Help optimising ASHP settings

samforward

We've recently had a Samsung Gen 6 ASHP with 200L cylinder by Joule. It was part of a grant including solar and insulation. The installers were in and out very quickly and more or less shrugged their shoulders when asked questions about settings, and the more I've been digging into the forums the more I've been feeling lost! 

- It's a small 2 bedroom terraced 1990s house with 1 zone set up, 6 radiators. No underfloor heating, fairly well insulated now. 
- It may be an oversized unit, they used a smaller unit on 2 neighbors houses of the same size. 
- 6 panels on the roof, no battery
- Octopus Agile so cheap electric apart from 4-7pm
- First 2 days have used 8kwh, and generated 22-24kwh based on the 'energy consumption' section of the panel. 


1. Water Law - it was set up as:

201* Outdoor temp 
Low (left of screen): 20C
High (right of screen): 0C

202* Water temp
Low (left of screen): 41C
High (right of screen): 55C

My understanding from the above is - at 20C, the water temp for the radiators will be limited to 41, and at 0C will target 55C as a max, with a line in between. Is that correct?

I'm not sure how I would go about optimizing this for my house, or if it's already perfect. What steps could I take to test this?

I've scheduled:
- DHW heats to 45C at 3pm, when solar will be strongest. (4pm is when the high electric costs would kick in).
- Heating is:
7am - 18C
13:30 - 19.5C (making use of solar and higher outside air temp to warm the house
16:00 - 18C (this is peak electric rates, so trying to avoid spending here, hoping that residual heat will keep it warm enough to avoid cycling until after 7. 
22:00 - 15C - we like it cold at night.

Questions:

- Is my schedule the correct way to make the most of cheap solar during the day and avoid peak tariffs between 4-7pm?
- How can I optimise my water law settings?
- The ASHP is fairly loud and cycling a lot, is there a way to reduce number of cycles per hour?
- What does quiet mode actually do? It didn't seem to change anything.
- Many others are sharing lots more data from their set-ups, I'm not sure how I can see this info?

Thank you in advance. 

 

Reed_Richards

samforward said:

1. Water Law - it was set up as:

201* Outdoor temp 
Low (left of screen): 20C
High (right of screen): 0C

202* Water temp
Low (left of screen): 41C
High (right of screen): 55C

My understanding from the above is - at 20C, the water temp for the radiators will be limited to 41, and at 0C will target 55C as a max, with a line in between. Is that correct?

I've read elsewhere that there can be some confusion about which way round the "Water Law" (Weather Compensation) settings go but assuming your installers got that right then your understanding is correct.  I'm hoping your installers were being over-conservative because because the operating temperature range that has been set is high.  My equivalent figures are 55 C water at -14 C outside and 20 C water at 22 C outside.  This means that when its 0 C outside my water temperature is about 42 C.  I know that is enough to keep my house suitably warm and only having to heat the water to 42 C will enable my heat pump to operate more efficiently than yours would heating the water to 55 C.  I can do this because the surface area of my radiators is large enough to cope with a lower water temperature.  Hopefully you will find the same.

samforward said:

I'm not sure how I would go about optimizing this for my house, or if it's already perfect. What steps could I take to test this?

Disable operation under "Water Law" and use a fixed output temperature.  See how low you can make that before you become unable to heat your house to the temperatures you want.  If the setting is too low you will find that it takes forever (or not at all) to get your house back up to temperature in the morning.  This is best done when the outside temperature is not varying too much and you may have to wait until next winter to explore what happens at low outside temperatures.

samforward said:

- Is my schedule the correct way to make the most of cheap solar during the day and avoid peak tariffs between 4-7pm?

I'm not particularly familiar with Octopus tariffs but it looks to be sensible.  Others will tell you that you need to maintain the same inside temperature 24/7.  I think this is debatably money-saving and in any case you should go with what makes you feel comfortable.

samforward said:

- is there a way to reduce number of cycles per hour?

The controller you are using to program your temperatures may be capable of this.  If I tell my controller it is controlling an oil boiler it will limit the number of cycles to 3 per hour; you may find you have more explicit control.

My heat pump does not report its heat energy output so others may be better placed to answer questions about that. 
       

samforward

Reed_Richards said:

Disable operation under "Water Law" and use a fixed output temperature.  

Thank you for the comprehensive reply, it's really helpful. To check i'm understanding you currently,  I would do the above to find out to the minimum water temperature that is sufficient to heat myself as a specific outdoor temperature? Ideally I'd do this at a very low temperature which gives me an 'upper water temperature' value, then again at a higher outdoor temperature to give a 'lower water temperature'? 

I'm surprised that modern ASHPs aren't smart enough to adjust water temperature constantly based on how successfully heating a space, it seems a simple thing to program. But I'm probably understanding it wrong. 

FreeBear

samforward said: I'm surprised that modern ASHPs aren't smart enough to adjust water temperature constantly based on how successfully heating a space, it seems a simple thing to program. But I'm probably understanding it wrong. 

If the heat pump is OpenTherm compatible (MBus is another), then the smart thermostat can tell the HP what flow temperature is needed. Some heat pumps have inverter control to reduce the flow (modulating down the heat output) and thus avoid constant cycling.

Heat pumps are getting smarter as the technology improves, but they also need smarter controls to get the best performance. It also takes time to tweak the settings to improve efficiency.

Reed_Richards

samforward said:

Reed_Richards said:

Disable operation under "Water Law" and use a fixed output temperature.  

Thank you for the comprehensive reply, it's really helpful. To check i'm understanding you currently,  I would do the above to find out to the minimum water temperature that is sufficient to heat myself as a specific outdoor temperature? Ideally I'd do this at a very low temperature which gives me an 'upper water temperature' value, then again at a higher outdoor temperature to give a 'lower water temperature'? 

I'm surprised that modern ASHPs aren't smart enough to adjust water temperature constantly based on how successfully heating a space, it seems a simple thing to program. But I'm probably understanding it wrong. 

Yes, your understanding is correct.  But you could try a range of outside temperatures to check you get a straight line between high and low.

The "smart" capability that you suggest is called "Load Compensation".  A gas boiler with an Opentherm controller could do that but AFAIK almost no heat pumps are Opentherm capable.   But if you are using the manufacturer's own controller it may have a Load Compensation capability.  I don't know enough about Samsung ASHPs to advise. 

Reed_Richards

Oh, and the cycling may be because your heat pump cannot modulate down low enough to run continuously.  This will happen if the outside temperature is too high.  But if the heat pump is more powerful then necessary then the minimum power it is capable of may be higher too making cycling more likely..

Netexporter

If they've fitted thermostatic radiator valves (which they shouldn't with a heat pump) then open them fully. You want as much water circulating, at all times, as possible, to stand a chance of getting a decent SCOP.

This thread is of interest to me as I'll be getting a Samsung 5kW fitted, under the ECO4 scheme, in the next few weeks. Having looked at the spec sheets, that the installer sent, the operating instructions look pretty incomprehensible, on paper at least. I'm hoping once I've got a few actual buttons to press they might become clearer.

samforward

Netexporter said:

If they've fitted thermostatic radiator valves (which they shouldn't with a heat pump) then open them fully. You want as much water circulating, at all times, as possible, to stand a chance of getting a decent SCOP.

This thread is of interest to me as I'll be getting a Samsung 5kW fitted, under the ECO4 scheme, in the next few weeks. Having looked at the spec sheets, that the installer sent, the operating instructions look pretty incomprehensible, on paper at least. I'm hoping once I've got a few actual buttons to press they might become clearer.

That's good advice, I had closed the valve to the spare room radiator, but now realising I'm in the old gas boiler mindset. 

It does seem like ignoring the massive amount of information, the only real variables are weather compensation and DHW temp, and any scheduling you choose to make for heating the rads or DHW at a favorable (cheap) time. 

Netexporter

Unfortunately, the minimum SCOP target allowed under MCS regulations is relatively low, basically it should match the cost of running a gas boiler, so under grant-aided schemes the installers haven't got much incentive to optimise the design.

As I was going to install a heat-pump, anyway, before I discovered I was eligible for ECO4, I'm just going to shake the system down, to make sure it is working, even if not optimally, then I'll spend the money I haven't had to lay out on underfloor heating, as I'm upgrading the house anyway. With luck I'll have a SCOP of over 5, then.

Reed_Richards

I think it's mandatory for any new heating system installation to include thermostatic valves on the radiators.  If the radiators are all correctly balanced then TRVs are unnecessary but your installers are unlikely to have taken the time to ensure fully correct balancing so TRVs act as a workaround.

Heat pumps like to work with a minimum volume of water but your system may have a buffer or volumizer tank to ensure this, in which case it doesn't matter if you or a TRV turn radiators off

But if you turn off the radiator in the spare room but the spare room is not well-insulated from the rest of the house then the remaining radiators will have to work harder and this could reduce your system efficiency.  This would apply to both gas boilers and heat pumps but the effect would be more significant for heat pumps.  Reduced efficiency means increased running cost and this could possibly outweigh the saving from reducing the average temperature of the house.   

tbaile

samforward said:

We've recently had a Samsung Gen 6 ASHP with 200L cylinder by Joule. It was part of a grant including solar and insulation. The installers were in and out very quickly and more or less shrugged their shoulders when asked questions about settings, and the more I've been digging into the forums the more I've been feeling lost! 

- It's a small 2 bedroom terraced 1990s house with 1 zone set up, 6 radiators. No underfloor heating, fairly well insulated now. 
- It may be an oversized unit, they used a smaller unit on 2 neighbors houses of the same size. 
- 6 panels on the roof, no battery
- Octopus Agile so cheap electric apart from 4-7pm
- First 2 days have used 8kwh, and generated 22-24kwh based on the 'energy consumption' section of the panel. 


1. Water Law - it was set up as:

201* Outdoor temp 
Low (left of screen): 20C
High (right of screen): 0C

202* Water temp
Low (left of screen): 41C
High (right of screen): 55C

My understanding from the above is - at 20C, the water temp for the radiators will be limited to 41, and at 0C will target 55C as a max, with a line in between. Is that correct?

I'm not sure how I would go about optimizing this for my house, or if it's already perfect. What steps could I take to test this?

I've scheduled:
- DHW heats to 45C at 3pm, when solar will be strongest. (4pm is when the high electric costs would kick in).
- Heating is:
7am - 18C
13:30 - 19.5C (making use of solar and higher outside air temp to warm the house
16:00 - 18C (this is peak electric rates, so trying to avoid spending here, hoping that residual heat will keep it warm enough to avoid cycling until after 7. 
22:00 - 15C - we like it cold at night.

Questions:

- Is my schedule the correct way to make the most of cheap solar during the day and avoid peak tariffs between 4-7pm?
- How can I optimise my water law settings?
- The ASHP is fairly loud and cycling a lot, is there a way to reduce number of cycles per hour?
- What does quiet mode actually do? It didn't seem to change anything.
- Many others are sharing lots more data from their set-ups, I'm not sure how I can see this info?

Thank you in advance. 

 

Yes the high temp seems high. Maybe try 25 at 20 degrees external for the top (warm) end. 202* are the weather comp settings for underfloor heating. But sometimes installers just use those for radiators (as it's the default) and as long as 2041 is set to WL1 it doesn't matter. 

If you want to configure it you can set the setpoint at its highest (e.g. 25 degrees) to always call for heat and then adjust the weather compensation curve (by reducing the flow temperature at the cold end of the curve) to as low as it will go whilst still maintaining your desired internal temperature and not overshooting on a cold winter day. 

Before you do that you should set 2091/92/93 to 3 as if it's set to 1 it allows the flow temp setpoint to overshoot if there's a call for heat.