JohnMo

I tried to get a smart meter, but they failed to get it to connect to the data collection centre. So I now have a dumb smart meter. I am the vast total of 1.5m away from a large village, and they couldn't get it to work, so no hope in a remote area.

Think of a storage heater, but with an air to water heat exchanger instead of and air to air exchange. Idea is pretty simple, would suspect its very heavy, filled with bricks similar to a storage heater. So its really a high density thermal store. Key advantage over water is installed space required is way less. 40kWh sounds great, BUT, if you take away 5kWh for DHW it only leaves 35kWh hours for heating (1.45kW per hour based on 24h) and also depends on the threshold of where in the 40kWh the heat becomes unusable from the store, due the heat exchanger performance and the delta T required. Also if a top up is required during the day - not cheap. According to the manual it looses 15-20% of its charge over 24hrs, which is huge. So 6-8 kWh, which is the equivently of about 3-4 300L cylinders. But 2x300L cylinders would hold about the same energy at 60 degs, with half the heat losses. So if you had space would be better and possibly cheaper run on the same E7 tariff or similar. Also when its cold outside you could charge to higher temperature (to store more energy), in the summer just charge one cylinder for DHW to save money. Something borrowed from another website, the Octopus refers to a heat pump run on the night time tariff.

My flaps work automatically, I cannot select manually (Titon MVHR), but they should only be open when the outside air is warmer than the inside (i.e. summer hot day). Various other thresholds are set like minimum temperatures, the summer by-pass is installed so as not to heat the house when it not needed or would make things uncomfortable.

Go on to sites like the one for FRESH-R and see how they implement MVHR. Very few inlets/outlets. Same thing can be done with MVHR with a little thought. Also look at condition based dMEV. only venting when required by internal humidity levels.

Remember MVHR is ventilation only, it does not provide enough flow to cool the house in summer. You have windows that open to allow cross flow ventilation to provide cooling as much as anything else.

I came from the military with the same definition. However this defined understanding does not exist in many walks of life - building regs included

You want summer by pass off. If it's on the incoming air does not go through the heat exchanger and will just come into the house without being warned by outgoing air. You need both fans on, one is for extract the other for supply air. Hope this helps

No not speaking about CO. Sorry it is a monitor not a sensor, but it is for CO2, also it is not an alarm. The monitor requirement pre dates COVID by 5 years. https://www.gov.scot/publications/carbon-dioxide-monitors-standard-3-14-letter-to-local-authority-verifiers/

If you look in Scottish building regs, they mandate CO2 sensor in the main bedroom, the regs also dictate the functions of the sensor. Other than that, there is nothing that says you must be below an upper threshold. That I am aware of for domestic properties.

I think the problem is although only 1345W that's 32kWh per day. E7 would be 4.5kWh per hour for 7 hours. PV is pretty rubbish in the winter, so I wouldn't bank on anything spare for heating in the winter. But in the summer most of your DHW would be PV heated. Think I would seperate DHW and UFH. Exhaust air heat pump cylinder for DHW, route the air from outside and back outside. Then a Willis x2, most of time only one required. Then batch charge the floor on E7. Or joules do a slightly bigger exhaust air heat pump that can do central heating also.

If your using 5.8kW on a cold day, that is 5.8x24=139kWh per day. So £70 per day at £0.50 per kWh. An electric boiler will give you 1kWh out for each kWh in. Never any better than that. An electric boiler is really just an immersion heater with some control. A heat pump on UFH should get a CoP of 3 or better on the coldest day, so would cost £23 per day instead of £70. A typical heat pump 3kWh out for each kWh in.

You even have to careful about which Freeview box you get, as some don't do all the channel apps, or don't allow you go back in time at all.

They leak air not water, your topic is ventilation, not water leaks. They will be water tight. The T&G, the joints between panel all leak air.

Mine came with a slot below the roof line that could be either filled in or left open, so just left the strips of wood out. But its a bit of a cop out, there should be no humidity being generated, unless you sleep in it, plus they do leak like a sieve generally.

What is your current heating demand? Have you looked at Exhaust Air Heat pump cylinders (heat pump and cylinder in one, such as the Dimplex edel for example. They would be a standalone hot water solution which can also be heated with PV or solar solar thermal.

Heat loss on a -5 day is about 3kW. The issue with short cycling, having to heat up the metal and any water that has cooled while the boiler is off. That all takes energy. In the heat pump most that metal is outside, on boiler I think a lot of heat gets wasted out the exhaust. By getting on top of short cycling and boiler control I have halved my gas consumption. Lots of cycles also mean additional wear and component life reduction.

It just a pressure drop (head loss) calculations, you can use to size the pump in big systems, but not really needed in domestic installs as the pump in most cases will be variable speed or automatically adjust to the pressure and flow required.

A, there weren't many low energy homes. B, gas was cheap and no one knew any better. C, People that knew better installed a buffer, I assume as they are not new. May even start short cycling before that at very low flow temps. You either need a big capacity system or a buffer. Most heat pump manufacturers mandate you have a buffer, or a minimum volume, and have a min flow rate all the time. I can still get it with a gas boiler and 160L buffer at very low flow temps. Have just increased buffer temp to compensate. Think when all heat pumps were non modulating the issue was seen and installs had to have a buffer. With inverter drives, there is more modulation but not as much as a gas boiler. Both will short cycle at low flow temps and low heat loading, unless you design around it.

Daft question, is the pre build one or as built post build. I made lots of changes to the as-built one to make sure thermal bridging wasn't generic etc. likes other have done. In the end it seems to a fairly close, on a monthly average basis. Although I don't recall seeing what the actual heat loss was on the coldest design day. Just monthly averages, which may not be that useful for heat pump sizing. Jeremy's tool may be better.

My heat demand is 14 W/m2 of the top of head. My spacing is 300mm, flow temps is about 27. The delta T of 10 isn't realistic it's likely to 4 or lower at those flow temps. High delta T means lower input of heat into the floor for a given flow temp, as the mean flow temp is lower. The higher the flow temperature the more likely the room temperature will overshoot. So it's all a bit of a suck and see and a balance trade off. Also floor finish has quite a big influence. So what correct in one room may need tweeking in another by changing the delta T.

Sorry miss read. No you don't take into account the flue pipes, although I assume you have room sealed stoves, with an outside air supply direct to the stove, not air bricks to provide the combustion air.

If the two manifold pumps have a mixer upstream, then there is hydraulic sepereration, so the pumps then have no interaction with each other. The manifold pumps pull the water through the mixer. The main system pump delivers flow to the mixers.

Are they stove connected ie sealed to the stove and open in the room?

If it arrives today I will be installing an Ivar mixer (to get a better control of flow temp), so may well give that a try also.

Interesting, you don't use the flow meter or have them all fully open?