Gilli99 Posted June 12 Share Posted June 12 Oh help! Our builder is pressing us to make a decision about our hot water requirements. scenario - new build storey and a half, 2200 sq ft. UFH on ground floor. Gas heating. Options: - combi boiler for DHW - boiler and tank curve ball - may look to install solar in a few years. What makes the most sense? Advice would be greatly appreciated. Thanks Link to comment Share on other sites More sharing options...
JohnMo Posted June 12 Share Posted June 12 So your doing a biggish house, a combi to supply a couple bathrooms will be quite high kW. The problem then is the boiler really ends up too big for the heating. I have had both a big combi and a hot water cylinder. If doing gas this is what I would do a system gas boiler sized as close as you can for the heating load. To do this you need to heat loss calculation. Then plumb for hot water priority, or X plan. Under no circumstances do S or Y plan, which the plumber will want to push on you. Priority hot water allows you run hot water heating and UFH at different flow temperatures and get the best efficiency from the boiler. Add to this a heat pump unvented cylinder, this has a huge 3m2 coil and give quick recovery times. A good video to watch Don't flood the house with thermostats, instead run the boiler on weather compensation. New houses have quite low heating demands and when we split the stop much the boilers just can't cope and are likely to short cycle - use loads of gas for heat given out. Good boilers are Intergas, Atag, Vaillant and Viessmann. There are others but no experience. Tell us more about your house, insulation levels air tightness ventilation etc Solar PV yes, solar thermal will disappoint. But all the above said you should really a do heat pump. Heat pump £2500, cylinder £1000, not much other costs, run the UFH direct from heat pump, 3 port valve to either cylinder or UFH. Link to comment Share on other sites More sharing options...
Gilli99 Posted June 12 Author Share Posted June 12 JohnMo That is really helpful thanks. The house is very well insulated, has triple glazing, and air tightness target is less than 1. Link to comment Share on other sites More sharing options...
JohnMo Posted June 12 Share Posted June 12 2 minutes ago, Gilli99 said: JohnMo That is really helpful thanks. The house is very well insulated, has triple glazing, and air tightness target is less than 1. I started combi, every room Thad a thermostat and my first quarter bill was a 100% more than expected. Over a couple of years got it down to one thermostat in the house and heated on a batch basis. So heated floor once a day for 4 to 7 hours, to compensate for the boiler being too big. Got the system really efficient. But doing it again X plan every time Another read IG_The-Knowledge_PDF_Final.pdf Link to comment Share on other sites More sharing options...
Gilli99 Posted June 16 Author Share Posted June 16 'JohnMo just another thought.... if I have a tank, is it the case that it just an immersion it needs to allow an Eddi system to work? The plumber says it needs a double coil cylinder which is about £400 more than a regular tank. I am so confused! Link to comment Share on other sites More sharing options...
JohnMo Posted June 16 Share Posted June 16 17 minutes ago, Gilli99 said: 'JohnMo just another thought.... if I have a tank, is it the case that it just an immersion it needs to allow an Eddi system to work? The plumber says it needs a double coil cylinder which is about £400 more than a regular tank. I am so confused! So I get notifications start by typing"@" then the user name from the drop down that appears. You only need a single coil. I use a cool energy diverter, this has a timer that allows to time immersion running or you can just leave it in diverter mode. So your plumber is talking rubbish, a double coil is for solar thermal, not for PV diversion. Above all else get a heat pump cylinder with as big coil as you can get, with X plan (or Priority demand hot water). Link to comment Share on other sites More sharing options...
Gilli99 Posted June 17 Author Share Posted June 17 @JohnMo thanks for the hint! Just to be clear, single coil with immersion is the way to go. My husband is convinced the double coil will work - big argument! Can the double coil work with PV or is it only paired with a solar system? thanks! Link to comment Share on other sites More sharing options...
JohnMo Posted June 17 Share Posted June 17 11 minutes ago, Gilli99 said: Can the double coil work with PV or is it only paired with a solar system Solar thermal is a water based system and it requires a coil to transfer the heat to the cylinder water. However a solar PV system is an electric system, so provides main voltage electric. The only practical way to get heat into the cylinder is via the immersion heater with PV. So the diverter goes between the your consumer unit and the immersion isolation switch. With a CT clamp on the tails to electric meter, when it detects outward electric flow (export) it switches on power to the immersion. So if you are exporting 1kW it diverts 1kW to the immersion. Link to comment Share on other sites More sharing options...
marshian Posted July 17 Share Posted July 17 On 16/06/2024 at 22:09, JohnMo said: So I get notifications start by typing"@" then the user name from the drop down that appears. @JohnMo my thanks also for that handy tip - could not work out how to tag users - so simple now you've pointed out how to do it Link to comment Share on other sites More sharing options...
sharpener Posted July 17 Share Posted July 17 On 16/06/2024 at 21:45, Gilli99 said: 'JohnMo just another thought.... if I have a tank, is it the case that it just an immersion it needs to allow an Eddi system to work? The plumber says it needs a double coil cylinder which is about £400 more than a regular tank. I am so confused! Total cobblers as @JohnMo has said. What is he proposing to connect the second coil to, the Eddi or directly to the PV panels<g>? If a well-insulated house you will only need a (proportionately) small HP so why not do it right away? If not then I agree, small system boiler plus heat-pump ready unvented cylinder. Not too big, guidance is 45 litres x (number of bedrooms +1). Explanation of different heating control wiring options at https://flameport.com/electric/central_heating/heating_wiring_S_plan.cs4. Link to comment Share on other sites More sharing options...
JohnMo Posted July 17 Share Posted July 17 12 minutes ago, sharpener said: well-insulated house you will only need a (proportionately) small HP As said above do it once, go straight to heat pump. Q On 12/06/2024 at 21:39, Gilli99 said: Gas heating. Not sure if your heating requirements but a 4 to 6kW Panasonic monobloc doing heat to ground floor UFH only. You need Cylinder with 3m² coil Diverter valve Heat pump UFH with 1.5 storey, do 150 to 200mm centres. Run all from a single manifold, no mixer no pump, no actuators. No thermostat needed either. Set to run weather compensation and then let it get on with it. It will self control itself, without intervention. I now have a single thermostat but use it to switch between heating and cooling only. Don't bother going MCS either, it's not worth the hassle and the rip off factor. Shop around you can do it £7k + cheaper ASHP £2k, cylinder £1k. Getting a combi to work is hard work Read up some of the steps I took getting the heat pump to run how I wanted it too. Miss out the hard work. Link to comment Share on other sites More sharing options...
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