ASHP control improvements

[JohnMo]

That's the idea of weather comp, you set the flow temp so you get your house at the temp you want today, as the weather cools, the flow temp increases to keep indoors stable.  If it starts getting cooler indoors the curve is to flat, if it gets hotter it's to steep

[Roby]

Yeah I understand ,it's simply that from all the other threads I've read on several forums ,the settings I am currently at and the original settings I was left with,I am  now miles away from that,always a worry for a newbie,beginning to think it hasn't been commissioned at all,plugged in heat coming out all good,kerching,thank you very much,pretty sure I'm not the only one this has happened to. With a lot of help from you guys hope to get it right and pass on info to others in the same area with similar kit so at least they would have a baseline starting point..p.s. can anyone give me the order details for a mitsu wireless controller that will allow me to try auto adaptation on a Ftc5.Sounds like a simpler solution. Have vulnerable people at home so no heating isn't an option determined to get this running at minimum cost.

[PhilT]

On 16/10/2022 at 12:02, Roby said:

I don't have a separate stat in the house just the one fitted in the FTC with trvs on the rads.Question is ,what controls the indoor temp,do I need to fit a separate stat?

I'm a little surprised by this I wasn't aware a stat was fitted to the actual FTC. Surely you need some kind of room stat for ultimate control, that's why your temp is running away to 24. Your WCC is way different from mine which is set to 50 at -3degC down to 35 at 15 ambient above which the heat pump almost never comes on as my room temp rarely falls below my target temp of 18 during the day. The advice I have received is that heat pump efficiency starts to fall when flow temp goes much lower than 35 due to more regular cycling.

[Roby]

6 hours ago, PhilT said:

I'm a little surprised by this I wasn't aware a stat was fitted to the actual FTC. Surely you need some kind of room stat for ultimate control, that's why your temp is running away to 24. Your WCC is way different from mine which is set to 50 at -3degC down to 35 at 15 ambient above which the heat pump almost never comes on as my room temp rarely falls below my target temp of 18 during the day. The advice I have received is that heat pump efficiency starts to fall when flow temp goes much lower than 35 due to more regular cycling.

23 hours ago, Roby said:

Thanks for that ,I'll try this, one at a time,the problems I'm having is that the more I look into the problem the more differing answers I get .I was just worried about bringing the flow temp down too much and it not being sufficient in the colder weather

 

[Roby]

Hi bud,no separate stat just a couple of holes in the controller fitted in the living room and trvs on the radiators.What im finding frustrating is, there is obviously a methodology to set the system up for optimum performance,size and circumstance dependant otherwise you'd be as well buying  two candles and if gets cold you could light them..i have very rarely(never) had a discussion with anyone who has had an ashp fitted and posted anywhere that it worked great after "commissioning" Without the people on these forums I would be  totally in the dark.All help much appreciated.

 

 

[Roby]

Hi,when running WC on an ecodan I seem to have a pump running almost constantly. Is this normal?Does it do this to constantly monitor the flow temps or do I have problem.

[JohnMo]

WC requires a flow all the time, your flow temp is right to match heat loss with heat input.  So you have lowest possible heat input. The heat pump/boiler, just monitors the return temp, adding heat as required.  At the moment my boiler fires up for 10mins or so every couple of hours. But the pumps run 24/7 in the heating season.

 

[Roby]

Thanks for that was worried about burning the pump out.Tanks between two bedrooms and can hear the pump during the night.Will soundproof the cupboard and continue with the adventure.By the way anyone tried auto adaptation with  mitsu .if so what do I need to buy.Sounds an easier option but don't know if it works

[JohnMo]

Someone said it doesn't work with UFH, so if your on radiators it should work 

[PhilT]

1 hour ago, Roby said:

Thanks for that was worried about burning the pump out.Tanks between two bedrooms and can hear the pump during the night.Will soundproof the cupboard and continue with the adventure.By the way anyone tried auto adaptation with  mitsu .if so what do I need to buy.Sounds an easier option but don't know if it works

Auto Adaptation only works with a Mitsubishi controller and they advise against using AA with UFH so probably WC mode best as others have said.

[Itrium]

After starting this discussion 18 months ago and seeing it is still active, it seems only right to share some of my experience.

The first problem I discovered was the installers had left a lot of insulation off the external pipework. They came back and corrected that.

The next problem was that the electric heaters were coming on at strange times. This I traced to the calibration of the flow and return thermistors. They were reading about 6’C low making everything hotter than it should be and the electric heaters kicked in to raise the temperature. The flow and return temperatures are easily checked with a digital thermometer. There is an option to calibrate the thermistors in the controller. Also, I disabled all the options for electric heating.

I asked a couple of water companies about the risk of legionnaires bacteria in their supply and was fobbed off with remarks like keeping within legislative limits. Thinking this through, the water tank bottom will never reach sterilising temperatures. There is a lot of dead pipe in the supplies to shower heads where bacteria could live, these would be nicely sprayed out before any hot water killed them. Everything is a sealed system with no open tanks for stagnant water. All in all, it seems very unlikely  there is legionella in the system and it would be flushed through by regular use anyway.I have set the tank to 40’C but it actually gets to about 50’C as the thermistor is towards the bottom of the tank. I’ve turned off the sterilising cycles and I am still alive!

I mentioned about there being 8 thermostats in this small mid terrace house. They are a complete waste of time, money and space. It takes about 4hrs to warm up 1’C with the UFH. The thermostats may react to short events like the sun coming out but it does nothing to control the room temperature. For the upstairs rooms, the quickest way to warm a room is to open the door and let the down stairs heat in. I never use the upstairs heating, enough heat comes from downstairs to do the job.

Down stairs I have unscrewed the valve actuators and wired in a TADO in the hall as an over temperature limit. This gives a limit to the house core temperature. I did try the auto adaptive control but this was not stable.

I think I understand why the heating can be left on 24/7 in a well insulated house. The heat loss depends on the difference between the inside temp and the outside. For example, if it is 20 inside and 0 outside the heat loss will be 20*const. If the heating is turned off overnight and the temp falls 1 deg, the heat loss will be 19.5* const. The difference in heat loss is 2.5%. Extra heat has now to be put back into the building to get back to 20 deg. Not worth worrying about trying to save money by setting back the temperature.

The conclusion is to use a slightly aggressive WC and let the TADO catch any over temp. I am currently trying to find the best WC settings by manually adjusting the flow temp now we are in a spell of much colder weather.

I would be interested to hear if you have any thoughts on these changes.

 

[Marvin]

2 hours ago, Itrium said:

After starting this discussion 18 months ago and seeing it is still active, it seems only right to share some of my experience.

The first problem I discovered was the installers had left a lot of insulation off the external pipework. They came back and corrected that.

The next problem was that the electric heaters were coming on at strange times. This I traced to the calibration of the flow and return thermistors. They were reading about 6’C low making everything hotter than it should be and the electric heaters kicked in to raise the temperature. The flow and return temperatures are easily checked with a digital thermometer. There is an option to calibrate the thermistors in the controller. Also, I disabled all the options for electric heating.

I asked a couple of water companies about the risk of legionnaires bacteria in their supply and was fobbed off with remarks like keeping within legislative limits. Thinking this through, the water tank bottom will never reach sterilising temperatures. There is a lot of dead pipe in the supplies to shower heads where bacteria could live, these would be nicely sprayed out before any hot water killed them. Everything is a sealed system with no open tanks for stagnant water. All in all, it seems very unlikely  there is legionella in the system and it would be flushed through by regular use anyway.I have set the tank to 40’C but it actually gets to about 50’C as the thermistor is towards the bottom of the tank. I’ve turned off the sterilising cycles and I am still alive!

I mentioned about there being 8 thermostats in this small mid terrace house. They are a complete waste of time, money and space. It takes about 4hrs to warm up 1’C with the UFH. The thermostats may react to short events like the sun coming out but it does nothing to control the room temperature. For the upstairs rooms, the quickest way to warm a room is to open the door and let the down stairs heat in. I never use the upstairs heating, enough heat comes from downstairs to do the job.

Down stairs I have unscrewed the valve actuators and wired in a TADO in the hall as an over temperature limit. This gives a limit to the house core temperature. I did try the auto adaptive control but this was not stable.

I think I understand why the heating can be left on 24/7 in a well insulated house. The heat loss depends on the difference between the inside temp and the outside. For example, if it is 20 inside and 0 outside the heat loss will be 20*const. If the heating is turned off overnight and the temp falls 1 deg, the heat loss will be 19.5* const. The difference in heat loss is 2.5%. Extra heat has now to be put back into the building to get back to 20 deg. Not worth worrying about trying to save money by setting back the temperature.

The conclusion is to use a slightly aggressive WC and let the TADO catch any over temp. I am currently trying to find the best WC settings by manually adjusting the flow temp now we are in a spell of much colder weather.

I would be interested to hear if you have any thoughts on these changes.

 

Hi @Itrium

 

Our ASHP external pipework is insulated within an inch of its life. Climaflex wrapped in Supasoft loft insulation, wrapped in EDPM. And taped up. Total about 200mm thick.

 

Yes all our electric heaters disabled but available.

 

Our 205ltr hot water tank registers about 20°C at the bottom, about 44°C ⅔ up and about 55°C near the top, all at the same time. 

 

Low and slow is the way to heat your home. We drop 2 degrees at night to sleep comfortably. 

With our Weather Compensation (WC), we adjusted at what points, what the set temperature, is.

 

Having about 5kW PV we have lowered the maximum ASHP  kW input demand by adjusting the compressor speed to take advantage of the PV, by trying to make our ASHP work lower for longer, also helping the cycling (starting heating length of time and turning off length of time) and also adjusted the ASHP stop differential temperature setting, which as @dpmiller says allows the inverter to wind down more progressively, lessening the chance of / ignoring an overshoot (lack of buffer capacity eg) and reduces short-cycling. Which is what is now happening.

 

In the last 24 hours here we have had an average of about 3°C and my meter for the ASHP shows we have used 8.99kWh for 104m2 floor area. That's about 3.6 Watts an hour per m2. (Although we do have AIM and APE. 

That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

Good luck with improvements

 

M