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Intergas boiler

Discussion in 'Plumbing and Central Heating' started by Mike2007, 10 Apr 2019.

  1. Razor900

    Razor900

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    Not going to get into a heated debate although you could mention that you work for a competitor but do you really still tell installers to set the flow temp to 80 degrees on Vokeras?

    Most boilers I attend set up by quality installers have a flow temp of somewhere around 65/68 degrees. The days of an 11 degree delta went out when steamers were made compulsory and systems are specced on a max of 70 degree flow to ensure the return is low enough to condense.

    How efficient are Vokeras when run at an 80 degree flow temp?
     
  2. Razor900

    Razor900

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    Actually he has a point although wildly exaggerated. If the boiler flow temperature is set to 90 degrees the first 'slug' of water out of the taps will not be far off that.

    That's an installation issue not the boilers fault. With modern insulation and windows the flow should not need to be set much more than about 65 degrees which will give an initial water temp of about 55 degrees C

    Modern controls are all aimed at keeping the flow temp as low as possible. Once up to temp the rads will be at less than 40 degrees...

    By the same token with the 80 degree plus flow temp that VC is recommending how long would it take to get serious burns when leaning against a radiator?
     
  3. bernardgreen

    bernardgreen

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    If the heat exchanger is running CH at 65°C then the water in the DHW coil in the heat exchange will also the very close to 65°C. Opening a hot water tap will release that slug of hot water out to the tap before cold water from the mains cools the heat exchanger.
     
  4. Razor900

    Razor900

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    It won't be at 65 degrees due to the layout of the coils in the hex.

    I've tested it personally have you?
     
  5. bernardgreen

    bernardgreen

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    Yes I know the DHW coil is further from the flames than the CH coil but the thermal gradient across the heat exchanger is not that great when CH has been running at 65°C for a while.

    So how hot was it. How far from the boiler along the hot water pipe did you place the temperature sensor ?
     
  6. Razor900

    Razor900

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    Perhaps you should actually read my earlier post.......

    And the data was taken directly from the temp sensor on the boiler
     
  7. bernardgreen

    bernardgreen

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    How does that happen.... a 10° difference across the solid aluminum heat exchanger. I can accept that heat removed from the heat exchanger by water flowing in the CH coil will create a shallow gradient but if CH is at 65°C then the heat exchanger will be hotter than 65°C.

    Directly from the sensor or via the boiler's processing to a display on the boiler.

    The tests I am aware of used PT100 thermometers to get accurate readings of water ( pipe surface ) temperatures.
     
  8. vulcancontinental

    vulcancontinental

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    I am an installer, I have installed bi-thermic heat exchangers, I've been aware of the problem. If you've never seen it it can't exist I guess. It's your grandchild not mine.

    "Hot water set at 65 Degrees and warms up gently with the eco function off that preheats the exchanger." suggests otherwise
     
  9. vulcancontinental

    vulcancontinental

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    I thought I was fair in my opinions, I didn't mention I worked for a boiler manufacturer as I wasn't recommending our product or in fact any product, just expressing an opinion. Crumbs, I even said I've recommended certain installers who fit Intergas to my old customers because I know they'll be put in by someone who knows what they're doing.

    I did not mention 80 degrees, I said rad outputs were certified with a flow at 75 degrees and if they're operated cooler the output to the room will be less so some users will turn the temperature of the heating supply up and that's where a problem can arise.

    Vokera boilers as you well know have a plate exchanger a diverter valve and a primary flow and a hot water thermistor all of which are used to ensure a DHW below 60 degrees as the heating circuit is kept separate, when they are parallel the separation is only made after hot water in the domestic section is exhausted, hopefully at a safe temperature.

    Generally Vokera's are very efficient at any temperature because of the design of the hex and you'd be looking at a differential of between 3 degrees to 14 degrees flue to return depending on whether it is an economy or commercial product. This very morning I was looking at a consistent dfferential of 6 degrees on a domestic evolve flue to return on maximum output. That's what tells the installer how much heat is leaving the boiler through the flue but because of the test rig I couldn't raise the flow to above 60.

    If the boiler can be set to 90 degrees output heating, and eco mentioned the hot water can too but I don't know whether I read that wrong, I don't think that is an installer fault.

    When are we going to meet, I'd like a good chat, are you going to Installer or there's loads of coffee shops near Colney?
     
  10. vulcancontinental

    vulcancontinental

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    burn.jpg

    This was NOT from an Intergas or combi boiler set too high but simply the burn you said didn't exist as you've not seen it.

    Hot water damage to human tissue; the regs were tightened regarding hot water supply a few years ago after two deaths of children and some serious eventually fatal burns to the elderly who cannot react quickly enough to get their bodies out of seriously hot water.

    See you at the sharp end.
     
    Last edited: 2 May 2019
  11. bernardgreen

    bernardgreen

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    There is also the harm that cold water shock can do. Being suddenly and un-expected immersed in cold water can be fatal. As in a shower when the boiler shuts down and hot water becomes cold without warning.

    The sudden cooling of the skin by cold water causes an involuntary gasp for breath. Breathing rates can change uncontrollably, sometimes increasing as much as tenfold.

    Cold water shock causes the blood vessels in the skin to close, which increases the resistance of blood flow. Heart rate is also increased. As a result the heart has to work harder and your blood pressure goes up. Cold water shock can therefore cause heart attacks, even in the relatively young and healthy.
     
  12. simond

    simond

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    I could summarize this latter debate by reminding everyone that there have been lots of bithermic heat exchanger boilers launched since the birth of the combi.

    Models from Ferroli, Potterton and Worcester I have worked on, and now I hear that Vokera also had one.

    All these manufacturers eventually dropped their bithermic designs and went back to plate heat exchangers. Limescale (not an issue in Holland) and dangerously hot slugs of water were their downfall.

    Intergas say that the flow temperature of the heating should be reduced and this mitigates the issue.

    The issue is that many of their boilers are being fitted in older UK housing stock where the radiators were sized appropriately for a Central Heating flow of up to 75-80c. I doubt many Intergas customers have had their radiators changed to increase their surface area; therefore on the coldest days a 60c flow temp will leave them cold.

    I don’t see many posts on here advocating to potentially clueless internet customers doing ‘research ‘ (eg: not heating professionals) that they may have to upsize their radiators.

    And here is the rub. If it were advertised as a boiler with less moving parts but in older retrofits you might need to change the radiators- they wouldn’t sell many.
     
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  13. Razor900

    Razor900

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    Interesting. So are you saying you regularly leave combi boilers with a set temp of 80 degrees. How do you manage that and stay boiler plus compliant?

    Can no one in your area afford double glazing?

    I wouldn't want your clients heating bills - some of us have moved on from the 70's :mrgreen:
     
  14. bernardgreen

    bernardgreen

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    Even with double glazing the existing radiators may be too small to provide adequate heat when CH water temperature is reduced down to 60°C

    When heating was installed the radiators would have been sized for 80°C water and double glazing in place.

    Perhaps an upgrade to triple glazing is the solution to preventing hazardous hot slugs in the domestic hot water supply from certain makes of combi boilers.
     
  15. vulcancontinental

    vulcancontinental

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    Radiators can be run at any temperature it's just the catalogue output figures for a particular size are determined with a flow of 75 and a return of 65 in a room at 20 degrees so if the heat loss calculation was correct, seldom the case, that's the output you'd expect from it. Lower temperature you'll get less output, higher more.

    If you're a fan of condensing try to run chilled water through them at below ambient room temp and harvest the latent heat given off when condensation forms on them; you'll need it as the room will be cooler due to the transfer of sensible heat.

    Not making a point it's all a matter of perspective.

    On a separate note a program called skylab on BBC iplayer was great at illustrating latent heat. By flying an airship through clouds slowly boffins were able to take readings of weight and temperature of clouds, how the water changes from vapour to ice to liquid. A small cloud weighed 4 tons and a larger one at higher altitude if the vapour was condensed contained energy equivalent to the Hiroshima bomb.

    I think it was over a hundred trillion tons of water above our heads in the air at any time.

    Off topic but fascinating to me, I would recommend it. My head has been in the clouds more than usual since watching it.
     
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