Search the Community

Plenty of information on ASHP is available on this site and very little on hybrid heating systems, i.e. boiler and ASHP. A few manufacturer designed hybrid systems are also available. When we built our house it was with an Atag gas combi boiler. We then installed an ASHP mostly for cooling, but it also heated our house well last winter and provided hot water via an UVC. The system below could easily be replicated by anyone wanting to install a hybrid heating system meaning little or no changes to heating system such as radiators. So the Atag boiler only 2 years old has sat idle for the last year. For periods where the CoP of the heat pump, means gas is cheaper why not marry the boiler and heat pump together. Most of the off shelf solutions, rely on the gas boiler doing the hot water, not what I wanted. Most the time the ASHP is way cheaper than gas (especially with solar). So makes sense to do hot water via the ASHP most of the time. Most ASHP already have all the control logic for hybrid mode built-in - mine does. I have a few location issues which makes the implementation a little more complex than I could be. Boiler and UVC are about 20m plus away from the ASHP, with UFH in the middle. The solution I chose to use has the boiler on a separate circuit to the ASHP. Combi DHW tails are not connected to anything and the isolation valves closed. Phase one Get hybrid hot water heating. Had a 40 plate PHE sitting doing nothing, so inserted in the flow line from the ASHP close to the UVC, the other side to combi boiler heating circuit. Set max flow temp to 60 on the gas boiler. I can change the rate at which the boiler adds heat (gradient), set to a max of 2 degs every minute. Initial run was all manually done to check concept. With ASHP only the reheat time of the UVC is around 40 to 45 mins, with boiler engaged about 20 to 25 mins. During test, I monitoring the ASHP and gas boiler and both work well together, neither running away temperature wise. Now how to automate. All control logic is in the ASHP, to use a boiler as a secondary heat source, you can set different outside temperatures for the following control schemes - 1. ASHP only, 2. ASHP leading, boiler following, 3. boiler leading ASHP following 4. boiler only. ASHP controller supplies 230v as a control signal to the boiler. But boiler is 20m plus away from the ASHP. So used a Shelly relay at the ASHP end and a remotely controlled Shelly relay at the boiler end. Set up a scene in the shelly app, switched live to ASHP end Shelly energised the boiler end Shelly relay. All worked fine. Set the hybrid mode (ASHP leading) to start at 7 degs and a delayed start of 10 minutes for the boiler, after cylinder heating starts with the ASHP. PHE, boiler on left side ASHP on the right. Phase 2 UFH - coming next.

So I have stripped out all the existing pipework, back to the incoming main, on my major renovation extension. I have an overall concept of what I am trying to do gleaned from reading this forum, but have many questions! Trying to make sure I am on the right track before buying all the kit. I have three bedrooms all with ensuite WC, basin and shower, one has a bath. Heating is UFH on ground and lower ground floor, radiator in each bedroom, and towel rail/radiator in each ensuite/bathroom. Downstairs also has a bathroom with shower, WC, basin. I have mains gas. so the concept is to have a new gas system boiler, an unvented cylinder and run UFH, heating and hot water, all from the tank. Is this how it works? The tank I am looking at is from AVChttps://www.acv.com/gb/professional/new_product/06627401-465/smart-e-plus-240#tabspace=unit&tabid=diagrams, and is a tank in tank system, so using the primary heating water as a buffer for the UFH and radiators. Using Hep20 from a manifold for hot and cold water, and run the upstairs radiators from another manifold upstairs. I know I need a double check valve and stop cock on the incoming main, and a PRV before the tank, the tank comes with a mixer valve. After that I am not sure what I need I have seen some on here use one large, valved, brass Hep20 manifold say in the utility room next to the boiler and tank, to feed everything, others have used sub manifolds for each room, using the much cheaper, plastic, non valved Hep20 manifolds. Is this purely to save money, I like the idea of being able to turn off individual consumers from the manifold, but unsure in real life how often this could happen, cost difference is considerable, but then it is a one off cost. Control wise I am planning on using Heatmiser Neo thermostats on each zone, and a Neohub and their wiring centre for the UFH and also for the radiator manifold circuits. Boiler was looking at Veissman Vitodan 200 series but unsure on sizing, these are available with weather compensation, but will this work with Heatmiser, how do they talk to each other? Was trying to find modulating thermostats but Heatmiser don't offer them. Also unsure on UVC sizing, as it appears I could run a smaller tank, 210 litres, if I have a large enough output boiler to reheat it fast enough, or is it better to have a larger tank, 300 litres and a smaller boiler, also have a solar array of 3.7KW so was hoping to use a diverter to an immersion in the tank for all excess solar. I apologise for so many questions, but feeling a bit overwhelmed by everything.

Hi, Trying to complete the garage before returning to the house and an imminent decision is about how to supply hot water to the basin in the toilet and the two sinks (one downstairs in a sort of utility room and one upstairs in my man cave). These are highly unlikely to be used simultaneously and in fact won't be used that frequently so I'd prefer whatever device I fit not to store hot water. The garage is detached. A quick internet search has come up with the following: 1. Stiebel eletron type boiler. Seen these in work supplying sinks. Seem to work well enough and not seen one replaced yet (even in our relatively hard water area) 2. Domestic shower plumbed in 3. DAFI water heater (on ebay). I've tried to put links in this post but failed (frustrated by the tablet and my lack of IT). I suspect several of you may be toying with this question. Any comments gratefully received. CC