Hot tub mod to make use of overnight cheap rate

Section62

ThisIsWeird said:

bintyandthebeast said:

A less crude version of this is what I need linked to a timer. I don’t think 2.5kw would be sufficient either: https://www.amazon.co.uk/tairong-Thermostat-Intelligent-Temperatue-Submersible/dp/B0B5DRMKL5/ref=pd_ci_mcx_mh_mcx_views_0?pd_rd_w=1GLXk&content-id=amzn1.sym.6aea875e-359f-49f3-864f-cff62d586b6a%3Aamzn1.symc.ca948091-a64d-450e-86d7-c161ca33337b&pf_rd_p=6aea875e-359f-49f3-864f-cff62d586b6a&pf_rd_r=4R4W8ZYFZJV0KFC76NNF&pd_rd_wg=rsiM5&pd_rd_r=c3e8800b-c6a2-4ea9-8785-d941f9eaeccf&pd_rd_i=B0B5DRMKL5

2.5kW - if it does have that power - should be fine.

Your tub will already be at - what? - 35+ degrees at the time the cheap leccy kicks in, and your timer switches on. A few hours to bring the water up to your required temp should be very doable.

Well done - you have found your own solution :-)

(It would need to be reliable, tho', with little risk of overheating.)

The product description says "Do not touch water or heated containers when boiling water"... which would be more than enough to put me off using this device anywhere near water, let alone in a hot tub.

There's no indication the device has any safety approvals, not even a 'CE' mark.

The only thing I'd do with one is to send it to BigClive, so he could do this with it...

https://www.youtube.com/watch?v=hIUJWIT9GrU&t=0s

Nobbie1967

This is designed for the job, maybe just need a mains timer plug on it.

https://supaheater.co.uk/product/supa/?gclid=CjwKCAjw4P6oBhBsEiwAKYVkq-a4CxAgkKn7YEq6cqn2wc7R3ZsxD9bizNCREMxAGhjINxT2GmgylxoCo2EQAvD_BwE

Just noticed this is gas powered, but I’m sure there is a similar mains one.

Maybe have a chat with these guys

https://www.elecro.co.uk/spa-electric-heaters/

FreeBear

bintyandthebeast said:

- there is no timer on the internal heater, it’s set-and-forget. If I wanted to raise temp I would need to go out at midnight every day to do this and shortly before 5am to reduce temp again manually (taking my sorry self outside in the cold and wet in the middle of the night!)

A programmable (smart ?) thermostat with a remote temperature sensor would do the job. But.... They are not designed for use outside, so would need a suitably sealed box. Nor are they capable of switching large loads, so you'd need to use a contactor (heavy duty industrial relay) to switch the heating element on/off.

bintyandthebeast

Section62 said:

bintyandthebeast said:

- regarding the manslaughter charge, I’m not looking to do something unsafe. There are CE approved floating heaters and fish tanks have a scaled down version, so in my mind surely there’s a safe option out there. 

The problem is there is a fair amount of stuff which is CE marked (note, not "approved") which is dangerous. A CE marking is no guarantee of safety.

Water+Electricity+People is not a good mix.  Add in heat and there are so many dangerous situations you need to avoid that I wouldn't be confident you'll be able to find anyone professional willing to help you, other than in installing the hot tub manufacturer's supplied heater unit (if they did one).

Aside from the risk of electric shock, you would need to ensure the heater fails safe, and that there is some form of anti-scald protection.  It isn't enough to rely on people dipping a toe in the water and going 'ouch!'... you (as the owner) would be expected to ensure the water temperature never exceeds a dangerous scald temperature.

On the point about there being a 16A supply - the electrician would have to take into account the load from the tub itself before adding a 13A socket. The tub plus 13A is likely to be more than 16A, therefore you will probably need to either have the supply upgraded, or else run a separate supply to the socket.

Valid points, thank you.
Would be very short sighted to assume that while I would expect that 99% of the time that the two heaters would not run concurrently it's the other 1% that would cause the issue.  

bintyandthebeast

ThisIsWeird said:

bintyandthebeast said:

A less crude version of this is what I need linked to a timer. I don’t think 2.5kw would be sufficient either: https://www.amazon.co.uk/tairong-Thermostat-Intelligent-Temperatue-Submersible/dp/B0B5DRMKL5/ref=pd_ci_mcx_mh_mcx_views_0?pd_rd_w=1GLXk&content-id=amzn1.sym.6aea875e-359f-49f3-864f-cff62d586b6a%3Aamzn1.symc.ca948091-a64d-450e-86d7-c161ca33337b&pf_rd_p=6aea875e-359f-49f3-864f-cff62d586b6a&pf_rd_r=4R4W8ZYFZJV0KFC76NNF&pd_rd_wg=rsiM5&pd_rd_r=c3e8800b-c6a2-4ea9-8785-d941f9eaeccf&pd_rd_i=B0B5DRMKL5

2.5kW - if it does have that power - should be fine.

Your tub will already be at - what? - 35+ degrees at the time the cheap leccy kicks in, and your timer switches on. A few hours to bring the water up to your required temp should be very doable.

Well done - you have found your own solution :-)

(It would need to be reliable, tho', with little risk of overheating.)

If only it were that easy!
Reliability, safety, longevity, etc.
I'm also not certain that a 2.5kw heater would be enough to make it as efficient as I'd want it to be to go through the hassle of setting up. I'm not up there with physics but the 16amp heater is there for a reason. I reckon it's a good cross between power and efficiency.

bintyandthebeast

moneysaver1978 said:

How is your hot tub connected? What about something like smart plugs and you can set it to turn on at specific times (or just set via your phone).

Apologies if this is a silly or crazy suggestion - I have never had a hot tub before so no idea how it is powered!

It's 16amp with lots of electronics, plus it's hard wired so not an option unfortunately.  

bintyandthebeast

Section62 said:

ThisIsWeird said:

bintyandthebeast said:

A less crude version of this is what I need linked to a timer. I don’t think 2.5kw would be sufficient either: https://www.amazon.co.uk/tairong-Thermostat-Intelligent-Temperatue-Submersible/dp/B0B5DRMKL5/ref=pd_ci_mcx_mh_mcx_views_0?pd_rd_w=1GLXk&content-id=amzn1.sym.6aea875e-359f-49f3-864f-cff62d586b6a%3Aamzn1.symc.ca948091-a64d-450e-86d7-c161ca33337b&pf_rd_p=6aea875e-359f-49f3-864f-cff62d586b6a&pf_rd_r=4R4W8ZYFZJV0KFC76NNF&pd_rd_wg=rsiM5&pd_rd_r=c3e8800b-c6a2-4ea9-8785-d941f9eaeccf&pd_rd_i=B0B5DRMKL5

2.5kW - if it does have that power - should be fine.

Your tub will already be at - what? - 35+ degrees at the time the cheap leccy kicks in, and your timer switches on. A few hours to bring the water up to your required temp should be very doable.

Well done - you have found your own solution :-)

(It would need to be reliable, tho', with little risk of overheating.)

The product description says "Do not touch water or heated containers when boiling water"... which would be more than enough to put me off using this device anywhere near water, let alone in a hot tub.

There's no indication the device has any safety approvals, not even a 'CE' mark.

The only thing I'd do with one is to send it to BigClive, so he could do this with it...

https://www.youtube.com/watch?v=hIUJWIT9GrU&t=0s

I'll maybe try and find something else to use 😳

bintyandthebeast

Nobbie1967 said:

This is designed for the job, maybe just need a mains timer plug on it.

https://supaheater.co.uk/product/supa/?gclid=CjwKCAjw4P6oBhBsEiwAKYVkq-a4CxAgkKn7YEq6cqn2wc7R3ZsxD9bizNCREMxAGhjINxT2GmgylxoCo2EQAvD_BwE

Just noticed this is gas powered, but I’m sure there is a similar mains one.

Maybe have a chat with these guys

https://www.elecro.co.uk/spa-electric-heaters/

That programmer on the electro weblink is the kind of functionality I'm looking for. I get it all from my immersion controller but just not suitable for outside use and I'd need a heater element to combine it with which is a an issue within the issue!

bintyandthebeast

FreeBear said:

bintyandthebeast said:

- there is no timer on the internal heater, it’s set-and-forget. If I wanted to raise temp I would need to go out at midnight every day to do this and shortly before 5am to reduce temp again manually (taking my sorry self outside in the cold and wet in the middle of the night!)

A programmable (smart ?) thermostat thermostat with a remote temperature sensor would do the job. But.... They are not designed for use outside, so would need a suitably sealed box. Nor are they capable of switching large loads, so you'd need to use a contactor (heavy duty industrial relay) to switch the heating element on/off.

Point me in the right direction and I'll take one!

bintyandthebeast

I've asked a question to the supplier to see if there's any option for an upgrade to the system that will allow a timer to be added.
While the cleanest option would be finding a way to jump the built in heater, it wouldn't be sufficient as would also need the circulation pump to run. 
It's irritating to know that I have a heater, pump, thermostat, and cabling in place. I just need a timer!

I also thought of running a circulating heating pump external to the tub. A flow and return pipe inside the tub and inline heater outside the tub. I can see some inflatable pumps work this way. I wonder whether the insulated cover being breached to slow unhindered access for the 2 pipes would offset the potential savings I'm trying to make.