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By Rjk983
FLYER Club Member  FLYER Club Member
#1870700
I'm sure this has cropped up before but a search for heating brought back far too many hits and the home automation thread long departed from the "101" of it's title :D

Looking for recommendations for smartening up the home heating system.

My main requirement is future adaptability (and obviously relative cheapness. I am a pilot...)

The current set up is extremely dumb. We are in a fairly new build which is built to passivhaus standard (but without the certification). So we should be able to have the house heated and controlled fairly efficiently.

Our current water set up is:

Cold Water:

  • Pumped cold water supply from next door's borehole - pressure is around 1.5-2 bar

Heating

  • Air Source Heat Pump (ASHP) which is a closed circuit for heating only
  • Upstairs - rooms are standard radiators controlled by TRV on each rad (They cope fine with heating the room to comfortable temp in the winter as the house is v.well insulated, windows are appropriately sized/oriented to minimise heat loss)
  • Downstairs - Under Floor Heating (UFH) split into four zones with local wall mounted mechanical thermostats wired back to the manifold. Each zone is split into two loops so in theory they could be broken into 8 control zones if we really wanted to go to town.
  • The absolute max water temp in the circuit is controlled by the ASHP control panel. The stats and TRVs then open/close on demand as required but with no control beyond a call for heat.

Domestic Hot Water:

  • Immersion heater in a water storage tank, controlled by mechanical time clock... I know! ...house was built by a farmer (not The Farmer I hasten to add)...

Over time I want to improve the overall system but I imagine costs will be fairly significant so I need to do it in chunks as and when required.

I have access to two plumbers in the family so installation isn't a problem. I also have a tame electrician for anything that is beyond me or needs certificates. I am fairly happy with the principles of coding / rasp pi / arduino etc but I would need to be pointed at some worked examples or github projects to stand a chance.

What do I want in the mix:

Initial priorities:

  1. Control of the immersion heater. It will remain my only hot water source for a while yet. Ideally, fully customisable timed switching on and off, plus a boost option. But as a minimum, a 7-day programme with at least 2 on/off periods per day
  2. Change over from mech stats in UFH zones to electronic sensors. Reporting back to a hub and allowing me to control temp of each zone remotely. The main ASHP controller is not able to be interfaced with so the heating circuit will continue to flow 24/7 with water temp at a set range. But I do want to have more control of the zones.
  3. Control of the rads. We would like to set an individual room temp, ideally without adding room stats but happy to look at that if required (these would have to be wi-fi to work in the house). Ideally with the ability to set a 7-day timer routine along with temp set limits for each room (one rad per room).

In the future we will add solar hot water heating into a thermal store with an immersion and the ASHP as alternate sources. At this point I expect to switch over to the thermal store providing all of the hot water be it through a closed heating circuit or a coil heating incoming drinking water for the hot water taps. I would expect whatever control system I put in now to continue to be able to operate albeit with additional control of the system pumps and valves so that the heat source and the heat supplied are separated with the heat store in the middle of the 3 supplied circuits and 3 heating sources.

So far I have found the Honeywell Evohome system, it seems to tick all of my immediate boxes and appears to be fairly adaptable.

Does anyone have any experience with it?

Any other recommendations?

medals will be awarded to anyone who made it this far :lol: thanks in advance for any advice.
By riverrock
FLYER Club Member  FLYER Club Member
#1870707
First question I always ask is what problem are are trying to solve, and is the effort worth the expense.

Modern hot water tank will hold hot enough throughout the day if you boost twice a day, so a simple mechanical timer for immersion is likely fine. Solar will do it's thing, then immersion will top up the heat. ASHP are poor at dealing with hot water - probably best to just keep it attached to CH loop and so keep the floor temperature down at it's most efficient levels.

Underfloor heating needs a long time ( days in some cases to become effective, so it isn't designed or useful to control it quickly. Better to set and forget.

You might want separate control over upstairs heating loop, so you don't hear it during the day. For individual rooms, how often do you need to change the temperatures? If an automated system useful?

I ask some of these questions as I know of various people who have tried remote controlled TRVs, got frustrated, and returned to manual ones. I'd make sure whatever system you put in can be independently run, so when company servers are turned off, support finishes, you aren't left cold ( litteraly).
By Rjk983
FLYER Club Member  FLYER Club Member
#1870715
@riverrock all fair points.

The current set up does work pretty much as you describe. And I’m happy with the principles of running the UFH (set and forget).

But I’m on my third mech timer for the immersion so my first problem to solve is a reliable timer. Going electronic would add flexibility to vary the daily hot water times as our week to week is a fairly fixed routine but it varies a lot from day to day. Hence we could get away with a 7 day timer, but it just seems like having control remotely would be better. Notwithstanding the very valid obsolescence issues.

The ASHP we have needs the loop to flow otherwise it trips out with an over pressure alarm. There is no bypass in the loop which would probably be the easiest way to solve this. At the minute the loop comes into the house, branches to the UFH manifold and upstairs Loop. The upstairs loop runs through each rad and the last rad is in an en-suite, we have had to remove the TRV from this rad so that is always demanding heat, this allows the circuit to flow and prevents the over-pressure trip. Obviously, if any other other TRV or UFH zone has opened up then this final rad could close. But the house does generally get to temp fairly quickly and then sits fairly stable as long as doors and windows stay shut, so all of the valves are quite often shut.

As for heating the water in the tank the solar with immersion for top up is probably the optimal solution. Is there a way of sensing the temp/volume of hot water in the tank so that if the solar hasn’t done the job the immersion can be turned on, or is it a manual boost?
By riverrock
FLYER Club Member  FLYER Club Member
#1870719
All the immersion systems I know (4 so hardly definitive) have a temperature sensor which controls the hot water temp. It may be built into the immersion element control box. If you didn't, the tank would boil and start venting / releasing water through pressure relief valves.
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By stevelup
FLYER Club Member  FLYER Club Member
#1871181
I have Evohome - so happy to answer any questions you have. Had it for years, has never missed a beat.

Never once had to re-pair any of the devices, it's never lost connectivity with the internet, and it's never done anything weird or unpredictable.

Before you do anything, you need an ABV on your ASHP... should have never been installed without one.
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By SafetyThird
FLYER Club Member  FLYER Club Member
#1871333
250 year old stone cottage here, previously heated with two woodburners and solar PV for hot water. Next month I'm having ground source heat pump central heating installed with radiators, I've decided to go with Tado as the controller along with wifi controlled valves on the radiators. Tado is compatible with most start home systems and the valves give individual control over each room.
By Rjk983
FLYER Club Member  FLYER Club Member
#1871388
Thanks for the comments and suggestions.

@stevelup thanks for the offer. I’ll drop you a pm with some more specific questions if that is ok.

@SafetyThird @Colonel Panic thanks, I hadn’t heard of TADO. I just had a look on their website and the help forum says it can’t run an immersion due to the max current limitation. Do either of you have it rigged to control an immersion at all? If not do you have an alternate control for an immersion to top up your cylinder temperature regularly to prevent legionella?