Michael_S

The heat meter measures the flow rate and flow and return temps and calculates a kwh heat transferred number which normally just increases like an electricity meter. Not sure if the return is warmer than the flow if it will decreases the total kwh transferred counter.

Not sure if we can calculate an EER, we have a heat meter but not sure if it counts backwards..... Gonna add some more fans to the rads and overvolt them a bit to see if we can get some more airflow - I know you can get actual sit on rad units but the fans are less than a quid each compared to about £100 for a unit that will only do about 1/3 the length of a fad and is probably louder too. Currently we are using our second hand heath robinson heat pump - hoping to move to a 'proper' set up but MCS sound rules mean our preferred placement is max 55db that seems to strictly limit the number of 8-10kw units available and the one that seems to be best fit (Grant) does not cool. Does anyone know of any other units that fit the 8-10kw and 55db or less sound power criteria and do cooling? Thanks

All the rads are ok except the bathroom that is sweating a little, I guess we could just turn that one off?

WE are running our flow at 16 (checking dew point to avoid condensation) and have some cooling. We have mounted 8 PC fans under one rad as a proof of concept and it helps creating a small local cool zone, they are silent but we could actually do with considerably more airflow, may try a higher voltage power supply. Currently they are fixed using mini magnets but not that secure so may try mounting them using plastic trim strips. Heat pump is drawing about 1/3 minimum input on an hourly basis and cycling frequently showing we are basically failing to extract nearly as much heat via the rads as the unit is capable of even at minimum modulation. Inside air temp is 26C compared to 35C outside but no idea what it would be without the cooling.

So I have upped the breaker a bit and it isn't tripping currently but that is obviously only a short term solution. Given the nature of compressors, fans etc what sort of level of leakage current is acceptable? AI suggested I try and watch to see if the break happens for example as the fan tries to start or as the compressor starts.

Any suggestions Our LG Therma V 12kw U32, about 10 years old works fine.... ...except when it gets warm and sunny when the unit suddenly decides it will trip the fuse with leakage overcurrent, it does this even if working at low power, heating or cooling. Any ideas why we might be getting leakage current only when the unit is exposed to hot sunshine? Thanks

To be fair, last week with the easterly flow DPs were very low across the board despite the solar warmth. I have just bought a bunch of computer case fans and and going to see how they work with our double rads and flow temp controlled to be above dew point; we will probably run the dehumidifiers in the summer when we have excess PV so minimal cost which should also help with this issue - at the expense of some additonal heat input from the dehumidifiers.

Just wondering how heat pump quotes are calculated. For example my quote of 6200+7500 for a zero disrupt install (no cylinder, no rads) with a heat pump costing 3.5k, a 10m cable run and a 3m pipe run just seems crazy unless I am missing something?

I would like an effective zero disruption install. I think I could use a 9kw Grant Heat Pump costing 3.3k inc VAT run the cabling and pipework myself and even position the unit (total cost about 5k?) so it would just need someone to connect the electricals at the meter end, sign off on everything, inform the DNO, confirm it meets the BUS requirements and whatever else in order to get the BUS grant. Even without this would seem cheaper than the 6k after BUS that I have been quoted. Thoughts?

Space is fine, existing cylinder is properly supported with a steel, but was installed during an extension and the loft hatch is too small for a 600 diameter cylinder to pass. I never understand how the quotes are so much - this one is 6200 after the 7.5k has been taken off for basically install unit on side of house, run about 3m of pipe and tee into existing heating/hot water circuit with a diverter valve needed.

Yeh - strange on the cylinder, with 5 beds I thought MCS would insist on bigger but the optional cylinder upgrades are only 175l or 210l ?? There is no specific mention of whether they would be using a plate heat exchanger rather than the existing coil. Our loft hatch won't fit a standard cylinder so keeping the current one has advantages.....

Yeah, currently we do immersion set to 70c heated overnight at 7p per unit which gives us 5 showers, at say 45C we would need to reheat during the morning shower period but should be doable at say 7kw reheating. [Say cold water is 10c, 70c x 180l gives us 360l at 40c whereas 180l at 45c only gives 210l so I will then need another 5.25kwh - say 45 mins - to heat the remaining 150l of 40C water needed each morning] Either way we also then need to reheat for evening showers. Zero disrupt - I have already changed enough rads that I know we stay warm with a flow temp of 45 (it went a bit higher when we were -5 and below outside but not over 47C) Plan is also to not change the DHW tank and accept the hit to COP.

Indirect 'gas' cylinder Viessmann 180l, about 15 years old

AL4 postcode district - I know the design temp is -2.7 for here but I also know what weather we get. I also currently have a heat meter so know that the heat loss calc is pretty much bang on the money with a 45 flow temp. The quote is using the existing hot water cylinder.

Thanks for the link to the Czech tables, have looked at them before - at 45c for the heating and -2 the output looks sufficient. What worries me is the hot water in addition, I know we use lots and with no tank upgrade we are talking a high flow temp to get the tank to a high enough temperature (happy to aim for 45-50c and use an immersion to do legionella cycle) but that still means a flow of 55-65, possibly towards the higher end due to having to limit tank heating time due to the space heating demand. At -2 / 55 the COP also falls off a cliff, again suggesting that a non-negligible part of the day will be needed to heat the water and thus wont be heating the house. Also these numbers don't include any allowance for defrost cycles.... I can see it might almost work if there was a slight overnight setback during which the hot water tank was heated and then perhaps in the middle of the day when it is warmest there could be another hot water window but this is -2.7. Most winters we have days that average this level or slightly below and we often have -8 coldest nights.