New CH system underpowered/ wrong layout?

[Alex100]

Hi all

I had a complete new CH system installed a few months back. I did some research, got multiple quotes, went with a guy with a few good references and checked he was Gas safe registered. He did work very fast though. Perhaps too fast.

It runs 9 radiators from a Greenstar 38 Cdi combi. It's a two storey end terrace house, with about 120 square metres of floor space. The carcass is 22mm copper, with 15mm branches to compact Stelrad radiators. The boiler is upstairs at the back of the house. Another plumber already told me the boiler is too big for this house and so inefficient - I did ask for good water heating power, so maybe that's why he chose that one.

Questions:
1. From installation I thought the rads are small, but the plumber told me that's because they are compact. Anyway, sure enough, it takes about 45-60 minutes per degree of room temp rise in the two living rooms, from when the radiators are really hot on a night, when outside is below about 7 degrees, and this is with the boiler at maximum CH heat setting. I think this is unacceptably slow, as if the heating comes on when the room is 16 degrees, takes 15 minutes to heat the rads, then I'm looking at 5 hours to get to 21 degrees, which is mad (and bedtime). I have checked this with an independent thermometer and it agrees with the thermostat on the rate of heating up the room. Needless to say, we're quite chilly with our brand new system.

The plumber is arguing that he's never had a problem with his BTU calculator and wants us to pay for the bigger radiators we need. I don't care about BTU calcs, as every house is unique and they are only a guide. I want to be sure this is an under-powered set of rads, based on how long it takes to heat up, before putting my foot down on who pays. Underpowered?

2. THE BIGGER QUESTION
With the above and other teething issues, it got me thinking to take a look at the piping. Now I realise that rather than take the flow and return to the front of the house upstairs, for the front and middle bedrooms (which are the lion's share of the upstairs floor space), he has instead taken a long two-pipe branch from the flow and return in the study at the back of house, where the boiler is, all the way to the farthest front room (8-10 metre), and also teed off this for the middle room. So two pipes emerge from study and run 8-10 metres along corridor into the master bedroom, one pipe into one end of a rad and one into the other. Near their beginning, outside the study, a tee is taken from each pipe to go 2-3 metres into and out of the middle bedroom's radiator. The pipework starts as 22mm and reduces to 15mm about 1metre from each radiator.

Is this just lazy but no great issue (the rads do heat up). I do have an attic conversion above the front bedroom, and the plumber knows I want to put a rad in there one day, but that means teeing off what is already an 8 metre branch.

3. The system used to creak terribly and woke us up in morning and kept us awake until fully cooled down at night. It's clearly the pipes touching joists and boards. We did manage to get the plumber back, grumbling somewhat that we're fussy, to put felting in the worst places. He said he's never had to put felt around joist notches for anyone before, but I find that odd, having read how common it is. Am I fussy or is felting standard? (better still, he could have cut floorboards so his pipes aren't touching them where they emerge). It still creaks a lot downstairs.

4. I don't know much about heating systems (obvious huh?). However, does the above indicate I should get a different plumber out to check the system?
If so, what are my rights? I paid about £7k for the system (No VAT, as he's not VAT registered).

Many thanks for any input.
Alex

 

[1967skyblue]

just somthing to throw into the mix. how many other gas appliances do you have in the house ? and did the other plumber who came round to have a look at your issues did he check the gas pipe size to the boiler ? have him check the boiler commisioning report.
but please for your own safety dont touch the boiler yourself.

 

[Alex100]

just somthing to throw into the mix. how many other gas appliances do you have in the house ? and did the other plumber who came round to have a look at your issues did he check the gas pipe size to the boiler ? have him check the boiler commisioning report.
but please for your own safety dont touch the boiler yourself.

Thanks 1967skyblue



Two small gas fires downstairs. But the boiler is run off a separate, dedicated new main supply from the meter. Not had someone come and look on site yet. What should I be getting them to look for? Does system sound in need of checking over for general competence?

 

[1967skyblue]

unfortunatly i can only say that your gas safe installer would understand what i was saying and might explain this to you in person, sorry.

 

[doitmyself]

Another plumber already told me the boiler is too big for this house and so inefficient

Is the boiler continually turning on and off while the house is heating up?

Did the installer measure the incoming cold water flow rate and dynamic pressure before recommending a 38kW boiler?

 

[Reg Man]

QUOTE: The plumber is arguing that he's never had a problem with his BTU calculator and wants us to pay for the bigger radiators we need. I don't care about BTU calcs, as every house is unique and they are only a guide. I want to be sure this is an under-powered set of rads, based on how long it takes to heat up, before putting my foot down on who pays. Underpowered?

BTU calculator? Hope he calculated the whole house heat loss method as well?

 

[Centralheatking]

Best plan is for you to measure the rooms width/length and height, post this on here with each room named and state no of windows, outside walls also.

Then measure the rad size installed in the room - and state wether its a single,
double, or 3x with fins or not - type radiator.

We (on here ) can work out what rads we would have supplied.

centralheatking

 

[chris watkins]

Simple ask him to provide the design & heatloss calculations he used to size & then select the rads, as you believe they are undersized & this is the cause of the system (product) you have paid a lot of money for not working correctly, give him a few days to provide these & the chance to correct the problem otherwise you will have to go see trading standards & the court. You may need to get another engineer in to prepare a report on the installation to back up your claim. (see CIPHE)

As others have said it could also be the boiler heating output is to large for the load but most likely it is the rad's.

 

[doitmyself]

As others have said it could also be the boiler heating output is to large for the load but most likely it is the rad's.

The OP has a boiler which modulates between 9.4kW and 30kW. He has 9 rads, which at, say, 1.5kW each is 13.5kW total load. Even if they were 2kw, which is doubtful, that would still be only 18kW. So whichever way you look at it the boiler is oversized for the heating load.

There's a good chance that the flow water temperature rises to 75, or whatever is set, but the return temperature keeps on rising, meaning the boiler then cuts out, waits and then restarts. So the mean water temperature is well below the required value, which means the rads are not giving off the correct amount of heat.

The OP should use Whole House Boiler Size Calculator to find out the heating requirement and Stelrad Elite Catalogue, first table to estimate the output of his radiators.

 

[chris watkins]

The OP has a boiler which modulates between 9.4kW and 30kW. He has 9 rads, which at, say, 1.5kW each is 13.5kW total load. Even if they were 2kw, which is doubtful, that would still be only 18kW. So whichever way you look at it the boiler is oversized for the heating load.

There's a good chance that the flow water temperature rises to 75, or whatever is set, but the return temperature keeps on rising, meaning the boiler then cuts out, waits and then restarts. So the mean water temperature is well below the required value, which means the rads are not giving off the correct amount of heat.

The OP should use Whole House Boiler Size Calculator to find out the heating requirement and Stelrad Elite Catalogue, first table to estimate the output of his radiators.

I agree totally with you on the technical bits above & asking the installer for his design criteria (or lack off) would provide proof of poor design practice be it the rads or boiler.
Is it not possible with these to down rate or limit the heating output to say 15-18kW, as with the Vaillants ?

Not so sure the OP should have to do any calculations to confirm one way or the other, there are to many variables, all they should have to point out is that it has been cold & the new heating was not heating the house to a normal standard.

 

[Centralheatking]

30 kw on 9 rads should mean the place is steaming hot - I run my place with a 30kw boiler - 5 bedrooms, 3 bathrooms and hot water cylinder and never have to go past 3/4 heat - thats 16 rads and none are small. r

The OP has a boiler which modulates between 9.4kW and 30kW. He has 9 rads, which at, say, 1.5kW each is 13.5kW total load. Even if they were 2kw, which is doubtful, that would still be only 18kW. So whichever way you look at it the boiler is oversized for the heating load.

There's a good chance that the flow water temperature rises to 75, or whatever is set, but the return temperature keeps on rising, meaning the boiler then cuts out, waits and then restarts. So the mean water temperature is well below the required value, which means the rads are not giving off the correct amount of heat.

The OP should use Whole House Boiler Size Calculator to find out the heating requirement and Stelrad Elite Catalogue, first table to estimate the output of his radiators.

 

[doitmyself]

Is it not possible with these to down rate or limit the heating output to say 15-18kW, as with the Vaillants?

According to the Installation Manual, the Max output can be adjusted but, unhelpfully, they don't tell you how to do it.

Not so sure the OP should have to do any calculations to confirm one way or the other

It won't do any harm to have some figures to back you up. "I feel cold; and this is why!"

 

[vern]

I have said it before but here goes COMBI'S ARE EXEMPT FROM WHOLE HOUSE HEAT CALCS!.......
due to many reasons but the main one is that their outputs are based upon hot water production, obviously this should be matched to incoming mains water pressure and gas runs from a responsible installer but often are not!

To get round this good manufactures get round this by allowing range rating.

Worcester bosch get around this on the junior and Si with a code plug that down rates from 24kw to 12 kw, the CDi can be adjusted from 30kw to around 9 kw on 38 and 42 CDi and 30 kw to 7 kw on 29 and 34 Cdi (this can only be accessed via installer menus, I am not posting how as the menu contains all stuff that should not be touched unless you are trained by WB, pump maps, turbine delays, and much more!

the 38 Cdi is actually 40 kw on DHW NOT 38 marketing bluff as not to pull sales from 42 cdi

i actually look after some trendy apartments that have 42cdi's and 2 rads and a towel rail! 42 kw for hot water due to silly sized baths!

 

[AWheating]

go on the worcester course and you will get taught how to range rate the cdi. Or phone the tech helpline and get talked through it.

 

[doitmyself]

I have said it before but here goes COMBI'S ARE EXEMPT FROM WHOLE HOUSE HEAT CALCS!.......
due to many reasons but the main one is that their outputs are based upon hot water production, obviously this should be matched to incoming mains water pressure and gas runs from a responsible installer but often are not!

I agree that Hot Water production is the overriding factor when sizing a combi boiler, but the specifier has to take the Central heating requirement into account. If he doesn't you can get the situation where the minimum CH output is above the CH requirement of the house. For example a house with an 8kW heating requirement which has a Vaillant 837 or 937 installed (12-28kW CH output)

 

[AWheating]

if the OP uses a online calculator he/she will get a decent idea if rads are sized well.

 

[stevetheplumber]

possibly the ops best course of action may be to get wb in to see whats wrong if he calls it in as a boiler fault they will then tell him if its an installation fault they may charge him if theres no boiler fault but then he will have an idea of whats wrong and can claim against the installer if there remedial work needed
the pipework sounds ok in that theres 2 pipes going every where and in 22 to within one meter of every rad sounds over kill

 

[chris watkins]

To add to doitmyself post above the problem is not always the down rating or modulation of these lager boilers the one thing that the engineers changes can't change (as far as I know) is the CPU's electric control routines which run the start-ups firings, modulations & anti cycling etc all of which remain pre-set for the largest outputs & can still effect the boilers performance even when down rated.

 

[vern]

I agree that Hot Water production is the overriding factor when sizing a combi boiler, but the specifier has to take the Central heating requirement into account. If he doesn't you can get the situation where the minimum CH output is above the CH requirement of the house. For example a house with an 8kW heating requirement which has a Vaillant 837 or 937 installed (12-28kW CH output)

The technical reason are turn down ratios.....but even the 42 CDI's i look after don't have this problem, with 3 rads if set up right, min output, anti cycle delay adjusted from standard 3 mins, for reference the Cdi does not have a return sensor, just flow with is mapped via PCB software to keep flow temp to within 5 dregs of set point on boiler stat, this can also be adjusted in menus but not if you don't know what you are doing, any GSR can fit a boiler ( commissioning and maintenance is altogether a much tougher job)

 

[vern]

To add to doitmyself post above the problem is not always the down rating or modulation of these lager boilers the one thing that the engineers changes can't change (as far as I know) is the CPU's electric control routines which run the start-ups firings, modulations & anti cycling etc all of which remain pre-set for the largest outputs & can still effect the boilers performance even when down rated.

Incorrect Chris on WB anyhow, I was typing the above whilst you replied

 

[SimonG]

To the op.

Just as an example, measure a room (length x width x height) and measure the radiator and the type of radiator and let us know.

 

[chris watkins]

Thanks vern, don't know much about WB (only that they are hard to work on LOL) much easer to have these adjustments on a combi rather than heat only but still it must have an effect if/when the heating load is so low doesn't it ?

 

[vern]

To the OP, I would be 90% certain your rads are undersized, probably due to installer using an heat pack from his suppliers, which limits the outputs of radiators before you pay more! At £7K you should be sweating!

 

[vern]

Thanks vern, don't know much about WB (only that they are hard to work on LOL) much easer to have these adjustments on a combi rather than heat only but still it must have an effect if/when the heating load is so low doesn't it ?

You can do this on all CDI range heat only and system and obviously combi, but you have to know what you are doing, I spent a day learning this alone, the pump can even be adjusted to suit micro / mini bore systems too obviously not heat only in this respect.

Never had trouble with low loads, as said if all parameters are set up correctly, if you are pushed you can fit an ABV across flow and return, to balance load, never had, always managed, using the 2 level installer menus.

 

[Alex100]

I have said it before but here goes COMBI'S ARE EXEMPT FROM WHOLE HOUSE HEAT CALCS!.......
due to many reasons but the main one is that their outputs are based upon hot water production, obviously this should be matched to incoming mains water pressure and gas runs from a responsible installer but often are not!

To get round this good manufactures get round this by allowing range rating.

Worcester bosch get around this on the junior and Si with a code plug that down rates from 24kw to 12 kw, the CDi can be adjusted from 30kw to around 9 kw on 38 and 42 CDi and 30 kw to 7 kw on 29 and 34 Cdi (this can only be accessed via installer menus, I am not posting how as the menu contains all stuff that should not be touched unless you are trained by WB, pump maps, turbine delays, and much more!

the 38 Cdi is actually 40 kw on DHW NOT 38 marketing bluff as not to pull sales from 42 cdi

i actually look after some trendy apartments that have 42cdi's and 2 rads and a towel rail! 42 kw for hot water due to silly sized baths!

Very interesting. Does this mean just the heating output and not the hot water heating rate can be downrated?

 

[chris watkins]

Very interesting. Does this mean just the heating output and not the hot water heating rate can be downrated?

Yes ......

 

[vern]

Very interesting. Does this mean just the heating output and not the hot water heating rate can be downrated?

Correct get your installer back......

 

[Alex100]

Many many thanks to all those helpful posts - and good to see people enjoy what they do too. In response to request for sizes, here are room sizes.


Room size examples:

Lounge - 3.45m x 4.25m x 2.5m high, two external walls of 18inch stone & rubble, 3.2m of double glazed and draughtproofed sash, timber floor with space beneath. In here he has placed a Stelrad K2 compact (450 x 1200mm) which gives about 5615 BTU

Dining - 3.45m x 4.2m x 2.5m high, one external wall, one single glazed window into the conservatory (so not really a window). In here a compact stelrad K2, slightly smaller, 450mm x 1100mm, giving about 5100 BTU

Kitchen - I wanted to get a rad and the installer didn't calculate what I'd need. I got a vertical semi designer thing from B&Q (i know, i know, but it was a weak moment) giving 2800 BTU. Looks alright but gurgles if turn TVR up beyond 3. Kitchen is 2.7m wide x 5m long x 2.2m high, one small double glazed window, one external wall (short side) and one wall has a door and window into the conservatory (antarctica).

Conservatory - a few installers who quoted suggested not trying to fully heat the conservatory but I though to put something in at least to take the edge off the cold. I suggested something under the interior window, so he put Stelrad K2, 300mm x 1500mm giving 5026 BTU. It's 2m x 5m long, and over 3m on high side. Also, that rad is teed off the dining room rad flow & return, not from the main flow/return circuit.

Hall & upstairs landings - incl stairs it's about 15 to 16 m long (horizontally) x 0.9m wide x 2.5 m ceiling. No outside walls (just party walls) or windows. There is one K1 downstairs (600mm x 11000mm = 3678 BTU) and one upstairs (600mm x 900mm giving 3009 BTU)

Master bed - 4.35m wide x 4.2m long x 2.4m high - he put in a K2 600 x 1000mm long, giving 5910. There are two external walls, like lounge, and three single glazed sashes but all secondary glazed so no draughts. There is about 75mm of loft insulation.

2nd bed - 2.55m x 4.2m x 2.4m high. Rad is K2, 450mm x 1100mm = 5100BTU. Two outside walls, one double glazed window, roof space insulated with 75mm insulation.

Bathroom - installer was arguing that I asked for a towel rail which he pointed out isn't as powerful as a panel radiator. I pointed out I never told him how big to make the towel rail! He installed one 500mm x 1200mm giving only about 1400 BTU. Bathroom is about 2.7m x 2.3m x 2.2m high, two external walls, one double glazed window.

Study - small room about 2.2m x 1.7m x 2.2m high. No radiator, just the boiler. One small dg window, one external wall.

That's it, so about 37600 BTU of radiators in house. Sounds like I need ask if he limited the boiler heat output yes?

 

[Alex100]

Hi Steve and others who can advise on the flow/return circuit

So just having two pipes to all rads is good enough? I expected to see two pipes passing close to every rad, and then tees going off to the rad from the circuit, one to each end of rad. As some of these branches/tees are 2 to 8 metres long (the flow/return circuit not coming near some rooms even), and one or two have a second radiator teed off mid-way, I was a bit worried the system may have curious eddies/turbulence and be difficult to balance.

Can I at least forget about this issue and not be expecting to see a nice two pipe circuit flowing round the house? It looks more like a set of long branches from a limited ring main.

 

[Alex100]

Is the boiler continually turning on and off while the house is heating up?

Did the installer measure the incoming cold water flow rate and dynamic pressure before recommending a 38kW boiler?

I haven't checked that. Do I need to just listen to the boiler? I assumed it would turn off every few minutes whilst the hot water pumped round, then come on again. What am I looking out for?

I asked for adequate hot water and he specified a 37CDi - I pointed out that had been discontinued and replaced with a 38CDi, which I said I presumed he would then get. He never mentioned matching a boiler size to house size, and I doubt he did that measurement - would it be in my commissioning booklet?

 

[vern]

Many many thanks to all those helpful posts - and good to see people enjoy what they do too. In response to request for sizes, here are room sizes.


Room size examples:

Lounge - 3.45m x 4.25m x 2.5m high, two external walls of 18inch stone & rubble, 3.2m of double glazed and draughtproofed sash, timber floor with space beneath. In here he has placed a Stelrad K2 compact (450 x 1200mm) which gives about 5615 BTU

Dining - 3.45m x 4.2m x 2.5m high, one external wall, one single glazed window into the conservatory (so not really a window). In here a compact stelrad K2, slightly smaller, 450mm x 1100mm, giving about 5100 BTU

Kitchen - I wanted to get a rad and the installer didn't calculate what I'd need. I got a vertical semi designer thing from B&Q (i know, i know, but it was a weak moment) giving 2800 BTU. Looks alright but gurgles if turn TVR up beyond 3. Kitchen is 2.7m wide x 5m long x 2.2m high, one small double glazed window, one external wall (short side) and one wall has a door and window into the conservatory (antarctica).

Conservatory - a few installers who quoted suggested not trying to fully heat the conservatory but I though to put something in at least to take the edge off the cold. I suggested something under the interior window, so he put Stelrad K2, 300mm x 1500mm giving 5026 BTU. It's 2m x 5m long, and over 3m on high side. Also, that rad is teed off the dining room rad flow & return, not from the main flow/return circuit.

Hall & upstairs landings - incl stairs it's about 15 to 16 m long (horizontally) x 0.9m wide x 2.5 m ceiling. No outside walls (just party walls) or windows. There is one K1 downstairs (600mm x 11000mm = 3678 BTU) and one upstairs (600mm x 900mm giving 3009 BTU)

Master bed - 4.35m wide x 4.2m long x 2.4m high - he put in a K2 600 x 1000mm long, giving 5910. There are two external walls, like lounge, and three single glazed sashes but all secondary glazed so no draughts. There is about 75mm of loft insulation.

2nd bed - 2.55m x 4.2m x 2.4m high. Rad is K2, 450mm x 1100mm = 5100BTU. Two outside walls, one double glazed window, roof space insulated with 75mm insulation.

Bathroom - installer was arguing that I asked for a towel rail which he pointed out isn't as powerful as a panel radiator. I pointed out I never told him how big to make the towel rail! He installed one 500mm x 1200mm giving only about 1400 BTU. Bathroom is about 2.7m x 2.3m x 2.2m high, two external walls, one double glazed window.

Study - small room about 2.2m x 1.7m x 2.2m high. No radiator, just the boiler. One small dg window, one external wall.

That's it, so about 37600 BTU of radiators in house. Sounds like I need ask if he limited the boiler heat output yes?

Alex,

i have not worked them out, but they all seem undersized to me at a glance someone will work them out!

looks like he bought a 40,000 btu heat pack don't hang him for this as i am guessing

B&Q rad noises as baffle will be missing to stop cross flow of flow and return check with them not big enough anyhow

why no rad in study? CDi's give off little heat, @£ 7k you should have

 

[SimonG]

There is about 75mm of loft insulation.
QUOTE]

Wel there's a big part of your problem.

 

[Alex100]

Simple ask him to provide the design & heatloss calculations he used to size & then select the rads, as you believe they are undersized & this is the cause of the system (product) you have paid a lot of money for not working correctly, give him a few days to provide these & the chance to correct the problem otherwise you will have to go see trading standards & the court. You may need to get another engineer in to prepare a report on the installation to back up your claim. (see CIPHE)

As others have said it could also be the boiler heating output is to large for the load but most likely it is the rad's.

Chris

Should he have a design and written calculations then? He said to me he used an online BTU calculator that he found very reliable and I did think blimey, I could do that myself (which I have many times, and his rads are either too small or marginal at best, depending on the website).

It is sounding like I need to find a respected heating surveyor and get this checked before he starts putting bigger rads in and charging me. He has said 4-6 weeks to put bigger rads in - I refused to just pay and said I'd ay the difference in cost of the rad for the lounge, dining and bathroom rads to be upgraded (not labour or other materials). Maybe others will find that the whole system is under powered and that will get interesting - I'd def need an independent report then.

Many thanks
Alex

 

[SafeGasInstall]

Its not about how powerful the boiler is
Its about how much can you prevent the HEAT LOST
If no one is using ch all day and you expect it to worm up the house in 15min this will never happen

Rads do seem a bit small , but then was there enough available space to install bigger rads ?

For any one to give right advice seen the job is best option to help out

Piping the system sounds ok to me tbh

 

[Alex100]

Its not about how powerful the boiler is
Its about how much can you prevent the HEAT LOST
If no one is using ch all day and you expect it to worm up the house in 15min this will never happen

Rads do seem a bit small , but then was there enough available space to install bigger rads ?

For any one to give right advice seen the job is best option to help out

Piping the system sounds ok to me tbh

Thanks for input. Yeah, plenty of space for bigger rads. It's not that I want house to heat up in 15 mins, but an hour would be nice. For example in cold spell the dining room was only up to 19.5 degrees after 3 hours of coming on (would have been about 15-16 when it came on), the lounge a degree colder, and rest of house similar.
Alex

 

[Alex100]

There is about 75mm of loft insulation.
QUOTE]

Wel there's a big part of your problem.

That's on my list. It's under boarding and carpet, so it's not a weekend job. Still, the heating system was installed knowing what is in the attic and I was never asked about that.

 

[mfgs]

I did a rough calculation on the lounge as per the info you gave and got about 2.2kw which I think is approx 7500btu's, so that one looks undersized.

 

[chris watkins]

Chris

Should he have a design and written calculations then? He said to me he used an online BTU calculator that he found very reliable and I did think blimey, I could do that myself (which I have many times, and his rads are either too small or marginal at best, depending on the website).

It is sounding like I need to find a respected heating surveyor and get this checked before he starts putting bigger rads in and charging me. He has said 4-6 weeks to put bigger rads in - I refused to just pay and said I'd ay the difference in cost of the rad for the lounge, dining and bathroom rads to be upgraded (not labour or other materials). Maybe others will find that the whole system is under powered and that will get interesting - I'd def need an independent report then.

Many thanks
Alex

You have to be fair to this guy & give him both the chance to show how he has size / designed the system to do the job you have paid for & if any mistakes have been made to correct these. Not withstanding that, the product he has provided you does not appear to be fit for purpose, he is obliged to provide information to show how he selected the components to do an acceptable job, what ever form this took (there are too many variables to start second guessing) with that info you can then see wether it is both works / is designed within the normally acceptable standards.
He can not make a charge of any kind (for the rads) for correcting his mistakes unless you had some kind of input into selecting these.
You need to write to him setting this out & tell him that 4-6 weeks is no good.

 

[aladin]

as previously said,
all seems well apart from the heat pack so undersized rads dont hang the guy simply ask the chap to recalculate and replace

 

[MRDrip]

Are all your "external walls of 18inch stone & rubble," the same ? is there any internal insulation on the walls?
Just wondering how many tons of stone need to be heated to warm the building.

 

[bewsh]

These online radiator sizing sites generally tend to over size them as it's difficult to accurately size a radiator without knowing the exact u values of the building materials in the property.

Also something to be mind full of is that for energy efficiency you have to follow building regulations/british standards which state the temperatures for each type of room, ie lounge=21C, bedroom=16-18C, or something like that.

 

[josh]

Simple thing, is the boiler stat turned up?
not another 'oh we'll set that at 45c to condense more' then wonder why rads only get warm.

 

[SafeGasInstall]

good work Josh

 

[Centralheatking]

Josh is right in some ways - in order to get these 'intermediate tech' condensing boilers to perform properly I understood the installer has to undersize the boiler in order to get it to operate at peak performance - that way it recovers the heat.

Mind you John Prescott was the minister that over saw this legislation - he was good with his fists but maybe not with a technical issue - he seemed to shoot from his hip and
sometimes below that - as his wife found out


centralheatking

 

[vern]

Simple thing, is the boiler stat turned up?
not another 'oh we'll set that at 45c to condense more' then wonder why rads only get warm.

Sorry to disappoint guys ........re read post number 1 the boiler radiator thermostat is set to max, which means flow of 88 degs, rads are undersized!

 

[richardgas]

has he put a room stat/programmer in correct position and in the hours it takes to heat house are all the rads hot to touch or just warm

 

[Nostrum]

He's probably used an online calculator which doesn't have the option of choosing rubble walls, I haven't seen many that do. If he's sized the rads for a cavity wall build with insulation etc, your going to be at a loss.

vern, are you saying the code plug allows the boiler to modulate lower than the minimum stated output? Most are able to limited the maximum output but the minimum remains the same.

 

[doitmyself]

in order to get these 'intermediate tech' condensing boilers to perform properly I understood the installer has to undersize the boiler in order to get it to operate at peak performance - that way it recovers the heat.

Whoever told you that didn't know what he was talking about!!

If a house has a 10kW heat loss it needs a 10kW boiler. Putting in a 5kW will just mean that the house will only reach the required temperature (21C) if the outside temperature is above 10C!

Heat recovery, i.e condensing, only occurs if the return temperature is below 55C; the lower it is the greater the condensing effect. Most boilers are designed to work with a 20C differential, which means a flow temperature of 75C if you want the return to be 55C. Unfortunately this reduces the output of radiators by about 15%, so you have to install rads which are 20% oversized.

 

[Alex100]

has he put a room stat/programmer in correct position and in the hours it takes to heat house are all the rads hot to touch or just warm

all hot to touch. i bleed regularly, which is the installer's mantra, but rarely any air.