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combi boiler - efficiency and cost
"JimGC" wrote in message ... Bear with me a moment ... I'm shocked at the cost of running my small flat's combi boiler compared to my previous terraced house boiler which had a hot water tank. The cost has doubled (3bd house HW/CH with 4 occupants was £360pa over the year, 1 bd flat combi HW/CH with 1 occupant ran up £60 in December alone!) The flat is fairly modern (1982) in good condition, and I have the water/ch on from 6-9am and from 4-11pm, turning it off when CH gets too hot. Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. The reason for posting here is that I have already asked about the inability of the boiler to provide a constant flow of hot water. (CH seems to be very hot whenever it's on whatever the thermostat on the boiler is set to). Is it possible that the boiler has faulty thermostats and is failing to provide constant hot water, but also using way too much gas to feed the CH? Or am I just paying the price for having this kind of boiler? Is it possible that I'm using the combi boiler in the wrong way, and that these fixed timing settings are not appropriate to combis? You are not heating the water with the timer when using a combi. It may be you need thermostatic radiator valves and a room thermostat fitting to make the system much more efficient, especially with the comment you have to turn the boiler off when the CH gets too hot. The TRVs I fitted payed for themselves in no time. Read http://www.diyfaq.org.uk/contents.html Adam |
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ARWadsworth wrote: "JimGC" wrote in message ... Bear with me a moment ... I'm shocked at the cost of running my small flat's combi boiler compared to my previous terraced house boiler which had a hot water tank. The cost has doubled (3bd house HW/CH with 4 occupants was =A3360pa over the year, 1 bd flat combi HW/CH with 1 occupant ran up =A360 in December alone!) The flat is fairly modern (1982) in good condition, and I have the water/ch on from 6-9am and from 4-11pm, turning it off when CH gets too hot. Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. The reason for posting here is that I have already asked about the inability of the boiler to provide a constant flow of hot water. (CH seems to be very hot whenever it's on whatever the thermostat on the boiler is set to). Is it possible that the boiler has faulty thermostats and is failing to provide constant hot water, but also using way too much gas to feed the CH? Or am I just paying the price for having this kind of boiler? Is it possible that I'm using the combi boiler in the wrong way, and that these fixed timing settings are not appropriate to combis? You are not heating the water with the timer when using a combi. It may be you need thermostatic radiator valves and a room thermostat fitting to make the system much more efficient, especially with the comment you have to turn the boiler off when the CH gets too hot. The TRVs I fitted payed for themselves in no time. Read http://www.diyfaq.org.uk/contents.html Adam Are you paying for the gas via a prepayment meter? If so, the charge rate could be set too high. |
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JimGC wrote:
Bear with me a moment ... I'm shocked at the cost of running my small flat's combi boiler compared to my previous terraced house boiler which had a hot water tank. The cost has doubled (3bd house HW/CH with 4 occupants was £360pa over the year, 1 bd flat combi HW/CH with 1 occupant ran up £60 in December alone!) The flat is fairly modern (1982) in good condition, and I have the water/ch on from 6-9am and from 4-11pm, turning it off when CH gets too hot. Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. Given that you currently have the heating on, and many months of the year you don't, I would expect to the difference between worst and best months to be closer to 90% (i.e. most hours of the day you won't be using any hot water and hence the boiler will be using no gas at all). So a sample of costs taken from one month like this tell you nothing really. The reason for posting here is that I have already asked about the inability of the boiler to provide a constant flow of hot water. (CH seems to be very hot whenever it's on whatever the thermostat on the boiler is set to). That sounds like you do not have full thermostatic control in place (i.e. room stat, and thermostatic radiator valves on all rads (except the one in the room with the room stat). Is it possible that the boiler has faulty thermostats and is failing to provide constant hot water, but also using way What do you mean by failing to provide constant hot water exactly? (i.e. it works when the tap is first turned on, but the goes completely cold, or does it run warm but not as hot as when you started etc). There are several issues he Firstly the thermostat for hot water in a combi just sets the upper limit on the temperature. i.e. if you are using hot water it should not supply it at a temperature exceeding that set on the stat. The lower limit is usually set by the laws of physics. The boiler can provide heat at a rate governed by its basic design (tell us the make/model number and we can give you more info). The more powerful the boiler, the more water it can heat in a given time. Hence if you ask for a small flow of hot water it will supply it at a temperature governed by the HW stat. As you turn the tap on more, you reach the limit of the boilers power where even running flat out it can still not heat the water to the stat temperature and the temperature of the water will begin to fall. Select a high enough flow rate and it will not be able to heat it enough to get it to a usable temperature. There is yet one more issue, that there can be times when you are asking for a small amount of hot water that the boiler is producing heat too fast such that it would end up exceeding the stat temperature an hence it has to turn off its burner. Some combis also use a relatively insensitive flow switch which requires a good flow of water to be requested before they will switch to hot water mode. The moral of the story is that you need to choose your combi carefully since there are lots of crap combis on the market, with too little power, and lots of quirks when running. Alas if you landlord made the choice for you you can probably guess what end of the market he went for! too much gas to feed the CH? Or am I just paying the price for having this kind of boiler? Is it possible that I'm All things being equal with the boilers efficiency, there is no reason for a combi to be less efficient than a system boiler with a hot water cylinder. In fact it will tend to be more efficient since there is less risk of you loosing energy from the stored hot water. Having said that, any boiler can be run inefficiently with poor (or no) control systems. You can also get a large variation in basic efficiency between different boilers (i.e. the worst will give perhaps 70p worth of heat for every pounds worth of gas, the best will give over 96p worth of heat). using the combi boiler in the wrong way, and that these fixed timing settings are not appropriate to combis? Could well be. I plan to get a CORGI man in early in the new year to give it the once over, landlord or not! May help. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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"JimGC" wrote in message ... Bear with me a moment ... I'm shocked at the cost of running my small flat's combi boiler compared to my previous terraced house boiler which had a hot water tank. The cost has doubled (3bd house HW/CH with 4 occupants was £360pa over the year, 1 bd flat combi HW/CH with 1 occupant ran up £60 in December alone!) The flat is fairly modern (1982) in good condition, and I have the water/ch on from 6-9am and from 4-11pm, turning it off when CH gets too hot. Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. The reason for posting here is that I have already asked about the inability of the boiler to provide a constant flow of hot water. (CH seems to be very hot whenever it's on whatever the thermostat on the boiler is set to). Is it possible that the boiler has faulty thermostats and is failing to provide constant hot water, but also using way too much gas to feed the CH? Or am I just paying the price for having this kind of boiler? Is it possible that I'm using the combi boiler in the wrong way, and that these fixed timing settings are not appropriate to combis? I plan to get a CORGI man in early in the new year to give it the once over, landlord or not! In a block of flats - two absurd questions? ) Are you reading *your* gas meter? Is another flat connected to your meter? Keith G. Powell |
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In article , JimGC wrote:
Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. FWIW the gas consumption for each quarter averaged over the last ten years here has been Feb bill: 45%; May: 32%; Aug: 8%; Nov: 15% -- Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm |
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"JimGC" wrote
| This flat is a 1982 conversion and the boiler is almost | certainly the original Worcester Heatslave 2+. I have | checked it for CO and it's okay, my landlord's agent tells | me it is checked annually. The landlord's agent might tell you that, but by law they MUST give you a copy of the Landlord's Gas Safety Certificate. Owain |
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"JimGC" wrote in message ... Bear with me a moment ... I'm shocked at the cost of running my small flat's combi boiler compared to my previous terraced house boiler which had a hot water tank. The cost has doubled (3bd house HW/CH with 4 occupants was £360pa over the year, 1 bd flat combi HW/CH with 1 occupant ran up £60 in December alone!) The flat is fairly modern (1982) in good condition, and I have the water/ch on from 6-9am and from 4-11pm, turning it off when CH gets too hot. Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. Can you clarify exactly what you mean by you have the water/ch on? Are you perhaps using a two channel programmer in error as most combis have the HW permanently available regardless of the timer function for the central heating. In this case perhaps the installer wired up the two channel programmer so that ch is on even if the programmer thinks it is switching the hot water. Try to tell us what make and model of combi, what make and model of programmer etc you have installed. The reason for posting here is that I have already asked about the inability of the boiler to provide a constant flow of hot water. (CH seems to be very hot whenever it's on whatever the thermostat on the boiler is set to). CH on some combis is a fixed temperature the thermostat on the front is for hot water, however you could have two adjustable thermostats again it depends on the make and model of combi. Is it possible that the boiler has faulty thermostats and is failing to provide constant hot water, but also using way too much gas to feed the CH? Or am I just paying the price for having this kind of boiler? Is it possible that I'm using the combi boiler in the wrong way, and that these fixed timing settings are not appropriate to combis? See above |
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JimGC wrote:
This flat is a 1982 conversion and the boiler is almost certainly the original Worcester Heatslave 2+. I have checked it for CO and it's okay, my landlord's agent tells me it is checked annually. Now I am a bit confused... the only "heatslave 2" models I could find are all conventional boilers and not combis. If yours is one of those then that would suggets that you have a hot water cylinder somewhere. (A combi heats the mains cold water directly - there is no stored hor water). I plan to turn the CH off and put the thermostat to High then try to run a bath. I think this would have happened in the autumn anyway (admittedly with the thermostat on low) and cold water after a few minutes still happened. Again witha combi this is normally a non issue. It has a CH mode and a HW one. When you turn on the hot tap the boiler goes to HW and stays there until you turn off the tap. Hence you get no heating when dawing hot water anyway. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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JimGC wrote:
HW/CH selection: ---------------- HW All day/CH Off HW All day/CH Twice HW All day/CH All day HW Twice/CH off HW Twice/CH Twice HW Twice/CH All day I usually have it on HW Twice/CH Twice. Is this programmer built into the boiler or separate? If it is built in, then I susspect were are not talking about a combi boiler here at all, since the concept of HW twice makes no sense. With a combi the HW should always be available. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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John Rumm wrote:
JimGC wrote: HW/CH selection: ---------------- HW All day/CH Off HW All day/CH Twice HW All day/CH All day HW Twice/CH off HW Twice/CH Twice HW Twice/CH All day I usually have it on HW Twice/CH Twice. Is this programmer built into the boiler or separate? If it is built in, then I susspect were are not talking about a combi boiler here at all, since the concept of HW twice makes no sense. With a combi the HW should always be available. If the Worcester Heatslave is the machine I'm thinking of it does indeed have a CH + HW programmer, and it is a combi. Some combis come on from time to time to keep the water in the heat exchanger hot so you have really instantaneous hot water when you turn on a hot tap, so I guess this boiler uses the HW programmer setting to determine when to do this. If the diverter valve is on the blink it might just explain why it carries on heating up for 10 minutes, and also whey you only get lukewarm water after the initial spurt of scalding hot water. It's probably also well past its sell-by date. |
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On Mon, 03 Jan 2005 00:22:55 GMT, JimGC
strung together this: Now I am a bit confused... the only "heatslave 2" models I could find are all conventional boilers and not combis. If yours is one of those then that would suggets that you have a hot water cylinder somewhere. Ah well, thanks - any more suggestions or help will be very welcome! Hmm, from information I've found it could be either so it's a draw! From some spares lists I've found it would appear that it is one of those conventional boilers with the pump and valves built into it. I think I've worked on a couple before, is it the one with a big turn dial programmer on the right? I could be way off the mark here but it is late! -- SJW Please reply to group or use 'usenet' in email subject |
#12
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John Stumbles wrote:
If the Worcester Heatslave is the machine I'm thinking of it does indeed have a CH + HW programmer, and it is a combi. There seems to be a huge number of "heatslaves" some combi and some not. Obviously decided that once they have a good name they ought to stick with it! Some combis come on from time to time to keep the water in the heat exchanger hot so you have really instantaneous hot water when you turn on a hot tap, so I guess this boiler uses the HW programmer setting to determine when to do this. If the diverter valve is on the blink it Yup could be... (My Isar does the pre tempering bit, but it is not something you can turn off as such) might just explain why it carries on heating up for 10 minutes, and also whey you only get lukewarm water after the initial spurt of scalding hot water. It's probably also well past its sell-by date. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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JimGC wrote:
John Stumbles wrote: If the Worcester Heatslave is the machine I'm thinking of it does indeed have a CH + HW programmer, and it is a combi. Now I've checked a little further, I'm sure it is. It's the programmable deluxe model, circa 1982! .... It's probably also well past its sell-by date. Absolutely. If I owned this flat it would be replaced tomorrow. As I don't, I'm not quite sure where I stand. Should the owner replace or repair it? Do you mean: should they do _something_ about it, or do you mean which? I assume it's the landlord's appliance (it'll say so on the landlord's gas safety certificate - which they _have_ given you a copy of, haven't they?!) so it's up to them to sort it out (though that's a matter between you and them and any tenancy agreement you have, as with any other repairs). As such I wouldn't be getting any repairs done off my own bat, though you may have to get a repairer in to testify that it's faulty to have leverage to get your landlord to deal with it. At £1000+ for the replacement, I'm not sure they'll take kindly to that.. ! But I'm certainly not paying £1000 in a flat with a short term arrangement such as I have right now .. If they can get it repaired (i.e. parts available and appliance is safe to use) then fair enough: once it's fixed it shouldn't be desperately expensive for you to run even if it's a pilot light model (which I think it is). However it's not going to last much longer so IMHO it would be a bit short sighted of your landlord to patch it up rather than replace it. But that's landlords for you :-) |
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JimGC wrote:
Now I am a bit confused... the only "heatslave 2" models I could find are all conventional boilers and not combis. If yours is one of those then that would suggets that you have a hot water cylinder somewhere. Ah! Now I'm confused too - but that's why I wrote to the group! The only Heatslave boilers I could find on a Yup, if you want confusing here is the place to come ;-) websearch were described as combi - I also wrote to Worcester Bosch Technical support describing the problem have received the following reply: "Thank you for your recent enquiry. Switch off the C/H demand and allow to cool, then with a demand for DHW check for power (230v AC) at terminal T4. If power present, it would indicate a possible fault with the DHW priority thermostat. If no power present, check the diverter valve for let by to C/H." (the fault finding info you got from WB would establish if the diverter valve is getting the right signal to switch to HW mode. The diverter is the bit of a combi that will "divert" the heated water away from the heating circuit, and toward (typically) a secondary heat exchanger to heat the water for the taps) Didn't make a lot of sense to me, but he didn't contradict my description of the boiler as a combi. If you look at the Sedbuk boiler database thingy (follow the link at the bottom of Tony Bryer's post to download a copy), they list some 35 different "heatslave" boilers. Some are combis, and some not. So it is not too supprising that they did not contradict your description given the range of boilers with the same name is vast. The Heatslave 2 G50 is shown in two versions - one conventional flue, one balanced. Neither are combis. Both have a lowish power output of under 15kW. Production date is shown as 1984 which sounds like the right sort of ball park. The maintenance and installation instructions for this boiler (hidden in an old box!) doesn't explicitly say it's one or the other, but it only talks of a feed and expansion cistern with no indication of a water tank. In fact it talks Again feed and expansion suggests an open vented heating system. Many combis would use a sealed system. Details of these he http://www.makewrite.demon.co.uk/SealedCH.html more about flow rate regulation etc which I assume is related to combis - it gives an Optimum Flow rate through the heat exchanger of 3gpm (whatever that is!) They could be talking about a flow rate through the boilers heat exchanger (i.e. the bit that transfers heat from the flame to the water) of three gallons per minute. Typically the heating system is a closed loop of pipework (and radiators) with a pump to circulate the water. Each pass made by the water through the boiler will raise its temperature a "bit" (the size of the "bit" will depend on many factors, but 10 to 20 degrees C per pass is quite common). If they were talking about the flow rate delivered by the HW side of a combi then 3gpm (or 13.5 litres/min) would suggest a pretty powerful boiler (say 35kW or more). None of the heatslaves seem to have that sort of power. I think it is a combi, (specifically, the Worcester Heatslave 2+ G50 Deluxe) though I'm happy to be proved wrong if it's not. I suspect my next move is to get a CORGI engineer in to do the above checks and give the thing a once over - not just for safety but for operating efficiency. I wonder whether this is my responsibility or the landlord? Ah well, thanks - any more suggestions or help will be very welcome! I could be wrong, but from your descriptions I would guess you have a conventional boiler. Which would mean you also have a hot water cylinder somewhere (airing cupboard?), and there would be a pump somewhere. If that is the case, then there could be a number of ways the whole thing is plumbed up, and hence a number of ways for it to go wrong. Either way describing your problem to a plumber who can actually look at the thing should get you closer to a solution. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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"John Stumbles" wrote
| JimGC wrote: | Absolutely. If I owned this flat it would be replaced | tomorrow. As I don't, I'm not quite sure where I stand. | Should the owner replace or repair it? | Do you mean: should they do _something_ about it, or do you mean which? | I assume it's the landlord's appliance (it'll say so on the landlord's | gas safety certificate - which they _have_ given you a copy of, haven't | they?!) so it's up to them to sort it out (though that's a matter | between you and them and any tenancy agreement you have, as with any | other repairs). Although for a short term rent it should be the landlord's responsibility (possibly even if the tenancy agreement says differently). The landlord can't let an uninhabitable house, which is what a house without hot water is considered to be nowadays. CAB might be a good point of contact, or some councils have housing advice services that will deal with private sector rents. | As such I wouldn't be getting any repairs done off my | own bat, though you may have to get a repairer in to testify that it's | faulty to have leverage to get your landlord to deal with it. It is probably against the tenancy agreement for the tenant to make any alteration to the property; if the OP does any work on the boiler the landlord might claim it is damaged and pursue the full costs of replacement against the tenant :-( | If they can get it repaired (i.e. parts available and appliance is safe | to use) then fair enough: once it's fixed it shouldn't be desperately | expensive for you to run even if it's a pilot light model (which I think | it is). However it's not going to last much longer so IMHO it would be a | bit short sighted of your landlord to patch it up rather than replace | it. But that's landlords for you :-) If it can be patched up to last until the warmer weather that might be preferable to leaving a tenant without heating. Owain |
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"JimGC" wrote
| I suspect my next move is to get a CORGI engineer in to | do the above checks and give the thing a once | over - not just for safety but for operating efficiency. I | wonder whether this is my responsibility or the landlord? It is your landlord's duty to provide you with a copy of the current annual Landlord's Gas Safety Certificate. Failure to do so is a criminal offence. It is also his responsibility to keep the heating and hot water systems in usable order which I think includes telling you how to work them. Operating efficiency (cost of running) is not an obligation, however, and will not be checked by a safety inspection. Owain |
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"JimGC" wrote in message ... "John" wrote: Can you clarify exactly what you mean by you have the water/ch on? Are you perhaps using a two channel programmer in error as most combis have the HW permanently available regardless of the timer function for the central heating. In this case perhaps the installer wired up the two channel programmer so that ch is on even if the programmer thinks it is switching the hot water. Try to tell us what make and model of combi, what make and model of programmer etc you have installed. It's a Worcester Heatslave 2+ from 1982 (when these flats were converted, I believe). As it's a rented flat I won't be likely to have it replace but I'm sure I can persuade the landlord to have it fixed, if possible! It has the following settings: Programme: ----------- Off Constant Programme (timer with 1-on,2-off,3-on,4-off) Temp: ------ High-Medium-Low HW/CH selection: ---------------- HW All day/CH Off HW All day/CH Twice HW All day/CH All day HW Twice/CH off HW Twice/CH Twice HW Twice/CH All day I usually have it on HW Twice/CH Twice. Ah then you do have a two channel programmer, the Heatslave is fairly unusual in this respect. Most folks would run this device HW all day, CH twice (YMMV) That way you can use hot water at any time you are awake i.e. dawn till bedtime. The heatslave has a primary hot water "store" which remains hot while the boiler is on duty and this is pumped around a secondary heat exchanger whose job is to use the high temperature primary water to heat up the secondary (tap) water. For the test tonight, I ran a bath with it set to HW All Day/CH Off, with Temp set to High, and the programme to Constant. Same story: the burner is going like the clappers (heard, not seen) but after a couple of minutes max of very hot water it gets cooler until lukewarm after 5 minutes. Burner still going like clappers, but radiators have cooled down. From the above I'm beginning to suspect that you may have an excessive flow rate for your secondary (tap) water and what is happening is the heat removed from the store is not replaced as fast as you are taking it away. It is possible also that your burner is not producing heat at the full rate it should be but I'd look at the tapwater flow rate before diving into the combustion side Given what I've read here it seems very strange that the burner is on (easy to hear it fire up) when only the HW is selected, and nothing is drawing on the water supply. Not really it is charging up the heatstore or replacing losses when it slowly cools down Hope this helps with some ideas! Thanks... To start with take a two gallon (9litre) bucket and fill it from your fastest flowing hot tap - usually the bathtap. Time this operation to a reasonable degree of accuracy and let us know what your results are. The more recent heatslaves are probably much better in all ways than the old ones but once you have carried out the timing test allow the heatstore to recover then try reducing the flow rate to something around two gallons a minute and see if the running out of hot water still persists. I don't have the performance figures of the heatslave to hand but you may find them in the installation and service booklet if its still with the boiler (faint hope). Otherwise Worcester can no doubt provide this info. |
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"John Stumbles" wrote in message ... JimGC wrote: John Stumbles wrote: If the Worcester Heatslave is the machine I'm thinking of it does indeed have a CH + HW programmer, and it is a combi. Now I've checked a little further, I'm sure it is. It's the programmable deluxe model, circa 1982! ... It's probably also well past its sell-by date. Absolutely. If I owned this flat it would be replaced tomorrow. As I don't, I'm not quite sure where I stand. Should the owner replace or repair it? Do you mean: should they do _something_ about it, or do you mean which? I assume it's the landlord's appliance (it'll say so on the landlord's gas safety certificate - which they _have_ given you a copy of, haven't they?!) so it's up to them to sort it out (though that's a matter between you and them and any tenancy agreement you have, as with any other repairs). As such I wouldn't be getting any repairs done off my own bat, though you may have to get a repairer in to testify that it's faulty to have leverage to get your landlord to deal with it. At £1000+ for the replacement, I'm not sure they'll take kindly to that.. ! But I'm certainly not paying £1000 in a flat with a short term arrangement such as I have right now .. If they can get it repaired (i.e. parts available and appliance is safe to use) then fair enough: once it's fixed it shouldn't be desperately expensive for you to run even if it's a pilot light model (which I think it is). However it's not going to last much longer so IMHO it would be a bit short sighted of your landlord to patch it up rather than replace it. But that's landlords for you :-) See my other post on this unit. The more modern heatslaves suffer from excessive numbers of plastic bits but generally are relatively simple if a bit on the bulky side. I could see everything about this combi even at its age being replaceable. In short unless the landlord is feeling particularly flush its gonna be a fixit job. :-) |
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"JimGC" wrote in message ... John Rumm wrote: So a sample of costs taken from one month like this tell you nothing really. Fair point, and if I optimistically assume the winter quarter as 50% of the annual bill, and assume December (with holidays) is 50% of the Winter quarter, I get an annual bill of £240 or £20pm which is much better, though my 3bd townhouse has an annual bill of £360 with 2-4 occupants! What do you mean by failing to provide constant hot water exactly? (i.e. it works when the tap is first turned on, but the goes completely cold, or does it run warm but not as hot as when you started etc). Get a thermostatic mixer valve inbetween the boiler DHW out and the hot water taps, that will minimize the temperature swings, but will not do anything to the boiler not being able to keep up with a large load! Combi boilers are a good idea on paper, because they make for a very simple installation (ie. you can get rid of the DHW tank) but are seldom up for the job simply because they cannot provide enough hot water when you want to take a good long shower. I have this in another thread, but briefly if I try to run a bath (however slowly) the hot tap runs very hot for 30secs then drops from warm to cold in 5 minutes or so. At best I can only get half a bath of comfortably hot water. Then get a thermostatic showervalve, that will use only the hot water required to satisfy your requirements regardless of water temperature comming from the boiler. The boilr will still have to be able to keep up with your use of hot water, but you don't get scalded and then waste a lot of hot water waiting for it too cool down or waste it trying to get the shower set correctly. There are several issues he Firstly the thermostat for hot water in a combi just sets the upper limit on the temperature. i.e. if you are using hot water it should not supply it at a temperature exceeding that set on the stat. I have the boiler thermostat on Low (out of L-M-H). I can here the thermostat click if I turn the dial up and down, but I still get steaming water for 30 seconds or so when I ri8unthe tap with the thermostat on Low. I tried running a bath with HW/CH running on High with no difference to the temperature of the flow. That maybe because some combi boilers come with a small hot water tank that is used to small loads, ie. a little bit of hot water to wash hands, but when a larger load comes along the boiler will fire up and try to keep up with the load. The lower limit is usually set by the laws of physics. The boiler can provide heat at a rate governed by its basic design (tell us the make/model number and we can give you more info). This flat is a 1982 conversion and the boiler is almost certainly the original Worcester Heatslave 2+. I have checked it for CO and it's okay, my landlord's agent tells me it is checked annually. The more powerful the boiler, the more water it can heat in a given time. Hence if you ask for a small flow of hot water it will supply it at a temperature governed by the HW stat. As you turn the tap on more, you reach the limit of the boilers power where even running flat out it can still not heat the water to the stat temperature and the temperature of the water will begin to fall. Select a high enough flow rate and it will not be able to heat it enough to get it to a usable temperature. I plan to turn the CH off and put the thermostat to High then try to run a bath. I think this would have happened in the autumn anyway (admittedly with the thermostat on low) and cold water after a few minutes still happened. Yes but in autumn the incomming water was probably warmer so less energy was required to heat the water to the required temperature, my incomming water swings between 5°C and 9°Cdepending on season... /Morten --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.825 / Virus Database: 563 - Release Date: 30/12/2004 |
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I have a Worcester Heatslave in a rented property - with the same symptoms.
The problem is almost certainly the diaphragm in the diverter valve.It's rubber and perishes. You find that the CH works fine, but the DHW is affected. You should find that the best temporary measure is to have the central heating ON, when you run the bath, and turn the flow down until the hot water runs hotter, and for longer. With the CH off - the DHW runs colder! The part is still available - diaphragm around £15, ot the complete diverter valve around £70. Get the part number from Worcester and you can get from Curzon - a nationwide chain 0870 5103030. My tenants are putting up with this because I'm replacing the boiler when the weather's a bit warmer , as well as carrying out other refurbishments. Yours is an old boiler, but could still give years of service, it's not necssarily a reflection on the landlord(s). -- ------------------------------------------------------------------------------------- view my philatelic items for sale on ebay at: http://tinyurl.com/l32i "JimGC" wrote in message ... Bear with me a moment ... I'm shocked at the cost of running my small flat's combi boiler compared to my previous terraced house boiler which had a hot water tank. The cost has doubled (3bd house HW/CH with 4 occupants was £360pa over the year, 1 bd flat combi HW/CH with 1 occupant ran up £60 in December alone!) The flat is fairly modern (1982) in good condition, and I have the water/ch on from 6-9am and from 4-11pm, turning it off when CH gets too hot. Dec. is the worst month of the year measure usage, but even if it all drops 50% for the rest of the year, it's still too high for my liking. The reason for posting here is that I have already asked about the inability of the boiler to provide a constant flow of hot water. (CH seems to be very hot whenever it's on whatever the thermostat on the boiler is set to). Is it possible that the boiler has faulty thermostats and is failing to provide constant hot water, but also using way too much gas to feed the CH? Or am I just paying the price for having this kind of boiler? Is it possible that I'm using the combi boiler in the wrong way, and that these fixed timing settings are not appropriate to combis? I plan to get a CORGI man in early in the new year to give it the once over, landlord or not! Thanks, Jim -------------------------------------------------- To email go to my address and take out the dog ... |
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"JimGC" wrote in message ... Thanks for all of that - noted. I think th only sensible thing is to get the agent to call in an engineer and have the whole thing assessed. I've spoken to the neighbours who had/have similar boilers, and they say they're all on their way out and need to be replaced. One neighbour had hers moved as well as replaced and it cost her £2500! Complicated - and expensive - business. No not really, it's fairly simple as long as you understand how things are done, unfortunately there's alot of work done that doesn't need to be done and quite a few cases of wrong advices and outright day-robbery by people who knows against the rest of us who don't know. Greed, that's what it is, people wan't more and are getting quite good at abusing the people who dont know... /Morten --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.825 / Virus Database: 563 - Release Date: 31/12/2004 |
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Morten wrote:
What do you mean by failing to provide constant hot water exactly? (i.e. it works when the tap is first turned on, but the goes completely cold, or does it run warm but not as hot as when you started etc). Get a thermostatic mixer valve inbetween the boiler DHW out and the hot water taps, that will minimize the temperature swings, but will not do anything to the boiler not being able to keep up with a large load! If there is no hot water coming from the boiler then a thermostatic mixer is not going to do anything useful, it can't heat the water! Combi boilers are a good idea on paper, because they make for a very simple installation (ie. you can get rid of the DHW tank) but are seldom up for the job simply because they cannot provide enough hot water when you want to take a good long shower. Sorry, but that is nonsense really. One of the things that most combis are very good at is showers. The time they can be poor (the lower powered ones at least) if providing the high flow rate of water required to run a bath quickly, or to provide for several users simultaneously. I have this in another thread, but briefly if I try to run a bath (however slowly) the hot tap runs very hot for 30secs then drops from warm to cold in 5 minutes or so. At best I can only get half a bath of comfortably hot water. Then get a thermostatic showervalve, that will use only the hot water required to satisfy your requirements regardless of water temperature comming from the boiler. The boilr will still have to be able to keep up with your use of hot water, but you don't get scalded and then waste a lot of hot water waiting for it too cool down or waste it trying to get the shower set correctly. He would be better spending the money to get the boiler to work. If it is a combi, it obviously has a fault. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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"John Rumm" wrote in message ... Get a thermostatic mixer valve inbetween the boiler DHW out and the hot water taps, that will minimize the temperature swings, but will not do anything to the boiler not being able to keep up with a large load! If there is no hot water coming from the boiler then a thermostatic mixer is not going to do anything useful, it can't heat the water! Correct, but it will make the too hot water last longer because you're mixing it with cold water intil the required temperature is reached. When the incomming water gets to cold you're back to sq1 but it will take longet to reach this state... /Morten --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.825 / Virus Database: 563 - Release Date: 30/12/2004 |
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Morten wrote:
If there is no hot water coming from the boiler then a thermostatic mixer is not going to do anything useful, it can't heat the water! Correct, but it will make the too hot water last longer because you're mixing it with cold water intil the required temperature is reached. When the incomming water gets to cold you're back to sq1 but it will take longet to reach this state... With a stored water system this will be true, with a combi that is working correctly it should not make any difference since the hot should not run out... (Still worth having a mixer mind you, to protect you from scalding / freezing every time a tape gets turned on elsewhere when you are in the shower!) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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