electrical gurus safety advice please. solar iboost modification.

[Gareth J]

I have a solar iboost diverter. It's great, it fires electric into the hot water cylinder instead of pumping it into the grid when consumption is low and generation is high. In this weather, it amply does all hw needs.

However, as days get cloudy, it won't. It can't heat the large hw tank effectively.

There is an option to buy a "solar iboost+" which does exactly the same thing but fires heat into a primary source before switching to a second one. HW tanks with a "boost" tank on top are ideal for this. I have one.

However, a new one of these is lots of cash and I *think* I can achieve the same with use of a NO/NC contactor.

My preliminary wiring diagram looks like this;

I'm fairly confident it should achieve what I want to do and I've ordered a suitable 16a contactor and enclosure to put it together.

However, I thought I'd just let anyone interested cast an eye on case I've made any serious electrical faux pas in my scheme. Maybe an issue if the first thermostat fails? But shouldn't be any different to if it were connected normally.

Assume everything will be suitably earthed, sheilded, properly connected etc, more about the principal of the idea...

Many thanks!

 

[Luke]

I've got an iBoost too and I like the idea.

It should work. Looking at potential failure modes, if the contactor failed, or wiring to the coil came loose, the top heater would keep heating the water, uncontrolled.

Can you leave the heater 'stats in series with their elements and add a separate tank 'stat to switch over?

 

[Kayos]

I've got an iBoost too and I like the idea.

It should work. Looking at potential failure modes, if the contactor failed, or wiring to the coil came loose, the top heater would keep heating the water, uncontrolled.

Can you leave the heater 'stats in series with their elements and add a separate tank 'stat to switch over?

Immersion heater should have a non auto resetting stat

 

[Gareth J]

Immersion heater should have a non auto resetting stat

Good point, pretty sure they do but something to double check.

 

[Gareth J]

I've got an iBoost too and I like the idea.

It should work. Looking at potential failure modes, if the contactor failed, or wiring to the coil came loose, the top heater would keep heating the water, uncontrolled.

Can you leave the heater 'stats in series with their elements and add a separate tank 'stat to switch over?

Thanks, I'll post how it goes. Should be able to cascade multiple loads with more relays too but I think that if there's that much sunshine around, the need for more than a couple simple resistive loads will never happen. For me at least.

 

[Gareth J]

Finally got round to sorting this and it works well.

In the end I used a 20A NO/NC contactor. The wiring diagram changed a bit but the principal is the same.

Downsides;
-if the top tank isn't up to temp, the contactor relay stays activated until it gets hot. I'd prefer it not to be activated all night doing nothing. It could be worked around with some timer or some other workaround but it's only a watt or two so hey ho.

- legionairres.
Need to make sure this isn't an issue. The iboost has a built in eco7 top-up feature so that can be used for an appropriate time to make sure at least the top tank is up to temp. I'll be using it in conjunction with an oil fire Rayburn in winter which keeps things pretty warm but something to consider.

I had hoped to think of a way to limit any eco7 boosting to the top tank... But I haven't yet!

 

[Kayos]

Finally got round to sorting this and it works well.

In the end I used a 20A NO/NC contactor. The wiring diagram changed a bit but the principal is the same.

Downsides;
-if the top tank isn't up to temp, the contactor relay stays activated until it gets hot. I'd prefer it not to be activated all night doing nothing. It could be worked around with some timer or some other workaround but it's only a watt or two so hey ho.

- legionairres.
Need to make sure this isn't an issue. The iboost has a built in eco7 top-up feature so that can be used for an appropriate time to make sure at least the top tank is up to temp. I'll be using it in conjunction with an oil fire Rayburn in winter which keeps things pretty warm but something to consider.

I had hoped to think of a way to limit any eco7 boosting to the top tank... But I haven't yet!

Keep your stores hot water at 60 degrees to reduce the chance of legionella, the way it’s piped and the cold tank are the other factors

Aga/Rayburn systems can get to 80 degrees so need a specialist TMV if you are feeding a shower pump

 

[Gareth J]

Keep your stores hot water at 60 degrees to reduce the chance of legionella, the way it’s piped and the cold tank are the other factors

Aga/Rayburn systems can get to 80 degrees so need a specialist TMV if you are feeding a shower pump

It's not so much of an issue with the Rayburn as there are two small thermosyphon rads that stop things going hot, hot.

... However, now it's summer and I've turned them off, the immersion 'stats are approaching that and I can see what you mean re. mixer tap issues. At the moment, when it's sunny, the shower mixer is a bit of a hair trigger!