The Worcester Greenstar 28i junior combi boiler is suitable for a medium sized, 1 bath flat, apartment or house.

  • It has a wall mounting frame with pipes behind leaving no exposed pipework.
  • The boiler is environmentally friendly with low NOx and CO2 emissions.
  • For convenience it has a keep hot facility giving you instantly heated hot water.
Worcester Greenstar 28i Junior Ratings
SEDBUK Rating % 90.1 5 stars
Built in Frost Stat Yes 5 stars
Height 700 mm
Width 400 mm
Depth 330 mm
CH Output (kW) 24 kwh 3 stars
Maximum Flow Rate 10 litre/min 3 stars

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47 Responses to “Greenstar 28i Junior”

  • holt says:

    What is the price?

  • holt says:

    is it suitable fot a 12 radiator property?

  • Boiler Systems says:

    This boiler is right on the border line for a 12 radiator property, it is possible but it depends on the size of radiators.

    As you need an accurate answer the best approach would be for an heating advisor to visit your property to complete a heat loss calculation for the house and this will give the exact size boiler needed.

  • trieneke says:

    Hi we are interested in having a quote done to see how much it would cost to remove our old boiler system and put in a combi. We have a small 1 bath flat and want an approx price of expected costs.

  • Boiler Systems says:

    We suggest you take advantage of an npower free no-obligation visit from a trained heating consultant to advise you on the best boiler for your property. They will be able to give you a firm quote based upon the survey so you can have confidence that the price will not change once the installers arrive.

  • JOSEPH says:



  • Boiler Systems says:

    To ensure that the right type of boiler is selected to meet the needs of your family npower are able to send a Home Energy Consultant to visit customers properties to complete an accurate survey before a firm quotation is issued.

    This visit is free and carried no obligation. Should you wish to proceed can we suggest you follow the links in this site to arrange for a boiler quotation You will be able to schedule the preferred time of the visit and ensure that you get an expert to survey your heating needs.

  • Mark says:

    Hi, I am in the process of buying a property and will take up the no obligation survey once I move in. In the meantime are you able to advise roughly what type of condensing combi boiler I should be looking at for a medium sized 2 bedroom semi, one bathroom, 2 people, approx 6 rads. Appreciate it may be too vague but wanted to do as much research into costs before moving in.
    Also, from what I gather, it depends on the mains pressure as too whether you use a combi or not, is that correct and how do I find out how good the mains pressure in Hertford is?
    thanks for your help.

  • Boiler Systems says:

    For a medium sized 2 bedroom semi, one bathroom, 2 people, approximately 6 radiators an 18kw combi boiler would easily meet the typical heating and hot water requirements you would have. Details of several of these are outlined within the site.

    You are correct that combi’s take their hot water feed direct from the mains and the mains water pressure determines the hot water flow. We do not have statistics on the water pressure across the Hertford area and believe that you would need to contact the local water supplier to ascertain whether any of their areas have a low pressure.

  • Damon says:


    Had a heating advisor out to do a quote and initially suggested the 28cdi as they said this was 24kw. I live in 3 bedroom semi with conservatory with 1 bathroom. There are 8 radiators in the house but when my existing boiler broke the engineer advised i should have a 30kw. I advised the advisor I didnt want a boiler working hard to meet its requirements and wondered if this machine could cope with my existing setup but also if I was to extend my property this may include another bedroom and another bathroom thus increasing another 2 radiators and bathroom. Obviously I may never do the extension but for a few hundred extra I dont want an underpowered machine in the future. I got a quote for the BG532 machine I think which I was advised is made by Worcester for BG. Is this machine worth the extra £400 and more suited to my needs ?.

  • Boiler Systems says:

    It is very difficult to answer this question online without having all the facts that were available to the advisor however we can advise you from the facts you have provided.

    A 24 kw boiler would easily serve an 8 radiator system but dependent upon the size of the proposed extension resulting in the the addition of the extra radiators and bathrooms a 24 kw boiler may struggle. The 30kw combi would accommodate the expanded system and will also give you an improved flow rate for your hot water in the meantime. [ PS Damon – the email address you gave was invalid so we hope that you visit us again and read this response here]

  • waccer says:

    What size / type combi boiler would we need for a 5 bed two bathroom house.

    Told need a higher litrege? what ever that means please advise

  • Boiler Systems says:

    It is impossible to provide an accurate answer without working out the heat losses for the property, to complete this accurately a trained heating advisor would need to visit your home. To give you a guide, typically a 35kw combi would meet the demands of a 5 bed, two bathroom house.

    Whoever advised you that you need a ‘higher literage’ could have been referring to the hot water flow rate from the boiler. A combi boiler takes water from the cold water mains supply and heats this on demand to provide you with hot water. The hot water flow rate is the hot water generation capacity of the boiler. A lower power boiler could struggle to supply hot water to a family if several hot water taps / baths were turned on at the same time.

  • akapaul says:

    i have a greenstar 28i junior boiler installed by it possible to install a shower directly onto this system.please advise

  • Boiler Systems says:

    In general the answer is yes assuming that this will not be a power shower, but you will need to contact Worcester Bosch direct with the make and model of shower you are wanting to install to check its compatibility with the boiler. Their telephone number is 08705 266241.

    For absolute clarity you cannot install a power shower to any combi boiler.

  • Mark says:

    Hi, this will sound like the craziest question you’ve ever had. From what I’ve read, condensing boilers produce acidic water waste. I have an idea, rather than pour this into our national water system, do you know if I can water my blueberries with it…. they thrive on acidic water/soil. Or could there be other by products harmful to plants?
    Might sound mad but I think it makes sense.

  • Boiler Systems says:

    The condensate does contain chemicals and the composition of this can vary from boiler to boiler so it is difficult to advise whether it would be harmful to the blueberries, and ultimately to you. The boiler manufacturer would have a better understanding of their boilers output and we suggest that you contact them direct for an opinion.

  • Jan says:

    Please can you forward a price for a Worcester Greenstar 28iHE combi c/w prog & w/less stat – no fitting, just the item cost.

    Thank you


  • Boiler Systems says:

    As per the frequently asked questions on the site we are sorry to advise that “the national installers offer a full boiler supply and installation service, they do not supply boilers to be installed by someone else and they do not quote a boiler price separately. They procure boilers direct from the major manufacturers and they also specify boiler designs for manufacture. All boilers are then installed by their own trained installers.”

  • alan says:

    I note your comment re; quoting prices. Could you tell me what would be the approx. cost of a full boiler supply and installation sevice for a Worcester Greenstar 28iHE combi?
    Incidentally, is the range of combi boiler makes limited to Worcester and Baxi?
    Thank you.

  • Boiler Systems says:

    We are sorry that we are not able to provide an approximate supply and installation cost as national companies will not quote without conducting a heating and installation survey of the property. The visit is free with no-obligations on your part and enables an accurate quotation to be developed for a new boiler. Often online ‘quotes’ can prove to be worthless as they cannot take into account the true installation costs associated with your installation. At times they can also be based upon the wrong boiler for your needs.

    The manufacturers often used are Worcester Bosch, Vaillant, Baxi , Glow worm and Caradon Ideal and they install all of their ranges going from 15kw up to 42kw.

  • JAMES INKPEN says:


  • Boiler Systems says:

    Some installers do have a number of LPG boilers that they install. All are manufactured by Bosch Worcester Group.

  • shanny says:

    hi, i am hoping to get a new heating system with 8 readiators. I live in a 3 bed semi with 1 bathroom. Can you please tell me what is the best boiler for me. I was looking at a bosch or a valliant. Many thanks

  • shanny says:

    hi, i am hoping to get a new heating system with 8 radiators. I live in a 3 bed semi with 1 bathroom. Can you please tell me what is the best boiler for me. I was looking at a bosch or a valliant. Many thanks

  • Boiler Systems says:

    It is impossible to say what is the best boiler for your home without working out the heat losses for the property. As a rough guide 18-24 kw would suffice for your needs so any boiler in Vaillant or Worcester Bosch range that is rated at this output this would fit.

  • J.NEAL says:

    I live in a 3BED Bungalow and wish to replace my existing conventional Boiler System with a Combi or System Condensing Boiler. I have 14radiators 1 en suite shower and bath- I have been advised that I will need a Worcester 28iJunior or 24i System (based on a survey carried out by others); based on some of your previous correspondents this sounds as if these may be too small – do you think this maybe the case; Could you advise on what your price to supply/install would be, including power flush.

  • Boiler Systems says:

    It is impossible to say what is the best boiler for your home without working out the heat losses for the property. Also an installation price cannot be accurately developed without a property survey to understand the installation challenges. We are therefore sorry that we cannot respond to your question, any answer would be liable to significant cost variation as the facts were established.

  • Mario says:

    Hi, I have a Worcester 28i Junior, pressure is almost zero and it won’t fire up, therefore no heating or hot water. Can someone tell me where the re-pressure thing on the boiler is, I’ve got the key but have no idea what to do with it.

  • Boiler Systems says:

    To top up your system and increase the pressure, you will need to locate your filling loop. It most usually resembles a stop tap and is connected to the central heating system by a metal hose. Occasionally you may find that one end of the this metal hose is not connected to the pipe work on your system. There may be a cap on the end of the pipe and it will need to be connected to the system to allow the water to be injected.

    If this is not obvious we suggest that you telephone Worcester Bosch technical help line on 08705 266241 and they should be able to explain where the valve is on all their variants of boiler.

  • Linda says:

    I need a new central heating system to replace an ancient defunct one!
    Terrace house 3 beds, 7 rads, but on a shared water main. The water goes through house no1 and onto number 4. If no 1turns their water off for maintenance, 2,3 and 4 dont get any.

    I have been advised both that I can and cant have a combi system. Would it affect a combi boiler if there was no supply for a short time or do they have a fail safe mechanism?

  • Boiler Systems says:

    If the water went off you would have no hot water at all. The boiler would not fire but any contaminants in the water flow when it was restored will cause problems in the boiler. Experts would advise you to install a regular condensing boiler and keep your cylinder, at least if the water goes off you will still have a tank full of hot water to use.

  • Iain Smart says:

    My existing boiler installation (non-condensing) is being replaced with a new condensing boiler. The existing gas supply pipework from the meter to the boiler is within the cavity wall and within a non-ventilated roofspace. The Building Regulations Part J Section 3 , Clause 3.5 f appear to infer that when a new boiler is installed the existing installation should be checked to ensure that no non-compliant elements are present. Supply pipework within cavity walls would be non-compliant in accordance with the Gas Safety Regulations 1998 Clause 19(3), but the word ‘installation’ is used. Do the Building Regulations and SI-1998 No 2451, taken together, require the existing pipework to be moved/reinstalled so that the regulations are completely compliant as if the supply pipework was being installed new at the same time?. Put another way, if the original supply pipework within the cavity was reused, would this be a non-compliant installation?.
    Please distinguish in your reply between ‘good practice’ and the legal requirements.

  • Boiler Systems says:

    We suggest that you discuss the interpretation of the regulations with the boiler installer you have already selected. We are unable to provide a legal interpretation of the regulations on third party installations.

  • Sam Read says:

    Can you tell me if the Worcester 28i junior is a condensing boiler please.

  • Boiler Systems says:

    Yes it is

  • ogee says:

    I had a quote for central heating installation from you guys sometime ago, i have since found a supplier with considerably lower prices for comparative items complete with manufacturers guarantee. why is this? secondly, can i source the materials while you provide the installion.

  • Boiler Systems says:

    The quotation will be for the supply AND installation of the boiler by Installation Engineers.

    We often have enquiries that some supplier has offered a boiler at a lower price but more often than not this alternative quotation is not based off the same details.

    Many companies and sole traders will happily provide an initial quote that beats a quote but will then be severely challenged to complete the installation to the same quality standards and provide you with the same confidence guarantee that a company like npower is able with its professionally trained installation engineers.

  • Lesley Tanner says:

    I have two boilers, the first gives instant hot water through out the house over 3 floors and is located on the first floor, the second is located on the 3rd floor and heats my central heating radiators 2 large double radiators & 3 large single radiators.

    I am wanting to replace the two boliers with one boiler & may add 2 extra radiators, would you be able to advise if this is possible and which of the 2 locations would the new boiler work best. Also if a survey was done how long would it take to replace the boilers, and how would I dispose of the old boliers

  • Boiler Systems says:

    It could be done but without knowing the combined output of both boilers it is impossible to give any more information. Also the length of the installation could not be determined without knowing more details of the proposed installation.

    Rather than engage is a series of emails to establish the information we suggest you take advantage of our FREE no-obligation service whereby npower are able to send a Home Energy Consultant to your home to review the installation options and help to select the right boiler for your home. This visit will enable an accurate quotation to be developed for a new boiler and identify any other installation issues, or opportunities, which perhaps would not come to light via email.

  • Bev Farrar says:

    what should the water pressure rating be for a baxi duotech 28kwh combi boiler please

  • Boiler Systems says:

    We do not have that information to hand nor is it within the Baxi website which we have searched.

    We suggest you contact Baxi support direct for the information, their telephone number is 08706 049049

  • Bev Farrar says:

    Boiler Systems commented on: May 9th, 2007 at 2:26 pm (question 15) “For absolute clarity you cannot install a power shower to any combi boiler”. My sister has a combi shower by Newteam 911 Flair fitted to her Worcester Bosh 240rsf combi boiler fitted by a national installer. Explain what type of system she has please, it is very efficient, economical and the shower is very very powerful. I would like something similar. A heating consultant is coming out next Tuesday and I would like to know by then please.

  • Boiler Systems says:

    The shower you refer to is a classic mixer shower. These showers can work on all types of water systems and are ideal if you have a good supply of hot water. They are also the most popular type of shower in the UK. It is very simple in design, no pumps , just relying on the mains pressure coming through to work it to its maximum efficiency.

    The comment on combi boilers not working with power showers refers to a shower driven by an electrical pump. If you have a combi boiler installed the water pressure to the shower will depend upon your mains cold water pressure. The heating advisor will be able to review this for you.

  • david cooke says:

    Can I use the radio frequency thermostat on the 28i Junior? Is the thermostat battery powered or does it need to be plugged into the mains electricity?

  • Neil says:

    Hi, I am looking at buying the WORCS GREENSTAR JUNIOR 28I. This will due to new regs have to be installed in the bed room. This has been recommended because of its low noise. Is this correct?
    many thanks

  • Boiler Systems says:

    We do not hold sound level information on boilers, although all are quiet these days. Worcester Bosch will be able to advise you correctly on the noise levels for their boilers.

    We can confirm that there is no problem with having a fanned flued boiler installed in a bedroom.

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