sharpener Posted April 1, 2023 Share Posted April 1, 2023 Chelmer Heating seem to design and supply integrated systems for self build and renovation projects. I wonder if anyone has used them in the past and can give me any pointers as to their capability? Link to comment Share on other sites More sharing options...
JohnMo Posted April 1, 2023 Share Posted April 1, 2023 I would get an idea of you want by asking and searching on here, then get quotes. Review quotes. Lot of words saying nothing much on the reference web site. Link to comment Share on other sites More sharing options...
Post and beam Posted April 1, 2023 Share Posted April 1, 2023 I have never previously heard of them but thought there was no harm in filling out their quote submission form. Who knows they may turn out to be good. Not too far from me in North hertforhsire. Link to comment Share on other sites More sharing options...
PeterW Posted April 1, 2023 Share Posted April 1, 2023 Been around years - one of the first in the renewables game from memory. Also used to do thermal stores that were very good quality - not sure who used to make them for them though.. Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 1, 2023 Share Posted April 1, 2023 Spoke to them ages ago about thermal stores for a log gasification boiler job I had on at the time. Seemed knowledgeable and helpful, from what I recollect, but I had to go with a turnkey supplier eventually as the RHI small-print meant the commissioning agent had to be direct to the client. Get a quote, no harm, no foul? Link to comment Share on other sites More sharing options...
sharpener Posted April 2, 2023 Author Share Posted April 2, 2023 Yes I was interested in them for the thermal store capability. As they are less than 50 miles away I will take advantage of their face-to-face consultation option since what I want to do is quite complicated. Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 2, 2023 Share Posted April 2, 2023 4 hours ago, sharpener said: Yes I was interested in them for the thermal store capability. As they are less than 50 miles away I will take advantage of their face-to-face consultation option since what I want to do is quite complicated. Let us know how you get on. 👍 Link to comment Share on other sites More sharing options...
sharpener Posted April 4, 2023 Author Share Posted April 4, 2023 (edited) Their web site is big on flexibility Each project has it's own specific heat requirements, room layouts and end user requirements, whilst each system component has different flow rate and temperature requirements in order to run efficiently. We take all of these variables and more into account when designing our systems to deliver you a comprehensive design that is simpler to install and guaranteed to perform. but in the end they have cancelled the pre-arranged visit to their offices and declined to bid. I think they are basically MCS designers and my wish to combine an HP system with the other heat sources I already have put them off, though they cite the difficulty of insulating the house to a higher standard and the need to replace radiators. As posted elsethread I am now looking into using the Daikin Altherma HT range as a way of achieving more of what I want without wholesale replacement of rads and HW cylinder. They are split systems but the overall capital cost might be much the same with less disruption. They also have a bi-zone add-on which allows rads and UFH to run at different temps which sounds promising. The CoP will not be wonderful but with free PV available might just be enough. Edited April 4, 2023 by sharpener Link to comment Share on other sites More sharing options...
JohnMo Posted April 4, 2023 Share Posted April 4, 2023 1 hour ago, sharpener said: They also have a bi-zone add-on Or in simple terms a mixing valve. UFH mixer valves do this anyway. If you want to keep an existing cylinder with a small coil you can always add a plate exchanger and pump (similar to mixergy cylinders). This would effectively increase heat transfer area and let the cylinder be heated by the heat pump. Trying to keep the radiators may be an expensive missed opportunity, as running cost will always be more expensive than needed. Link to comment Share on other sites More sharing options...
sharpener Posted April 4, 2023 Author Share Posted April 4, 2023 1 hour ago, JohnMo said: Or in simple terms a mixing valve. UFH mixer valves do this anyway. It's a bit more sophisticated than that, and it seems to have a wireless OAT sensor as well 1 hour ago, JohnMo said: If you want to keep an existing cylinder with a small coil you can always add a plate exchanger and pump (similar to mixergy cylinders). This would effectively increase heat transfer area and let the cylinder be heated by the heat pump. Trying to keep the radiators may be an expensive missed opportunity, as running cost will always be more expensive than needed. No it wouldn't. The limiting thermal resistance in the path from HP to DHW will still be the degK/kW of the existing coil, the thermal resistances are all in series just like an electrical circuit. And you have interposed the HX which will introduce an extra temperature drop. It's all a balance between doing nothing and hoping the existing boiler keeps going, replacing it with a new one and continuing to use fossil fuel, or switching to an HP. I suspect that in a DCF calculation the capital cost of replacing the cylinder and rads might well counter the additional running costs from the poorer CoP but I do not yet have all the figures (and it will of course depend on the discount rate you choose anyway). Link to comment Share on other sites More sharing options...
JohnMo Posted April 4, 2023 Share Posted April 4, 2023 Bi zone package - Operation principal › serves to distribute and regulate two zones in which the water temperatures are different. › The heat pump produces water at the temperature of the zone where the control requires a higher water temperature (radiators or fan coil units). The bi-zone kit will adjust that temperature to the one set for the underfloor heating. › That water temperature is constantly adjusted based on the exterior temperature. › The ambient temperature thermostats in each zone simultaneously communicate with the receiver, located near the heat pump, and with the bi-zone kit controller. The controller, by means of the signals received, communicates with the exterior probe to provide the ideal temperature based on the parameters selected. 2 hours ago, sharpener said: It's a bit more sophisticated than that So a 3 way mixer valve pump and weather compensation - which the ASHP provides anyway. Nothing different to a UFH mixer pump assembly. 2 hours ago, sharpener said: No it wouldn't. Funny how it does work with thermal store Flow path is boiler PHE, cylinder coil then back to boiler. Other of side PHE is bottom or cylinder to top of cylinder via a pump. Link to comment Share on other sites More sharing options...
JamesPa Posted April 4, 2023 Share Posted April 4, 2023 (edited) 3 hours ago, sharpener said: 5 hours ago, JohnMo said: If you want to keep an existing cylinder with a small coil you can always add a plate exchanger and pump (similar to mixergy cylinders). This would effectively increase heat transfer area and let the cylinder be heated by the heat pump. Trying to keep the radiators may be an expensive missed opportunity, as running cost will always be more expensive than needed. No it wouldn't. The limiting thermal resistance in the path from HP to DHW will still be the degK/kW of the existing coil, the thermal resistances are all in series just like an electrical circuit. And you have interposed the HX which will introduce an extra temperature drop. Actually @JohnMo has suggested a faintly interesting idea. @sharpener is correct that putting the HX in a loop with the internal coil wont work, but (as I understand it) this is not how mixergy cylinders work either. The HX (in the mixergy) is in a loop with the stored water. This presumably will work provided the HX has sufficient transfer capability. Its making me think about whether to retain my exiting vented cylinder, thus avoiding lots of replumbing, and fit a HX alongside to turn it into a vented mixergy clone for a relatively small cost and lots hassle avoided. Also it means I can 'DiY it' because no G3 requirement. Of course its yet another pump! Has anyone actually done this? I was anyway going to ask what people think of the basic Mixergy idea as it relates to ASHPs. My initial view based on a skim read only was that its silly and that the complex scheduling idea is a gimic, but Im probably missing something Edited April 4, 2023 by JamesPa Link to comment Share on other sites More sharing options...
JohnMo Posted April 4, 2023 Share Posted April 4, 2023 A simple drawing of the circuit diagram with PHE. Link to comment Share on other sites More sharing options...
JamesPa Posted April 4, 2023 Share Posted April 4, 2023 Ok @JohnMo that drawing confused me. I assumed you simply pump water out of the cylinder through the phe cold side and then back into the cylinder, and on the hot side of the phe connect up flow and return from the hp, ignoring the coil in the cylinder altogether. Your drawing looks more complex, is there any chance you could explain? Link to comment Share on other sites More sharing options...
sharpener Posted April 4, 2023 Author Share Posted April 4, 2023 I looked into the Mixergy a while ago and while I can't remember exactly how it was supposed to work yes I thought it was gimmicky and not worth the money. If the idea is to recirculate the stored water through an external HX then that should work and be relatively cheap. It would help in my case where the tank is boxed in as part of the airing cupboard construction so would be a major undertaking to replace though am hoping to avoid the need. AIUI a plate-to-plate HX has two separate circuits so four connections hence I don't understand it either (have designed various all-plastic air-to-air HXs for heat recovery). Link to comment Share on other sites More sharing options...
JohnMo Posted April 4, 2023 Share Posted April 4, 2023 Hot side of PHE. Water from boiler, to PHE, out of PHE in to coil and out back to boiler. Other side of PHE, water is pumped from the bottom of cylinder through PHE to top of cylinder. The cylinder is connected as a two port buffer with oversized tees at the cylinder. The other side of the oversized tee goes to the UFH. The cylinder also has a DHW coil not shown on this drawing. In my case it's a thermal store, but could work with an UVC or any cylinder. Prior to PHE install at 30 degrees flow temps, boiler run for about 1 to 2 mins and shutdown on high temp. Following PHE install boiler runs for about 10 to 20 minutes. The increased area allowing much more heat to be transferred to cylinder. The approach temperature of PHE is about 2 to 3 degrees depending on flow temp. Link to comment Share on other sites More sharing options...
SteamyTea Posted April 5, 2023 Share Posted April 5, 2023 @JohnMo You seem to be going down the same path that @Jeremy Harris went down a fair few years ago. Real shame that his blog is not about anymore (possible wayback machine has a copy). In the end he dumped it all and got a Sunamp for the DHW. No idea if that is still going well, he had trouble with one of them. Link to comment Share on other sites More sharing options...
JamesPa Posted April 5, 2023 Share Posted April 5, 2023 OK @JohnMo that now makes sense. The idea of a PHE separate to the DHW tank merits some exploration, I feel as it has some interesting properties (albeit that it may be a dead end): Mixergy claim it makes the tank smaller and the the HP more efficient. The first is true, 3sq m of 22mm internal coil (the typical area for a HP) has a volume of 33l which subtracts from the available volume of stored DHW. Thats not the 40% they claim though in most cases. The second is true if you can achieve a lower delta T between flow temp and DHW temp with the PHE. Possibly you can, depending on the heat transfer function of the PHE. I looked at a couple of PHE specs and decided I dont know how to interpret them! The spec for the Mixergy one is below so perhaps someone else does. I guess the 'exchanger rating' tells us about the heat transfer - but under what conditions. Also it says it has an equivalent coil surface area of 3sq m, the same as a typical HP DHW coil, in which case Im not so sure about the claim that HP efficiency is increased. I calculate that a 5C temp difference is required with a 3sqm coil to maintain 4kW heat transfer (a figure chosen because its the minimum output of my target 11.2kW HP), so for a 50C water temp you need a 55C flow temp. It would be good to do better! The pump (presumably) more or less completely de-stratifies the stored DHW (in contrast to the Mixergy tank behaviour when its used without a HP). Im not sure if this is good or bad, but probably does serve to reduce a bit the deltaT between the DHW temp and the flow temp, because you are not relying on convection to shift the hot water away from the coil and replace it with cold water. The two points above, if they can be got to work, will presumably reduce recovery time. Pulling the heat exchanger outside the tank also means that it can be swapped out occasionally without swapping out the tank. In hard water areas that may be a benefit. Against this a PHE will presumably be more susceptible to limescale formation (or will the speed of the water negate this) It would in principle (I think)be possible in principle to locate the PHE at a location remote to the cylinder. This might be useful if the cylinder is, for example, in an airing cupboard next to a bedroom and it was desirable to locate the pump somewhere else to reduce noise nuisance. Last, but not least (and of interest to me and, it seems, @sharpener), its a possible way to retrofit an existing cylinder (with an insufficiently large coil) for HP operation - effectively what Mixergy do with their HP conversion kit. The Mixergy has dedicated tappings for this, an existing cylinder wouldn't, so one would have to find a way to tee off from the existing input and output tappings, which might require a non return valve or two to ensure that the pump did 'the right thing'. Link to comment Share on other sites More sharing options...
sharpener Posted April 5, 2023 Author Share Posted April 5, 2023 12 hours ago, JamesPa said: I was anyway going to ask what people think of the basic Mixergy idea as it relates to ASHPs. My initial view based on a skim read only was that its silly and that the complex scheduling idea is a gimic, but Im probably missing something Out of interest had a look at Mixergy web site. They claim Mixergy tanks are proven to deliver up to 30% more usable hot water when compared to a conventional cylinder* with a reference to the NPL. The energy savings seem to stem from stratification and heating variable amounts of water according to a demand profile - which also enables you to get away with a smaller tank. Nowhere can I see an explanation of how it actually works. Compatibility with heat pumps is achieved with a control box and and external plate heat exchanger(!). If you are going to need that I would say @JamesPa's idea is at least as good. See you have cross-posted, will read yours and then maybe edit this. Link to comment Share on other sites More sharing options...
sharpener Posted April 5, 2023 Author Share Posted April 5, 2023 (edited) 34 minutes ago, JamesPa said: The pump (presumably) more or less completely de-stratifies the stored DHW (in contrast to the Mixergy tank behaviour when its used without a HP). Im not sure if this is good or bad, but probably does serve to reduce a bit the deltaT between the DHW temp and the flow temp, because you are not relying on convection to shift the hot water away from the coil and replace it with cold water. The two points above, if they can be got to work, will presumably reduce recovery time. Pulling the heat exchanger outside the tank also means that it can be swapped out occasionally without swapping out the tank. In hard water areas that may be a benefit. Against this a PHE will presumably be more susceptible to limescale formation (or will the speed of the water negate this) It would in principle (I think)be possible in principle to locate the PHE at a location remote to the cylinder. This might be useful if the cylinder is, for example, in an airing cupboard next to a bedroom and it was desirable to locate the pump somewhere else to reduce noise nuisance. Yes to all the above. Even with a HX rated at 44kW(!) (with Tin = 80C, don't know what else is in BS12897) deltaT is 5deg, I would go to some lengths to avoid that in my system. You can tap into the HW flow anywhere there is a hot water tap, but the feed is difficult because for an unvented tank you have to get to the tank side of the pressure regulator. Is this G3 work? If the HX fails you might contaminate the DHW with antifreeze, don't know if propylene glycol is classified as toxic but ethylene glycol certainly is. Or conversely over-pressurise the HP loop, dumping it to waste or conceivably causing damage. I have not heard of big scaling problems with combi boilers in Cambridge (v. hard water) so perhaps that is not an issue ?because of the flow rates ?=> noise?. Edited April 5, 2023 by sharpener Link to comment Share on other sites More sharing options...
JamesPa Posted April 5, 2023 Share Posted April 5, 2023 (edited) 1 hour ago, sharpener said: Even with a HX rated at 44kW(!) (with Tin = 80C, don't know what else is in BS12897) deltaT is 5deg According to my calculations that's the best I will achieve with the standard 3sq m coil and the minimum operating o/p of my HP (4kW). I suspect the actual will be a bit worse. 1 hour ago, sharpener said: You can tap into the HW flow anywhere there is a hot water tap, but the feed is difficult because for an unvented tank you have to get to the tank side of the pressure regulator. Is this G3 work? No idea. I have a vented tank so am now wondering about retaining it and using the PHE trick 1 hour ago, sharpener said: If the HX fails you might contaminate the DHW with antifreeze, don't know if propylene glycol is classified as toxic but ethylene glycol certainly is. Or conversely over-pressurise the HP loop, dumping it to waste or conceivably causing damage. That's true, but its true also if the coil fails in a regular cylinder. Frankly I don't much like the idea of glycol circulating so plan to use anti freeze valves instead. Having said that CH inhibitor probably isnt very good for you. On the other hand most people don't drink hot water. Perhaps CH water should be treated with a dye, then you could spot cross contamination. Edited April 5, 2023 by JamesPa Link to comment Share on other sites More sharing options...
sharpener Posted April 5, 2023 Author Share Posted April 5, 2023 I like the dye idea. If vented tank then much easier, and unless your header is very high no risk of overpressuring the HP, go for it! Or you could adopt a wait-and-see approach, if the existing tank is large for your usage and/or recovery time is unimportant (both true in my case) then you might get away with charging the tank albeit slowly on E7 and topping up in the afternoon when heating demand is low or non-existent. Retrofitting the HX sounds like a free-standing mini-project anyway. Something related that I have considered doing if I have to have a new cylinder for the HP is re-purposing the old one as the buffer tank to offset some of the cost. Link to comment Share on other sites More sharing options...
JamesPa Posted April 5, 2023 Share Posted April 5, 2023 4 hours ago, sharpener said: Or you could adopt a wait-and-see approach, if the existing tank is large for your usage and/or recovery time is unimportant (both true in my case) then you might get away with charging the tank albeit slowly on E7 and topping up in the afternoon when heating demand is low or non-existent. I thought this too until one prospective installer, who was otherwise hopeless, pointed out that the current 0.8m coil would cause bad short cycling. I did the math and he was right assuming I stick with a min deltaT between flow temp and target water temp of 5C. The potential problems with a small coil are both re-heat time (which doesn't matter for me) and short cycling (which does). Like you Im loathe to discard a perfectly satisfactory tank, its just not environmentally responsible. Link to comment Share on other sites More sharing options...
sharpener Posted April 5, 2023 Author Share Posted April 5, 2023 9 minutes ago, JamesPa said: I thought this too until one prospective installer, who was otherwise hopeless, pointed out that the current 0.8m coil would cause bad short cycling. I did the math and he was right assuming I stick with a min deltaT between flow temp and target water temp of 5C. Buffer? I'm thinking of a layout which while charging the tank albeit slowly on E7 and topping up in the afternoon will also charge a buffer tank to Tmax (?70) in order to feed the bedroom rads am and late evening while the HP is simultaneously running the UFH at a lower temp with better CoP. This will minimise the operating time at high temp whilst also keeping a good load on the HP to reduce cycling. A 200 litre store will fall at 10 deg/hour while putting out 2.5kW which sounds about right for this application. The TRVs start to close after about half an hour anyway, we lie in bed listening to the gears whizzing round. Link to comment Share on other sites More sharing options...
JamesPa Posted April 5, 2023 Share Posted April 5, 2023 30 minutes ago, sharpener said: Buffer? Trying to avoid for reasons of space and also why would I want to buffer at 55C when my CH runs at 45C. Based on these discussions (which are really off-topic) Im going to start a new thread with a related off the wall proposal for people to shoot down. Link to comment Share on other sites More sharing options...
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