My aim with this post is to see whether there is scope to improve my setup physically (more insulation) and through settings and whether it has been competently done.
The installer (sub contractor) seemed to do a decent job, I have added extra insulation myself already which I’ll detail later. I wasn’t very happy with the company that did it as we (builders and I) did a lot of work ourselves, which was discussed beforehand and meant that the installer was finished in a day (meant to be 2 – 3 days). The company eventually knocked off just enough to cover materials but nothing for labour and held me to ransom with the RHI information. They’ve since gone bust and have a lot of negative reviews (which have been posted since I set them on), so it’s not just me.
The house is a 4 bed detached, built in 1983, we bought it a year ago and had to gut it and do quite a bit of work prior to moving in. I had cavity wall insulation (beads) added and I put in an additional 200mm of loft insulation myself above the 100mm that was there already. Most windows are original double glazed, we replaced the two front bedrooms as the old units were on their way out. I plan to do everything eventually when we can afford it, the recent cold snap has set a priority hierarchy.
The HP is a PUZ-WM85VAA(-BS) Ecodan R32 with a Joule 200L HW cylinder, we replaced all of the original radiators. On the performance estimate it gives 14,688kWh to heat the house and 2,224 kWh to heat the hot water annually.
I have included 3 pics of the external installation (yes the wisteria needs trimming back and they used copper for the overflow which thankfully hasn’t been stolen yet). The installer left gaps in the insulation on the flow and return pipes at the back of the unit which I’ve circled in red, so I’ve added some myself. I took off the bottom part of the conduit when I did this and found that the insulation was not wrapped around the pipe here.
Inside I have added a few more bits of insulation on the HW tank where the pipes go in/come out as they were warm to the touch. Is it worth adding insulation around the valves? The loft gets very little heat from the house due to the 300mm of insulation. On the flow and return in the loft to the HP there were some gaps on the bends which I’ve tried to plug and wrap some loft insulation around. I need to get a roll of loft insulation to cover the batteries as they died during the cold snap, so I’ll use what is left over to cover the flow/return pipes some more. Is it ok if the temperature probes are loosely covered with loft insulation?
On to settings, I have included a pic of our compensation curve, I haven’t touched this, and have no idea if it’s optimal, the installer set it up. We leave the wireless thermostat in the lounge set at 19 degrees C in the daytime and 18 degrees at night and this keeps the temperature upstairs comfortable. The installer had set the HW to top itself up when it dropped by 5 degrees, but I found that it was coming on too often for my liking. I’ve set it to come on once per day for an hour at midday (will change to 1pm though when I hopefully move to the Octopus Cosy tariff soon) as this is usually about the warmest part of the day and has the best chance of solar PV. I find that there is enough HW to cover us, sometimes we need to do an additional heating cycle. When our kids grow up and start having showers then we’re going to be running more cycles as there will not be enough. The settings are;
DHW max temp: 50 degrees
DHW max temp drop: 10 degrees (was 5)
DHW max operation time: 60 min
DHW mode restriction: 30 min
DHW recharge: Large
It typically takes about 45 – 50 minutes for the tank to get to 51.5 degrees from cold.
For Legionella, the settings are;
Hot Water temp: 61 degrees
Frequency: 10 days
Start time: 1pm
Max Operation time: 2hrs
Duration of max temp: 5 min
Lately I’ve found that the Legionella cycle seems to be lasting a lot longer than previously which is annoying as the heating obviously doesn’t come on, the tank temp will hover around 59 degrees with little seemingly happening so I end up turning the HP off and on again through the MELCloud app to get the heating to initiate.
After looking at other similar posts I see that I have missed off useful information (I can’t see an edit post option), the house is 139 sq m, November average daily usage 22kWh (34kWh peak), December average daily usage 35kWh (56kWh peak). Usually the HP maintains the target room temperature going on and off as needed, when the temperature dropped below 0ish it was on pretty much the entire time, I guess that is normal? It managed to maintain the room temperature throughout the cold snap, the average daily usage was 49kWh.
My aim with this post is to see whether there is scope to improve my setup physically (more insulation) and through settings and whether it has been competently done.
The installer (sub contractor) seemed to do a decent job, I have added extra insulation myself already which I’ll detail later. I wasn’t very happy with the company that did it as we (builders and I) did a lot of work ourselves, which was discussed beforehand and meant that the installer was finished in a day (meant to be 2 – 3 days). The company eventually knocked off just enough to cover materials but nothing for labour and held me to ransom with the RHI information. They’ve since gone bust and have a lot of negative reviews (which have been posted since I set them on), so it’s not just me.
The house is a 4 bed detached, built in 1983, we bought it a year ago and had to gut it and do quite a bit of work prior to moving in. I had cavity wall insulation (beads) added and I put in an additional 200mm of loft insulation myself above the 100mm that was there already. Most windows are original double glazed, we replaced the two front bedrooms as the old units were on their way out. I plan to do everything eventually when we can afford it, the recent cold snap has set a priority hierarchy.
The HP is a PUZ-WM85VAA(-BS) Ecodan R32 with a Joule 200L HW cylinder, we replaced all of the original radiators. On the performance estimate it gives 14,688kWh to heat the house and 2,224 kWh to heat the hot water annually.
I have included 3 pics of the external installation (yes the wisteria needs trimming back and they used copper for the overflow which thankfully hasn’t been stolen yet). The installer left gaps in the insulation on the flow and return pipes at the back of the unit which I’ve circled in red, so I’ve added some myself. I took off the bottom part of the conduit when I did this and found that the insulation was not wrapped around the pipe here.
Inside I have added a few more bits of insulation on the HW tank where the pipes go in/come out as they were warm to the touch. Is it worth adding insulation around the valves? The loft gets very little heat from the house due to the 300mm of insulation. On the flow and return in the loft to the HP there were some gaps on the bends which I’ve tried to plug and wrap some loft insulation around. I need to get a roll of loft insulation to cover the batteries as they died during the cold snap, so I’ll use what is left over to cover the flow/return pipes some more. Is it ok if the temperature probes are loosely covered with loft insulation?
On to settings, I have included a pic of our compensation curve, I haven’t touched this, and have no idea if it’s optimal, the installer set it up. We leave the wireless thermostat in the lounge set at 19 degrees C in the daytime and 18 degrees at night and this keeps the temperature upstairs comfortable. The installer had set the HW to top itself up when it dropped by 5 degrees, but I found that it was coming on too often for my liking. I’ve set it to come on once per day for an hour at midday (will change to 1pm though when I hopefully move to the Octopus Cosy tariff soon) as this is usually about the warmest part of the day and has the best chance of solar PV. I find that there is enough HW to cover us, sometimes we need to do an additional heating cycle. When our kids grow up and start having showers then we’re going to be running more cycles as there will not be enough. The settings are;
DHW max temp: 50 degrees
DHW max temp drop: 10 degrees (was 5)
DHW max operation time: 60 min
DHW mode restriction: 30 min
DHW recharge: Large
It typically takes about 45 – 50 minutes for the tank to get to 51.5 degrees from cold.
For Legionella, the settings are;
Hot Water temp: 61 degrees
Frequency: 10 days
Start time: 1pm
Max Operation time: 2hrs
Duration of max temp: 5 min
Lately I’ve found that the Legionella cycle seems to be lasting a lot longer than previously which is annoying as the heating obviously doesn’t come on, the tank temp will hover around 59 degrees with little seemingly happening so I end up turning the HP off and on again through the MELCloud app to get the heating to initiate.
Your external installation looks similar to ours and I was told it was a decent job. Anything you can do to insulate pipes in unheated parts of the house is a good thing. You should put pipe insulation over the pipe temp sensors.
Your WC curve is a little hotter than mine. If you want to see how well matched it is to your house heat loss, turn the thermostats up and see if the house gets hotter. If so you can probably afford to adjust the curve down. It's better to try and avoid the thermostat being the limiting factor too much and let the weather compensation control the room temperature. If you can lower the flow temperature and still keep the house warm it's going to be more efficient. My thermostats are set 1-2 degrees hotter than I want the house but it rarely reaches the set temperature. If you do lower the flow temp it may take longer to warm the house up from cooler.
HW settings are similar to mine and seem OK. I have mine a little cooler at 48 deg.
Not sure about your Legionella. It sounds like the ASHP is struggling to get to 60 degrees. Do you know if your immersion is working?
Your usage sounds in the right ballpark but as I said, if you can get away with lower flow temps your bills will probably also be lower. It does look like you are on the right track though. Do you know what your COP is btw?
@trbob Is the daily kWh usage you quote just for the heat pump, or is it your total usage, and where are you taking it from?
I have found the Mitsubishi controller (FTC6) reports about 10% more kWh consumed than the separate heat pump electric meter. (The energy produced according to the FTC6 implies a COP of 2 or less but that's another story, and I don't quite believe that either).
Your external installation looks similar to ours and I was told it was a decent job. Anything you can do to insulate pipes in unheated parts of the house is a good thing. You should put pipe insulation over the pipe temp sensors.
Your WC curve is a little hotter than mine. If you want to see how well matched it is to your house heat loss, turn the thermostats up and see if the house gets hotter. If so you can probably afford to adjust the curve down. It's better to try and avoid the thermostat being the limiting factor too much and let the weather compensation control the room temperature. If you can lower the flow temperature and still keep the house warm it's going to be more efficient. My thermostats are set 1-2 degrees hotter than I want the house but it rarely reaches the set temperature. If you do lower the flow temp it may take longer to warm the house up from cooler.
HW settings are similar to mine and seem OK. I have mine a little cooler at 48 deg.
Not sure about your Legionella. It sounds like the ASHP is struggling to get to 60 degrees. Do you know if your immersion is working?
Your usage sounds in the right ballpark but as I said, if you can get away with lower flow temps your bills will probably also be lower. It does look like you are on the right track though. Do you know what your COP is btw?
Thank you Kev, I'll get some rockwool over it at the back and try to get some lagging around the valves.
When the thermostat is turned up it makes the house hotter, above 20.5, my wife says it's too hot. Also now that it's a bit milder, 18 over night in the lounge makes upstairs a bit too warm when the heating kicks in, so I've changed it back down to 17.5.
I'm trying to get my head around letting the WC dictate the house temp over the thermostat. How do you adjust the flow temp, is it by altering the WC or a separate setting? Is the WC easy to adjust and not make a hash of it?
I'm fairly certain the immersion is working, the HP seems to stop after 50 degrees and there is a load showing on my inverter app.
@trbob Is the daily kWh usage you quote just for the heat pump, or is it your total usage, and where are you taking it from?
I have found the Mitsubishi controller (FTC6) reports about 10% more kWh consumed than the separate heat pump electric meter. (The energy produced according to the FTC6 implies a COP of 2 or less but that's another story, and I don't quite believe that either).
Thank you RedBuzzard, it's my total usage, taken from my inverter data. Can the HP only usage be accessed through MELCloud or is it just on the controller? I haven't looked at the meter by the controls, does that display electrical usage or heat output or both?
When the thermostat is turned up it makes the house hotter, above 20.5, my wife says it's too hot. Also now that it's a bit milder, 18 over night in the lounge makes upstairs a bit too warm when the heating kicks in, so I've changed it back down to 17.5.
I'm trying to get my head around letting the WC dictate the house temp over the thermostat. How do you adjust the flow temp, is it by altering the WC or a separate setting? Is the WC easy to adjust and not make a hash of it?
Hi TRBob, I’ve been fine tuning our WCcurve and it’s quite effective.
and as Kev M suggested above in he’s reply you need to prevent room stats from interfering with the HP operation.
We put the thermostat up so it wouldn’t shut the HP down and we allowed the WCcurve to operate at its existing set temperature. if the room got hot we simply put a minus adjustment on the main screen of the ftc6 controller screen. Once we felt the room temp was at the desired level we noted the outside thermistor temp and the adjusted set flow temperature which was now adjusted based on the plus/minus adjustments we had made. We did this test for 2 extremes of outside weather eg -1 and +7 so that then gave us 2 points on a sloping line when the room temp was sustained at 20deg at 2 different flow temperatures. We then extended the sloping line to give us flow temps at -6 and +10 to draw our own weather compensation curve.
We are still watching it but not that often now. hope this is of interest.
Your external installation looks similar to ours and I was told it was a decent job. Anything you can do to insulate pipes in unheated parts of the house is a good thing. You should put pipe insulation over the pipe temp sensors.
Your WC curve is a little hotter than mine. If you want to see how well matched it is to your house heat loss, turn the thermostats up and see if the house gets hotter. If so you can probably afford to adjust the curve down. It's better to try and avoid the thermostat being the limiting factor too much and let the weather compensation control the room temperature. If you can lower the flow temperature and still keep the house warm it's going to be more efficient. My thermostats are set 1-2 degrees hotter than I want the house but it rarely reaches the set temperature. If you do lower the flow temp it may take longer to warm the house up from cooler.
HW settings are similar to mine and seem OK. I have mine a little cooler at 48 deg.
Not sure about your Legionella. It sounds like the ASHP is struggling to get to 60 degrees. Do you know if your immersion is working?
Your usage sounds in the right ballpark but as I said, if you can get away with lower flow temps your bills will probably also be lower. It does look like you are on the right track though. Do you know what your COP is btw?
Thank you Kev, I'll get some rockwool over it at the back and try to get some lagging around the valves.
When the thermostat is turned up it makes the house hotter, above 20.5, my wife says it's too hot. Also now that it's a bit milder, 18 over night in the lounge makes upstairs a bit too warm when the heating kicks in, so I've changed it back down to 17.5.
I'm trying to get my head around letting the WC dictate the house temp over the thermostat. How do you adjust the flow temp, is it by altering the WC or a separate setting? Is the WC easy to adjust and not make a hash of it?
I'm fairly certain the immersion is working, the HP seems to stop after 50 degrees and there is a load showing on my inverter app.
Assuming yours is the same as mine, if you wake up the control panel and press the top right button you should see power delivered and consumed. Pressing it again access HW and heating separately. delivered/consumed =COP. This updates every day then stores the whole month.
@trbob Is the daily kWh usage you quote just for the heat pump, or is it your total usage, and where are you taking it from?
I have found the Mitsubishi controller (FTC6) reports about 10% more kWh consumed than the separate heat pump electric meter. (The energy produced according to the FTC6 implies a COP of 2 or less but that's another story, and I don't quite believe that either).
Thank you RedBuzzard, it's my total usage, taken from my inverter data. Can the HP only usage be accessed through MELCloud or is it just on the controller? I haven't looked at the meter by the controls, does that display electrical usage or heat output or both?
I have 3 electric meters - the main one obviously which I get billed from, one on the heat pump supply which is located by the consumer unit, and one for the immersion heater. I assumed this was for MCS requirements but I don't know.
The last few days while it has been up to 10/12 degrees outside, the heat pump has used 12-14 kWh daily (I can't split heating and DHW although DHW alone in the summer was only using about 2 units per day). In the December "freeze" it averaged about 40 kWh per day. The house is kept at about 20-21C.
The FTC6 is the only source I have for heat output - I have been told that it is only an estimate and not a bassis for assuming there is anything wrong with the installation! Apparently I would need a heat meter to get a good number for the output energy.
When the thermostat is turned up it makes the house hotter, above 20.5, my wife says it's too hot. Also now that it's a bit milder, 18 over night in the lounge makes upstairs a bit too warm when the heating kicks in, so I've changed it back down to 17.5.
I'm trying to get my head around letting the WC dictate the house temp over the thermostat. How do you adjust the flow temp, is it by altering the WC or a separate setting? Is the WC easy to adjust and not make a hash of it?
Hi TRBob, I’ve been fine tuning our WCcurve and it’s quite effective.
and as Kev M suggested above in he’s reply you need to prevent room stats from interfering with the HP operation.
We put the thermostat up so it wouldn’t shut the HP down and we allowed the WCcurve to operate at its existing set temperature. if the room got hot we simply put a minus adjustment on the main screen of the ftc6 controller screen. Once we felt the room temp was at the desired level we noted the outside thermistor temp and the adjusted set flow temperature which was now adjusted based on the plus/minus adjustments we had made. We did this test for 2 extremes of outside weather eg -1 and +7 so that then gave us 2 points on a sloping line when the room temp was sustained at 20deg at 2 different flow temperatures. We then extended the sloping line to give us flow temps at -6 and +10 to draw our own weather compensation curve.
We are still watching it but not that often now. hope this is of interest.
Assuming yours is the same as mine, if you wake up the control panel and press the top right button you should see power delivered and consumed. Pressing it again access HW and heating separately. delivered/consumed =COP. This updates every day then stores the whole month.
Yes it is, all in kWh, my install date was mid Feb 2022, kept the temp turned down until we moved in at the end of March, I can't remember exactly when I changed the DHW from topping up every 5 degree drop, maybe April or May.
I have 3 electric meters - the main one obviously which I get billed from, one on the heat pump supply which is located by the consumer unit, and one for the immersion heater. I assumed this was for MCS requirements but I don't know.
The last few days while it has been up to 10/12 degrees outside, the heat pump has used 12-14 kWh daily (I can't split heating and DHW although DHW alone in the summer was only using about 2 units per day). In the December "freeze" it averaged about 40 kWh per day. The house is kept at about 20-21C.
The FTC6 is the only source I have for heat output - I have been told that it is only an estimate and not a bassis for assuming there is anything wrong with the installation! Apparently I would need a heat meter to get a good number for the output energy.
Thanks, I've posted my data above in response to Kev, the only meter for the HP that I can see is right next to the immersion isolator, it reads 2631kWh so I guess that is the HP as the immersion should be no where near that much, maybe ~100kWh since install? Plus the figure is close to the consumed amount I gave above.
Thinking about installing a heat pump but unsure where to start? Already have one but it’s not performing as expected? Or are you locked in a frustrating dispute with an installer or manufacturer? We’re here to help.
