MattT2

Thanks again guys. You have given me some stuff to research / think about. The fog is lifting! MattT2

Many thanks for the replies & advice. I wonder which of these I need: * Storage tank (aka cylinder) * Buffer tank * Volumizer tank * Expansion tank Looking at the ASHP documentation for the Bosch AW/AWE, the https://www.worcester-bosch.co.uk/professional/products/cylinders/green-storage-wb-range-cylinders looks like the conventional choice - for DHW. IanR's response intrigued me. If the output of the ASHP is, say 35 deg, what component in the system raises this temp for DHW? (isn't it the immersion in the Storage tank?) A couple of more general notes; I don't see an issue with having a significant volume of the UFH 'always open' - especially if it means I can avoid a separate buffer tank. I see in other threads that there are ways to calculate what a reasonable volume is - and that 10-15l for each kW (ASHP rating) was a rule of thumb. We are space (& budget constrained). More tanks = more space, cost & complexity. We are also considering having no Storage tank, and just a Buffer tank - and using electric taps / showers for DHW. Thanks again. This forum is amazing. I got 3 replies within an hour of posting. I hope I can contribute in the future (rather than just being the one asking dumb questions). MattT

Hi Folks, I'm new here so be gentle with me. Our project is a 125m2 extension to a derelict 75m2 Victorian lodge in the Scottish highlands. We have no heating currently. We are not on the gas grid. We are on the electricity grid. We are considering ASHP (versus tanked LPG or Oil). We will have a total of 150m2 of UFH. The Bosch 7001iAW looks suitable, along with the AWE indoor unit. I'm trying to understand buffer tanks & storage tanks. From what I have read, my understanding is this: The purpose of a buffer tank is to prevent short-cycling of the ASHP - which we don't because our UFH will have so much water in it that it will achieve the same outcome (it is effectively a buffer tank). The temp in a buffer tank is the same as the output temp of the ASHP - which should be as cool as possible for the ASHP to run efficiently (in the range 35 deg -> 55 deg, depending on season). Although the ASHP can run hotter, it gets * very * inefficient if you do. So... a buffer tank is NOT for DHW. A storage tank is for DHW - it gets the water from the ASHP (in the range 35 deg -> 55 deg) and then elevates it for DHW (it is also an immersion heater). Is this basically correct? If so, my conclusion is that we don't need a buffer tank, but we do need a storage tank (for DHW). All advice / education gratefully received. Thanks, MattT