@derek-m I’ve checked the pipes under sink in kitchen and bathroom but they are not hot until I run the hot water. Even with the pump on it sometimes takes a while for the hot water to come through, and it can fluctuate in temperature and splutter for a while…
Hi… starting from the premise that all components are working and that your installer has set the UFHeating to an efficient (low flow temp) then I’m immediately drawn to your cylinder reheating parameters. This may create the following imagined scenario… Eg you only have a 5deg drop which means it will frequently try to stop space heating (at say 35 degrees) then try to heat the 45 degree cylinder with 35degree flow. This will cool the cyl temp until the ASHP catches up and finally delivers the required 50deg flow. It will then switch back to space heating…. Whereupon the HP might now need defrosting…. Etc etc
if you can have a wider water heating temperature cycle say 50deg down to 38deg you may find the water stays hotter for longer. Also ensure “Large Tank”monitoring is selected so you have a fuller volume of hot water….
BTW (and as an aside) I have a Tempest tank with a secondary exchanger heat source from Wet Solar Thermal tubes mounted on the roof. This, on an ice cold clear blue winters day 0degC can deliver 35degC to the bottom of our cylinder.
if you’ve moved the thermistor to the bottom location of the cylinder it will send the wrong message to the HP controller.
In that; after the fixed ‘rest’ period the system will automatically try to reheat the water in the cylinder because it reads the thermistor temperature which is now in a cooler location - calling for more heat. Ergo the now cooler primary pipes will try to heat the already hot cylinder. they are complicated beasts…😂
@sunandair thanks so much for your message. I’ve set the parameters wider for re-heating this evening so will see. I can’t find the setting for ‘large tank’ monitoring…
the heating engineer had set the UF heating flow temp to 55 and told me not to change it… but after lots of reading have set it to use weather compensation but not sure if that’s the right thing?!
I have just ran a bath for my son- temp in tank 44 degrees but water only luke warm upstairs… but hot downstairs so had to run up and down with a jug on hot water 🙈
so I think there are 2 issues- the temp dropping in the tank and intermittent hot water upstairs…
Heating engineer has agreed to come next week but he said the shower head use 19l/min of water so if may only last 1 shower!! Not sure about this as we had an unvented cylinder in our old house and never ran out??
it’s all very complicated but I love learning how it all works so very grateful for everyone’s replies!!
@sunandair thanks so much for your message. I’ve set the parameters wider for re-heating this evening so will see. I can’t find the setting for ‘large tank’ monitoring…
the heating engineer had set the UF heating flow temp to 55 and told me not to change it… but after lots of reading have set it to use weather compensation but not sure if that’s the right thing?!
I have just ran a bath for my son- temp in tank 44 degrees but water only luke warm upstairs… but hot downstairs so had to run up and down with a jug on hot water 🙈
so I think there are 2 issues- the temp dropping in the tank and intermittent hot water upstairs…
Heating engineer has agreed to come next week but he said the shower head use 19l/min of water so if may only last 1 shower!! Not sure about this as we had an unvented cylinder in our old house and never ran out??
it’s all very complicated but I love learning how it all works so very grateful for everyone’s replies!!
katie
Hi Katie,
As you have not yet resolved your problem, I suggest that we go through your system in a logical and systematic manner. I have attached a copy of the installation manual, which I believe shows the internals of your particular cylinder on page 6.
The heating coil, connected to the heat pump, should be located in the lower section of the cylinder, so should heat most of the 300 litres of water to the required temperature.
I assume that the temperature sensor that you moved is connected to the Midea controller, and will probably indicate the cylinder water temperature. If you don't have a suitable thermometer, you may be able to use this for temperature measurements, so initially remove the sensor from the pocket and confirm that the temperature reading falls to indicate the indoor temperature.
I think that the green water pump, that we discussed previously, is actually a secondary pump, and could be a prime suspect. Have a look at the brass body of the pump and see if there is an arrow which would indicate the direction of flow. Put your hand on the green section to see if it is warm and vibrating slightly, this would indicate that the pump is running.
Now remove the temperature sensor and see if the green pump starts or stops once the temperature has fallen.
Please carryout the above and post back the results.
@sunandair thanks so much for your message. I’ve set the parameters wider for re-heating this evening so will see. I can’t find the setting for ‘large tank’ monitoring…
the heating engineer had set the UF heating flow temp to 55 and told me not to change it…
Hi Katie
Derek is running through some system checks with you so I won’t add any other comments just now. Other than, It’s likely that not all manufacturers have large tank monitoring so your system may not have it as an option. And is designed to work off a single thermistor.
@curlykatie just a quick one - derek-m is going through diagnosing the secondary DHW circulation pump which is very likely to be part of the issue so won't add to that .
buy a few of these : fish tank temp monitors they are cheap as chips. insert into all available probe holes on the cylinder , and if you can put one where you can tape the probes to a suitable pipe location or two (and wrap a bit of pipe insulation round it to get a better reading). the probes in the cylinder will give you a quick indication of how far down the cylinder the water is still hot (i.e. how "full" of hot water your tank is) .
Tank DHW reading 50 degrees- green pump hot and vibrating
Thermostat removed- dropped to 21, when water started to re-heat green pump stopped vibrating and re-started once it had stopped heating the water.
hope that makes sense! I’ve attached a picture of the brass body of the pump- arrow pointing downwards. Of note, there’s a dial on the side of the pump which has 1-3 and it’s set to 3
Tank DHW reading 50 degrees- green pump hot and vibrating
Thermostat removed- dropped to 21, when water started to re-heat green pump stopped vibrating and re-started once it had stopped heating the water.
hope that makes sense! I’ve attached a picture of the brass body of the pump- arrow pointing downwards. Of note, there’s a dial on the side of the pump which has 1-3 and it’s set to 3
thanks again,
katie
Hi Katie,
Okay, the next thing to ascertain is where the pipework is going.
The pipework coming out of the top of the hot water cylinder is the supply to your hot water taps and shower. Near the top of the tank you should find this pipe is quite hot, but the further away from the tank it should be cooler, particularly since it does not look to be insulated.
The pipe connected to the top of the pump I believe is the return flow from the secondary water circulation system. The way that this works is that the water pump draws the hot water up the pipe at the top of the cylinder, the water flows around a pipework circuit connected to all the hot water outlet points (taps, shower, bath etc.) and then flows back down the pipe to the water pump. So it would appear that the pump is running almost constantly, taking the hot water out of the top of the cylinder, running the hot water around the pipework which may or may not be insulated, and in the process cooling the water in your hot water cylinder. I think that this could be the main problem.
I would suggest that you start by turning the pump speed down from 3 to 1, this will at least reduce the flow rate, and may in the process reduce the heat loss.
The next thing to do would be to have the pump switched off, either by having it disconnected, or having an on - off switch installed on its supply cable, so that you can switch on back on during periods when you may need fairly instant hot water at the taps.
I think that you mentioned that on occasions the water was spluttering at the hot taps, this would indicate that their could be some air in the system, which again may be caused by the pump.
So, turn the pump speed down, then get it disconnected or at least switched off, and report back.
@derek-m thank you. Do you mean the pipe the is in the center top of the tank? I have added a photo.
I have switched the green pump to 1 and will look into getting a switch added and let you know how it goes!
Another quick question!! With regards to our heating we have UF throughout controlled by tio thermostats in each room. I have set the weather compensation to curve 5 at the moment. On the controller it has zone1 and 2 and high and low mode- do you know what this means? Pic attached! is the aim that we are able to heat the house at the lowest flow temp with the pump on most of the time? Feels so counterintuitive to have it running all the time!! At the moment the pump is off for large parts of the day as the house has reached temp on the stats.
apologies for all the questions, this is all new and just trying to get my head around it!!
@derek-m thank you. Do you mean the pipe the is in the center top of the tank? I have added a photo.
I have switched the green pump to 1 and will look into getting a switch added and let you know how it goes!
Another quick question!! With regards to our heating we have UF throughout controlled by tio thermostats in each room. I have set the weather compensation to curve 5 at the moment. On the controller it has zone1 and 2 and high and low mode- do you know what this means? Pic attached! is the aim that we are able to heat the house at the lowest flow temp with the pump on most of the time? Feels so counterintuitive to have it running all the time!! At the moment the pump is off for large parts of the day as the house has reached temp on the stats.
apologies for all the questions, this is all new and just trying to get my head around it!!
Hi Katie,
Sorry for the delay in replying, I have been looking through the Midea manual to check on a few things.
The pipe coming out of the centre section at the top of the hot water cylinder is indeed the hot water supply to the taps and shower etc. I can't tell from the photo if this pipework is actually insulated, which it needs to be. Have a look at this video.
The photo of your controller appears to show that the UFH in zone 1 is On, but the UFH in zone 2 is Off. Try the following test to see if the controller display changes and the two zone valves actually operate.
Turn all the thermostats down to say 15C and see if the controller display shows both zones to be Off. Also try moving the lever on each of the zone valve actuators from the auto position to the manual position. You should feel some resistance whilst pushing the lever, then the lever should slowly return to the auto position when released, this would indicate that the valve is closed.
Turn one of the thermostats up to say 25C in the downstairs area and note any changes on the controller display. Recheck the zone valves, the lever on one should now move freely, this should be the zone valve for the downstairs area.
Turn the downstairs thermostat back down to 15C, and repeat the above procedure using one of the upstairs thermostats.
Return all thermostats to your desired setting once completed then post the results.
I have attached a copy of the Midea manual which was kindly provided by Batalto, the required password is midea2020. I would suggest that you have a look at the section from page 81, which details the required settings for the controller. Don't panic, it may seem quite complex but the forum will guide you through any changes that may be necessary.
