Upgrading heating system

[grommett]

Hi

I am currently upgrading my heating system and have a couple of questions. My house was turned into two flats in the 60's and back into a house in the 80's. I am now replacing two gas boilers with a new one and joining the two systems together. Also replacing the cold water storage tanks in the loft with one large new one together with a 200litre indirect cylinder. I intend to use a standard 'Y' plan heating system.

I am considering open vented, modulating, condensing boilers from Halstead, Glow Worm and Worcester, does anyone have preferences? It is a straightforward installation with no special flue requirements.

Am I right in thinking that cold feed and vent should be on the flow between the boiler and the diverter valve?

Do I need to incorporate any kind of bypass in the system?

I have tried using the energy efficiency "Whole House Calculater" for calculating boiler size but it only allows 2kW for the hot water and the rating lable on my cylinder says 22kW, how much should I allow? The reccomended boiler size was 16kW which seems too small to me. I have a large 5-bed (including a 14' x 16' loft room) Edwardian house (approx 2000 square feet) with 9' high ceilings, UPVC double glazing, new cavity wall and loft insulation. Would 30-32kW sound too much?

I thought about going for a system boiler but I am worried that the water content of the whole system (12 radiators) would be too much for a built-in expansion tank, I could put a pressure vessel in the airing cupboard but would I gain much compared to using a f/e tank?

Thanks in advance to anyone taking the trouble help me, it is much appreciated.

Ian

 

[Agile]

When the calculations give you 16 kW then why do you want to double it?

You lose all the efficiency benefits of a condensing boilerwhen you over size it.

Use the 16 kW given by the calculations but you would have to range rate the Halstead or use the 18 kW Worcester Ri. Dont know about the GlowWorm as they have plastic bits inside.

The cylinder shows the maximum absorption but this only occurs for a few minutes when heating up from cold. The 18 kW will be fine.

Tony

 

[gas4you]

If you must go the open vented route then I would fit the Vaillant Ecotec Plus 418.

I would recommend that you go the system boiler route as the system will last longer.

Vaillant or Worcester would be the best mainstream choices.

 

[loisj]

Hi Ian
A vent pipe should never be fitted too close to either side of the pump, because of sucking in or pumping over in the future.
Usually its a good idea to take a feed from the flow and return from the boiler to a bathroom radiator as a by-pass. In case you have TRVs everywhere else, prevents overheating and locking out on the boiler.
(PS we all like warm towels from a hot shower summer or winter)
Enjoy your project
Lois

 

[grommett]

When the calculations give you 16 kW then why do you want to double it?]

Hi Tony

I understand that it is inefficient to oversize a boiler but I am not sure about the calculater. My house is not a regular rectangle, it has staggered outside walls which increases the overall wall area. It also has dormer windows on the first and second floors. Also I made a typing error - it should have said 18kW.

I added up the outputs for all of the radiators in the house which comes to 75,500 btu's (22kW I think) add in 2kW for water and it comes to 24kW.

These boilers are advertised as "Fully modulating" and literature quotes an output range (typically 18kW to 32 kW). So I thought that as long as my requirement falls in the middle of this range I would be OK and there would be no danger of being too cold in the winter! I know I might be wrong which is why I am greatful for the advice from those who know.

Ian

 

[simond]

I would suggest fitting a system boiler as per Dave's suggestion, you do not have to worry about pump siting and a sealed system usually keeps the water cleaner longer. It is also slightly more efficient in terms of circulation.

Regarding the boiler sizing, if your room by room calculations have been carried out using a Mears (or similar) calculator making allowances for internal/ext walls, height of room and insulation, then go for a 24Kw. Tony (Agile) was working on the original figures you supplied.

I have to admit I was a little surprised that the Whole House Calc ended up significantly different to the room by room total. Being doubtful of internet calcs, I have in the past cross referenced my rooms calcs a few times and never got a deviation of more than 10%.

Whilst it is probably great fun installing the boiler yourself, if anything is wrong with it you could end up in a world of bother getting it replaced. The plumbing industry is very sceptical of DIY boiler fitting and although you may have done nothing wrong, it can be difficult when you are arguing that point on the trade counter with a queue of Corgis waiting behind you.


More cheese, Grommet?

 

[Dan Robinson]

I would be surpirsed if you needed 30+kW.

24 would probably be ample.

Don't use a Y-plan, use an S-plan. It passes more heat and you need sprung loaded vavle for the cylinder; but then you G3 installer would be able to tell you that

You need a differential by-pass too.

You know roughly, what you want so I would leave the finer points to the CORGI guy who will be doing the boiler; I shall leave the boiler choice itself to you and he, but there is more than enough debate here over the different brands.

 

[Doctor Drivel]

Hi

I am currently upgrading my heating system and have a couple of questions. My house was turned into two flats in the 60's and back into a house in the 80's. I am now replacing two gas boilers with a new one and joining the two systems together. Also replacing the cold water storage tanks in the loft with one large new one together with a 200litre indirect cylinder. I intend to use a standard 'Y' plan heating system.

I am considering open vented, modulating, condensing boilers from Halstead, Glow Worm and Worcester, does anyone have preferences? It is a straightforward installation with no special flue requirements.

Am I right in thinking that cold feed and vent should be on the flow between the boiler and the diverter valve?

Do I need to incorporate any kind of bypass in the system?

I have tried using the energy efficiency "Whole House Calculater" for calculating boiler size but it only allows 2kW for the hot water and the rating lable on my cylinder says 22kW, how much should I allow? The reccomended boiler size was 16kW which seems too small to me. I have a large 5-bed (including a 14' x 16' loft room) Edwardian house (approx 2000 square feet) with 9' high ceilings, UPVC double glazing, new cavity wall and loft insulation. Would 30-32kW sound too much?

I thought about going for a system boiler but I am worried that the water content of the whole system (12 radiators) would be too much for a built-in expansion tank, I could put a pressure vessel in the airing cupboard but would I gain much compared to using a f/e tank?

Thanks in advance to anyone taking the trouble help me, it is much appreciated.

Ian

I would advise not to join the systems and keep the "zoning" aspect. This means have the upstairs and downstairs on separate circuits to control them individually, having them on time clocks. This saves energy as you then do not heat parts of the house unnecessarily.

What is the mains pressure like at the house? How many baths? Showers?

If the mains is good and delivers a good flow then I would go for a heat bank and have the two CH circuits off this using Grundfos Alpha smart pumps. Then TRVs can be fitted on each rad and no nuisance wall thermostats or silly by-pass valves, power shower pumps etc.

The heat bank is a great neutral point and heat buffer. The boiler will also be operating in a hydraulically superior environment with no boiler cycling. The boiler will last longer, be more reliable and more efficient as a result.

 

[simond]

Have I read this somewhere before?

Wake me up when he's done.....

 

[Doctor Drivel]

Have I read this somewhere before?

Wake me up when he's done.....

Please pay attention. This is good for you.

 

[grommett]

I would advise not to join the systems and keep the "zoning" aspect. This means have the upstairs and downstairs on separate circuits to control them individually, having them on time clocks. This saves energy as you then do not heat parts of the house unnecessarily.

What is the mains pressure like at the house? How many baths? Showers?

If the mains is good and delivers a good flow then I would go for a heat bank and have the two CH circuits off this using Grundfos Alpha smart pumps. Then TRVs can be fitted on each rad and no nuisance wall thermostats or silly by-pass valves, power shower pumps etc.

The heat bank is a great neutral point and heat buffer. The boiler will also be operating in a hydraulically superior environment with no boiler cycling. The boiler will last longer, be more reliable and more efficient as a result.

I did look into heatbanks but decided against because of the install cost and the fairly poor mains water pressure (and the fact that the washing machine is on most of the time when I want a shower!).

I will be getting a Corgi installer to fit/commission the boiler but he is old school and advised against a system boiler as the built in tank would be too small for the water volume of my system - I still have an open mind.

 

[gas4you]

If upon calcualtion you need a larger expansion vessel, then this can be added as a seperate unit. Quite common on larger properties.