call) which is what’s worrying us about them coming out. We’ve had this before where the manufacturer doesn’t understand their own system, blames the installation, then disappears into the ether. Any advice you can offer in approaching this would be much appreciated.

My simple mind says that, if the flow temps go back up when the milder weather comes (hopefully this week), the pump has a cold weather issue (maybe overdoing the defrost cycle?). If the flow temps stay low in mild weather, then it’s an issue with the pump. It’s a shame we haven’t checked flow readings before but haven’t needed to as it’s performed really well.

Thanks for any help with this!

Sentinam

@mab My defrost cycles are still on-going, and have been for the last 66 hours solidly, apart from that hour when the HW heating happens, when LWT shoots up to over 55C easily (I realise this is because much less heat is being lost to the HW cylinder than to the house during CH times - it's just annoying to see). I'm trying to reconcile myself that these bad days are infrequent in the UK, although likely to increase, and I have at least 2 major things I can do to improve heat retention in the house. Not for this year tho.

My plan to stop the secondary pump would be to just switch off the zone valves (i.e. turn off heating) whenever a defrost cycle is detected, as no heating is actually happening at that time.

Last night I was reading up on the immersion heater in the LLH that all Grants have, but generally aren't wired up. I'm wondering if that will help - in two ways: during colder spells help the HP hit target LWT, and also make the defrost cycles less hard hitting on the HP itself. It has a set-up specifically for defrosting. The wiring seems fairly straightforward (power will need looking at with a 3kW element) and simple control feed from HP.

I'll create a new topic to see if other Grant owners have tried this and what impact it's had, then maybe look at trying it out.

@mikefl I'd be interested in that thread.

@mikefl I'll be interested in that thread too.

As an experiment i monitored the HP running the UFH this pm - and i was hoping to see when it would trigger a defrost if it had been running >40mins - but actually,  it needed to defrost by 40mins anyway, but i did get the following readings (via the remote controller so too rounded for precision):-

Power  defrost  OAT  LWT   RWT

  W            c         c        c         c

1900      -1          6       26       21

1900      -4          5       25       21

1900      -7          5       24       21

1800     -12         5       23/4   21

1800     -14         5       23       20

1800     -16         5       22       20

1700     -18         5       22       19

1700     -19         4       21       19

Defrost (at about 40mins since the last one)

Hope the diy formatting above isn't completely lost.

Flow rate is 28l/m so heat output at Dt 5c is roughly 10kw.

So it goes from a heat o/p of about 10kw and a cop of about 5, down to a heat output of about 4kw and a cop of about 2. Suggesting an average cop of about 3 -

except...

I didn't think to record times til it was too late which is a pity, as it took something like 20mins to go from -1 to -4, but as the ice builds up, the airflow drops, and the rate of deterioration increases. So the average cop is better than 3, guessing 3.5ish, maybe more. So not as terrible as i had guessed.

But it also shows that as well as actually losing heat from the house during the defrost cycle, heat output is significantly down during the 2nd half of the 40min heating phase.

Probably a dumb question but why isn’t there a more efficient way of defrosting the fins? How can sucking back heat from the house make sense in cold weather?

Posted by: @sentinam

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Probably a dumb question but why isn’t there a more efficient way of defrosting the fins? How can sucking back heat from the house make sense in cold weather?

I'm afraid that it is the Laws of Physics to blame, as just like a wife, they insist upon being obeyed. 🙄 (sorry Amanda, or whoever it was complained about my previous attempts at humour).

The ice forms on the evaporator fins, because the moisture in the air condenses when it comes into contact with a cold surface, and since the refrigerant gas inside the evaporator is in the region of -40C, then the evaporator fins become cold. Soon after condensing the water on the fins will start to freeze, and in the process will reduce the air flow and make the heat pump less efficient.

The present method of removing the ice is to reverse the refrigerant gas flow, so instead of absorbing thermal energy at the evaporator and transferring this energy to the central heating water, via a heat exchanger called the 'condenser', it does the opposite. The heat pump therefore takes thermal energy from the CH water and uses it to heat up the evaporator.

Alternatively you could buy a very large quantity of clean, dry, air (preferably warm) and use this as the air supply for your heat pump. 😋