Yes our only option if we wanted a cylinder would have been to locate it in the loft (which is already converted into a room apart from some crawl spaces in the eaves). However, doing all the plumbing associated with running pipes from the ASHP (outside at the back of the house) up 2 floors into the loft would have been costly and disruptive. The additional cost of the Sunamp set up was offset by these practical considerations.
Re-igniting (!) this conversation… I’m still wondering why teh Sunamp can’t supply all the hot water needs for a house.
We have an ASHP that doesn’t do hot water 
so we still ahve a combi boiler for that. I’d like to replace the combi (and therefore gas) completely; I don’t easily have anywhere to put a hot water cylinder and like the claim that the Sunamp only loses about 0.5kw/h per day.
Can someone persuade me for or against?
Meanwhile, when I got a quite the electrician wanted £1500 to wire in a spur via an Eddi to run the Sunamp. From what I can see it is just a 13amp feed, and there was one of these already adjacent to teh target Sunamp location - why would I need an extra feed?
My caveat is that I have no experience of Sunamp but have read numerous posts on the subject.
That depends on your hot water requirements. If you need a mega sized one consider 2 smaller ones located nearer to their outlets.
If it only needs a 13 amp feed the existing cable might be ok but if it will be drawing full power over extended periods you would be better off with more robust cabling.
If you want to stick with the existing cable it just needs diverting via the Eddi.
Fining some to install the Sunamp who understand how it works will be your biggest challenge.
As for the Eddi, it may be that they misunderstood that it has 2 outputs (so can connect to a tank with two seperate immersions heaters), it sounds like you only need one connected?
I’d only be rehashing my comments above, but in summary:
Problem with sunamp is that it uses paraffin, which does not conduct heat readily and requires a large heat sink for a given amount of power, so it’s an expensive form of storage /kwh, with limited output. I also deeply suspect their fossil fuel funding.
The storage only gains value if you can load shift when you use the electricity, so you will need a variable tariff or economy 7. In which case it will save operational costs compared to producing DHW using ohmic/resistive heat on demand.
However, on demand heat requires powerful electric showers (40A!), and there’s often load limits if you have multiple electric showers, which can be managed with a controller only allowing one on at a time. It’s expensive too, so there’s that to consider.
Other options are to use a water cylinder with a dedicated air source high temperature heat pump. They can draw heat from inside, outside, or the exhaust on your ventilation system, if you have one. The water cylinder is there to provide peak power, and doesn’t need to be large. This would be my choice.
1 Like
I’m not sure what you would like to be persuaded “against”?
A suitably sized Sunamp unit (eg the Thermino 210 size perhaps) can easily supply all your hot water. This is 87cm tall with a footprint of 57.5 x 36.5cm. Some space around this will be needed for pipework connections, but all in all it works out very compact. NB they are heavy so lugging the unit upstairs will take some logistics (a stair climbing system can be used).
You will of course need to consider where the electricity is coming from (primarily to assess running costs). So if you have solar PV you could get a lot of free electricity from that source.
Also if you on a tariff like Octopus Go then you could top up the Sunamp using over-night cheap electricity, especially during the winter months. I hop that helps.
1 Like
Yes if you are wanting to have PV divert then you will need an Eddi (or similar).
You can wire the Eddi / Sunamp as a spur off an existing ring main (assuming the ring main doesn’t have a number of other heavy elec loads attached). It draws a maximum of 3.5kW but obviously that could last up to 1.5hrs ish to fully boost a larger Sunamp unit. Wiring in a spur off an existing (ring main) circuit does not cost anything like £1500, so worth getting a 2nd or 3rd quote. A qualified electrician can advise obviously.
1 Like
As I understand it Sunamp use mainly Sodium Accetate (with some additives) as the phase change material in their thermal storage units. The phase change from solid to liquid and back means that the Sunamp units can store approx 2.5x the quantity of heat energy for the same physical volume of a water cylinder.
The Sunamp units release their heat into water at mains pressure and the delivery of heat is pretty much instant, hence ideal for supplying a shower (or possibly more than 1 shower). In our set up if someone draws hot water for washing up dishes whilst someone else is using the shower then the loss of heat to the shower is much less noticeable than when we had a combi boiler.
So all in all the Sunamp is a good product with much to recommend it, especially if you need to store hot water and don’t quite have enough space for an adequately sized hot water cylinder.
1 Like
Could well be, I went to a talk they gave some 5 years ago. The two main approaches were aqueous salt solutions and organic compounds. I’m pretty sure they were using a mix of alkanes/paraffin then. But I could be wrong. I’m pretty sure it’ll still have low power output though without more expensive heat exchangers, so there must be some other reason they use it.
ref: https://www.jouleuk.co.uk/victorum-air-exhaust-systems/
To give you an idea of the alternative. The source would be from an airing cupboard, bathroom or kitchen, or some combination of them if it’s convenient. Make space for the largests water cylinder you can fit, wherever you can fit it (attic, garage, accessible crawl space, or mini shed/mechanical room in the garden).
A few nice thing with this is setup are: a) that your ASHP for central heating acts as the first stage to provide high enough temperature heat for the DHW heat pump to work efficiently (second stage), as different refrigerants work better across different temperatures. b) waste heat leaving the house as humidity gets recovered by condensing on the evaporator.
Problems are that building code and the wierd interactions between seperate mechanical systems.
All these caveats are the reason I like CO2 heat pumps to work across the whole temperature range with one system!