We have a long thin property where we are converting the two rooms at one for my mum in law to live with us, so will have a small kitchenette and bathroom at the opposite end from where the current DHW cylinder is. We like the idea of adding a heatgeek cylinder to that end of the property so that hot water doesn’t take an age to come through, and to reduce the chance of our main cylinder being used up in the mornings.
We have a Samsung 6th gen ashp with the standard controller that only expects one cylinder. We are only using one zone for all the heating.
Would running a second cylinder need a different controller? Would it be possible to set up zone 2 in the controller to actually run the second cylinder. Part of thinking about the heatgeek approach is because there is no need for the legionella cycling - so perhaps more possible for zone 2 to be repurposed to heat it up?
It’s possible to connect two cylinders in parallel, you don’t need any additional controls for this. However, both cylinders would really need to be located next to each other.
Adding a 2nd cylinder in a different location would be challenging from a pipework perspective.
If the reason for wanting a 2nd cylinder is long DHW draw time, then fitting a DHW circulation loop pump could be a solution? Or maybe even a small point-of-use direct electric water heater might be the easiest solution.
Draw time is indeed a factor, available hot water volume is probably the more major concern. This is a conversion of part of the property to supportive living. Our main existing dhw system will provide the main proportion of our family, this ‘secondary’ hot water supply will provide a somewhat isolated hot water demand for baths and showers that may not be entirely predictable.
I am fairly convinced that we want to decouple these usages, but could be convinced otherwise.
My instinct is that the heatgeek mini store would help here.
But i also know the difference between describing the problem vs wanting advice on my perception of the solution! So:
Given my perceived solution could zone2 drive a heatgeek mini.
What other options would mean we could provide relatively arbitrary, and sometimes significant hot water to the conversion - with low latency, and not significantly impact the existing standard usage (250L Telford Tempest)
I think the Mini store should really only be considered if you haven’t got space for a larger cylinder. If you have got space, then a standalone heat pump cylinder could be an option, eg.
or
This could be installed standalone to the existing heating system.
This is probably the best solution, but if you wanted a more complex, but possibly slightly cheaper solution, then you could pipe up a 2nd cylinder on the DHW circuit that is isolated by a 2 way valve that you could open when you have guests, so that during a DHW reheat, it would heat both cylinders. You could use a manual valve or a motorised valve that you can power with a switch or a smart relay.
My concerns with this solution are that:
The Samsung controller would only know the temperature of the primary cylinder, so would only heat the 2nd cylinder if the primary one needed heating.
How you would balance the circuit so that you get the right flow through both cylinders, Could be tricky. If 1 cylinder is much further away from the heat pump and has significantly more resistance in the circuit, the water will take the path of least resistance and most of the water will go around the nearest cylinder unless you add resistance to the primary circuit.
I faced a similar problem many years ago. A friend was the proprietor of a farmhouse Bed & Breakfast. I still have the details if anyone wants them, I have no idea whether this would help. The control scheme involved thermostats with changeover contacts (already present) and a zone valve for each tank. Two relays were needed for the additional logic. The heat source was a wood chip boiler with oil as a standby.
Thanks @Robert.Wall yah sounds reassuringly similar, appreciate you commenting. I am fairly comfortable with the control part of things (though still learning about the capabilities (and limitations) of the modern Samsung MIM.
This is not a bad plan, not vastly difference from the recirculating pump approach.
But after also thinking about the heating over there more we are going to need to run v well insulated pipework through the loft in any case for that, so valving over that side of the house will save two lots of flow and return piping.
I use a secondary circulation pump, but it only runs for 50 seconds ‘on demand’ (presence sensor or push button, time delay so presence sensor only triggers ever 25 mins or so). My cylinder is near the bathrooms (power showers etc) and the secondary loop is to the kitchen / utility, 10+ meters away. You do lose heat (hopefully into the house) but save water.. Decision time.
Bear in mind unused storage / dead legs need more legionella etc thought than actively used circuits.
I did the calcs on the heat store. I can see that modifying the cupboard space to get an efficient cylinder in place - (since we need the primary circuit bringing over there for heat) - is going to work out better overall.
I think the heatpump cylinder would have been the best option IF we had not needed to alter the hearing pipework as well.
Don’t overlook a system setup with an emersion heater that runs on off peak electricity. It needs many years of DHW usage for anything else to work out cheaper.
. That could save on some expensive pipework