puntloos Posted October 31, 2021 Share Posted October 31, 2021 To my mind there are a few spots in my house that will generate a lot of heat for a low amount of volume. - Kitchen Oven and hob, obviously Probably (?) okay to not do too much fancy stuff beyond a few MVHR inlets - Projector enclosure in Livingoom 400W projector that needs to be sealed, at least in the front (into the livingroom) for noise reasons - Networking cabinet in Office This is the big one. Network switches, home automation, a powerful PC and suchlike might hit 1000W heat generation in a 600x600x2000 box It's in the office, but bordering the livingroom. > Do I feed direct cold air into it, or should I just pull air from the room? > Do I pull air out with MVHR? I suspect I need a special high-speed air pipe? My main service riser is thankfully very close, so a big pipe is doable but noisy fans are not.. (can I have some device in the loft suck the air rather than push the air in?) - Plant/Utility room in Loft HWC prob not leaking too much, but MVHR device KNX boards, smart home control stuff ASHP endpoint For all of these, it would be great if a MVHR could, well, 'recover the heat' and somehow use it wisely, but I understand that a MVHR really doesn't capture that much heat. What do? Install a simple split AC into the loft that will just pull heat in and out of the hot air inlet and put it into the cold air outlets? (yes I have an ASHP too, at that location, perhaps it can actually handle the hot air? Duct the hot air outside? (sucking the house vacuum doesn't seem ideal ... ) More powerful MVHR that can handle meaningful heat spikes? Can I store the captured heat into the hot water cylinder or is the recovered heat really not worth "doing stuff with"? Leave it all be? Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2021 Share Posted October 31, 2021 (edited) How about ducting in an exhaust air heat pump, then doing something useful with the energy. I wonder if a relatively cheap dehumidifier could be useful. Edited October 31, 2021 by SteamyTea Link to comment Share on other sites More sharing options...
Ferdinand Posted October 31, 2021 Share Posted October 31, 2021 Why not leave it in the room and use less heating? Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 46 minutes ago, SteamyTea said: How about ducting in an exhaust air heat pump, then doing something useful with the energy. Well I guess it's the 'something useful' part, right? I'm sure that I can pull hot air from somewhere relatively easily, but now do I use it? 46 minutes ago, SteamyTea said: I wonder if a relatively cheap dehumidifier could be useful. I'm not quite seeing how a humidifier helps? 42 minutes ago, Ferdinand said: Why not leave it in the room and use less heating? Well, since the house is near-passivhaus-level I'm not sure that excess heat is not going to be a problem? Even in my current 'standard 70s' home, just my PC running a game very clearly increases the heat in the room. If we can spread it around the house, maybe that would suffice? Frankly the math here is too alien for me for now, not sure where to start digging in to how (e.g.) a 8kW ASHP can handle 1KW of actual heat generated? Obviously it sounds like it would easily work but I'm sure reality is different? 1 Link to comment Share on other sites More sharing options...
ProDave Posted October 31, 2021 Share Posted October 31, 2021 You are tackling this from the wrong angle. Rather than work out how to use the "spare heat" i would be looking at how to eliminate or reduce the spare heat creation. 400W projector? do they not yet make LED ones? If not I bet they will soon. 1000W for an IT cupboard. You need to re think from first principles exactly what you are trying to achieve there? Something that consumes 1000W for long periods of time has no place in a modern low energy house (unless it happens to be the heating system) 1 Link to comment Share on other sites More sharing options...
Marvin Posted October 31, 2021 Share Posted October 31, 2021 My MVHR has to be balanced between air coming into the building and air going out. It also mixes the temprature in the building air with the temprature of the outside air coming in, OR, expells the inside air temprature and just supplies outside temprature air into the building. If your have the same set-up my thoughts would be: You could push the hotter air out of your office by supplying outside temp air in, however where will it go? Into the rest of the building. Will this be ok during the summer when the air coming in could already be 25 degrees C? My utility room is always to hot. I only extract the air from the room. In the winter my MVHR recycles the heat as in my first paragraph and in the summer expells the heat. Link to comment Share on other sites More sharing options...
Marvin Posted October 31, 2021 Share Posted October 31, 2021 I'm also with ProDave. The outside temp has to be below 8C and or windy. otherwise we slowly overheat. If I was burning 1000W continual this place would cook. I mostly view the electricity I use in the house as creating heat in the building ( apart from charging the car, ASHP and outside lights). All cooking, Internet, TV, washing and dishwasher have this effect. The other item I'm working on is the solar gain: although only for short periods it requires as much power per hour to keep the place cool as heating does per hour in the dead of winter. Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2021 Share Posted October 31, 2021 42 minutes ago, puntloos said: but now do I use it Warm up water, or bricks. 43 minutes ago, puntloos said: I'm not quite seeing how a humidifier helps You get extra energy from the fusion phase, a lot more energy for no change in temperature. 1 Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 49 minutes ago, ProDave said: You are tackling this from the wrong angle. Rather than work out how to use the "spare heat" i would be looking at how to eliminate or reduce the spare heat creation. 400W projector? do they not yet make LED ones? If not I bet they will soon. Actually this is a LED projector ? 49 minutes ago, ProDave said: 1000W for an IT cupboard. You need to re think from first principles exactly what you are trying to achieve there? Something that consumes 1000W for long periods of time has no place in a modern low energy house (unless it happens to be the heating system) I'll certainly be looking to minimize, but my desktop PC by itself runs at 550W when gaming. Then I rounded up for a few of the other pieces bits and bobs. Certainly the PC won't be on permanently, or gaming even when it is on, but you have to take peaks into account not just averages. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2021 Share Posted October 31, 2021 4 minutes ago, puntloos said: PC by itself runs at 550W when gaming That is enough to heat my whole house. My PC uses 8W 1 Link to comment Share on other sites More sharing options...
Marvin Posted October 31, 2021 Share Posted October 31, 2021 14 minutes ago, puntloos said: I'll certainly be looking to minimize, but my desktop PC by itself runs at 550W when gaming. Then I rounded up for a few of the other pieces bits and bobs. Certainly the PC won't be on permanently, or gaming even when it is on, but you have to take peaks into account not just averages. Then IMHO I think you will only get success from an independent system in the office using an inlet and exhaust and air sealing the door if you have an MVHR. Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 6 minutes ago, SteamyTea said: That is enough to heat my whole house. My PC uses 8W I doubt it . Even the lightest device that you could consider a PC (a chromebook) does something like 30-45W. Either way, both my projector and my PC certainly are thirsty, even though they are modern. And no I'm not bitcoin mining or something like that. Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 1 hour ago, SteamyTea said: Warm up water, or bricks. I wasn't aware you could do this with warmish air. Do you have a link for a device that does this? Or is it effectively a "chiller coil" but running in reverse? 1 hour ago, SteamyTea said: You get extra energy from the fusion phase, a lot more energy for no change in temperature. Hmm. So you would put the dehumidifier.. in the cabinet? Or somehow inline with an MVHR? 14 minutes ago, Marvin said: Then IMHO I think you will only get success from an independent system in the office using an inlet and exhaust and air sealing the door if you have an MVHR. It's a good point to air seal the office door. I'll make a note of it. What type of independent system are you thinking of? FWIW: As you can see the service riser goes through the entire house, so I might just be able to pull the hot air up to the plant room and potentially exhaust towards the skylight if I'm really desparate. But indeed some optimized way to not have the heat go to waste would be great. There will be a chiller coil near, so perhaps it can do some useful work? Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2021 Share Posted October 31, 2021 15 minutes ago, puntloos said: wasn't aware you could do this with warmish air Something like this. Pull the air our if the hot parts with a bit of creative ducting. https://www.directheatingsupplies.co.uk/vaillant-200l-heat-pump-cylinder-20235272 Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2021 Share Posted October 31, 2021 (edited) 37 minutes ago, puntloos said: does something like 30-45W. My cheap Acer laptop pulls a maximum of 30W. Most if the time it is just idling with the screen asleep. A few years back I put an energy monitor in it and was really amazed how little it used. Edited October 31, 2021 by SteamyTea Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 1 minute ago, SteamyTea said: Something like this. Pull the air our if the hot parts with a bit of creative ducting. https://www.directheatingsupplies.co.uk/vaillant-200l-heat-pump-cylinder-20235272 Actually this one - https://www.gledhill.net/products/alternative-energy/stainlesslite-heat-pump/ - was already my top choice. Same type of idea it seems. But this one takes fluids for the coil (aka 'warm water from the heat pump') - I think I'm missing some type of extra device to collect energy (heat into the water, or electricity) from the hot air? Link to comment Share on other sites More sharing options...
joth Posted October 31, 2021 Share Posted October 31, 2021 Just leaving the heat where it's created doesn't work. I have a overheating comms cupboard that warms up the bedroom next to it and it has much less power demand than you are talking about. We put an MVHR extract in there but it's no where near enough even for just a network switch, multizone amplifier, and the loxone server and dimmers. Pumping cold air in is annoying as that is automatically wasted energy during the winter heating period. Pumping warm air out to redistribute is the obvious first choice. Perhaps doing so via an exhaust air heat pump would make sense and direct the hot water generated into the hot cylinder and UFH, but what you do with the excess in summer is then the challenge. At some point luxury domestic installs might as well go for 4 pipe refrigeration like a commercial system then you can simultaneously heat and cool rooms depending on their needs, but 4 pipe heat pumps don't really come in small enough sizes for domestic use. Link to comment Share on other sites More sharing options...
SteamyTea Posted October 31, 2021 Share Posted October 31, 2021 1 minute ago, puntloos said: think I'm missing some type of extra device to collect energy (heat into the water, or electricity) from the hot air? They are just A2AHPs, so the pull the energy our the air, cool it a bit then expell it to outside. Once you have a tank of hot water, you can do what you like with that, use it as DHW, pipe it into a radiator, plumb in an W2A heat exchanger and pre heat the air coming into the house. Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 (edited) 54 minutes ago, joth said: Just leaving the heat where it's created doesn't work. I have a overheating comms cupboard that warms up the bedroom next to it and it has much less power demand than you are talking about. We put an MVHR extract in there but it's no where near enough even for just a network switch, multizone amplifier, and the loxone server and dimmers. Pumping cold air in is annoying as that is automatically wasted energy during the winter heating period. Pumping warm air out to redistribute is the obvious first choice. Perhaps doing so via an exhaust air heat pump would make sense and direct the hot water generated into the hot cylinder and UFH, but what you do with the excess in summer is then the challenge. Thing is, I'm indeed struggling to picture a sensible way to indeed think about the location of available water of both hot(ish) and cold(ish) varieties and where it makes sense to add/remove heat from it. Does anyone have some sketch on how this works? For one I do have a hot and a cold buffer planned, so presumably I could perhaps try to heat the hot buffer with hot air (probably via heated water with @SteamyTea's A2AHP point? Quote At some point luxury domestic installs might as well go for 4 pipe refrigeration like a commercial system then you can simultaneously heat and cool rooms depending on their needs, but 4 pipe heat pumps don't really come in small enough sizes for domestic use. Actually - https://www.hidros.eu/uploads/ART/1LZTP4/BRO_LZT-P4_ENG.pdf - ok, it's a bit beefy - 25kw - but the size is "sort of okayish" - 2000x1500 footprint. And it's fairly noisy I think. (but it's far in the garden..) Edited October 31, 2021 by puntloos Link to comment Share on other sites More sharing options...
Marvin Posted October 31, 2021 Share Posted October 31, 2021 1 hour ago, puntloos said: It's a good point to air seal the office door. I'll make a note of it. What type of independent system are you thinking of? Hi @puntloos I could not name one but if you have an external wall to the office I know there are some available in the market, and that sort (in and out external wall would be most sensible rather than ducting across the universe) Other people here will be able to help. (My guess is search single room MVHR or AIRCON). M Link to comment Share on other sites More sharing options...
puntloos Posted October 31, 2021 Author Share Posted October 31, 2021 9 minutes ago, Marvin said: Hi @puntloos I could not name one but if you have an external wall to the office I know there are some available in the market, and that sort (in and out external wall would be most sensible rather than ducting across the universe) Other people here will be able to help. (My guess is search single room MVHR or AIRCON). You have a certain point it might not be a crazy idea to have a separate system, but like I said my office kind of has a direct air duct to the loft so while 'ducting across the universe' has some downsides, it feels having an ancillary aircon (ASHP?) right next to my plant room on the roof might not be crazy Link to comment Share on other sites More sharing options...
Marvin Posted October 31, 2021 Share Posted October 31, 2021 5 minutes ago, puntloos said: You have a certain point it might not be a crazy idea to have a separate system, but like I said my office kind of has a direct air duct to the loft so while 'ducting across the universe' has some downsides, it feels having an ancillary aircon (ASHP?) right next to my plant room on the roof might not be crazy Yes each individual property has its own drawbacks and benefits. No one size fits all! I could not sensibly position the ASHP on an outside wall so it is on a flat roof! Link to comment Share on other sites More sharing options...
Ferdinand Posted October 31, 2021 Share Posted October 31, 2021 1 hour ago, puntloos said: I wasn't aware you could do this with warmish air. Do you have a link for a device that does this? Or is it effectively a "chiller coil" but running in reverse? See Hypocaust ?. Link to comment Share on other sites More sharing options...
puntloos Posted November 1, 2021 Author Share Posted November 1, 2021 4 hours ago, Ferdinand said: See Hypocaust ?. Ha, ancient roman technique. You have any modern implementations? In geneal I don't think I should go nuts with all technologies I could find.. Link to comment Share on other sites More sharing options...
Marvin Posted November 1, 2021 Share Posted November 1, 2021 (edited) 1 hour ago, puntloos said: Ha, ancient roman technique. You have any modern implementations? In geneal I don't think I should go nuts with all technologies I could find.. Yes, I avoided the heat recovery system for the shower waste, turbines for the rainwater down pipes and the solar panel following the reflective sun off the moon. But still considering the turbine driven by mains water Edited November 1, 2021 by Marvin Add info Link to comment Share on other sites More sharing options...
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