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Beelbeebub

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Beelbeebub last won the day on January 12

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  1. The effect on CCGT efficency of any renewable fluctuations is fairly irrelevant to the "but more co2" argument. In order to produce less CO2 per kwh(t) than a gas boiler, HPs need only hit 2:1 efficency which is almost always the case for UK temperatures. Even for the few days a yer that the HP's might drop below 2:1 and the instantaneous co2 emissions go above those of a gas boiler, the annual efficiency (aka SCOP) of a HP will always be well above 2 (for any reasonably installed system). And the above calculation assumes *all* electricity was produced from gas ie the grid carbon intensity is 400g. In reality the grid intensity is far below that. For example the worst week of 2024 for grid co2 emissions was 220g. So for all of 2024 a resistively heated house produced less carbon than an equivilent gas boiler heated house.
  2. You're always going to be a bit buggered if the external wall is opposite the heat source. You'll just get a steeper gradient if you up the flow temp. Is there any prospect of moving the rad to the outside wall? Your only other alternative would be some sort of forced air movement - there are fans that are pretty much silent, you don't need alot of air movement to make a big difference. Maybe a large diameter, low speed ceiling fan?
  3. That CO2 per kwh thermal of natural gas is about 200g/kwh. This tallies with around 220g per kwh(thermal) for a 90% efficency boiler. CCGT plants are upwards of 50% efficient at converting thermal energy to electricity. Which tallies with the 400g of CO2 per kwh (electrical). With flow temp of 45c or less most modern HPs can achive better than 2:1 down to well below 0C. Even at 55C flows they achive 2:1 down to -2C There are valid reasons why we can't replace every gas boiler with a HP but "you will increace co2 emissions from electricity by more than you will save by stopping direct burning" isn't one of them.
  4. From the stelrad catalog. Remember it's the dT of the mean temp ie DT50 would be something like a flow of 80C and return of 60C (assuming room temp of 20C) So a typical HP with a flow of 45C and return of 40C would be midway between DT20 and dt25 so about 1/3 the rated output.
  5. An efficient gas boiler emits around 220g of CO2 per kwh of heat. A gas power plant emitts just under 400g of CO2 per kwh delivered. So burning gas in a power plant then using an ASHP operating at a Cop of 2:1 would have lower co2/kwh than burning the gas in a domestic boiler. 2:1 CoP is achievable in all but the most ham fisted installation. So if we could snap out fingers and replace every gas boiler with an ASHP (and build some extra gas power stations etc) we would reduce our co2 emissions.
  6. Is this the touch screen one?
  7. Thats what the auto actuators would sort out. They would regulate the flow so the dt was 7/5C. The alternative is to manually balance the ufh and rads so the dt was to the HP's liking and run it all (ufh and rads) as one big zone. From the HP's point of view there isn't any difference between a rad and a UFH. All it sees is a flow rate at a given pump speed and a dT and will adjust it's power to achive the setpoint temp. If you are hitting the maximum power and are unable to achive the set temp then isn't the problem is your HP is too small?
  8. Hang on how is your setup. Is you ufh via a "standard for boilers" manifold with it's own pump and mixing valve? Is your flow and return direct from the HP or. Is there a thermal store/buffer?
  9. The lowest flow temp for a given power output is going to be with the ufh and rads both on together (and balanced) because that is the largest emmiter area. So you could run open loop WC, and just balance the UFH and rad flows to give you the best results. What about the salus autobalancing trv/actuators? They monitor the flow and return and adjust the flow (they sit on standard trv valves or even ufh loop actuators) so the dT is 7c (or maybe 5c, I forget)
  10. Understood, but is the root problem that there are some rooms that cannot be heated without using rads at 45C and UFH at 40C at the same time? What is the.max temp the UFH can stand?
  11. Not scare mongering. *if* the heat exchanger freezes, it's buggered. As you correctly point out, it won't freeze that easily. The only real possibility is a long power cut during a persistent cold snap eg beast from the east (the conditions when the electrical hearing trace won't help) However, in the unlikely event that happens you are onky concerned with draining down the HP. The buried portion prob won't freeze and even if it did it's not that big a disaster. So an AF valve will still provide protection as long as it is positioned to drain out the HP. The rest doesn't matter
  12. If you go with an AF valve below the HP but out of the ground - ideally just as the pipe emerges then it should protect your HP should there be an extended power cut and cold spell. Ultimately if your bit of pipe sticking up from the ground to you AF valve freezes it's not that big a deal. The goal is to stop freeze damage to the heat exchanger in the HP. If that freezes you HP is scrap. Even if the pump inside freezes it's not the end of the world, so all you need is thr freeze valves to be such that the HP drains down. I would argue a single one on the lowest outlet (doesn't matter if flow or return) is enough. The goal is to get a flow of water through the HP so it can't freeze solid. If the valve opens and some water flows out that achives the goal. If enough water flows out to empty the HP, that also achieves the goal.
  13. S I can get this straight in my head. You want to run in 3 conditions 1) Just rads at WC curve suited to rads 2) Just UFH at WC curve suited to UFH 3) Both rads & UFH with HP outputting WC curve for rads You can currently run 1 & 2 no problem, the issue is with 3 where the UFH circuit drops the return temp so much the HP cannot achive the desired rad temp? Is that correct? Assuming it is, I imagine you essentially have 2 choices. During the overlap time you can either run with Rads WC, and (as you suggest) have a lower flow rate through the UFH such that the return flow/temp doesn't drag the bulk flow down and cause the HP problems. The other option is the inverse, run both at the UFH WC temp. The UFH will be fine (obviously) the rads will be a bit cooler and output a bit less but the return temp shouldn't be an issue for the HP. The downside of this is the rad zones will be a little underpowered but this could be compensated for by switching to rads only for periods to "blip" a bit more heat into the zones. The upside is there shouldn't be any plumbing changes.
  14. Thanks all. I'll have a chat with Octopus to see what the best way is. Exporting to the grid would be a nice bonus to help the payback.
  15. Are your rads on separate circuit to your ufh? Ie can you run just rads and just ufh? If so, and your controller has the facility for separate wc curves per zone you should be able to run each set of emitters at the optimum temp. It might be worth working out which emitter is your "worst" ie needs the highest flow temp. It might be that it is just one or two rads are markedly worse. If those were upgraded it might allow a significant drop to a lower temp.
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