Any experience of the GS200 small ASHP?

[DamonHD]

Hi,

 

Does anyone have any views on this?

 

https://www.groundsun.co.uk/small-home-and-apartment-heat-pumps/

 

Just ran across it today.

 

Rgds

 

Damon

[Jeremy Harris]

Looks like a variation on the  popular integrated heat pump and water cylinder units that are common in China.  ESP do a similar unit, the Ecocent, that I looked at a few years ago (at that time the Ecocent was definitely a re-badged Chinese unit).  Lots of similar units on places like Alibaba:

 

 

 

 

 

[DamonHD]

Thanks!

 

When I hear "Ecocent" I think of the unit that drew its heat from the house internal air, which is definitely a no-no for me.  But this is clearly simply avoiding the fan unit being external.

 

Rgds

 

Damon

[Jeremy Harris]

14 minutes ago, DamonHD said:

Thanks!

 

When I hear "Ecocent" I think of the unit that drew its heat from the house internal air, which is definitely a no-no for me.  But this is clearly simply avoiding the fan unit being external.

 

Rgds

 

Damon

 

 

The Ecocent could just be ducted outside, I believe that is how the very similar units are often used in China.  I'm pretty sure it was just an ESP idea to use air from inside the house, as they came up with a way of combining the Ecocent with their MVHR unit.

 

 

[DamonHD]

Just had an interesting chat with a chap from Ground Sun, and he'll send me over a datasheet to think about.

 

Rgds

 

Damon

[Thedreamer]

I've ordered a similar system but called a Joule Aero.

 

I was put off by some of other similar models as the cylinder might not be very long lasting. 

 

I've ducted mine from the bathroom, en-suite and utility as it's also providing my ventilation.  I'm going to lose some heat from air but I hope this is not noticeable. 

[DamonHD]

Hi,

 

This one?

 

https://www.jouleuk.co.uk/knowledge-centre/?_sft_wpdmcategory=heat-pumps&_sf_s=Aero Hot Water Pump

 

Rgds

 

Damon

[Jeremy Harris]

Looks to be very similar to the Ecocent and all the dozens of Chinese integrated heat pump cylinders.  They've been around for well over 10 years now in China, with many manufacturers of the components.

[DamonHD]

That would be comforting.

 

Any particular downsides, eg having all the works inside including the air side, is presumably going to be quite noisy?

 

Rgds

 

Damon

[Jeremy Harris]

1 hour ago, DamonHD said:

That would be comforting.

 

Any particular downsides, eg having all the works inside including the air side, is presumably going to be quite noisy?

 

Rgds

 

Damon

 

 

I looked closely at the Ecocent some years ago and it wasn't very noisy.  Admittedly I only stood next to it running on their stand at the Swindon show, but it didn't seem to be any noisier than something like a bathroom extract fan.  I would guess that all these heat pump cylinders most probably use a very similar design, maybe even identical components, as seems very commonplace in Chinese made products of this type, so would guess that they are all pretty similar in terms of noise level.  None, as far as I know, are inverter controlled, as for just heating water this doesn't really offer any advantages, so they are pretty simple devices, really not much different to a freezer compressor working in reverse.

[ProDave]

What would worry me is the accounts you hear of Ecocent cylinder failure meaning the whole thing is scrap.  I had to do some work at a house last year where the less than 10 year old Ecocent cylinder was leaking.  It was replaced with a Mitsubishi outside ASHP but I was there to reinstate extract fans to the bathroom as by ripping out the EAHP system it had left them with no ventilation.

[Jeremy Harris]

3 minutes ago, ProDave said:

What would worry me is the accounts you hear of Ecocent cylinder failure meaning the whole thing is scrap.  I had to do some work at a house last year where the less than 10 year old Ecocent cylinder was leaking.  It was replaced with a Mitsubishi outside ASHP but I was there to reinstate extract fans to the bathroom as by ripping out the EAHP system it had left them with no ventilation.

 

 

Seems to be a relatively common problem.  I believe there are a couple of issues that contribute to this.  The first is that there is a sacrificial anode fitted inside the cylinder, that needs to be replaced regularly.  If this isn't done, then the cylinder may fail.  The second issue is with the vitreous lining failing.  The cylinders are, I believe, enamelled internally for corrosion protection, and this enamel has been known to crack.

 

The solution seems to be to mate the Chinese heat pump technology, with its pretty efficient direct refrigerant to water heat exchanger, with well-proven British cylinder design and construction.  This may well be what the British companies selling this type of unit are now doing.  ESP were originally just importing complete units from China, making them safe to use, and compliant with our regs, and then re-selling them.  I believe they switched to doing assembly here at some stage, perhaps to overcome some of the issues that were arising.

 

As the longest standing importer of these things, I'd suggest that ESP probably has more knowledge of them than most, so they might be a slightly better bet than the other companies that seem to be importing them, or at least importing the key sub-assemblies.  The whole area surrounding the import and re-badging of stuff like this seems a bit fraught, as it can be really challenging to know just what any supposed UK "manufacturer" is actually manufacturing, and how much they are just buying in as almost complete assemblies.  A friend makes custom bicycles, fairly high end stuff, and buys parts from China (technically Taiwan).  His biggest single problem is getting manufacturers to stick to his specifications, as he's found that they will always try to reduce cost, thinking that's what he really needs.  He's resorted to using the services of a Brit living in Taiwan as a quality manager, to go around and physically check that cheaper materials aren't being substituted in his parts.

[Thedreamer]

This was the main reason I went with the Joule product. 

 

The cylinder (stainless steel) should be a higher quality material when compared with some of other similar systems.

 

If you change the anode annually there is no reason why the other systems would not work well. 

 

The heat pump is small but simple technology.

 

The tank I'm purchasing is around £2,500 which is quite cheap when you consider that it's has a small heat pump, hot water tank and also provides outwards ventilation.

 

Of course I don't really know how well it will perform until it's all commissioned. The heat pump should work very efficiently in the summer but in the winter I will probably need to use more of the back up electricity to heat up the water. 

 

I have also made extra consideration to the noise of the system. Fitted a good silencer, going with a flexible duct for the last bit and using a thick anti vibration mat 

 

The alternative I was considering was splitting the heat pump and hot water cylinder. 

[Jeremy Harris]

Why should the heat pump not work as well in winter?  Our experience has been that ours seems to work with a COP of well over 3 (often over 3.5) in winter.  These direct heat transfer heat pumps are a bit more efficient, as the condenser is in the water cylinder, so even if run at a higher water temperature I'd by very surprised indeed if they don't deliver a COP of at least 2 in sub-zero conditions.  Even a COP of 1.1 is cheaper than using direct electric heating, and the outside air temperature would probably need to be around -20°C or so for the performance to be that poor.

 

How does an externally ducted heat pump like this provide ventilation?    ESP tried to integrate their Ecocent with an MVHR and when I looked at the data the results didn't look at all good, due to the gross imbalance in the MVHR part.  The air flow rate through the ducts of one of these units has to be very high, much higher than that through an MVHR, just because of the low heat capacity of air.  I've also seen some claim that the cool air output from a unit like this can provide cooling inside the house in summer, if the exhaust duct has a valve to redirect air inside the house.  Five minutes with a calculator reveals this to only have a very limited impact, probably not worth the hassle of the additional ducting.  These heat pump units are usually rated at between 2 and 3 kW heat output, so they will provide enough hot water to recharge the tank in about 2 to 3 hours, then they will shut off.  Solar gain on a hot day can be around 800 W or so per m², so it's pretty easy for a house to receive a few kW of heat for more than just a couple of hours, plus there will be times when the need for hot water does not align with the need for air cooling. 

 

 

[Thedreamer]

20 minutes ago, Jeremy Harris said:

Why should the heat pump not work as well in winter?  Our experience has been that ours seems to work with a COP of well over 3 (often over 3.5) in winter.  These direct heat transfer heat pumps are a bit more efficient, as the condenser is in the water cylinder, so even if run at a higher water temperature I'd by very surprised indeed if they don't deliver a COP of at least 2 in sub-zero conditions.  Even a COP of 1.1 is cheaper than using direct electric heating, and the outside air temperature would probably need to be around -20°C or so for the performance to be that poor.

 

How does an externally ducted heat pump like this provide ventilation?    ESP tried to integrate their Ecocent with an MVHR and when I looked at the data the results didn't look at all good, due to the gross imbalance in the MVHR part.  The air flow rate through the ducts of one of these units has to be very high, much higher than that through an MVHR, just because of the low heat capacity of air.  I've also seen some claim that the cool air output from a unit like this can provide cooling inside the house in summer, if the exhaust duct has a valve to redirect air inside the house.  Five minutes with a calculator reveals this to only have a very limited impact, probably not worth the hassle of the additional ducting.  These heat pump units are usually rated at between 2 and 3 kW heat output, so they will provide enough hot water to recharge the tank in about 2 to 3 hours, then they will shut off.  Solar gain on a hot day can be around 800 W or so per m², so it's pretty easy for a house to receive a few kW of heat for more than just a couple of hours, plus there will be times when the need for hot water does not align with the need for air cooling. 

 

 

 

Thanks for this, interesting comments.

 

I was thinking that the heat taken up the duct into the heat pump would need to be replaced by heat from some other form. They say it can be 1 to 4 efficiency, which I should get in the summer, but in the winter I don't know what I will get. 

 

The moist air (from the bathroom, ensuite and utility) will be extracted up into the duct and the heat used in the pump and the moisture dumped outside. This is more extraction as there is no intake of air. The ducting is running one way.

 

Once it's all installed than I plan to crunch some number to find out how efficient this system is.

 

 

[Jeremy Harris]

So, are you planning to use this with the very high air flow rate for this unit somehow integrated into an MVHR (problematic, as it gives a massive air flow imbalance) or as a stand alone extract system, with no MVHR? 

 

The Joule unit was, I thought, designed to just have two external terminals, one drawing in outside air, the other discharging cooled exhaust air, pretty much like any outdoor ASHP, but just with the pump itself inside the house. 

 

Drawing air from inside the house would work, although it will significantly increase the heat loss from the house when the heat pump is running (the heat loss would be about the same as the heat delivered to the hot water, so the heating system would need to replace this "lost" heat).

 

It's worth looking at how much air needs to flow through a heat pump to deliver the specified output.  The heat capacity of air is typically about 1.2J per litre per K.  If the cylinder capacity was 200 litres, and the minimum temperature was 35°C and the maximum 55°C, then the water in the cylinder is going to need about 16.8 MJ of heat energy delivered from the heat pump.  If the heat pump takes 2 hours to heat the tank, then that means it has to deliver about 2.33 kW (J/s) of heat.  If about 2000 W of this heat comes from the air flowing through the ducts, and if the heat pump is working with a differential temperature of, say, 25°C (pretty much how it may operate when drawing air from inside a house and discharging it outside) then it's going to be shifting about 67 litres/second of air through the ducts.  

 

The building regs extract rate from an intermittent bathroom extractor fan (no MVHR system) is 15l/s, that from a utility is 30l/s, so extracting from three in-use rooms would be a bit high in terms of extract rate, but two hours is a lot longer time period than needed (10 to 15 minutes would be OK usually).  This unit is going to extract around 4 kWh of heat from these rooms, so not only will the heating system need to provide this heat (accepting that maybe 10% might be recovered from the hot water use - most will go down the drain) but the air vents in the house will need to allow 67 litres per second of cold outside air in to balance the extract air flow.  That's a fair bit of air, so will need fairly large air vents into the house, and probably create some unwanted cold drafts.

 

 

[Thedreamer]

2 hours ago, Jeremy Harris said:

So, are you planning to use this with the very high air flow rate for this unit somehow integrated into an MVHR (problematic, as it gives a massive air flow imbalance) or as a stand alone extract system, with no MVHR? 

 

The Joule unit was, I thought, designed to just have two external terminals, one drawing in outside air, the other discharging cooled exhaust air, pretty much like any outdoor ASHP, but just with the pump itself inside the house. 

 

Drawing air from inside the house would work, although it will significantly increase the heat loss from the house when the heat pump is running (the heat loss would be about the same as the heat delivered to the hot water, so the heating system would need to replace this "lost" heat).

 

It's worth looking at how much air needs to flow through a heat pump to deliver the specified output.  The heat capacity of air is typically about 1.2J per litre per K.  If the cylinder capacity was 200 litres, and the minimum temperature was 35°C and the maximum 55°C, then the water in the cylinder is going to need about 16.8 MJ of heat energy delivered from the heat pump.  If the heat pump takes 2 hours to heat the tank, then that means it has to deliver about 2.33 kW (J/s) of heat.  If about 2000 W of this heat comes from the air flowing through the ducts, and if the heat pump is working with a differential temperature of, say, 25°C (pretty much how it may operate when drawing air from inside a house and discharging it outside) then it's going to be shifting about 67 litres/second of air through the ducts.  

 

The building regs extract rate from an intermittent bathroom extractor fan (no MVHR system) is 15l/s, that from a utility is 30l/s, so extracting from three in-use rooms would be a bit high in terms of extract rate, but two hours is a lot longer time period than needed (10 to 15 minutes would be OK usually).  This unit is going to extract around 4 kWh of heat from these rooms, so not only will the heating system need to provide this heat (accepting that maybe 10% might be recovered from the hot water use - most will go down the drain) but the air vents in the house will need to allow 67 litres per second of cold outside air in to balance the extract air flow.  That's a fair bit of air, so will need fairly large air vents into the house, and probably create some unwanted cold drafts.

 

 

 

Stand alone as we have no MVHR.

 

No like the ecocent you can set-up these up to extract moist stale air from bathrooms, utility etc. I've been in two new builds that use this system and it appears to works well. The only slight concern has been noise. But I've put steps in place to minimise this.

 

I am not sure on the air moving through the tank I looked over the specification but can't see this. We are putting in the 260 litre tank.

In the summer the heat loss will be fine as the house won't miss this heat. In the winter I'll need to cover this heat loss with electric heating but as I mentioned previously I have endless amount of timber. The stove therefore is going to be more important than a top heater that other might use. The stove air intake is fed via a duct under the floor.

 

We do have ventilators in the windows. The house will be air tight but not to the levels most have on the forum.

 

 

 

 

 

[Jeremy Harris]

Not surprised that they don't mention the air flow rate, TBH.  You will have to ensure there are big vents into the house to let enough air in, so best not to aim for a good airtightness level.  Those figures show that the heat output is a fair bit lower than I'd assumed, but when the heat pump is running you will still need to allow for around 50l/s of outside air freely flowing into the house to balance the air that the heat pump is extracting from the house.

 

This is the primary reason I decided to not opt to use an Ecocent, as the very high airflow rate into the house, together with the need to provide a much higher heat input to the house all the time that the heat pump was running, meant that it was going to have a significant impact on overall energy use.

 

If these units are installed with both the intake and exhaust ducts running outside the house, then the COP reduces, but that is more than offset by the big reduction in drafts and heat loss from the house.

[Gone West]

11 hours ago, Jeremy Harris said:

Not surprised that they don't mention the air flow rate, TBH.  You will have to ensure there are big vents into the house to let enough air in, so best not to aim for a good airtightness level.  Those figures show that the heat output is a fair bit lower than I'd assumed, but when the heat pump is running you will still need to allow for around 50l/s of outside air freely flowing into the house to balance the air that the heat pump is extracting from the house.

Wouldn't it be possible to have connected ducting for say three internal extracts and one external extract, balanced, so the internal extracts are extracting at the correct rate for the room type?

[Jeremy Harris]

2 minutes ago, PeterStarck said:

Wouldn't it be possible to have connected ducting for say three internal extracts and one external extract, balanced, so the internal extracts are extracting at the correct rate for the room type?

 

 

Yes, but that still means that for a few hours per day the vents into the house need to bring outside air in at a rate of around 50l/s.  The problem isn't connecting the extracts, it's dealing with the replacement outside air into the house.  For minimal flow noise the velocity through the external replacement air intake vent into the house needs to be no more than 2.5m/s, so that means a 160 mm diameter equivalent vent need to be fitted into the outside wall somewhere to bring in the ~50l/s replacement air for that being drawn out by the heat pump.  That's likely to create a bit of a cold draft, as well as cool the house down for much of the year.  Also, having a ~160mm hole through an outside wall will have a pretty massive impact on airtightness, and make it challenging to get the DER to an acceptable level.

 

This is the major snag with any simple exhaust air heat pump, that doesn't have a properly integrated MVHR, with air balancing system.  The Genvex that you have, and the similar Nibe units, get around the problem by balancing the internal and external flows such that the MVHR part remains efficient and the replacement fresh air delivered to the house is also heated by the heat pump.  The simple units don't do that, they just suck air in one duct, and out another, at a fixed rate, all the time they are running.  If they are ducted outside, so they draw in outside air and discharge the exhaust outside then there's no problem at all, other than a reduction in COP in cold, damp, weather, much like any other ASHP.

 

I think the thing that causes confusion, and has been discussed previously when the Ecocent has been debated, is that the heat all these simple integrated cylinder ASHPs extract has to come from somewhere, and if that heat is drawn from inside the house then the house heating system has to work harder and longer to keep the house warm, as it needs to heat the cold replacement air that has to come in from outside at the same rate as the unit is extracting.

 

If the hot water cylinder is required to deliver 6 kWh worth of hot water per day (about enough for two people) then that 6 kWh of heat has to come from somewhere.  If extracted from the outside air, like any other ASHP, then that heat is coming from the sun, in effect.  If extracted from air inside the house then almost all the heat will have been provided by the heating system, at least during the heating season.  The heating season will be extended if such an arrangement is used, too, as the house will need an additional 6 kWh of heat per day, so that probably means heating the house for a month or two longer every year.

 

The only Ecocent installation I've heard of that used semi-internal air and worked pretty well was a chap on Skye who had one installed such that it drew its air from a South facing conservatory, and where the replacement air into that conservatory came from a workshop with a combustion stove.  This arrangement meant that the air in the house was unaffected, so there were no cold drafts or need for additional heating, and as they tended not to use the conservatory in winter cooling it down a bit wasn't an issue.

 

[Gone West]

52 minutes ago, Jeremy Harris said:

Yes, but that still means that for a few hours per day the vents into the house need to bring outside air in at a rate of around 50l/s.

I'm not explaining myself very well. Taking my house as an example. The bathroom needs ventilation at 7l/s, kitchen at 8.5l/s and shower at 3l/s giving a total of 18.5l/s to ventilate those rooms sufficiently. That leaves a requirement of 31.5l/s from the external vent to give the required flow for the heat pump. The four vents could be balanced to provide the correct flows. The rooms need ventilating at that rate and therefore heating whatever system is used. Most houses have trickle vents which would provide the required airflow into those rooms. It's not perfect by any means but for a lot of houses would be a good solution.

[Jeremy Harris]

1 minute ago, PeterStarck said:

I'm not explaining myself very well. Taking my house as an example. The bathroom needs ventilation at 7l/s, kitchen at 8.5l/s and shower at 3l/s giving a total of 18.5l/s to ventilate those rooms sufficiently. That leaves a requirement of 31.5l/s from the external vent to give the required flow for the heat pump. The four vents could be balanced to provide the correct flows. The rooms need ventilating at that rate and therefore heating whatever system is used. Most houses have trickle vents which would provide the required airflow into those rooms. It's not perfect by any means but for a lot of houses would be a good solution.

 

 

Yes, but those are the flow rates for continuous ventilation, using MVHR, PIV or low rate continuous ventilation.  Building regs require higher rates for houses that are not fitted with MVHR, 15l/s for bathrooms and 30l/s from a utility room, so if two bathrooms plus a utility room were connected to this unit there would still be a need for an additional ~10l/s intermittent extract in one of them.

 

The problem is that the building regs requirement for intermittent extract fans assumes that they will only be run for relatively short periods of time, maybe 20 to 30 minutes or so.  Using one of these ASHPs with the intake ducted to extract from the bathrooms and utility would result in the run time being a lot longer.  The spec sheet gives a run time to heat the full 260 litre cylinder from cold of 10 hours 38 minutes.  For all that time there will be around 50l/s of cold outside air being drawn into the house through the needed 160mm diameter equivalent outside air vent.

[Gone West]

3 hours ago, Jeremy Harris said:

 

 

Yes, but those are the flow rates for continuous ventilation, using MVHR, PIV or low rate continuous ventilation.  Building regs require higher rates for houses that are not fitted with MVHR, 15l/s for bathrooms and 30l/s from a utility room, so if two bathrooms plus a utility room were connected to this unit there would still be a need for an additional ~10l/s intermittent extract in one of them.

 

The problem is that the building regs requirement for intermittent extract fans assumes that they will only be run for relatively short periods of time, maybe 20 to 30 minutes or so.  Using one of these ASHPs with the intake ducted to extract from the bathrooms and utility would result in the run time being a lot longer.  The spec sheet gives a run time to heat the full 260 litre cylinder from cold of 10 hours 38 minutes.  For all that time there will be around 50l/s of cold outside air being drawn into the house through the needed 160mm diameter equivalent outside air vent.

 

I understand what you're saying but from a practical point of view if I still lived in my old house with trickle vents I could fit one of these units and draw 35% of the air from inside the house and 65% from outside the house. I would not be replacing any existing ventilation just enhancing the ventilation that already exists. I think the confusion is that you are referring to a new ventilation system using one of these units and I am talking about enhancing an existing system which uses trickle vents in an older house.

[Jeremy Harris]

27 minutes ago, PeterStarck said:

 

I understand what you're saying but from a practical point of view if I still lived in my old house with trickle vents I could fit one of these units and draw 35% of the air from inside the house and 65% from outside the house. I would not be replacing any existing ventilation just enhancing the ventilation that already exists. I think the confusion is that you are referring to a new ventilation system using one of these units and I am talking about enhancing an existing system which uses trickle vents in an older house.

 

 

It would make the trickle vents howl a bit though!  In order to keep the intake air velocity down below the 2.5m/s noise threshold, the sum of the areas of the trickle vents would have to give an equivalent area to a 160mm diameter hole through the wall.   50l/s is a lot of air to try and deliver through lots of small holes.

 

To comply with building regs you need to make the bathrooms extract at 15l/s and the utility at 30l/s.

[Gone West]

Just now, Jeremy Harris said:

 

 

It would make the trickle vents howl a bit though!  In order to keep the intake air velocity down below the 2.5m/s noise threshold, the sum of the areas of the trickle vents would have to give an equivalent area to a 160mm diameter hole through the wall.   50l/s is a lot of air to try and deliver through lots of small holes.

No it wouldn't because I would only be drawing, in my example, 17.5l/s the remaining 32.5l/s would be coming from the external vent.