Short cycling on hot water demand.
I was wondering if anyone has come across a similar problem.
I have a fairly simple setup- gravity fed system with “Ideal logic heat 24ie” boiler and “Tado-v3-black-edition-wireless-heating-hot-water-smart-thermostat-starter-kit.”
So I have no radiator control or multiple zones just one tado temp sensor sitting in central location wireless receiver next to boiler and, just 2 motorised valves one for heating and another for hot water, the valves and the pump are sitting on the return pipe instead of the flow.
Sort of S-plan, but modified due to system having had back boiler stove at some point in the past. I don’t think later is the cause of the problem but I wanted to give good description of the system.
So when it comes to heating control I have no issues with the way Tado does its thing in the gravity system regime.
But the moment it’s only hot water on
( My hot water cylinder thermostat is wired and set at 65 degrees demand; My boiler flow is set at 60 degrees ).
Tado starts to short cycle my boiler in a bizarre way. It fires up the furnace heats up the boiler flow to 60 degrees at the same time not running the pump but than shuts off the flame and starts running the hot water around the system, until it drops in boilers furnace to about 49 degrees. Then again switching off the pump and warming the water within boiler to 60 degrees and repeating this cycle over and over. It takes about 5 minutes or less between firing up of furnace for about 10-20 seconds.
As I have mentioned when it is winter and heating demand is there the tado runs the whole system as a gravity fed setup - running both water and heating at the same time and not doing any crazy short cycles. But now that temperature in my house is above the temperature preset for the heating I am concerned as this hot water cycle is going to kill my boiler.
Any advice is appreciated.
Comments
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No suggestion at all?0
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@Svolkov ( My hot water cylinder thermostat is wired and set at 65 degrees demand; My boiler flow is set at 60 degrees ). The temperature settings are a likely problem.
Where the boiler flow temperature is 60 deg C and the hot water tank thermostat 'demand' is set for 65 deg C, the controls will always 'call for heat'. When the HW tank reaches 60 deg C, the return water temperature will be almost the same as the flow. I'd not be surprised to find the boiler is always cycling.
When you have the CH on, the radiators will emit heat and the return water temperature will be much lower, reducing the likelihood of the boiler cycling.
The minimum temperature for killing Legionella should be observed. HSE: Hot water storage cylinders (calorifiers) should store water at 60°C or higher. Low temperature systems, e.g. ASHP, have a hot water tank/control that cycle once a week to heat the water above 60 deg C.
If in any doubt, consult a professional heating engineer that knows your system.
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Thank you for the effort, but the only issue in this logic is that system carries on SHORT cycling even when the cylinder was completely emptied out of hot water and is cold.
I guess I should emphasise that the problem that I am investigating is not the “always cycling” but “always SHORT cycling “
Regarding the heating engineer - it appears to me as a tados algorithm issue not the heating engineer query and I was hoping on dev feedback, but I may be wrong and I will check my cylinder thermostat wiring.
Thank you for your comment0 -
@Svolkov sorry, I’m just a simple user, not the algorithm developer or boiler engineer. From experience, incorrect wiring is a potential problem with strange HW happenings when it all appears to work when the heating is ON.
With Tado Hot water, it’s a relay on/off. Our boiler does not short cycle in these circumstances. For short cycling when the tank is cold, I’d be suspicious of wiring, a faulty zone valve, or bypass, and/or boiler. No good reason to suspect Tado. To start to figure out what is happening, I’d check the flow/return water temperatures around the system.
Good luck Svolkov.
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