The Grant Vortex Condensing Combi Boiler – Outdoor Models 26kw/36kw/90 v3/Max

Grants as a boiler manufacturer have been trading for over 35 years. In this time they have produced some exceptional models of heating boiler.

The Grant Vortex Condensing Combi Boiler, outdoor model is no exception. It has a heat store of 35 litres for hot taps and baths, and can heat a radiator system of 128 litres. It is SEDBUK band efficiency A and could save you a small fortune in heating bills.

All Grant Vortex boilers are for use with 28 sec light Kerosene and all require a pressurized heating system. (fill loop, expansion vessel and high pressure relief valve all supplied)


This outdoor boiler model has been perfectly designed to give optimum performance to the home without being inside the home. It can supply hot water to your taps at a rate of 17 litres a minute and also supplies heating water to your radiators; all for a fraction of the price. I cannot stress enough how many of these boilers I have installed and how happy the customer is with the looks of the boiler and its performance. Everybody should consider installing one of these when replacing their old boiler or installing a new system.

Where to buy Grant Vortex Boilers and why buy one yourself?

So we’ve had a quick look at how the Grant Vortex Combi boiler works. What if you’re looking to buy one? Most customers find it easier to allow their installation engineer to buy the boiler. Think again. If you buy the boiler and get the engineer to fix it for you, then you avoid their mark up and save money. If you aren’t sure which boiler to buy then ask your installing engineer what Kilowatt or BTU rating you will need and buy the boiler accordingly.

Buying boilers online is relatively simple. We found a few suppliers that deliver boilers next day and gave them a try.

Installation (pipework):

Installation for heating flow and return pipes is an easy task compared to some boilers. Removing the top cover exposes all the connections for easy access. They use a Hep20 type push fitting eradicating the need for nuts and olives. The boiler casing has many different combinations for pipe entry and exit making it flexible when choosing a position. There are even openings on the base of the unit for pipes to come from underground.

The heating flow and return pipe, the cold water main inlet pipe and hot water outlet sizes are:

26kw – 22mm, 15mm and 15mm

36kw – 22mm, 15mm and 15mm

90v3 – 22mm, 15mm and 15mm (although the hot water outlet can be 22mm)

Max – 22mm, 15mm and 15mm (although the hot water outlet can be 22mm)

All of the above boiler models have a 15mm high pressure discharge pipe.

The boiler is supplied with two circulating pumps neatly situated inside the boiler casing. One is a circulating pump for the hot water store; the other is the circulating pump for the radiators. These can be accessed by removing the front panel. All the air vents are easy to access from above.

The cold water inlet for the fill loop and cold water supply to be converted to hot water for the taps is situated at the top of the boiler. The boiler comes with a non-return valve to prevent water going back into the cold main. Pipe sizes for cold water connections are 15mm for 26kw and 22mm for 36kw.

As we have mentioned, a condensing boiler produces lightly acidic water. The boiler is supplied with a condense trap that must be terminated into a main drain if not treated. The connections are push fit 3/4″ plastic pipe. This can be found if you remove the rear panel of the boiler. However if there is no suitable drain near the installation an inline acidic neutraliser like a Calmag Caldensate can treat the water so it can be safely terminated to a soak-away. The Calmag is easy to install (again 3/4″ push fit plastic) and comes supplied with a wall clip.

The oil line connection is a flexible braided hose (provided with the boiler) 1/4″ BSP male. Most UK domestic oil lines are 10mm copper, therefore a bush is usually required to convert. All oil installations require a fire safety valve.

When installation is complete and the system has been re-filled with water and tested for leaks. Flush the system and re-fill with a suitable inhibitor. If you don’t perform this action it will void the warranty.

Installation (flue):

The outdoor models have an ingenious flue arrangement that can exit the boiler on 4 different sides – rear, top, left and right. The boiler also comes with a stainless steel protection grill.

All the outdoor models have one right angle flue part that terminates with a 45 degree. The flue is attached to the boiler with three wing nuts. This is the whole flue arrangement. Easy to install and cheap (you don’t have to buy a flue kit)

All their flue connections are sealed using a fitted rubber sleeve. They come with lubricant for easy installation and are secured with screws. Use a flue flashing kit to seal the flue as it goes through the roof slates. These can be used on flat or pitched roof. Slot them in then lightly tap the soft lead around the slates.

Installation (electrical)

Always use a qualified electrician who has experience working on heating systems.

The electrical connections are easy to access from above. The Grant is easy to install with different controls and programmers. Just follow the instructions provided with the boiler.

All Grant outdoor models have a built in frost thermostat to protect them from freezing in cold conditions. THIS MUST HAVE A PERMENENT 240V LIVE SUPPLY.


Always employ a qualified heating engineer when servicing any heating appliance. Always switch off the boiler, remove any fuses and turn off the oil supply.

The Grant Vortex Combi outdoor boiler is relatively easy to service. The combustion chamber is accessible once the expansion vessel is released from its bracket. It can be removed without having to drain the system as it is connected by a flexible connection and can rest on the floor.

Once the combustion door is removed the baffles are easily removed taking note of their position. The chamber can then be cleaned out and inspected.

The burner is secured by a 13mm nut. Once removed, depending on the burner model (grant use RDB and Riello) the oil nozzle, flame tube and electrodes can be serviced and changed where required (see my other post on detailed information on the maintenance of oil burners)

The Grant has a small bolt toward the top of the combustion chamber that can be removed to perform a combustion analysis

When someone thought it was a good idea to design a manifold in the middle of the room! @wright_heating_and_plumbing Send your pics/video & tag @plumberparts with #PlumbingDisaster 
#Plumbing #Plumber #Apprentice #apprenticeship #Tradesman #Trade #OnTheTools #SiteBanter #DIY #DoItYourself #Pipework  #worldplumbers #PipePerfect #PlumberLife #hvaclife #plombier #Plomoro #Plomberie #FindYourPlumber
Howard Funnell found this cheeky #FlexiFriday hidden in his sons loft! Send your pics/video & tag @plumberparts with #PlumbingDisaster 
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Good way to start the year, Blocked cold feed and vent at HOME!!! @Bertmick heating stopped working to find THIS! Offffft! Send your pics/video & tag @plumberparts with #PlumbingDisaster 
#Plumbing #Plumber #Apprentice #apprenticeship #Tradesman #Trade #OnTheTools #SiteBanter #DIY #DoItYourself #Pipework  #worldplumbers #PipePerfect #PlumberLife #hvaclife #plombier #Plomoro #Plomberie #FindYourPlumber
This flue looks like its a bit on the angle. How did that even happen? Like the cored it whilst playing twister... @lutherplumbing 
Send your pics/video & tag @plumberparts with #PlumbingDisaster 
#Plumbing #Plumber #Apprentice #apprenticeship #Tradesman #Trade #OnTheTools #SiteBanter #DIY #DoItYourself #Pipework  #worldplumbers #PipePerfect #PlumberLife #hvaclife #plombier #Plomoro #Plomberie #FindYourPlumber