Which combination storage boiler should i go for?

Hi

This is my first posting so apologies f this has already been discussed to death

I live in a medium to large sized house which has a terrible heating system - Johnson starley hot air system (heater on teh ground floor). The hot water is heated via an immersion heater in a tank on the first floor.

The fan unit has brunt out (woke up to burnt plastic smell) - quotes to have it repaired seem seem (£400-600) SO i thought i bite the bullet and go for a new install.

At my work place we have an alpha cd50 storage combination boiler with 50 lites tank - its excellent for that purpose (which is just taps being used simultaneously)

At home i have 2 bathrooms with mixers.

I have 5 questions:

1) As i live alone and look to start a family over 5 years or so i presume a combination storage boiler will be sufficient? Do you agree?

2) I have been advised by my plumber to go for one with a big tank (i.e. the potterton storage combination boiler which can hold 150 litres on demand.

I see the choice for storage combination boilers as alpha vs potterton vs worcester (small tank) vs valliant (my plumber is not a fan)

He is pushing either alpha or potterton and thinks it will not make a difference - his preference for me wanting a future proof system is the potterton

I do not know what the pressure of the water inlet is

3) my plumber does not like the sound of my suggestion to pipe the house up in 22mm copper instead of 15mm to all to the radiators. My lay thought about this is i can heat the house up quicker. Is this is a good idea if i`m happy to spend more now?

4) can someone suggest the best quality radiator that is not overpriced.

5) he mentioned useing plastic piping in some places - is this ok . my father suggests this should be all copper - any problems with going with some plastic in places.

the house is basically been renovated soon and i would prefer this to be the system which is used for the next 20 years. I am happy to replace the boiler but would prefer not to have to redo the pipework after.

Thanks for your help in advance

1) No, I'd recommend a system boiler and hot water cylinder, unvented if your mains will take it otherwise low pressure with a cold tank in the loft. Storage combis only give large hot water outputs for a short time, until the store is exhausted, then they revert to relatively low-flow hot water. Alternatively a Rinnai Twinflow may be an option for you. Plan for the long-term, a good boiler well-maintained will last you a long time so get the right system installed now.

2) If you do not know what your pressure/flow rate is, presumably your plumber has not measured it. This should be checked before doing anything at all.

3) Main runs should be in 22mm, or even 28mm for a while if it's a large house, with 15mm tails to the rads teed off the main runs.

4) If you're intending to purchase yourself, get Stelrad Compacts from Discounted Heating online, but of course make sure they're correctly sized for the room! Otherwise your plumber will supply good quality rads if he's any good.

5) Plastic is OK but our own preference is copper wherever possible.

Hope this helps

I would advice to keep the air system. J&S do replacement units that a world away from old units. They have electrostatic air filters rated for asthmatics.

I would also consider installing a Multicalor air handling unit. This is just a copper coil, like a car radiator, and fan. They will fit in the same space as the J&S unit. It requires no servicing, just cleaning the air filter which is a user function. A J&S electrostatic air filter can be installed in the ductwork just before the unit, if you want one.
http://www.dbgreen-warmair.co.uk/air.html

A high flow combi can then heat the Multicalor. That is all it heats. This means no black corrosive magentite in the system as you get with rads. It is simple. No zone valves, magnetic filters or the likes. The Multicalor's fan is activated when there is heat in the copper coil. It can be plugged in with a 13A plug. The combi's stat programmer does the temperature work.

Now which high flow combi. You need one which can give a constant flow temperature. The makers tech dept will let you know. Get it in writing if you can. Or if it cannot, fit a UFH mixing valve to the boiler return pipe set to 60C, then the boiler will always send out high temp water top the Multicalor.
http://www.toolstation.com/shop/Plumbing/Valves/d20/sd2696

ATAG make a 51kW combi with no stored water that will work with the UFH blending valve and give great performance for the two bathrooms.

A storage combi? The floor mounted W-Bosch 550 Highflow is excellent.
The Alpha Smartflow using a 50 litre storage cylinder is also good. The cylinder is small, but separate not all in one box.

The whole thing will be far better in your situation. And cheaper. The house is not ripped to bits and you will still have no ugly rads on walls. The air system can intake some fresh air from outside. It can be switched on in summer, without heat, to circulate air cooling the house. You can even have a humidifier installed in the ductwork. So, great advantages which rads could ever give you.

A "plumber" will always divert you to pipes with water inside, so these are not the ideal people to contact. It is best you get in touch with proper heating people who know all types of heating.

If I was designing my own new house I would have a two-duct air system with heat recovery and vent. They are the best.

totallymedicine said:

I live in a medium to large sized house

I have 2 bathrooms with mixers.

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A combi will not be suitable. go for a vented or unvented cylinder - provided the cold water flow rate and pressure is sufficient.

I live alone and look to start a family over 5 years or so

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As Mrs Beeton said: First catch your rabbit.

I do not know what the pressure of the water inlet is

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That's easy to check. Fill up a bucket (most have litre markings) at the kitchen cold tap and time it with a watch. If you have a garden tap off the mains, also check that tap as some kitchen taps can be restrictive and reduce the flow quite a bit. You need at least 20 litres/minute.

My plumber does not like the sound of my suggestion to pipe the house up in 22mm copper instead of 15mm to all to the radiators.

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Your plumber is quite correct. The size of pipe is related to the amount of heat which has to flow through it. Read Small Bore Heating Systems.

If you want to know how the flows are calculated, read Copper Tubes in Domestic Heating Systems. However most installers just rely on experience and use 22mm for the main loops and 15mm drops to each radiator.

Can someone suggest the best quality radiator that is not overpriced.

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Stelrad, Myson and Quinn all make radiators which meet the appropriate British Standard.

As the system is being designed from scratch, you should read the requirements laid down in the Domestic Building Services Compliance Guide

In this scenario we would firstly advise replacing the warm air heater with a condensing Lennox G61 series warm air unit.

Around 94-95% efficient, can be used upflow or downflow.

American technology, quiet, built like a proverbial brick outhouse and uber efficient.

Our customers have been delighted with them, we usually use Trion electronic air cleaners.

We gave up fitting J&S a few years back; the Lennox is expensive but everything about it is on a different level.

simond said:

In this scenario we would firstly advise replacing the warm air heater with a condensing Lennox G61 series warm air unit.

Around 94-95% efficient, can be used upflow or downflow.

American technology, quiet, built like a proverbial brick outhouse and uber efficient.

Our customers have been delighted with them, we usually use Trion electronic air cleaners.

We gave up fitting J&S a few years back; the Lennox is expensive but everything about it is on a different level.

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I agree the Lennox is quality. But so is the MultiCalor and simple and upflow and downflow. I have done a number of setups using a combi and 20kW Multicalor. They replace J&S units directly. Normal combi servicing is all that is needed, as the combi control system is not connected the Multicalors. They are cost effective all around and save space as cylinders are eliminated. The high power of combis ensures the heat up from cold is rapid.

Another alternative is to use two small J&S 8kW Aquair units
http://www.johnsonandstarley.co.uk/warm-air/aquair.asp
These are only 8KW unlike the 20 kW minimum Multicalors. But using one for each floor gives zoning and the upstairs can be off saving money on heating bills. Of course it would require some ductwork to get two in. They also supply them with integrated electrostatic air filters.

D_Hailsham said:

A combi will not be suitable. go for a vented or unvented cylinder - provided the cold water flow rate and pressure is sufficient.

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I assume you have limited exposure to modern high flow combis. The ATAG 51kW, without stored water will do two bathrooms. The stored water W-B highflow 550 will clearly do two bathrooms. The 42kW W-B is good for 1.5 baths and 2 bathrooms at a push as long as two baths are not being filled at once, which is a rare event in a domestic house. It will supply two average showers subcutaneously.

Of course the mains pressure and flow has to be suitable.

GaytonTonner said:

Of course the mains pressure and flow has to be suitable.

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You say this as if it is incidental; but it's fundamental. The incoming water has to be shared between all hot and cold outlets - and that includes washing machines, dishwashers and the tap in the garden used to clean the car.

I am not familiar with the ATAG Q51C; so I check the spec, which frankly does not make sense. For example:

DHW flow (at 38°C) l/min 23.2
DHW flow (at 60°C) l/min 13

Are the flow temperatures of 38°C and 60°C the actual temperatures of the water leaving the tap or are they the rises in temperature? If they are actual temperatures. what is the temperature rise?

If they are rises, a 38°C rise at 23.2 l/min requires a boiler output of 61.5kW; a 60°C rise at 13 l/min requires a boiler output of 54.3kW. Both of which are above the boiler's actual output.

D_Hailsham said:

GaytonTonner said:

Of course the mains pressure and flow has to be suitable.

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You say this as if it is incidental; but it's fundamental. The incoming water has to be shared between all hot and cold outlets - and that includes washing machines, dishwashers and the tap in the garden used to clean the car.

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I am quite specific on this, of course. I find it is best to balance the water system using flow regulators in some cases. BES sell them on-line. The dishwasher and washing machine do not need high water flows in hot or cold. They can trickle in water if need be. The bathroom basin only needs a trickle really. As long as all the flow is directed to the shower it is usually all fine.

I am not familiar with the ATAG Q51C; so I check the spec, which frankly does not make sense. For example:

DHW flow (at 38°C) l/min 23.2
DHW flow (at 60°C) l/min 13

Are the flow temperatures of 38°C and 60°C the actual temperatures of the water leaving the tap or are they the rises in temperature? If they are actual temperatures. what is the temperature rise?

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That is tap temperature. Believe me, the flowrate is excellent on these combis. No one complains. They comfortably do two showers at once and handle one big body jet shower without having very large expensive cylinders. ATAG have an integrated GasSaver on the DHW on the 325C combi. This raises the flow rate by around 1 litre per minute which is a good rise from using heat that would be wasted. I hear they are to put a Gas Saver on a highflow model, thus raising the DHW flowrate by around 1.5 litres per minute. The Gas Saver does reduce gas bills.

The Highflow 550 impressed the hell out of me in DHW delivery. 25 litres per minute, until the store is exhausted. More than enough to fill a bath very fast. The water store recovery was in minutes. It also drops to around 16 to 17 litres per minute, if the store is exhausted.

The W-Bosch 550 stored water combi, which has an integral heat bank. It delivers 25 litres per min while the store is charged. It will deliver 180 litres in 3 minutes, then reverts to what the burner gives. 41.1kW is approx 17 litres/min. That is, in 30 mins this will deliver 180 litres + 459 = 639 litres in 30 minutes. All uninterrupted DHW flow.

A W-Bosch HighFlow 550 costs under £2,000. How much would a 650 litre unvented cylinder, system boiler and all the controls cost? A lot more. The 550 is washing machine sized and fits under a standard worktop. They have a condensing pump option as well, so it is easy to fit anywhere.

Er, am I getting a feeling that George Bramwell and his aliases are amongst us again?

simond said:

Er, am I getting a feeling that George Bramwell and his aliases are amongst us again?

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I did get the info from a post and it may have been his. I assess what the DHW requirements are and work back. It is amazing that instant DHW from modern equipment fits most of the bills these day.

Hi thanks for all your responses:

I am fairly certain i do not want a hot air system and happy to go with radiators for a wet system

I am still unclear what to go for though

it sounds like people are plugging the worcester bosch storage highflow which appears to give teh best flow rates once the store is finished

if i do decide to go for a storage combination system.......

which the best out of the alpha cd50 storage combi vs highflow WB with storage vs potterton storage combi (150 litres)

again thanks for all your opinions

totallymedicine said:

I am still unclear what to go for.

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There are three large housing developments under construction near where I live. None of the three or four bed houses, some with two bathrooms, have combi boilers installed. They all have system boilers and Range Tribune type cylinders.

I still do not understand one point

there is mention that a house of this size should not have a combi - this is fair enough and never suggested

A combi storage ,which from what i understand is basically a normal boiler with a cylinder but built in so better than an ordinary combi

there has been mention of the atag, the german make above but not much mention of the potterton or alpha really - is this because they are no good or just not used much because there are better options

is it the case having a bigger storage i.e. the potterton is better than the bosch or alpha which is only 50 - or is the recharge time more inportant?

i get the impression the storage combination boilers do not get fitted much and amybe there is not a push towards them. my simple mind cannot see why they would not be a good choice in my situation[/quote]

mysteryman said:

I don't like hot air either, or the 'subcutaneous' remark.

Please do consider a Viessmann Vitodens 222-F storage combi. There's a 35kW version which includes a 130 litre cylinder. This can be thought of as a storage combi, or as a boiler with an integral 130 litre cylinder - it's all much the same. Get it with built-in weather compensation, and you have the best German technology in both software and hardware. Simple to install. Check the dynamic water flow rate on your mains.

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this does seem prety decent especially with the 5 year warranty if the isntaller is viessman trained - however i`m guessing most installers including my own arent so i will not benefit from this without probably paying over the odds for specific installer. What are your thoughts - do you know a decent installer that covers the wolverhampton area as i see your not far from me in shropshire