PeterW

Cost of a plate flow with buffer - and finding the space for another 200 litre tank - you may as well put a bigger tank in in the first place. And waste water heat recovery only works with showers - it doesn’t work with baths which is a serious limitation. As I said, min 400 litres in a house that size as for the £75 difference it’s just not worth the hassle.

So a big boiler and UFH will need a buffer tank or it will short cycle. Does theTado do multiple zones for UFH or does it just do one or two zones...?

I’m sure there is an offer on Veissman in Wolseleys at the moment as this is the second question about these this week ..! Rule on boilers is simple - how many installers can you find to install it is one thing, but what about service and maintain it ..? Lots of PHEs do Worcester Bosch, Baxi, Ideal and Vaillant. They reduce quickly when you go down to Vokera, Alpha and Veissman so when it goes wrong who can you call ..? Are you having UFH or rads ..?

There is a legal requirement for a bath to be fitted with a TMV3, or the supply limited to below 48°C and I have seen BCOs check this. The quickest and easiest way to do this is blend the whole system from the UVC at the outset. It is easy to do, and they aren’t expensive. I usually specify Reliance TMVs as they are maintainable. You will comfortably get 35 litres/min through which is more than enough for two or more showers running simultaneously. The other issue with higher temperatures is higher standing losses, and in certain circumstances you will loose the efficiency of condensing on the boiler.

not really - you’ll get another 25 litres at best, so an extra minute per shower. You’re not getting 67°C to the taps if you can put a hand under it as that is enough to scald within 3 seconds. I expect your settings are as accurate on the tank and it’s closer to 55°C and also is losing heat if it’s an older smaller tank due to fluid turbulence. It is best practice (and a legal requirement for a bath) to install mixing valves or TMVs on baths and ideally all hot water from an unvented cylinder. So the heat loss in 24 hours from a 250 is 2.16kW, from a 300 it is 2.32kW and a 400 it is 2.58kW so not worth even considering Why horizontal ..?? A vertical cylinder needs 710mm, and you can get all the pipe work within the 10-2 area on the front of a tank as all Telford cylinders are built to order. That would fit in a space 800mm wide, the 400 has a 40 litre expansion vessel that can be mounted above it and the whole lot is only 2.1m tall including the expansion. If I specified a 120 litre tank for a flat where it would drain it dry with a 10 minute shower I would be crucified ... Price differential between 250 - 300 - 400 is about £35-40 each time so it’s not costing that much more in the scheme of things to install a decent hot water system. Is this boiler or ASHP out of interest ..?

Use a 12 litre expansion vessel and drop the precharge pressure to 1.5 bar when you install it. also get a Wilo pump - Toolstation have them on offer and they are virtually silent. https://www.toolstation.com/wilo-yonos-pico-circulating-pump/p75983

That’s any concrete then ... if you dump a wet mix in it will displace the water anyway

4,000 litres isn’t that much ..!! A standard 10x8 house roof will collect 40,000 litres on average in a year. This pump would empty that in a bit over 20 minutes too https://www.amazon.co.uk/dp/B07PJSB314/ref=cm_sw_r_cp_api_fabc_VmUaGbB5X9SVK?_encoding=UTF8&psc=1

So at -2°C it’s trying to give you 45°C water into the floor. What is the mixer valve on the UFH set at ..?? I would be looking at -5°C High and 10°C low, and 35/42 as the values.

How about one of these ..?? Right size, fill with water then just pour mass concrete round the outside and when it’s set cut your way in ..?? https://www.ebay.co.uk/itm/Wydale-5500-litre-Storage-tank-/174593316195?_trksid=p2349624.m46890.l49292

I converted an old garage pit into a cellar and if I did it again I would use the concrete rings. I would cast rectangular pad 150mm thick and reinforced with something like A393 and loop some lift points into the corners and then set a 300mm ring on to this with a decent mortar and haunch the ring. Then lift this into the bottom of your hole and set level and stack the rings on top - yes you may have a water table issue but if you then line it with a butyl liner it will stay dry. Cap it at the top with a standard man access cap and then you can do whatever you need to bring it up to level

You have a flow to return delta of 8°C as a composite view which is ~20% which seems high. Also, the pipe stat you are using will be quite slow to respond and pretty inaccurate so may be worth getting some digital sensors and sticking them on the pipes under some insulation. May have a better view of the settings then. Does the buffer have any spare pockets for sensors ..?

Can you change the delta setting ..?

Ds02 : 12 ds04 : -3 ds06 : -2 Means that the temperature will increase at -2°C by 3°C and will ramp down to 0°C increase over 12 degrees so at 10°C your set point will be the same. What is current set point out of interest ..?

So for an increase of 15°C of outside temp (-5°C to 10°C) the heat pump will reduce the flow temperature set point by 5°C reading that. So if you set it at 35°C and it’s 10°C outside, then the HP will change it to 40°C when it’s -5°C or lower. I would possibly move the curve up slightly (although this looks linear ..!) and move the differential start (ds06) to -2°C but make it -3°C on ds04 to begin with. Nice and simple this one to understand ..!

Any reason the HP doesn’t do the hot water to at least 40°C as it would be a massive improvement on the immersion. Does the tank have just the solar thermal coil..??

Bit of pipe insulation in there wouldn’t go amiss ... ? GP..?? Grundfoss Pump ..? What is doing the hot water in the house ..?

Thanks for that - interesting that on the Lossnay the recovery efficiency seems to increase with flow rate which is a bit odd as it’s supposed to decrease ..!! I’ll download the data from the Shelley’s that are on the ducts as it’s looking like for a fairly average install the efficiency is 78.8-82.3% which isn’t far off the actual numbers quoted by the manufacturer. This may be affected by the long run in an unheated but insulated service cavity for the en-suite (17m) and bathroom (10m) extract ducts. Interestingly the extract temperature increases on boost which makes me think some heat is lost in this duct.

That’s not strictly correct, as it depends on the usage class of the land. If the land is used for grazing only - that is they are turned out and are not being exercised or fed additionally - then horses are classed the same as any other grazing animal. Any field shelters have to be moveable and not permanently sited. If you exercise the horses in the field, provide coats and covers or substantial additional feed then they are counted as recreational animals and the usage law changes. If you want to confuse the council even further, just stick a couple of sheep in the field with the horses and at that point it really muddies the water !!

Solar gain for a heat pump is negligible but the air sensor on the back may be susceptible to solar warming. There is nothing intrinsically wrong with that set up. Emmeti are a decent brand, it just seems like it has been half installed ..! Depending on how “handy” you are then you can probably re-pipe a lot of that as it stands with some off the shelf components rather than use a new manifold and pump set. Couple of things to check though. Is there a sensor or thermostat on the buffer tank ..? What triggers the circulation pump to run..? What triggers the heat pump to run ..? What timer / controller is installed ..?

How are you storing heated DHW from a combi..? Or are you suggesting that you use the heating circuit to keep a local tank hot and then replenish it from the combo flow when it kicks in ..?? Not likely at all. A 250 litre tank at 60°C holds around 330 litres of shower temperature water when blended down. That’s around 14 minutes for a pair of showers running together before the tank is cold. In a 5 bed/ 3 bath I would recommend 400 litres in a UVC. Anything smaller and you will need a bigger system boiler with a higher output to keep up with usage. Secondary circulation loop would work here but you need to design in the outlets too - which need hot water “instantly” and which can wait. If you go the traditional route of running large bore to the bathrooms and then tee off from this for the shower / basin / bath you need to get the return as close to the basin as possible as otherwise the response time will be too slowed @Temp points out. Baths and to a point showers are less of an issue due to the volume of water involved, so consider a secondary loop run in 10mm that only serves the basins and kitchen / utility tap as that will be more than adequate. We changed a permanent running install to one that ran 5 minutes every hour in a commercial building and reduced the water heating costs by £100/yr using a £20 timer. A well insulated pipe doesn’t lose that much heat and usage will also ensure it stays hot.

That’s helpful, do you know the flow rates ..? And what heat transfer you are getting from intake to supply and the extract temperatures ..?

Yes and .. yes.. So that needs re-fitting with a mixer if possible - you may have to take the manifold off the wall although it looks like someone removed the board with a spoon anyway ... Depending on how far from the buffer that manifold is, the manifold pump may well pull the hot water into the system anyway. If you can move the “other” pump and make sure it’s before any tee to the mandifold even better. You could wire the rads to a zone valve - use that to switch the pump on only when the rads want heat and let the manifold pump be controlled by the actuators. All pretty easily doable

Haven’t fitted a pre heater but have fitted a post heater as I’m not convinced that heating the cold air coming in will extract as much heat from the outgoing air. Out of interest does anyone else have sensors in their intake / extracts and can log the temperatures..?

Double charged could be what they are referring to. That means they get double thickness of the glaze or pattern applied. @nod may be able to elaborate a bit more.