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  1. I seem to have what must be a common problem when using underfloor heating with a boiler however I haven’t managed to find a standard solution online. The boiler cycles at a high frequency due to the difference in boiler power compared to what the underfloor heating manifold will accept. Setup (underfloor heating recently added by local plumber) – see image below Worcester Greenstar Highflow 440CDI combi boiler (Central heating power of ~29kW down to ~7.6kW) Radiators upstairs with separate thermostat and actuated valve on the CH flow. Underfloor heating downstairs with separate thermostat and actuated valve on the CH flow. Manifold including recirculation pump and mixer valve to maintain the inlet manifold temperature at ~40C. " class="bbCodeImage LbImage" alt="" data-url="http://<a href=""><img src="" alt="UFH-current" border="0"></a>" /> Issue The Combi boiler cannot modulate low enough when running the underfloor heating on it’s own therefore it cycles frequently on and off. At a high level, The thermostatic valve on the underfloor heating manifold gets close to the required temperature and throttles flow from the boiler. Boiler flow then bypasses the manifold through the pressure relief circuit and causes the boiler flame to turn off. The flow temperature drops The thermostatic valve on the underfloor heating manifold then starts to open because it’s not getting heat, pulling in cool flow and opening more and more. The boiler restarts when it’s anti cycling timer or temperature limits have been reached and quickly exceeds the underfloor heating thermostatic control valve temperature so the process restarts. If the anti cycle timer is put to it’s minimum of 1 minute, the boiler will run for 1 minute and turn off for one minute (the run time will further reduce when the underfloor heating gets up to temperature). At this frequency the flow temperature remains above the temperature setting of the underfloor heating thermostatic valve so the underfloor is happy. I assume that this boiler operation isn’t efficient and I doubt it’s doing the boiler any favours? When the radiators are operated concurrently with the underfloor heating the CH flow temperature remain stable and the system works nicely. Variables currently available in the system Boiler cycle time or temperature limit, currently 1 minute – If this is increased above 1 minute the underfloor manifold pulls in low temperature water as it cycles and therefore takes a long time to heat up. CH flow temperature, currently 60C – If this is increased it takes a little longer for the boiler to achieve the temperature however an increase of 10C only added 25s to the cycle time (by the time the high temperatures are achieved the boiler is mostly short circuiting around the bypass). Boiler pump speed, currently set to three – Assume a reduction would result in higher temperatures (lower flowrate with the same burner rate?) may also impact on the boiler/radiator operation? Boiler pump operation modes – Don’t know enough Underfloor heating pump speed, currently set to three – Don’t think this will have a significant affect. Underfloor heating thermostatic valve, currently 40C – Increasing this temperature risks overheating the engineered wood flooring. Next steps – help please! Is it a problem to leave the boiler cycling so frequently (1 min on then 1 min off)? Can any of the existing settings be adjusted to help? If current operation is a problem the only significant improvement I can think of is to add thermal mass between the boiler and underfloor heating manifold as follows (see image), any tips on these or is there a better alternative? a. Add pressurised tank (are these referred to as heat banks/or thermal stores?) upstream of the underfloor heating bypass loop. b. Draw the underfloor heating flow through the heat store in the boiler. This is the wild card option and I don’t like it because a connection would need to be made within the boiler (although it is accessible) and there may be an unforeseen impact on the hot water supply. I’ve mentioned it because it wouldn’t require another tank to locate, continually heat or pay for! " class="bbCodeImage LbImage" alt="" data-url="http://<a href=""><img src="" alt="UFH-options" border="0"></a>" />
  2. This story seems to come up every so often, regarding people with electric boilers and massive electricity bills. It allows the Daily Mail to pander to their older readers who believe everything new is bad. Reading this story though, I couldn't help but wonder did Falkirk Council deliberately install boilers that would be very expensive to run as I suspect installing electric boilers was a lot cheaper for them than installing gas boilers and the running costs weren't their problem. It is now exacerbated by people being locked into some very expensive electricity pricing, but anyone who knows the price of electricity versus gas knows that this would create a massive increase in heating costs. The story keeps calling them eco boilers. In no way should an electric combi be called an eco boiler, clearly people have no idea of the difference between these and ASHPs. The DM then have a further story today about banning every new home being connected to the gas grid, that ASHPs will cost £10k to fit and that they won't work in older poorly insulated houses. Assuming that gas boilers are eventually banned, then over time they can be replaced with ASHPs, however, I was thinking is this as simple as it seems? Even relatively modern houses will have heating systems designed to use 75C hot water from a gas boiler. Is the replacement of boilers as simple as it seems?
  3. Grateful for advice on the following. I'm doing a self build in the Stirling area. Its a five bed property (180m2 in total) with ufh downstairs (120m2) including three bedrooms downstairs and two bedrooms upstairs with rads. One bathroom and three en-suites in total. I was hoping for some advice on boiler and UVC sizing? We will be required to install PVs so I'm also wondering what issues to consider in terms of integrating it with the heating system/hot water? Looking for the most cost effective option. I did consider ASHP but have decided to opt for LPG and PVs. Any pointers much appreciated.
  4. Hi everyone. New to the group and was hoping for some advise. I have a JG underfloor heating system installed under my kitchen and through to a downstairs toilet where the pump and manifold are fitted. In the loft above the toilet run the 25mm flow and return direct from the boiler. Can I tee into these to supply the ufh? I have a cable run in from this (ufh thermostat)to the controller in the airing cupboard which I was hoping to link across the heating switch?? Sorry if this is vague or my terminology is not very good. Any advise appreciated. Thanks in advance
  5. Hi everyone. New to the group and was hoping for some advise. I have a JG underfloor heating system installed under my kitchen and through to a downstairs toilet where the pump and manifold are fitted. In the loft above the toilet run the 25mm flow and return direct from the boiler. Can I tee into these to supply the ufh? I have a cable run in from this (ufh thermostat)to the controller in the airing cupboard which I was hoping to link across the heating switch?? Sorry if this is vague or my terminology is not very good. Any advise appreciated. Thanks in advance
  6. I was just lloking into the different systems available for heating/Hot water. Some Great systems are used by the members on here and I am tempted to use a Genvex Combi like @PeterStarck as it seems amazing logical to combine it all with the MVHR. However, i just found this : It seems an incredible good system, even though not including the MVHR , but still a very good, space saving method which seems easy to use/install. Website is in Norge so anybody wanting a look might need to look at their NZ distributor as I couldn t find UK or even US website Anybody on here ever looked into this? Is it a good system, or not really worth the trouble ordering from Norway as similar exists in the uk(which ones>? )
  7. My builders plumber is recommending a WB Greenstar 30i as a new boiler to replace my (very old but very reliable) Potterton Prima 50F. In terms of output the WB is about twice that of the Potterton (30kw compared to 15) so presumably should easily cope with the existing upstairs rads (4 beds, 2 baths & landing) and the new UFH we're installing downstairs (around 110m2, approx 7kw total output). I notice its a system boiler with built in pump so presumably my existing circulation pump will be redundant. Any advice on this boiler or things to look out for? Thanks
  8. Of getting someone to commision a boiler/ufh system when it is already installed but not commissioned or pressure tested. So much for having plumbers I can rely on. They installed the boiler and ufh control last week. Everything was supposed to be finished by last Friday but unfortunately it wasn't. They left at 8pm last Friday with promises to come back today (Thursday) to complete. Couldn't get before then because of other promised work. Message at lunchtime today to say that they couldn't make it but 'should' be able to come next Thursday or Friday. The week after next, one is going away for the week (and the van is his). Absolutely fed up with this now. I should have been able to move in next week.
  9. I have a feeling I'm being taken for a ride. The chap we've used for around 15 years or so to service our boiler retired a year or so ago, and now the house is up for sale I've been advised that I need to provide evidence of an up-to-date service, which is fair enough. I've witnessed every service on this boiler, and on average it's taken under an hour, and has essentially been a visual inspection inside the boiler, a flue gas check, gas pressure check and a quick test to make sure the controls are working. If asked the chap would also have checked and cleaned the Magnaclean and topped up the inhibitor, but I usually do that every year anyway, so that's never been included. I can't remember what we used to pay, but I'm pretty sure it was well under £100. I asked around last week to try and find someone to come out and do a service and check, and those that have come back so far are looking for well North of £200. I reckon this is OTT, but maybe I've just been getting a good deal from the chap I've been using for years. The boiler in question is a wall mounted and easy to access Vaillant EcoTec Plus 831, with just a single wired programmable thermostat. Everything is easy to access, and nothing needs to be moved to get at either the boiler or the Magnaclean, which is mounted on the wall next to it. Am I just out of touch with boiler servicing costs?
  10. Needing to focus on my next project after my UFH fiasco and being in a holiday rental place where the DHW is very hit and miss reminds me that I need to get some specs laid down before I start ordering stuff! Having read so much over the past couple of years, I feel a lot more informed but also a bit bamboozled at the same time. UVC or TS, buffer tanks, what size..... So my main questions (so far): 1) what type of gas boiler to go for? 2) Thermal store or UVC? 3) Buffer tank needed? My setup will be: 4kw solar PV Mains gas 2 UFH manifolds (upstairs and groundfloor - so I can choose the flow temps accordingly to get the maximum comfort levels) Room stats in all areas 2 Bathrooms (2 showers, 2 baths) MHVR Although not going to be a passivhaus, I’m hopeful it'll be a bloody whole let better than your standard newbuild: 2 SIP extensions 300mm EPS floor insulation 3G windows/doors 100mm EWI on existing house DHW requirement: 2 adults and two soon to be teenagers (so they will hardly wash reducing the DHW figures a bit) 2 morning showers 2 evening baths Hot water for washing up (though may get a boiler-type tap for most hot water needs in the kitchen) Occupancy: Wife and kids out and I although I work from home, my office will be one of the sheds out the back so main house can either be set to off or very low temps during the day. UFH demands: Groundfloor: Water volume: 129L; Estimated loading: 9.45Kw Upstairs: Water volume: 25L; Estimated loading: 2.03Kw BOILER QUESTION: Before I start getting plumbers out to fit a boiler system, I’d like to get people’s advice on whether to go for system or combi. Combi = don’t need a water storage cylinder = no need for cistern in loft = combi boilers don’t supply enough hot water = better to use a separate cylinder for the hot water supply. = combi boilers can be quite noisy. System = Store hot water in a cylinder, so they can feed several outlets at once at mains pressure. = no need for a cistern in the loft and the expansion vessel is built in. = Flow rates will be high as water is delivered at mains pressure, and hot water is instantaneous. I'm thinking to go for a system boiler at this stage (easier/quicker install) and then to use excess PV with the cylinder. THERMAL STORE OR UVC? My thoughts so far are to have a 300L UVC fed partly by the solar PV during the day (using an Immersun type of device) with maybe E10/E7 at night and then also the gas boiler. I would end up with two circuits – one for DHW and one for UFH. The boiler would kick in for the UFH when the UVC doesn’t require heat. BUFFER TANK? I'm also thinking that if I go for a UVC rather than thermal store (from what I have read on here) I would need a buffer store seeing I will have UFH. But I've read that if I opt for a TS, that can be my buffer tank also. So perhaps I should go for a TS rather than a UVC? Confused.... Hoping someone (AKA: @Nickfromwales etc) is able to assist..... Thanks, OB
  11. Hi, I'm not entirely sure if this post belongs here but there are several components that I think I should consider as part of one solution: Heating and Hot Water. You may be familiar with my project from the introductions forum but I'll present you with my circumstances in any case. I currently have a Combi Boiler heating our traditionally constructed 2700sq.ft bungalow and providing hot water to 2 showers (right now we use 14000 kWh Electricity and 48907 kWh Gas per annum!). We will be updating the current building with thicker loft insulation and better windows, but will still use rads to heat this portion of the house when we complete the renovation. The new part of the house will add around 6000sq.ft and will be built to much better u values using ICF walls and SIPS roof. Here's where I'm confused, I don't know what the best system will be that can provide loads of hot water (7 showers), heat UFH in the new part and also heat the rads in the old part. I'm further confused by mhrv, I've heard this is a necessity in ICF homes, but then heard the speaker at the homebuilding show at NEC state that they're pointless for homes over a certain size. I'm open to installing an ASHP but I'm not sure whether it's necessary or even beneficial when I have the option of mains gas. Lastly, I've a good size roof pointing SE without any shading to speak of so we could potentially generate a considerable amount electricity, but I would have to consider the regulations of having a system over 4kWh and the costs associated, also factoring potential battery storage over and above Sunamp if this too makes sense to use. I don't have a clue where the feed in tariff comes in to all this! There will also be a detached annexe of around 800sq.ft and we will most likely go with UFH and 1 shower, I'm not sure how this should be incorporated in to the overall scheme or whether I should treat it separate. I know its probably a good idea to speak with an energy solutions firm and will most likely speak with Stratford Energy Solutions who have been recommended to me, however, I also know that they may have commercial interests that don't take in to account all of the factors we self builders consider.
  12. Just on the off chance, does anyone know what the diameter of the fire rope for the Fire Door is? I have the manual, (it doesn't say what the diameter is) I have rung the supplier; the lass had no idea what the diameter is. So, as usual, I end up on BH asking everyone else. Phhh....
  13. @Nickfromwales Telford seem a good bet for supplying my UVC. As per other post on UFH with rads but I will now site the tank in the cellar and have an external boiler (fluing from the cellar is a pig and looks expensive). So presume new system boiler and UVC or TS. Can't invest in solar now, or air-source hp as no funds left. See system below I got quoted from Greensquare. Should I not have a buffer if going uvc?
  14. Having over spent on unexpected items we've had to put our plans for a garage to a halt. We planned to put the boiler in garage but without the garage where to we locate the boiler, inside or outside? Ufh downstairs and rads upstairs. Any thoughts would be appreciated
  15. Hi all, Just looking for some views on what system we should put into our self build. Some details. Timber frame - walls at 0.14, floor 0.1, ceiling 0.1. Ufh downstairs with rads upstairs. Mains gas available. 4 bed, 3 bathrooms. May fit solar pv if we can get panels at the right price. Was thinking of gas boiler feeding into thermal store. Immersion top & bottom ready for pv or as a backup. Any thoughts? CC
  16. Excerpt from a previous thread. A member asked..... "Starting our extension and renovation fairly soon so I am now looking at the type of heating system to go for. The house is roughly 100m² footprint and 450m³ volume. Insulation levels are expected to be better than building reg standard but not upto PH standard. Plan for heating and DHW in the house is as follows: UFH throughout with no rads, two towels warmers to be used though. One bath, two showers and four sinks (not decided whether both showers will be DHW or one electric yet but say both DHW for this example). Average usage of one shower and one bath per day From jsharris spreadsheet I figure that my worst month at minimum OAT heat input would be 1398kWh based on daily heat loss power of 1878W. Ideally we would like the boiler hidden from view and this could be house in either the garage or loft as both have ample space. We have both gas and electricity to the house so we are open to a wide range of possiblilities. Anyone have any thoughts on which type of boilers I should be considering? As far as manufacturers go I am willing to invest a little more for better quality (brands I have investigated so far are Valliant, Baxi and Ideal).