new valliant boiler & rads help please

hi newbie here,

the council put in a new valliant boiler, cylinder and new rads throughout as part of the homes standard they have to adhere to these days. I'm disabled and live in a small bungalow so it's only 3 rads and hot water. i don't have a bath, the shower is electric and heats itself, so the hot water to kitchen and bathroom hot taps should come from the valliant boiler. the old larger twin panel rads have been replaced with smaller single panel rads. the replacement cylinder is a surprise as i was told during design stage that i wouldn't need one, i'd just get a new boiler (used to be a back boiler on the fire). Why is there a cylinder (1600x300 hw & top immersion heater) on this system and is it interfering?

principally, i want to try and work out how efficient my system as it's using more gas and the heating is poor without it being really cold. there should be heat available below a certain level of cost, if not there's either a faulty setup or design flaw, so i'm dubious about whether this setup is fit for purpose. can anyone help me defunk my brain about what to investigate?

the boiler is a Valliant ecotec plus 615 which the installing engineer said exchanges heat or something, and CAN be cheaper but depends how it's used.

on the design sheet that the heating engineer did for my bungalow, there is a graphic table with the rooms, rad sizes and types, trv's, and a column that says load (no units specified). what do you think this could mean?
i've found the manufacturers radiator specs (myson HE), and the load quoted on the design sheet is more than the maximum output for each radiator he quoted. i wondered if load meant what the engineer had calculated the required heating output to be for each room? the fact that the load on the table is larger than the rad max output, but considerably smaller than any wattage i get from a radiator size calculator is a bit worrying. do you know if they take things like furniture into the equation when calculating room heating requirements or is it mostly cubic size?

eg, if i said my bedroom was 4.1x3x2.4m, south facing with one single glazed window the load next to the rad he's specified is 767 (no units). the max output of the rad he's chosen is 660w. the wattage i get from a calculator is 1183. that's a big difference.
the lounge specs are out too- load 1691, rad output 1463, approx calc wattage 2000w.
does this sound wrong to you too?

finally, and sorry this is so long, how do i work out whether it's cheaper to have the boiler at lower or higher temp setting to maintain thermostat setting? it burns at both and i'm not sure how to run it economically.
appreciate any help thanks

bump!

See Clueless10. You were told what to do there.

Thought this looked familiar, pretty sure ive seen it on this page too.

ok i've finally had an email back from the council's contracted engineer in which he says:

for this property the loads have been divided by the correction factor (as opposed to multiplied as we thought for two of the rads). Having said that the resident is not correct with regards to the value for the correction factor. All of our heatloss calculations are based on a mean water temperature of 76.5°C not 65°C, which is shown as an example in the Myson literature. Using 76.5°C the temperature difference will be 55.5°C and not 45°C therefore the correction factor is 1.17. (as opposed to 0.87 at 45 degrees C). The load value (1691) is then divided by the correction factor and gives a required radiator output of 1436W for the Living Room. The radiator selected for the Living Room will give an output of 1463W and therefore is adequate for the room. Please also note that the external air temperature that the heat losses are calculated at is -3°C.

Just so i know he hasn't just massaged the numbers to give a higher factor, does this 76.5C sound ok? Does this also mean that my boiler should be set to 76.5C and not 70C which the installer said was when the boiler was most efficient? Burning 2 gas units in 12 hours for 20C at the moment and my bedroom is still cold. I'm using a third more gas than the old back boiler system and gunked up double rads they took out. I'll buy a thermometer and see what room temps i get.

I'd asked some of my neighbours who have identical bungalows about their heating and they had varying radiators, some the same dimensions but double panelled, some had combi boilers and some had the ecotec plus 615 like me. one had the combi replaced as it kept flooding and another has to use a fan heater to supplement the tiny rad in her bathroom. I'd assumed a bathroom would have an additional load to dry out the moisture rather than just like living space, is this right? Figured that's why i got a double panel in mine. I'd asked the engineer why the installations vary and he said:

Each property's radiators are calculated on an individual basis. The difference in radiators between the properties is down to the preference of the individual designer; however all radiators meet the heatloss. The reason that a system boiler has been installed with a hot water cylinder is because this is the clients preference. Where we have space for a cylinder and system boiler we are to install these items.

the other thing with the boiler choice is it's not even the smallest one they do, they make an ecotec plus 612 rated 4.9 to 12kw, and the 615 is 4.9 to 15kw. the radiator loads add up to 3126watts for my property. Will this larger boiler cost more to run for the same output than the 612? i note the neighbour's combi pro 24 has a higher minimum heat at 6.7kw. Would this system be cheaper to run without the cylinder, considering i hardly use hot water and have no bath?

hard to know how these systems have been specified or if designers have followed the same guidelines. if the engineer is right about the 76.5C then we are all ok, those getting bigger rads or double panels are clear winners though it shouldn't be like that, and if unneccessary it would mean money has been wasted or profit made, quite a lot potentially over a big contract. meanwhile the tenants are cold and skint. aarrggh

numpty2010 said:

All of our heatloss calculations are based on a mean water temperature of 76.5°C not 65°C, which is shown as an example in the Myson literature.

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I would ask him why they are using so high a mean temperature, which implies that the flow temperature is 82°C and the return temperature is 71°C -an 11°C difference. By doing this they have effectively undersized the radiators, so the boiler will rarely run at its most efficient.

This goes against the advice given in the Domestic Building Compliance Guide (October 2010) which recommends designing systems with a return temperature less than 55°C.

Does this also mean that my boiler should be set to 76.5C and not 70C which the installer said was when the boiler was most efficient?

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No, it will have to be set to 82°C

some had the ecotec plus 615 like me. ... the radiator loads add up to 3126watts for my property. Will this larger boiler cost more to run for the same output than the 612?

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There shouldn't be any difference as both boilers can adjust their output to provide the necessary heat.

The Ecotec is designed to work with a 20°C difference between flow and return so if the mean temperature is 76.5°C the flow would be 86.5°C and the return 66.5°C, which is way above Vaillant's recommended temperatures.

ok i've noticed in the benchmark log book for the boiler it says flow temp 75C and return 65C, which i've had wrong as the installer told me to run it at 70C. perhaps he meant it's mean temp. So i'll try that first off but i'm sure the bedroom temp won't match the thermostat, it was 4 degrees less with the boiler running at 70C. What sort of temps would you expect me to run a boiler at for a bungalow and 20C?

D_hailsham i didn't understand where you got the 82, 71 and 11 degrees from, is there generally a 10C drop in F & R and the mean in the middle?

in all honesty do you think he's just trying to cover for a miscalculation in multiplying the correction factor, or is he saying that in my instance, the rads were specified first and i'll have to hammer the boiler to get my 20C out of them? Do you think there would be any circumstances when his mean 76.5C would be used in council houses let alone bungalows, he did say 'all our heatloss calculations'. i'll follow up that 76.5C mean with Vaillant and with the domestic building compliance guide.

i just need to find another resident with their design sheet and it'll show either similar or different loads and all sizes of rads (we all seem to have mixed sizes and double and single panels), it either shows they had no calculations or didn't follow them i guess.

thanks
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The Ecotec is designed to work with a 20°C difference between flow and return so if the mean temperature is 76.5°C the flow would be 86.5°C and the return 66.5°C, which is way above Vaillant's recommended temperatures.

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the benchmark page in the back of the boiler's instructions says flow 75C and return 65C. Is this indicative of a working but poorly matched system, or done in a test mode just to indicate system function?

appreciate any help thanks

numpty2010 said:

ok i've noticed in the benchmark log book for the boiler it says flow temp 75C and return 65C, which i've had wrong as the installer told me to run it at 70C. perhaps he meant it's mean temp. So i'll try that first off but i'm sure the bedroom temp won't match the thermostat, it was 4 degrees less with the boiler running at 70C. What sort of temps would you expect me to run a boiler at for a bungalow and 20C?

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That's interesting, and another reason for going back to the guy who said the rads were sized for a mean temperature of 76.5°C (Mean is the average of flow and return)

I didn't understand where you got the 82, 71 and 11 degrees from, is there generally a 10C drop in F & R and the mean in the middle?

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Two reasons:

1. A mean of 76.5°C suggests that the difference between flow and return temperatures is an Odd number.

2. In the early days, when Fahrenheit temperatures were used, systems were designed based on a 20°F difference between flow and return. 20°F is equivalent to 11.111°C, which rounds of to 11°C.

I therefore assumed that, if the mean was 76.5°C, the flow was 5.5°C higher (82°C) and the return 5.5°C lower (71°C).

do you think he's just trying to cover for a miscalculation in multiplying the correction factor, or is he saying that in my instance, the rads were specified first and i'll have to hammer the boiler to get my 20C out of them?

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If the boiler is running with a 75°C flow and a 65°C return, the correction factor is one (1).

Do you think there would be any circumstances when his mean 76.5C would be used in council houses let alone bungalows, he did say 'all our heatloss calculations'.

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NO!

The factor of 0.87 is correct for the 82°C/71°C. However, the reply you received for the contractor says that the loads have been divided by the correction factor. This is definitely incorrect - they have been multiplied. To use the examples you gave originally:

Load 1691 - Rad 1463. (1691 x 0.87 = 1471)
Load 767 - Rad 660. (767 x 0.87 = 667)

The rads have definitely been undersized.

I think the competence of the Council's contractor need to be queried. He probably was the one who came in with the lowest price.

You should certainly speak to all your neighbours and compare the data sheets they provide. If they all show the same error and your neighbours have the same problems, you should contact the council directly and tell them your concerns. If necessary involve your local Councillors.

I dont know why your so bothered by this, im sure it will be more efficient than the old back boiler, regardless of the settings.

londonboy said:

I dont know why your so bothered by this, im sure it will be more efficient than the old back boiler, regardless of the settings.

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i'm not sure if efficiency means boiler rating or how it runs allied to the system components. I'm using a third more gas units than the old back boiler that's why, largely due we think to 2 undersize rads, but i'm heating a cylinder i don't need and have an oversize boiler that i'm investigating.

furthermore if even one of the council's contractors installations were inefficient, potentially illsuited, miscalculated and unaffordable to the tenants then it should be corrected.

How many fume producing, natural resource consuming boilers do you think we should have running inefficiently?

The factor of 0.87 is correct for the 82°C/71°C. However, the reply you received for the contractor says that the loads have been divided by the correction factor. This is definitely incorrect - they have been multiplied. To use the examples you gave originally:

Load 1691 - Rad 1463. (1691 x 0.87 = 1471)
Load 767 - Rad 660. (767 x 0.87 = 667)

The rads have definitely been undersized.

I think the competence of the Council's contractor need to be queried. He probably was the one who came in with the lowest price.

You should certainly speak to all your neighbours and compare the data sheets they provide. If they all show the same error and your neighbours have the same problems, you should contact the council directly and tell them your concerns. If necessary involve your local Councillors.

Click to expand...

just to correct you slightly, he did say for the mean of 76.5C he divided by the correction factor of 1.17 temp diff of 55.5C on the myson chart, but i understand what you're saying.

so that domestic building compliance guide return temp of 55*C, i'm already 10*C over that on the benchmark statement. How do they get away with that?

can i ask, i can see there are regulations if that's the right word for boiler efficiency ratings, but when a system is fitted are there any guidelines to say it must function within a specified input/output range? i expect if i measured my gas use, per hour or some set time period, compared to temp output it wouldn't be anywhere near efficient i would think. is there any standard to adhere to?

appreciate any help thanks

numpty2010 said:

Load 1691 - Rad 1463. (1691 x 0.87 = 1471)
Load 767 - Rad 660. (767 x 0.87 = 667)

Click to expand...

just to correct you slightly, he did say for the mean of 76.5C he divided by the correction factor of 1.17 temp diff of 55.5C on the myson chart, but i understand what you're saying.

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1691 ÷ 1.17 = 1445
767 ÷ 1.17 = 656

The difference is negligible and, in any case you are limited to what is manufactured.

I can see there are regulations if that's the right word for boiler efficiency ratings, but when a system is fitted are there any guidelines to say it must function within a specified input/output range?

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Provided the system complies with the Guidance given in the Domestic Building Compliance Guide, that's all that is required.

The Guide does not lay down any requirements about room temperatures or warming up times. However Council owned property has to meet the "Decent Homes" standard, which requires the living room to be able to reach 21degC and other rooms 18degC.

londonboy said:

I dont know why your so bothered by this, im sure it will be more efficient than the old back boiler, regardless of the settings.

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On the contrary; an incorrectly configured oversized boiler supplying undersized radiators will be inefficient due to cycling. Furthermore, it may never be able to adequately heat the property despite burning continuously or requiring extended warm-up times to do so.

Mathew

i've been asked to see if there is an ABV (automatic bypass) valve on my new heating system as all the rads have trv's. these apparently should be on a loop somewhere, but i can't see anything in the boiler cupboard other than the flushing connection. could this be up in the loft? where would you expect to see it on on a new system?


i'm still waiting to hear back from the engineer about the rad and boiler info. bah humbug

appreciate any help thanks