Hi, i have a need to develop a system its a complex S plan heating system with two sources one a air source heat pump that will be primary and another a 63a electrical boiler only used when the air source isnt achieving needed temperature which should be able to be learnt based on the external temperature i capture, the heating user control will be via web interface, the house thermostat will be ds18b20 x 4 for error checking, the load of the boiler is high so will be checking the house load with ct clamps to stop the boiler if house load is over a certain level, various relays to eliminate back feeds opening other zone values.
So i have an arduino that is programmed to get a temperature or control a relay on the fly just given a certain command and digital pin, this works great for my needs and i can complete the whole system with this and node red logic.
The question is should I do it this way or should i hard code the arduino with the logic and pipe in the data needed i.e temperatures and current electrical load only using the node red web interface to set times, wanted temperature etc.
Does anyone have experience with something like this, im also very aware that there will be no manual thermostat or heating controls and im considering the possibility of a manual switch over between smart and manual incase of smart system error.
Never designed a heat pump system but have worked with a few. This was around the mid 80s and I hope their efficiency has improved. When the OAT (Outside Air Temperature) dropped below 32 F or 0 C you had to manually turn on what they called emergency heat. The system was blowing cold air with OAT below 32 F. Useless as teats on a bull. Turning on emergency heat just added some electric elements to make heat.
Take measurements to determine your system efficiency. Rather than mess around with CT Clamps if this will be permanent I would just use regular current transformers like this.
Add a burden resistance and offset the AC voltage developed across the burden resistance then feed that into your Arduino or like uC. Your code can decide how to handle the loads. No clue as to
So you want to average the four readings?
All in all you can look at the blower air out to determine when to kick in electric elements or the OAT. You mention a 63 amp load so for the electric heating element(s) I would just go with a good quality SSR and that's all you should need. The SSR is in a permissive loop where the main current draw is not to exceed whatever you have available and make sure you consider changing loads. Projects like this work much better when the supply is more than adequate for all loads.
I would sit down with a piece of blank white paper and a pencil with a large eraser and start listing what you want to happen and when. Step by step. Manual On/Off bypass is simple enough to incorporate. Web based user interface (GUI) should not be a problem.
Do the heat pump and electric heating system already have the 24 volt control system for a regular thermostat? That would relieve the arduino of the need to switch large loads.
Thank you your input makes a lot of sense, some topics you talk about im not too familiar with but it will give me a research point, the house is all electric no gas and the 100a supply is all that is available. i doubt even with the electric boiler on for a while it would reach over 100a as the rest of the house will be light loads. The 4x ds18b20 will be averaged and checked for outliers, all ds18b20s in the project will be grouped this way to catch bad readings early.
Both heating systems just accept a 230v trigger input so the Arduino only needs to switch a 5v relay and that will pass a switched live back to the boiler or air source heat pump, no load involved.
I think i have a good plan in mind i was just concerned if node-red as the main logic running on a rasp pi would be a source of failure and if i should move the logic to the Arduino but that would be harder to fine tune, possibly once the logic is set then i could test moving it over.
This is for a US heat pump and air handler where the winter temperature may get to -15 F for several days, so the supplemental electrical heat must produce a lot of heat.
My system is similar but I have gas hot air, and a hot water boiler along with the heat pump. Works extremely well. Depending on the cost per therm it will run primary on gas or electric (heat pump) for heat. I still have manual thermostats, that detect if the home gets to warm or cold. This would be caused by the main controller failing, it is my fail safe backup. We have seen temperatures to about -40 and a high of about 118 so a failure can be disastrous.
i can imagine with those extremes it could be disastrous, i think my code will fail to run if i lose a sensor or something else breaks so i think i will need to figure out a way to keep the manual and the smart and for them to work together.
