iBoost doesn't reheat tank once hot?

Hello, I noticed yesterday that my iBoost had fully heated my hot water tank (great) but when I encouraged my son to have a shower while the sun was still out so it could reheat the tank, it just sat there doing nothing and displaying 'WATER HOT' despite excess solar being exported.

I switched it off and on and only then did it start to heat the hot water tank again. Is this a quirk of the iBoost system? I know the tank needed to be heated as I have a Shelley thermocouple system fitted to monitor tank temps which told me the bottom of the tank was cold.

Many thanks!!

Hi Ra,

You will get better answers if you provide some information on what your entire system consists of.

Inverter Size, Type & Gen, Battery & PV Size Peak

Switching on and off at least shows that the device is working (ie setup correctly).

The iBoost (and other devices) need a little adjustment on the values that they see and response time to those values when there is a battery installed in the system or it gets confused for want of a better term.

I can't recall offhand what the recommended numbers are for the iBoost but a search of the forum will provide the answer or someone will pop in with that information.

On a side note would love to know more about your Shelley Thermocouple.

Ra

I'm assuming there is some timer internally, once it gets the water hot, it doesn't keep re-attempting to heat it.

The immersion itself tells it it's already hot enough, as inverter effectively won't turn on. Once it's done that I expect the iBoost stops trying for a while... not sure how long though. Anyway I've seen mine come back on and heat eventually. I don't expect its more than an hour... did you wait long?

dragon2905 Sorry bud, I didn't provide any additional information as I felt it wasn't needed. Everything is working fairly well at the moment, its just that at this time of year it is a rare occurence for the hot water tank to be fully heated as the dishwasher/washing machine etc are normally on sucking energy away from it.

It was about 5pm and my system was exporting about 2kWh of energy so didn't want to just export it for very lightly money and then have to heat the hot water again using gas hence I asked the boy to get in the shower and start using some of the hot water so it could be reheated.

This is what I use to monitor tank temperatures >> https://shellystore.co.uk/product/shelly-temp-addon-3-sensors/ (unfortunately it looks like it is out of stock now 🙁 ) Works great and has its own little app so I can just have a quick look

pacemaker Didn't wait long, I just assumed (wrongly) as soon as the temperature dropped off it would start to heat again, I guess as you say it would eventually try again and start but as the sun was only starting to go down I wanted to make the most of it.

Couldn't find anything in the documentation but will see if I can keep an eye on it going forward as the tank will only be heated fully more and more going towards the summer

Ra

yeah because I don't think the iBoost actually knows the temperature or has access to the thermometer on the immersion... its just assuming "I can't turn on the immersion so it must be hot". I've seen mine get to WATER HOT and keep trying to heat it, then eventually it gives up after a few times...

iBoost, like most solar immersion diverters, use the immersion thermostat to determine whether the water is hot or not.

If they didn't then they would continue to heat the water until it boils.

Assuming that your Cylinder Thermostat isn't used by your heating system to determine the temperature of your hot water - eg. you turn the Cylinder Thermostat Temperature up or down to set your hot water temp as opposed to a system where the hot water temperature is set directly on the boiler.

You could adjust your temperature up a little, whist still keeping it safe for use.

The manual doesn't mention it but searched iboost on the forum and this was what I was looking for:

I needed to set the trigger level to 200w otherwise the transient exports caused by battery and / or large household loads coming off did set the iBoost to draw from the battery. At the 200w setting you do get some incorrect minor runs of teh iBoost. My daily pattern since March has been PV online, supplying house load, charges battery, then heats hot water then runs export.

One last, unlikely, thing that comes to mind is whether the CT clamp is connected around the correct wire?
It should be on the Live - Brown Wire (sometimes Red) pointing in the direction of the consumer fuseboard. If it is connected around the Neutral - Blue Wire (sometimes Black) then your iBoost will sense import as export effectively heating the water when you are drawing load from the grid instead of when solar is being exported.

pacemaker It does have direct access to the immersion thermostat, however exactly how it works is guess work. I would imagine that it maintains an attempt to pass a low current through the immersion to see if the thermostat is open or closed, perhaps it does this on a timer cycle, say every ten minutes after a 'hot tank' situation. Turning off the IBoost and switching it back on probably just reset the cycle.
The only way to be sure would be to actually monitor a "hot tank" > have a shower > "how long before IBoost restarts" controlled test.

Water stratification is the reason. Hot water stays at the top which does not trigger the thermostat to call for heat

I guess that it will depend on there the immersion heater thermostat is located. On my Megaflo tank the immersion and thermostat is at the bottom of the tank. As soon as hot water is used, cold water enters the tank and the immersion thermostat closes and calls for heat. That call can only be satisfied if the boiler is on or if the iBoost senses that there is spare PV production being exported.

The iBoost has no way of reading the immersion thermostat, it can only sense if power is flowing through the immersion element or not. It knows nothing directly about the water temperature, only if the immersion thermostat will allow power to flow through the element. If the immersion thermostat is open as it senses that the water is hot then the iBoost will return a "Water hot" message.

If, as @ispookie666 has said your immersion is at the top of the tank then its thermostat may stay open as there will be hot water at the top of the tank.

Ra I encouraged my son to have a shower while the sun was still out so it could reheat the tank, it just sat there doing nothing and displaying 'WATER HOT' despite excess solar being exported.

Just had this same issue.

I think its as Zakalwe mentioned above^

Zakalwe I guess that it will depend on there the immersion heater thermostat is located

I had a long shower but it's refusing to heat my tank right now, says it's HOT. So I guess my thermostat is at the top