JohnMo

People generally do it to get to a plant room in the middle of the house. I would just run pipe along wall and cover in 25mm external insulation. Does that give any fire protection?

My cylinder and heat pump are long from each other and it was difficult wire, so I use the following - cheaper than a UPS A normal cylinder thermostat - like this - https://www.buildandplumb.co.uk//plumbing-heating-c36/heating-c264/heating-controls-c219/pipe-cylinder-thermostats-c358/eph-controls-eph-digital-cylinder-thermostat-with-high-limit-edbs-p11357/s29376 This operates via a time switch. So I have time and temperature sorted, this then powers a radio switch, which in turn powers a relay - but you could just use a wire to power a relay. The relay just moves to simulate the cylinder temp sensor, one setting is a resistor that simulates 20 degs, the other 50 degs. The heat pump controller is looking for 45 degs for DHW. So call for heat, relay moves to give a resistance equal to 20, once cylinder thermostat is happy relay is switched off, and heat pump thinks the cylinder is at 50 degs, so switches off all calls for DHW heating.

Going to add an automatic sanitizer to add chlorine (?) as needed, plus sand filter.

Manufacturers trying to be clever, without stepping back to understand what happens in reality. Ways around it?

Thanks all So looks like XPS300 should be ok,compressive strength wise. But I may need to to cover it with something to load spread to stop any point loads. So maybe slabs?

Think the bend radius for getting pipes through is way to small, firstly. Why run pipes through floor at all. Take them from outside direct in to house.

Need some help My next job is a hot tub, will be a round wooden one, heated by a heat pump. Looking to build an insulated base for it to sit on. Weight approx 2.4Te, diameter approx 1700mm. My initial thoughts were, dig down, DPM, PIR insulation 100-150mm thick covered in slabs (have loads to use up). But base will be square, hot tub round, heat will just move sideways out of the base and make the insulation useless. So not sure that works. Anyone any ideas?

Think you have the task of going the manual and the actual settings. There should be something that is flagged to do DHW as a priority after a power cut. It's not a normal ASHP behaviour. Normally resumes the last mode active.

In Scotland air tightness better than 3.0, balance inlet outlet ventilation mandatory, so MVHR. 3 to 5 MEV or dMEV (with trickle vents), after that whatever fancy passive vent intermittent fans etc, all with trickle vents.

There effectively a piece of string, but the string expands and contracts with changes in humidity - it senses room humidity it changes length as the humidity increases to open the vent more. You to have them coupled with MEV or dMEV fans in wet rooms. If these boost automatically, you get a system that self compensates for changes in room habitation etc. So example everyone in lounge in evening, vents in lounge window open, but rest of house vents go to min position, fans draw air through house taking most air from lounge. Everyone goes to bed, lounge vents close and bedroom vents start to open etc

Be careful using nameplate rating - you need a heat pump that does just under 6kW at -3 as you are England. Your defrost derate and DHW allowance takes it to just under 6kW. Most important bit is modulation at 7 to 10 degs, that where the heat pump operates most the time - long steady running at there temps makes the difference between SCoP of 4 or 5. They will come in thousands above grant, so why are you wasting your time. Your not going to get any change from the grant especially with SteibelEltron, as will cost as much as the grant just buying the unit.

You have what you have, you seem to want run an on off system and have loads of modulation immediately. It isn't going to happen, the boiler has plenty of work to do playing catch up. Then you switch it off again. Thick stuff - 25mm wall thickness, cover in aluminium tape to stop mice eating it.

As I said, you have made a simple system very complex. I think you are trying to reinvent the wheel. For systems that have already been designed tested and approved, overlaying a 24v system, just seems OTT.

So based on the flow rates, it's around 400m² property - that's a big retirement pad. If it isn't that big you are going to massively over ventilate and maybe suffer a very dry indoor environment in winter to get 6kW.

Gee you were either wrapped off, massive house and or tiny centres. I have 600m in the floor (192m²), so about £350 today. That must be a massive house? If it's passive? I would definitely not do heat and ventilation as individual items. One dead both dead, when combined. Also look at the hot water generation time with your combined unit. How are you getting that much energy out of a micro HP? Any links to the product?