ASHP PID query

[ReedRichards]

Since batteries are not mentioned I think that must mean that it is not battery compatible.

[Marvin]

How are you charging the batteries?

 

Hi @ReedRichardsI think it will work in mode 2 if the CT clip is connected to the cable running to the mains.

 

 

Edited January 17, 2022 by Marvin

[Wil]

Interesting topic. I have 2 of the Cool Energy pumps installed before Christmas and still trying to work out what the best way to run them is. My elec bills are horrific in these low temp days. The only setting I was brave enough to change in the 9999 menu was the 0degree heating curve to 42.5 so the weather compensation is a bit warmer at 0 than the default 40.

 

For those with these systems @dpmiller@Marvin Did you change any of the pump settings at all? I often see them running at 50% which is the set minimum- is there any harm in letting them ramp lower or is it an efficiency measure? 

My current 'best guess' setup is Weather Compensation with DHW set to 48 and standard curve with change as I mentioned above. Before this I tried to time the DHW to go to 50 at 6am and 50 at 5pm for our showers/ kids bathtime, but it only ever came on once the first shower was had in the morning. Then it went into defrost and sucked the rest of the heat out of the tank and the second shower was... chilly... did you have this issue with the time programmes?

 

Now I just need them to come and visit and do my MCS cert!

[dpmiller]

I've reduced the pump minimum to 30% and the max to 70% but with the startup at 80 to ensure the flow switch gets triggered. I've got another pump in series with it in the house, so this lets the pump modulate down and assist in managing the deltaT and I presume overall efficiency

 

I'm not convinced that the weather compensation makes a lot of difference tbh, the daily variance in external temps means any improvements are lost in statistical noise...

 

On the DHW settings, what difference and overshoot do you have in User Mask? Try reducing the difference by a degree or two it should then cut in sooner as the tank cools, but for a shorter time which might miss the defrost then. You might also be able to stretch the defrost period and lose a little of it's duration, depending on your ambient conditions.

 

@Wil are yours separate or cascaded?

[Wil]

36 minutes ago, dpmiller said:

@Wil are yours separate or cascaded?

They're independent but hit the same buffer tank so I suppose also cascaded. the 18 does heating and DHW, the 26 does heating only. The stat for the 26 is higher up the buffer tank so always reads a little higher and therefore allows the 18to lead until it can't cope/ goes off to service DHW and then the 26 comes in. It then drops off earlier and lets the 18 finish off the heating cycle.

 

They'e at Diff 5/ Stop 0 for DHW and 3/2 for Heating.

 

I also have another pump doing the whole heating circuit (rads until we refurb, pump set at max speed) so the HPs pumps are only really circulating to the coils/ buffer. I'll try dropping the min speed to 30 and see if that helps at all.

 

Interesting you think the WC won't do much, because of minimal variance in daily temps? today is 8 high low of 0 so I know I want the temps around the 42/43 mark to keep us comfortable tonight. I should just set them there and leave it to do it's thing?

 

Do you also have an internal heating constant? I'm potentially overcomplicating at the moment with morning and evening warmer and setbacks during the day and night.

 

 

[Marvin]

All interesting stuff.

 

This bungalow's temperature rises and falls slowly so the difference between the day and night temperature ( set on a separate digital thermostat to turn the heating circulating pump on) is very little about 2 degrees.

 

Hi @Wil  the only thing I have altered is the Weather Compensation Ambient Temperature / System Water Temperature, and the temperature differential and stop, at present as I do not understand what effect changing the compressor frequency or pump speed will have. I believe that turning the settings to a small difference between the outside temperature and the temperature required to heat the building is important, however I have also witnessed the fact that during the early stages of the ASHP start up (cycle)  a lot of energy is used to get going in the first few minutes with what seems to be little result. I think this is why it is suggested that the ASHP unit should come on for at least 10 minutes. 

 

I am presently fiddling with these parameters to find our best result.

 

As a yard stick:

 

From Sunday at 8 am to Monday at 8 am we used 7.25 kWh. About 5kWh on heating and 2.25 on hot water for 2 people. The average temperature over the whole day taken at 3 hour intervals was about 9C and the floor area is about 100m2, at an average internal temperature of about 20C during a dryish sunny day with about 14mph wind speed  So we are achieved about 50Wh per day per m2 floor. However there was cooking being completed which adds to the warmth.

 

M

 

 

 

 

 

[Wil]

45 minutes ago, Marvin said:

As a yard stick:

 

From Sunday at 8 am to Monday at 8 am we used 7.25 kWh. About 5kWh on heating and 2.25 on hot water for 2 people. The average temperature over the whole day taken at 3 hour intervals was about 9C and the floor area is about 100m2, at an average internal temperature of about 20C during a dryish sunny day with about 14mph wind speed  So we are achieved about 50Wh per day per m2 floor. However there was cooking being completed which adds to the warmth.

 

M

 

7.25kWh- What a lovely thought. I monitor my electricity closely and my daily usage before heat pumps was around 25kWh to 32kWh depending on PHEV charging. I had a day earlier this week with an average temp of around 2-3degreesC and my usage was 100kWh. We had the log burner on in the living room too.. This is a family of 4 in a leaky 300m2 farmhouse exposed to the elements though.

 

I've gone about it a bit backward in putting the pumps in then doing the renovation and insulation in order to try and get in on the RHI... hopefully things will improve from here.. Hence any efficiency measure possible would be a bonus to get me away from 333Wh/m2!

[Marvin]

Hi @Wil

 

Hmm... Leaky buildings are a big problem. Make the building as air tight as possible.... fill every gap, seal round every pipe on the inside and outside of the external wall. 

Are you fitting mechanical ventilation?  How are you supplying air to the wood burner?  Of course we had to have a new EPC certificate, as our one was older than 2 years, before we could apply for RHI....

 

This is a timber framed 1970's bungalow with a timber floor. We have roughly 400mm fluffy in the loft, 150mm Celotex in the walls and 200mm Celotex in the floor. We have a MVHR system for the fresh air.  When renovating our bungalow we sealed every join between wall and wall, wall and floor, wall and ceiling and vapour barriered every wall and ceiling. We have no trickle vents in the windows, no cat flap, although we have a letterbox in the front door and only 18m2 of glazing.

 

As the ASHP heating water temperature is already lower than that from a boiler every loss from the ASHP pipe work is a greater percentage.  These are some of the other items we have worked on:

 

• Made the length of pipe work between the ASHP and hot water tank and buffer tank as short as possible: less than 5 meters in one direction.
• Insulated the ASHP to tanks pipework to within an inch of its life. 25 -  28 - 25mm walled Climaflex minimum with additional insulation where possible, especially the pipes from the ASHP which are outside the thermal envelope (an additional 100 to 150mm thick fluffy wrapped in EDPM and taped together.)
• Additionally insulated the buffer tank and hot water tank even though both are within the thermal envelope.
• Additional insulation to all heating pipework where possible.

Finally completed my RHI application today.

 

 

M

 

 

 

 

 

 

 

[Marvin]

Primary pipework insulation with additional insulation

 

 

Buffer tank on the right. Gaps for pump and port valves

 

Hot water tank hiding