Frozen Heat Pump

matt_drummer

That is a bit of a problem!

I would head over to openenergymonitor.org for some advice on the forum.

All other Samsung owners are talking about their heat pumps defrosting at regular intervals, they have very robust anti freeze systems.

It shouldn't look at all like that, it will barely be working.

If you have turned it off what frost protection do you have?

Do you have glycol in it?

I would be concerned that is is frozen and when it thaws you will have damaged something.

matelodave

What we really need to know is whether the heatpump sits like that all day or does it actually defrost - mine looks like that before it does a defrost cycle and is clear after a defrost cycle.

the_lunatic_is_in_my_head

QrizB said:

the_lunatic_is_in_my_head said:

I'll pop the photos over to the installers on Monday and see what they come back with. 

It's due to warm up from Sunday, so with a bit of luck it'll have thawed itself by then!

Plus temperature this afternoon has seen a fair bit melt away already so I'm sure it will be fine going forward but as it was only installed in August if there was something not quite right the installer is more likely to be helpful the sooner it's pointed out (He says hopefully!). 

Thanks @matelodave

It was fine yesterday morning as I put the HW on and it heated up within the usual 1 hourish. I only noticed today as the HW went from 15 to just 26 in a hour.

Similar to yourself it used around 48kw yesterday, and generated 48kw as well, but when I noticed the problem earlier today it was clear by standing in front of it that there wasn't much air being pulling through the heat pump and I switched it off in a bit of panic wondering if stressing the thing with little air flowing through it would cause damage.

The heating is on all the time it's only HW I turn on/off, if 3 of us have a bath at say 7pm and we don't need HW for another 24 hours it seems pointless to heat it up straight away. I know these cylinders are very well insulated and don't lose much heat but you are paying for whatever it does lose in those 24 hours. 

Is your system set to hot water or heating priority?

Yes HW first but obviously not if HW switched off and temp on thermostat was 0.5 below target earlier today which I've not seen before.

Have you got TRV's on your rads as well. If so they'll reduce the volume of water going round the system which will reduce the system capacity to defrost.

We do but they are all open on max apart from on in the landing as the wood burning stove heats the landing more than is needed and would rather the CH was doing it's best in the bedrooms.  

The whole thing seems to work very well, just todays blip is due to the thing being frozen and air not getting through. 

As an aside I'm not sure why we have a 12Kw pump (they did a heat loss calculation and said that's what we needed but), checking the usage it mainly pulls 1.5Kw for heating (or just under 4Kw if temp is heading towards zero), around 4kw for HW. I don't think it's ever pulled anywhere near 12kw out of the mains. 

matt_drummer said:

Do you have glycol in it?

Honestly I have no idea, the installers basically said leave the HW on, leave the CH on and only touch the thermostat to adjust CH temp and that was it.

Other than looking at how much energy it uses/generates I don't touch the controls and it's been working fine so I assumed it was set up as required (installer was a massive company so the quality of work should be consistent). 

matt_drummer said:

If you have turned it off what frost protection do you have?

I didn't turn the pump off with the kill switch, just HW and CH off at control pannel, as it's thawed a bit the HW has just gone back on now so will check it in half hour and if all seems well put the CH back on too. 

michaels

Max draw for a 12kw heat pump will be about 4kw, the 12kw is output not input.

Ours has frosted up too for first time ever  
May try asking it to run AC mode for a bit as the defrost cycles don't seem to be long enough to melt it clean

Grumpy_chap

matelodave said:

We chewed through around 47kwh yesterday for all our electricity (about 37kwh for heating) and it ran for 24 hours and we still woke up with a warm cozy house and a tank full of hot water

Sorry if this is a thread hijack.  So far today we used 11 kWh electricity and 146 kWh gas, which is heating, hot water, some cooking.
If we could have the whole house down to 50 kWh energy that would be amazing.

As for the OP, heat pumps don't heat as quickly in the cold but will run auto-defrost cycles if left to their own devices.

matelodave

Grumpy_chap said:

matelodave said:

We chewed through around 47kwh yesterday for all our electricity (about 37kwh for heating) and it ran for 24 hours and we still woke up with a warm cozy house and a tank full of hot water

Sorry if this is a thread hijack.  So far today we used 11 kWh electricity and 146 kWh gas, which is heating, hot water, some cooking.
If we could have the whole house down to 50 kWh energy that would be amazing.

As for the OP, heat pumps don't heat as quickly in the cold but will run auto-defrost cycles if left to their own devices.

Yes but your 140kwh of gas would have cost you around £9.49 (at 6,5p) plus 11kwh of leccy at 25p = £2.75 - a total of £12.24

You do need to do the sums  - my 40kwh of leccy would produce 120kwh of heat so not much difference from your gas boiler and you would have to tweak it a bit to achieve a decent efficiency

My 50kwh at 25p = £12.50 so it's not exactly cheaper than gas although you do save on the gas standing charge. Dont forget that a heatpump could easily cost you £8-10k compared with £4k or so for gas unles you can get an advantageous instal using the £7.5k grant.

Grumpy_chap

matelodave said:

Dont forget that a heatpump could easily cost you £8-10k compared with £4k or so for gas unles you can get an advantageous instal using the £7.5k grant.

Well, the gas system is installed and paid for and done the necessary years service so  it has no further capital cost / depreciation.

I do keep getting the calls about the air source heat pump grants but never trust the callers.  I assume there are some eligibility criteria.

matelodave

I have a heat pump because there is no gas where I live. The alternatives are Oil, LPG or storage heaters and I chose a heatpump but  IMO it's not cheaper to run, than mains gas or even oil at the moment and probably wont be until something is done to equalise the cost of gas and leccy.

 If mains gas was available that's what I'd have, even after having a heatpump for 14 years'

 It does what we want and we are happy with it but mains gas is still cheaper and easier to live with, unless you put a fair amount of effort to getting a well specified, properly installed and commissioned system and learn how to drive it.

Do your sums, my leccy bill over 12 months comes out at around £2k a year (£166 a month) how does that compare with your combined gas/leccy bills.

NedS

Getting back on topic, it's perfectly normal for heat pumps to frost up like that. We don't have temperatures that cold here, but my Samsung unit starts frosting up below around 2C, and we typically do not see temps below -2C.

If you look in the control panel in the gear icon, the first option (top left) will list a defrost mode. This will be highlighted in blue when the system is running a defrost cycle.

The system will draw heat from whichever circuit is active at the time, either heating or DHW, and you will see the flow temps plummet as heat is drawn out of the circulating water to defrost the unit. It typically takes around 5 mins for a defrost cycle which should completely melt the ice on the unit assuming there is sufficient heat in the heating or DHW circuit. If you stand outside and observe, you will see the fan stop and hear the compressor running, and the ice should start to thaw. Once completed, the fan will restart, normally blowing out a plume of warm moist air

If there isn't sufficient heat in the system then you can enter into a defrost death spiral where the system can never effectively defrost itself - you probably need more system volume so a volumiser will help.

How often the system frosts up depends on a number of factors - how cold it is, how much moisture there is in the air (there tends to be less moisture at very cold temps so frosting is worst between 2C and -5C) and how hard the system is working (if it's pulling 4kW, it's working pretty hard). When ticking over maintaining heating, my system defrosts around once per hour, but when the DHW cycle kicks in and the heat pump is running flat out, it can frost up within 20-30mins, before the DHW cycle has a chance to finish.

I would sit and observe it for a couple hours. Is it trying to run a defrost cycle (if not, you have an issue). If it is, can the defrost cycle complete normally (if not, you likely need more volume/heat in the system)

Reed_Richards

But if the heat pump is badly frosted now that may be as the result of a "death spiral".  So I would wait until temperatures warm up before doing anything. That will be on Monday, according to the weather forecast.