What are you trying to achieve with a smart controller that your 2 channel programmable controller won't do ?

I am assuming your stove is a typical type of room heater with a water jacket. These are typically difficult to automate because their output is fairly uncontrollable automatically because most have manual air vents or sometimes mechanical thermostats and all will need a heat dump permanently open.

What ever you do by way of automation nothing should override the function of the top stat that is (as you say) there to stop the tank from boiling. (Although this can't do its job if the tank is the heat dump for the stove)

I have Heatmiser controls https://www.heatmiser.com/en/neo-smart-thermostat/ .I have Gledhill store but that is not controlled direct neither is the boiler. Have room stats in each room and are meshed together and communicate with a hub that you can communicate with and control any stat via an app. The stats control the system so boiler won't fire unless triggered by frost protection if you have turned them off. So wherever you are you can monitor the temps in your rooms and turn on and off and change temp etc. There are other makes available

Posted By: BenMThat’s really interesting. How do you control the temperature of the thermal store? Do you use a back boiler stove in addition to the gas boiler?

My bottom stat controls the boiler. If system calls for heat and TS too low a temp it switches boiler on. Guess the stove complicates things a bit for you. But if you are not in the property, you would not be running the stove? I did not fit a wood boiler stove as due to pipe layouts I would have needed a pressure system and the ensuing safety issues auto vent valves etc and annual testing regime was a step to far. How you control your system will depend on your layout. As PIH says it is difficult to control solid fuel stove outputs. I assume your system is open vented what does your top stat control? On my store I did not fit a top stat but the ST thermocouple uses that pocket and controls the ST from overheating the TS (set to 80c on the ST controller max for the TS). The lower pocket houses the boiler stat. There is a thermocouple at bottom of the store and middle and top as mentioned. Depending on these temperatures the controller switches on the ST pump and varies its speed depending on temp differentials. Does your CH come off the TS? I run U/F off our store.

Posted By: BenMThe top stat (set at 85c)

Without getting the manual out I think the Gledhill instruction state 80 max.

Posted By: BenMIdeally looking for a system that you could set the tank stats and room stats via an app.

You will definitely be able to control room stats via a system but cannot see why and when you would need to change the ST stats via an app.
I do not keep a constant temp in the TS it is usually about 55 and above just from solar thermal panels if we want it hotter, I just nudge the thermostat up to switch boiler on for 10mins. During winter we hardly have the UF heating on usually just the kitchen and lounge. In the lounge use a wood burner in the evening if needed. We do not heat upstairs. I set the thermostat at about 40 C which is positioned level with the U/F return the flow from the TS to the UFH will be at a higher temperature due to stratification. The UFH manifold controls the water temp to 40 which circulates around the loops and will take up water from the store when it needs to top up the temperature. The room stats control the valves on the UFH manifold, either on or off. Also due to the stratification the top of the tank where the draw off is for the DHW heat exchanger will be hotter still. We do not have a stat in the top of the tank as the space is used for the ST max temp thermocouple. The boiler cannot overheat the TS as the lower TS stat that controls the boiler is around 40 and the boiler itself has 2 Over temp shut off devices. Due to the boiler flow running and take off for UFH this disturbs the stratification more than if it was just solar thermal feeding the TS. But because of not taking much flow to heat the house we still have good temp gradient in the store. Having the extra heat source, you have from the solid fuel stove, adds a greater complexity which is why you have the top stat in the store.

I struggle to understand why you would want to do that. By turning off any call on the boiler effectively turns it off. I suppose you could control it via a smart socket adapter and plug the boiler in that but if its anything like my boiler if you turn off power to it, you lose your settings. I think it may be designed that way as if you have a power cut and power comes back on you could have a situation that may be unsafe. Does anyone know? Certainly, is the reason if an oven powers off it needs manual intervention to resume cooking. Certainly, ours does.

I control my boiler and all my heating via HomeAssistant. Hot water and main UFH are gas, other smaller rooms electric heaters.

I have a number of Bluetooth BLE temperature sensors around (one per room) and on/off is controlled by various things such as presence etc. as well as temperature.

For the boiler and UFH control, I have fitted a 4 Channel relay (not sure you can still get this one) in parallel to existing controls so if the relay fails, the other controls work. This provides a fail safe for the tank ('hard' thermostat is set at maximum) although your boler will only heat to a certain temperature.

The relays are NO & NC (Normally Open or Normally Closed) so if power is lost they default back to eith NC/NO depending on what it is controlling. I wrote a bit of firmware for them years ago. I'd probably use Tasmota now.

Currently tweaking the temperatures the tank are at for the boiler to come on/off. Only when you try and automate things, do you realise how much processing power the brain has!

The purpose of the thermal store is to provide a 'cool' volume of water which is available at the right time to soak up the output from the ST and multifuel stove. Then stay 'warm' until the right time when hot water or heating are required for the house. You don't want (eg) to be running the gas boiler on summer mornings and heating up the TS, as then there won't be capacity available to store the day's ST. Likewise on winter evenings when you might light the stove. A successful TS should swing from cold to hot every day, otherwise it's not doing 'storing'.

So the time controls for the TS need to be scheduled around the *availability* of heat. That's completely different from the usual (smart) controls which are based on non-TS systems, and schedule around *demand* for heat (eg turn on the boiler if I'm coming home early).

I would consider splitting the controls into two sub systems:

System A monitors the temperature in the rooms and pumps heat from the boiler to the radiators at times when it thinks you'll want heating - this could be an ordinary timed thermostat, or a smart internet wireless thingy that talks to your radiators and your phone.

System B monitors the temperature of the different zones of the TS and considers whether there is enough spare capacity for forthcoming ST or stove heat in the next few hours, and whether to fire the gas boiler to top it up. That could be a couple of thermostats each with a time clock, - eg the top stat inhibits the boiler on summer mornings before ST begins, and fires it later if there's not been enough ST to heat the top section in time for your shower, and turns off the ST and stove pumps if the tank gets hot. The bottom stat does the same but errs more towards reserving storage space for very sunny days or long stove burns. The timing schedules would be different in solar season from stove season.

Edit : By law there must be an independent temperature cutout that trips off all the heat sources if the tank gets dangerously hot (boiler, stove, ST, immersion). Often this has a tiny button which you use to reset it when triggered. If you have been to 85⁰ and not triggered it, it could be worth testing it to see if it still works. My factory-fitted one didn't after a few years service, and neither did the brand new generic replacement I bought, I had to get a reputable make .

Posted By: WillInAberdeenThe purpose of the thermal store is to provide a 'cool' volume of water which is available at the right time to soak up the output from the ST and multifuel stove. Then stay 'warm' until the right time when hot water or heating are required for the house. You don't want (eg) to be running the gas boiler on summer mornings and heating up the TS, as then there won't be capacity available to store the day's ST. Likewise on winter evenings when you might light the stove. A successful TS should swing from cold to hot every day, otherwise it's not doing 'storing'.

I agree with everything except the last sentence. Our TS is heated either by solar PV or by mains immersion. It's just used for DHW. If there's a sunny day then I want the TS to get hot and store enough heat that it doesn't need to see the sun again the next day or even the day after. So I think a TS should get hot whenever 'free' heat is available, and get cold as slowly as it is allowed to. Definitely not every day.

Posted By: Gareth JIf you have the overheat stat near the top of the tank, the top 6" of water might approach maximum safe tank limits (80-85?) But the lower portions might still be plenty cool enough. If your overheat stat is right at the bottom, you wait until the entire tank is up to temperature before dumping excess heat via a dump load. That's the way it was explained to me anyway.

The current crop of Gledhill Solar Thermal Stores with solid fuel has an overheat stat in the top 3rd of the store set at 82degrees. There's a control stat installed at the bottom third of the store. If the control stat at the bottom of the store is set too high, it can trigger the overheat stat, so it's recommended the control stat at the bottom is set at 75 degrees so there's a minimum 7 degree difference to the overheat. I've noticed Advance Appliances also has an overheat stat right at the top of the store on its multifuel model, but it's at the bottom for the standard thermal store.

Posted By: BenMSorry, I find this forum awful to use on a phone.

Can't help with that, I'm afraid.

Also can’t figure out how to delete a post!

AFAIK you can't. I always just change it to a single dot, or something more meaningful if appropriate.

Posted By: philedge

Maybe worth investigating and understanding why the boiler is short cycling before throwing money at a new boiler

Intergas have been saying it’s a circulation issue, hence the chemical flush. I’m hoping it is, as reluctant to get a new boiler, but it is 10 years old.

By the sounds of it, updating the control (and possibly the boiler) it’s worth getting new tank stats too.

Posted By: SimonD

Posted By: BenMIt’s an Intergas 36/30, but we may be changing it as we’ve had issues with it short cycling. It currently has another week to go on a chemical flush to see if that fixes it, and if not, it’s being changed to an Ideal Heat Only boiler.

That's quite a beast and if it's been range rated ch output can only be reduce to just over 7kw, so unless you're using the TS as a buffer tank, or you have a massive and leaky property, you're going to see some cycling.

If going for Ideal, why not the system version? If you went for a Vogue Max system boiler, you get the best modulation ratio in their line up and you can wire it up for separate dhw and ch flow temps. DHW flow temp will be approx 80degrees C which is ideal when you want to top up the TS and then when using Opentherm, the CH temp will be fully modulated down to about 3kW.

Apologies, I should have been clearer. The intergas boiler was shutting down even when the cylinder stat was calling for heat. For whatever reason, it would get to about 62c and shut down. The chemical flush seems to be working, as the tank is now getting up for 70c and staying there when the heating comes on. Previously it just couldn’t cope with a heat demand and the tank then struggle to maintain about 50c.

The reason we were looking at a heat only version of the Max is because it’s an open vented TS, as we have multi fuel stove inputting too. It’s also a 350l store in a large 5 bed Victorian semi (I.e. big leaky old house!)

Just to check, is an Intergas 36/30 an opentherm system and thus you can use smart controls more easily? Apologies for my ignorance in advance!

Posted By: BenM

Apologies, I should have been clearer. The intergas boiler was shutting down even when the cylinder stat was calling for heat. For whatever reason, it would get to about 62c and shut down. The chemical flush seems to be working, as the tank is now getting up for 70c and staying there when the heating comes on. Previously it just couldn’t cope with a heat demand and the tank then struggle to maintain about 50c.

The reason we were looking at a heat only version of the Max is because it’s an open vented TS, as we have multi fuel stove inputting too. It’s also a 350l store in a large 5 bed Victorian semi (I.e. big leaky old house!)

Just to check, is an Intergas 36/30 an opentherm system and thus you can use smart controls more easily? Apologies for my ignorance in advance!

It would probably be best to fully describe your system setup for us.

The Intergas 36/30 is a combi boiler which would use a sealed ch system. So if it's plugged into a thermal store, it's going to be plugged in as a sealed system - the heating circuit between boiler and thermal store is sealed but the thermal store itself is open vented as always.

You can have gledhill thermal stores configured as either open-vented or sealed heating system.

Yes Intergas is compatible with Opentherm thermostats.