Combi Boiler question

Discussion in 'Plumbers' Talk' started by Pincera, Sep 15, 2018.

  1. Pincera

    Pincera New Member

    I am having a Combi boiler fitted in the next few weeks and have a question that I hope someone can answer.

    My current system has a conventional boiler which uses\diverts the hot water circulating in the coil, in the cylinder, to heat 2 towel rails, this is useful in the summer when the heating is not used.

    And now the question

    As the combi boiler has two separate circuits, hot water and heating, I will no longer be able have heated towel rails without the heating being on ( I understand I could have electrically heated towel rails). My thinking is that my Install guy will remove\disconnect\cap off the "hot water" towel piping when he removes the cylinder, 3 port valve, pump and the water tanks is this correct?

    I had never come across this method of heating the towel rails, without the heating being on, before I moved into this property it is such a simple but clever idea. When we first moved in I thought there must be something wrong with the system as the towel rails were hot without the heating being on, I thought the 3 port valve had a problem but then realised that only the towel rails were affected.
  2. terrymac

    terrymac Well-Known Member

    The answer to your question is yes.All will be stripped out and you will not get hot towel rads unless c/ heating is on.
  3. The Teach

    The Teach Well-Known Member

    Hopefully the combination boiler installer will marry up the pipes to provide heat to your towel rails,the radiators & towel rails will be on one circuit and all heat together.
    Pincera,was that not discussed when your system was surveyed for a combination boiler ? sometimes electric heating elements can be fitted to towel rails to provide dual fuel operation.

    An electrician would need to wire up the electric elements and carry out any necessary additional works. Heated towel rails are a nice luxury :)
  4. Mike83

    Mike83 Well-Known Member

    I’m not sure if the heating could be zoned by changing it to an s-plan system.
    The towel rails could be on their own zone but not sure about regulating the temperature.
    Far cheaper heating the towel rails with gas than electric.
    Interesting one.
    Allsorts likes this.
  5. Allsorts

    Allsorts Well-Known Member

    Your original setup was quite doable since the DHW from your old boiler would typically run for a goodly half-hour or so to recharge your hot cylinder, so the towel rad would get some of this water and be hot for that useful amount of time - and your hot cylinder would not lose out from this either as the boiler is more than capable of supplying both.

    In theory your plumber could divert your combi's DHW outlet to your taps via the towel rad, but that would be nuts - it would take much longer for hot water to come out the tap, and also your towel rad would only get hot for the few seconds a tap would be run. As I said, nuts... :)

    Hopefully, tho', your plumber would have replumbed these towel rails back in to the 'proper' CH side of the combi, and as said above you can always add (or replace with) an electrical element in the rads.
  6. Allsorts

    Allsorts Well-Known Member

    Good theory, but would a modern boiler struggle with such a light load as a couple of towel rads, so would be cycling quite a bit? But perhaps that isn't an issue, in which case cracking idea; fully independently heated towel rads.
  7. Mike83

    Mike83 Well-Known Member

    The combi will be modulating and can probably be range rated for heating demand.
    Allsorts likes this.
  8. kiaora

    kiaora Well-Known Member

    Take this opportunity, if possible, to create zone valves for upstairs,(bedrooms) downstairs and towel rails, well worth the effort at this stage.

    You could even zone the cylinder, for baths, and combi for shower and sink!

    Will save lots of gas

    longboat likes this.
  9. Pincera

    Pincera New Member

    Thank you for the replies, I did not specifically speak the install guy about the towel rails as he is my regular boiler service and central heating guy so he knows the system. Our conversation was mainly centered around the rating and make of the combi boiler and the feeds it needs and where they would come from and, of course, the cost. It was only later that the odd arrangement with the towel rails came into my mind. I am happy to exchange the (HW) heated towel rails for a reliable boiler and the increased efficiency it brings, just glad our 17 year old boiler failed now rather than when the weather gets colder.

    Every cloud has a silver lining:D

    I read up on the combi boiler system, very interesting.
  10. Allsorts

    Allsorts Well-Known Member

    Is it a fait accompli, Pincera?

    If not, bear in mind your plumber would have to replumb these towel rails anyway as they wouldn't be connected to the rest of the CH system, so I bet it would be little extra work to do as Mike suggests above - zone them to have their own control. That way they can work independently of the otrher rads and come on at whatever rate you want even in Summer.

    As Kiaora adds, it makes HUGE sense to take this opportunity to also zone off any other obvious set of rads like the bedroom ones if they share a flow pipe. You will usually only want your bedrooms heated first thing in t'morn and just before bed, and having their own zone and Prog Stat will do this automatically.
  11. Allsorts

    Allsorts Well-Known Member

    Yes, although most would struggle to modulate down to supplying a couple of towel rails. But it's still a good idea even if the boiler would be cycling a bit. I guess in Summer - when only these towel rails are needed - the CH output could be dialled right down low.
  12. Mike83

    Mike83 Well-Known Member

    If the total heating load is 8kw for example then just range rate the combi to 8kw heating output.
    Modulation will take care of the rest.

    Zoning with potential cycling is better than no zoning in my opinion.
    Allsorts likes this.
  13. Pincera

    Pincera New Member

    I will talk to my Installer, thanks for the advice
  14. Pincera

    Pincera New Member

    The Baxi 630 boiler now fitted and running perfectly, we decided not to go with the zoning, I do like the ESRTP4RF thermostat and its Chronoproportional Control it makes so much sense. The boiler is so quiet we can not believe its on.
    The Teach likes this.

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