Hybrid boiler v combi boiler

MBKent21

I previously posted re changing my boiler for the most energy efficient / cost effective alternative and came to the conclusion that a highly efficient gas combi boiler would be the best solution right now.

I have just been reading about hybrid boilers eg by Vaillant. Does anyone have any experience of these? Are they worth the extra cost and do they save in fuel costs? I previously lived somewhere with an air source heat pump which cost huge amounts to try and get some heat into the property so I wouldn't want to go full heat pump but I wonder if this could be a good alternative?

Reed_Richards

To heat your house you need the right boiler and the right radiators.  If the radiator output is too small then you'll never get your house warm in cold weather.  If the radiators are too small and the boiler is a heat pump then the struggle it has to try to get heat out of your radiators will cause it to raise the water temperature too high and it will cost you a lot of money to run and you'll still be cold.

My impression of a hybrid boiler is that it serves two possible purposes. 

• It can be used to give a bigger heat output than you can get with a heat pump alone,  You might need this if you have a large house or one that is badly insulated.
• You could use it to make your water hotter than a heat pump can do on its own.  You could do this if you don't want to replace your existing radiators but that's probably a more expensive option.

I looked at a hybrid boiler when considering a heat pump but it turned out I did not need the extra power and I really didn't want all the faff of oil.
  

arty688

most heat pump systems are already hybridish as the have an immersion heater in the tank. I guess you are just replacing the immersion with a gas boiler.

Reed_Richards

arty688 said:

most heat pump systems are already hybridish as the have an immersion heater in the tank. I guess you are just replacing the immersion with a gas boiler.

I have an ASHP and the immersion heater comes on once a week for an hour to heat the hot water tank up to 60 C.  That's all (well actually I also use it with spare solar electricity in the summer but that is by-the-by).  The way a hybrid system was explained to me, the heat pump would take the water from cold to "warm" and then the boiler would kick-in to take it from warm to hot.  This probably means that you barely use the conventional boiler in summer and barely use the heat pump in winter.    

arty688

i know I was just saying you could do the same with an immersion heater which would be far simpler / greener but more expensive but a halfway house between a electric boiler and ASHP if you need higher temps. The problem at lot of people will have with an ASHP is the tank we have spent the last 20-30 years ripping tanks out of houses.

tacpot12

Those tanks we have been ripping out for the last 20-30 years didn't have anything like the right amount of insulation. Replacing an old tank with a well insulated replacement is highly desirable. 

arty688

Yes but there was a place in the home for a tank, i would guess in most homes that have gone to a combi they won't want a big tank back in the airing cupboard if there is still one.

Reed_Richards

Cupboards don't disappear.  The cupboard may have been repurposed for storage rather than airing but it's likely to still be there.

My old combi was a complete disaster because all the hot water pipes emanated from a central point where the cylinder had been originally.  Getting water to this central point from the combi made every pipe run at least twice as long as it had been before and made for an excruciatingly long wait to get any hot water out of a hot tap.  

matelodave

arty688 said:

most heat pump systems are already hybridish as the have an immersion heater in the tank. I guess you are just replacing the immersion with a gas boiler.

what are you talking about.

Having an immersion heater in the tank is no more "hybridish" than having an immersion heater in the tank with a gas, oil, biomass or lpg boiler.

Exiled_Tyke

Reed_Richards said:

Cupboards don't disappear.  The cupboard may have been repurposed for storage rather than airing but it's likely to still be there.

My old combi was a complete disaster because all the hot water pipes emanated from a central point where the cylinder had been originally.  Getting water to this central point from the combi made every pipe run at least twice as long as it had been before and made for an excruciatingly long wait to get any hot water out of a hot tap.  

Mine has. It was in the bathroom and now the shower sits in its place! 

I also have the same problem with pipes running all the way round the house unnecessarily to the non-existent cylinder and back. It's getting sorted as I write while we are in the process of getting a new kitchen installed.

arty688

matelodave said:

arty688 said:

most heat pump systems are already hybridish as the have an immersion heater in the tank. I guess you are just replacing the immersion with a gas boiler.

what are you talking about.

Having an immersion heater in the tank is no more "hybridish" than having an immersion heater in the tank with a gas, oil, biomass or lpg boiler.

Your right they are not hybridish they are hybrid , as the definition of hybrid is ' combining 2 elements ' in case you didn't understand the term. ASHP is electric the same as the immersion hence my new work hybridish. I hope that clarifies it for you .