@markc do not expect to improve your COP very much, if you do not do anything. By the way, you only need 1 valve and about 3 hours of a good plumbers time, arround £400.00. You will save more than that this winter in lower electricity bills and have better comfort levels.
How come only 1 valve? Your comments on the diagram seem to suggest replacing most of the synchron valves.
@markc You only need 1 valve to divert the water from heating to hot water. I have left the one in your anex as you may not use it all the time and will only need frost protection. The valves you have, have a very high friction loss, (it is like driving you car in to a 100 mile an hour wind) and require a huge ammount of energy (pumping cost) to push enough water throught them for a heat pump. Heat pumps require significantly more water flow to transmit the heat at the lower tenpoerature. If you do not have the flow, you have to have higher temperature, higher temperature = low COP.
@markc You only need 1 valve to divert the water from heating to hot water. I have left the one in your anex as you may not use it all the time and will only need frost protection. The valves you have, have a very high friction loss, (it is like driving you car in to a 100 mile an hour wind) and require a huge ammount of energy (pumping cost) to push enough water throught them for a heat pump. Heat pumps require significantly more water flow to transmit the heat at the lower tenpoerature. If you do not have the flow, you have to have higher temperature, higher temperature = low COP.
Ah! I understand that now. Thanks.
If the synchron valves to UFH and upstairs rads are locked in the open position, is that the same as removing them?
As suggested, I'm posting my system details here for comments; especially from @derek-m and @heacol Brendan. Hopefully it's self explanatory, although I apologise in advance for any basic errors as this is definitely not my specialist subject.
Although I initially thought the system looked complicated, I don't think it is. It's quite a simple setup; two zones and all radiators. The house is a bungalow of about 150m2. The rads are all new stelrad K2s. It's running on weather compensation as set up by the installer but I'm currently using a bit like a boiler based system. It's always on but the thermostats are turned down to 18 ish during the days and night and up to 21 ish in the mornings and evenings. Although I have the two zones set a little differently to each other, they are not physically closed off from each other and on reflection I could easily live with one. The ASHP actually does what it's currently doing very effectively. Is it doing it efficiently though?
For those that don't know this, the Mitsubishi Ecodan has three ways of running, (1) flow temperature set manually (2) Weather Compensation - flow temperature varies according to outside temp (3) auto adaptation - uses a combination of weather compensation and room temperatures. Note - (3) is not available with 3rd party thermostats.
I have MMSP so can see minute by minute the flow temp, outside temp and power consumption, for a day, week hour or whatever. I can't see the COP at the moment because MMSP isn't working properly.
The two graphs are for 24 hrs 5/11/21. You can see the frost protection overnight, the thermostats kicking in morning and evening and the HW in the middle of the day. Definitely not the slow, steady output ASHPs are said to be suited to! Both power and flow temps are up and down a lot; on the other hand, it's using no power at all a lot of the time. Total ASHP energy consumed was 30.6kWh.
That's about it really, any comments and suggestions welcome.
I'll probably start a new thread if/when I make changes.
Your ASHP is operating how I run my gas boiler, it switches on periodically to top up the temperature of the radiators and then switches off for lengthy periods of time.
Looking at the graphs, I would initially suggest setting your control for a constant 20C or 21C, which will help reduce the large surges in energy consumption, it will also allow better comparison of the effect of ambient air temperature changes throughout the day.
Your weather compensation curve is not yet optimised, I would suggest that you try the following settings:-
45C water flow temp. @ 0C outside air temperature.
20C water flow temp. @ 20C outside air temperature.
Give those settings a try for a day or so and then post the results.
Thanks Kev, I will try to be gentle!! 😀 You have just given me all the evidence I need to prove that you are running your system incorrectly.
It is very encouraging that you do not have a buffer tank.
Firstly, just a quick explanation, the thermostat, sends an on-off signal to the heat pump. It switches the heat pump on and off and nothing else, the Ecodan controller is fairly rudimentary compared to others.
As you can see on this graph, when your thermostat is calling for heat and switching off. As you can see, by the electricity usage during these periods that the heat pump is working very hard and switching off, the flow temperature rises very quickly then slowly drops. This equates to you driving down the motorway, with your foot flat on the accelerator, and controlling your speed with the key. No-one in their right mind would think that it would be an efficient way of driving. Cruise control (weather or load compensation) would be.
As you are only actually heating for a very small portion of the time, your flow temperature has to be much higher to get the required heat in to the property to keep you comfortable. High temperature = High electricity bill. It really is that simple.
You are running at about 48 Deg C, with the heat pump running flat out at it's most inefficient point, clearly indicated by your COP graphs, You are running at a COP of about 1.5. This is horrendous, you would have been much better off, going to Tesco and buying a £5.00 blower heater for each room instead of installing the heat pump, it would have cost you less over the life of the heat pump, even at the current electricity prices. I estimate your flow temperature should be about 25 Deg C with a COP of around 5, which would equate to a theoretical energy usage of 9 Kw hours but it would probably be between 10 and 15.
Here is a picture, taken by one of my customers on Thursday at 8.26 am with an outside temperature of 3 Deg C and a room temperature of 21 deg C. I am not saying that your system will produce this but it should be close.
The problem with lowering the flow temperature, is to transmit the same amount of heat, you need a much higher flow rate. Think of flow temperature as the size of a bucket. If you need 100 units to heat your house and are moving it with buckets, high temperature = big bucket, low temperature = small bucket. Due to this, you have to be very careful with the choice of piping, valves and other fittings to enable the water to travel freely through the systems. Your valves are low flow valves, it is like driving your car in to a 100 mile an hour head wind, as opposed to no wind.
You need to remove VM3 and replace VM1 and VM2 with this (1 1/4”) which diverts the flow from heating to hot water to allow free flow of water.
Your pumps look fine, I would set them to constant head, speed 3 now, and after modifications speed 1 or 2.
Your system is not too bad but so close but so far comes to mind. As a trial, turn your thermostats to full, set your compensation curve down to 25-45 (I think this may be a bit high though), open all your TRV vales full (except your bedrooms) and try it. Then look at your data, I think you will be pleasantly surprised.
@markc You only need 1 valve to divert the water from heating to hot water. I have left the one in your anex as you may not use it all the time and will only need frost protection. The valves you have, have a very high friction loss, (it is like driving you car in to a 100 mile an hour wind) and require a huge ammount of energy (pumping cost) to push enough water throught them for a heat pump. Heat pumps require significantly more water flow to transmit the heat at the lower tenpoerature. If you do not have the flow, you have to have higher temperature, higher temperature = low COP.
Ah! I understand that now. Thanks.
If the synchron valves to UFH and upstairs rads are locked in the open position, is that the same as removing them?
No, it is still like driving a car in to a 100 mile an hour head wind.
This is what they look like inside
and this is how they work, the water has to force it's way arround the ball.
Google is very healpull!! 😀
However as a trial if they are continually open, it will improve the system but not by as much as without them. Do not lock them, or you will have no hot water.
Thanks Kev, I will try to be gentle!! 😀 You have just given me all the evidence I need to prove that you are running your system incorrectly.
It is very encouraging that you do not have a buffer tank.
Firstly, just a quick explanation, the thermostat, sends an on-off signal to the heat pump. It switches the heat pump on and off and nothing else, the Ecodan controller is fairly rudimentary compared to others.
As you can see on this graph, when your thermostat is calling for heat and switching off. As you can see, by the electricity usage during these periods that the heat pump is working very hard and switching off, the flow temperature rises very quickly then slowly drops. This equates to you driving down the motorway, with your foot flat on the accelerator, and controlling your speed with the key. No-one in their right mind would think that it would be an efficient way of driving. Cruise control (weather or load compensation) would be.
As you are only actually heating for a very small portion of the time, your flow temperature has to be much higher to get the required heat in to the property to keep you comfortable. High temperature = High electricity bill. It really is that simple.
You are running at about 48 Deg C, with the heat pump running flat out at it's most inefficient point, clearly indicated by your COP graphs, You are running at a COP of about 1.5. This is horrendous, you would have been much better off, going to Tesco and buying a £5.00 blower heater for each room instead of installing the heat pump, it would have cost you less over the life of the heat pump, even at the current electricity prices. I estimate your flow temperature should be about 25 Deg C with a COP of around 5, which would equate to a theoretical energy usage of 9 Kw hours but it would probably be between 10 and 15.
Here is a picture, taken by one of my customers on Thursday at 8.26 am with an outside temperature of 3 Deg C and a room temperature of 21 deg C. I am not saying that your system will produce this but it should be close.
The problem with lowering the flow temperature, is to transmit the same amount of heat, you need a much higher flow rate. Think of flow temperature as the size of a bucket. If you need 100 units to heat your house and are moving it with buckets, high temperature = big bucket, low temperature = small bucket. Due to this, you have to be very careful with the choice of piping, valves and other fittings to enable the water to travel freely through the systems. Your valves are low flow valves, it is like driving your car in to a 100 mile an hour head wind, as opposed to no wind.
You need to remove VM3 and replace VM1 and VM2 with this (1 1/4”) which diverts the flow from heating to hot water to allow free flow of water.
Your pumps look fine, I would set them to constant head, speed 3 now, and after modifications speed 1 or 2.
Your system is not too bad but so close but so far comes to mind. As a trial, turn your thermostats to full, set your compensation curve down to 25-45 (I think this may be a bit high though), open all your TRV vales full (except your bedrooms) and try it. Then look at your data, I think you will be pleasantly surprised.
You're confirming what I already suspected. As soon as I started looking at the MMSP data a month ago I could see what was happening. It's only become apparent how extreme it is with the recent colder weather. Actually my COP isn't as bad as that (I'm not sure how you can tell from my graph? It's just energy used, outside temp and flow temp). Last year it averaged about 3 using the system like this; nowhere near your numbers but still. I was acually pleased because energy use was much lower than the storage heaters we had.
(I can't calculate COP now; the Ecodan controller used to display energy delivered and consumed and I could work it out but since I had MMSP installed last month, it no longer displays energy delivered. Since the MMSP package isn't recording energy delivered either, I suspect the two are linked. I'm trying to get the supplier back.)
BTW during that 24 hours, the maximum flow temp was 45 and the average 27 so you're not far off!
Here is what I'll try for a week starting tonight:
Compensation curve set to 25-45
Thermostats up to 25, no timings
TRVs all open apart from 2 bedrooms
If the house is too warm I'll move the curve down a few degrees; that's very easy to do on my controller.
it refers to the weather compensation curve. It means a flow temp of 25 at 20 degrees ambient (outside) temp and 45 at zero. It you look at my current graph in my post a few posts up, it's currently at 30 at 20 degrees ambient and 50 at zero. The consensus is that's too high if I'm going to try running the ASHP 24/7
You can see yours by doing this on your main controller:
press bottom left button
use arrows to select heating (the house symbol) and press the tick symbol
press the button under the compensation curve.
To go back or if you're worried about changing something you don't want to, press the button with the return symbol a few times.
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