Megaflo or pump

Discussion in 'Plumbers' Talk' started by acm718, Jan 12, 2007.

  1. acm718

    acm718 New Member

    Which is best?!
    We want a system capable of providing a big silly shower at 15 litres a minute, at 2 bar or above. Our mains water pressure is about 3.5 bar, 15mm pipe coming into the property. We have a condensing boiler, currently with 115 litre vented indirect cylinder and old twin booster pump that's just blown a seal. New shower not fitted yet.
    Megaflo say their 300 litre (capacity actually 250l) will do all the hot water we need, as it has a bladder to keep pressure and flowrate up - will it really keep it up (oo-er missus) for a good 10-15 minute drenching? Yearly service also needs to be factored into costs, but I do like the simplicity of having no header tanks, pumps etc, although the pipework and pressure relief valves will be more 'involved' - yes I know this is NOT a diy proposition due to the unvented cylinder! Heatrae have apparently joined forces with Baxi, who do a premier plus 300 litre jobbie for way less ££ than the megaflo - any opnions on either, or another preferred brand? Stainless steel sounds good but is it worth the £££?

    Other option is currently a resited 200 litre replacement indirect vented cylinder and bigger coldwater tank together with a top quality stuart turner 3 bar twin pump - slightly more complex, more noisy, but which option is best?
    Struggling to get objective comparative advice, everyone seems to know about one system only.
    Ta in advance :)
     
  2. Water Systems

    Water Systems New Member

    A heat bank thermals store is what you <u>need</u>. Look at a Flowmax, which has been mentioned previously on this forum, by Range.
    http://www.rangecylinders.co.uk/products/flowmax/storage/index.html

    That should solve your problems - it will do the CH off the heat bank cylinder too. DHW and CH all in one cylinder. The boiler only heats the cylinder under ideal conditions in one long efficient burn. The CH circuit can have TRVs on all rads using a Grundfoss Alpha pump (no wall stat) Can take your full 3.5 bar.

    An unvented cylidner (mageflow) needs a BBA approved fitter (not cheap) and an annual; service costing £60-100 per ann. That is £2,000 over 20 years to have a cylinder of water before you pay to heat it - no service on heat bank and it can be DIYed. Unvented cylinders can do this:
    http://www.waterheaterblast.com

    About the same cost but far more advantages to the heat bank which also gives essential boiler and CH buffering for free. Make sure you have a Magnaclean filter on the CH return to the cylinder and enough inhibitor in it.

    Also Gledhill do them. http://www.gledhill.net

    Only one choice.

    Cheers & at your service :)
     
  3. rcplumber

    rcplumber New Member

    If you fit a thermal store and you live in a hard water area you will probably need a water softener as your store will probably scale up in a few months and your hot water flow will slow down to a trickle, this is a problem that will happen to a megaflo or any other hot water system but can and is often over looked.
    The service cost of an unvented cylinder are usually included in the cost of your boiler service if your boiler engineer has his unvented ticket,but not £60-£100 per time (around here anyway).

    As for the exploding cylinder.... that's a load of made up scare mungering
     
  4. Water Systems

    Water Systems New Member

    If you fit a thermal store and you live in a hard
    water area you will probably need a water softener as
    your store will probably scale up in a few months and
    your hot water flow will slow down to a trickle,

    Nope. The plate heat exchanger has flexible plates to resist scale. Although anti-scale measures should be taken in any hard water area on any system. Even if there is problems then the plate can be unscrewed and descaled (the size of a book).

    this is a problem that will happen to a megaflo or any
    other hot water system but can and is often over
    looked.

    Yep, Take measures.

    The service cost of an unvented cylinder are usually
    included in the cost of your boiler service if your
    boiler engineer has his unvented ticket,but not
    £60-£100 per time (around here anyway).

    Few boiler servicemen have an unvented ticket. If they say they do and "service" the cylinder and an leak within the next year, the insurance company will want to see the ticket.

    <u>Not having the annual service is like driving around without an MOT</u> - have a crash and the insurance company will disown you.

    As for the exploding cylinder.... that's a load of
    made up scare mungering

    Is it? Screw up the pressure relief and take the controls off. Total failure can result in the side of your house dropping off. That cannot happen with a vented thermal store.

    A thermal store offers far more advantages all around than a potential unvented bomb.
     
  5. r2d2

    r2d2 New Member

  6. rcplumber

    rcplumber New Member

    I know of a thermal store that is so scaled up there is no hot water to speak of and it has only been in service for 18 months! A unvented cylinder will last longer than that before problems set in.

    There are people who do boilers and unvented services.

    Total failure can happen with anything, Evan a thermal store can be a dangerous thing if not fitted correctly

    If you screw up the pressure relief and take the controls off then you deserve to blow your house up!

    Total failure can result in the side
    of your house dropping off. That cannot happen with
    a vented thermal store.

    True but if you have a <u>sealed</u> primary circuit then there is still the hazard of hot water under pressure

    A professional fitted unvented cylinder with all the controls working and all safety devices fitted and working offers a far better system than a thermal store.

    In MY Opinion
     
  7. rcplumber

    rcplumber New Member

  8. r2d2

    r2d2 New Member

    I know of a thermal store that is so scaled up there is no hot water to speak of

    An immersed coil type ?.
     
  9. bleve?

    bleve? New Member

    as someone who services and installs all types of boilers and hot water sys i have to admit i prefer thermal stores where appropriate i do try to give customers what they want but someone keeps trying to scare people away from unvented with that link just to balance the argument i just repaired and serviced a heat bank with plate heat exchanger the cost of refurbishing the plate exchanger was £1500 without labour.the cost of a new plate exchanger was £1500 without fitting.the plate heat exchanger had all the required filters and strainers fitted but the plates had been damaged/distorted by what i do not know nor can the manufacturers explain how or why it happened, what i do know is the client is not a happy person as this equipment is less than seven years old and they have to pay thousands to have it repaired/refurbished
     
  10. r2d2

    r2d2 New Member

    the cost of a new plate exchanger was £1500 without fitting.

    Your not talking about a domestic system I take it ?.
     
  11. Water Systems

    Water Systems New Member

    the cost of a new plate exchanger was £1500
    without fitting.


    Your not talking about a domestic system I take it
    ?.

    At that price? Certainly not! I was talking to Range and they said not one of the plate Heat exchangers they have supplied has ever needed replacing.
     
  12. Water Systems

    Water Systems New Member

    A professional fitted unvented cylinder with all the
    controls working and all safety devices fitted and
    working offers a far better system than a thermal
    store.

    In MY Opinion

    Opinion has little to do with it. Itemise the advantanges and disadvatages and an unvented cylinder v heat bank is left for dead. It is worth getting a thermal store for the buffering of CH and the boiler alone. And that £60-100 a year service charge just to hold hot water?
     
  13. acm718

    acm718 New Member

    Many thanks for the replies and the stuff to mentally chew over regarding the thermal store - I'm reading up on thermal store stuff, quite interesting as it makes your boiler effectively more efficient....but...
    one thing that's been pointed out to me now is that a thermal store or megaflo/unvented cylinder both work off incoming townswater pressure at the same time as the cold feed to the shower/sink/bath, a vented cylinder and pump don't - they pump x litres a minute of hot AND cold.
    I'm leaning towards a twin pumped/vented cylinder, just because it's 'old tech' and easily installed and repaired by any plumber, and isn't notifiable or needing tlc every 12 months. Pump £400, cylinder £400, bits £200 + labour. Megaflo £800-£1200 before anything else, thermal store £gawd-knows.
    Vented efficiency is rubbish compared to the thermal/unvented routes, but with good insulation (cylinder will be in warm/habitable area, not stuck up in loft), it should be better than what we have now.
    More headscratching to follow!
     
  14. Water Systems

    Water Systems New Member

    Many thanks for the replies and the stuff to mentally
    chew over regarding the thermal store - I'm reading
    up on thermal store stuff, quite interesting as it
    makes your boiler effectively more
    efficient....but...
    one thing that's been pointed out to me now is that a
    thermal store or megaflo/unvented cylinder both work
    off incoming townswater pressure at the same time as
    the cold feed to the shower/sink/bath, a vented
    cylinder and pump don't - they pump x litres a minute
    of hot AND cold.

    What is your concern?

    I'm leaning towards a twin pumped/vented cylinder,
    just because it's 'old tech' and easily installed and
    repaired by any plumber, and isn't notifiable or
    needing tlc every 12 months. Pump £400, cylinder
    £400, bits £200 + labour. Megaflo £800-£1200 before
    anything else, thermal store £gawd-knows.

    Check out a Range or Gledhill store and others too. They all make them. DPS do the DHW only Pandora which is amined at the unvented cylinder market with a directly heated CH system and heated cylidner. The Pandora is maintenance free and does not need an overflow pipe or mains connection - filled by hose and the screw tightened after.

    Best get an integrated store (heat bank) and have the CH off it as well. Boiler and CH buffering. A Grundfos Alpha pump can be on the CH with TRVs all around and no wall stat. A store heats the house instantly as the stored hot water is pumped into the rads immediately. The CH circuit may just need a samll amunt of heat, say 1kW or less. This is easy as the cope winds up and down to suit - no inefficient boiler cycling (wearing out parts) as when on a direct rads system. A store copes with part load brilliantly (the CH buffer). Decoupling the boiler (it only heats the cylinder in one long efficient burn)- again increases efficiency and longevity.

    Vented efficiency is rubbish compared to the
    thermal/unvented routes, but with good insulation
    (cylinder will be in warm/habitable area, not stuck
    up in loft), it should be better than what we have
    now.
    More headscratching to follow!

    What you are saying is the price is about the same, so I'll go for outdated technology. How long will the pump last? The another £400, then. They make a <u>"noise"</u> too. A tank also collects debris inside. A heat bank can be in the loft saving space below.
     
  15. acm718

    acm718 New Member

    Right, research now well and truly done - thanks for the input!
    Our coldwater flowrate drops to only 9 to 10 litres a minute, depending on the time of day, measured between the two cold taps nearest to the stopcock (15mm copper mains feed), minimum pressure I've seen with no demand has been just over 3 bar, so I reckon megaflo or a thermal store is a no-go - with the low flowrate, I need a booster pump, even with a thermal store, I'd need a pump and storage tank upwind of it, and that'll be too expensive.
    Cheapest option is going to be a twin neg head pump and new indirect vented cylinder and header tank. Pump can be sited far enough away from the bedrooms as to be effectively silent.
    What I would say, having read and read on the internet, is that the thermal store does seem to be a clever and relatively simple solution, despite scale problems, and even the scale can be got round by an easily stripped plate heat exchanger, something I'm kind of familiar with having worked in the brewing industry years ago.
    Gas prices are going up, so making a boiler more efficient by working it harder for less burn time or cycles is definitely the next step - give it a few years, and thermal stores will become the norm (just not round here with the pants flowrate)
     
  16. Water Systems

    Water Systems New Member

    You still have options:

    1. Upgrade the mains (once done it is done for ever), then fit heat bank.

    2. Fit a cold water accumulator (I, assisted by others here, can tell you how to build your own [simple]). This will improve the cold water water flow, and then fit a heat bank.

    3. Fit a cold water accumulator (I, assisted by others here, can tell you how to build your own [simple]) and then fit a two bathroom Rinnai multi-point water heater. They have models that can be fitted outside to save space inside. The Rinnais are cheaper than a 300 litre megaflow and <u>never</u> run out hot water. The existing boier can be for CH only making the system simpler with no zone valves, etc.
     
  17. Water Systems

    Water Systems New Member

    Right, research now well and truly done - thanks for
    the input!
    Our coldwater flowrate drops to only 9 to 10 litres a
    minute, depending on the time of day, measured
    between the two cold taps nearest to the stopcock
    (15mm copper mains feed), minimum pressure I've seen
    with no demand has been just over 3 bar, so I reckon
    megaflo or a thermal store is a no-go - with the low
    flowrate, I need a booster pump, even with a thermal
    store, I'd need a pump and storage tank upwind of it,
    and that'll be too expensive.
    Cheapest option is going to be a twin neg head pump
    and new indirect vented cylinder and header tank.
    Pump can be sited far enough away from the bedrooms
    as to be effectively silent.
    What I would say, having read and read on the
    internet, is that the thermal store does seem to be a
    clever and relatively simple solution, despite scale
    problems, and even the scale can be got round by an
    easily stripped plate heat exchanger, something I'm
    kind of familiar with having worked in the brewing
    industry years ago.

    Scaling up of plate heat exchangers is only in the worst cases of hard water in the country. The flexible plates in the larger plate Heat Xs resist scale formation. If you have a scale problem, irespective of system type, it should be tackled at source. Fit a phospher canister.
     
  18. boilerservice

    boilerservice New Member

    If you fit a thermal store and you live in a hard water area you will probably need a water softener as your store will probably scale up in a few months. While surfing online I have found http://www.northerngasheating.com and started using their service and I have found that there services are really good.
     
  19. Mr Ian

    Mr Ian New Member

    Horses for courses. Accumulators, etc. cost lots of money. Pumps wear out and can be noisy, and you'll need a big cold tank. A thermal store and unvented give similar results for similar costs and are as safe as each other.

    Pays your money and takes your choice. Personally I fit a lot of UV. Lots of people have tickets to install them, they work well in hard water areas and deliver good performance. Forget what WS says - they are totally safe and, just like your boiler, you can choose whether to get it serviced or not (though I have yet to charge anyone for doing it!).
     
  20. Mr Ian

    Mr Ian New Member

    The CH
    circuit can have TRVs on all rads using a Grundfoss
    Alpha pump (no wall stat)

    Not without contravening Building Regs Part L

    An unvented cylidner (mageflow) needs a BBA approved
    fitter (not cheap) and an annual; service costing
    £60-100 per ann.

    No they don't. They need to be fitted with someone with Part G certificate, which can be got from a 1 day course. They do not NEED an annual service, but of course should be checked as part of your boiler service, for which I've yet to find a plumber who will charge.

    Unvented cylinders can do this:
    http://www.waterheaterblast.com

    Your boiler and car will also kill you if you disable every safety device like this.

    Nothing wrong with a heat bank, but if I were you I wouldn't take advice from someone who talks rubbish and knowingly tells lies to infuence your decision.
     

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