Upgrading central heating for old stone cottage

[Giles Mann]

I have been going round in circles trying to decide the best way to upgrade the CH of our 2.5 bedroom single glazed cottage. Currently we have a conventional system with tanks in the attic and HWC in the bathroom cupboard. There is an approx 30 year old AGA oil fired boiler which has not put a foot wrong since we moved in at the start of winter. We are going to be building a small extension this year and want to get the system upgraded at the same time (boiler location needs to be moved also).

The options I am considering are:
1) replace boiler with new one and keep the system as it is (with minor alterations to account for new boiler location) - heating engineer had no problems with rest of system (except oil tank will need replacing in a few years time). The engineer recommended an external boiler.
2) oil fired combi boiler - we only have one bathroom so thought this was a good option but have started to read a lot of negative things about combis. Would be nice to gain back the space of the HWC (but not essential)
3) Air source heat pump - even with adding secondary I am worried that we may not be warm enough. I was originally thinking we go for UFH but would require disruption of digging down. I feel like this option will require lots of rads and take up valuable space in our small house.

I know that it is probably difficult to say over a forum without all the information but does option 1 seem like the sensible approach?

 

[DP]

Option one would be belt and braces. If boiler fails then hw heated electrically. Fit better controls to minimise fuel useage

 

[fixitflav]

Currently we have a conventional system with tanks in the attic and HWC in the bathroom cupboard.

What do you mean by conventional system? Pumped CH, gravity HW, with no motorised valves?

 

[bernardgreen]

but does option 1 seem like the sensible approach?

Yes in my opinion it is

2) oil fired combi boiler - we only have one bathroom so thought this was a good option but have started to read a lot of negative things about combis. Would be nice to gain back the space of the HWC (but not essential)

Combi boilers can be a nightmare to repair when things go wrong because all the critical components are crammed into the boiler's case

For what it is worth :-

My cottage is stone, thatched, open plan stairs ( zoning nigh on impossible ) and had storage heaters when I bought it.

I installed a vented heating system using a heat only boiler, two hot water cylinders ( HWC ) and 4 radiators.

( boiler installed by GasSafe engineer )

Two HWC ( one in kitchen and one in the bathroom ) to reduce water wastage while waiting for hot water to reach the taps. The heat loss from the HWCs while very low is enough to keep the chill of the rooms.

Vented with tank ( cistern ) to ensure there is some water available if there is ever a problem with the water supply. Also allows taps to be low pressure and less likely to fail. Shower is mains pressure heated by a shower coil in the bathroom HWC

 

[Giles Mann]

What do you mean by conventional system? Pumped CH, gravity HW, with no motorised valves?

There is a motorised valve to be able to operate central heating and hot water separately but otherwise as you said yes

 

[ericmark]

Using fan assisted radiators does take up less room, and also ensures air is circuited so faster heat up times. The old model I had did not have any timer but was thermostatically controlled, but motor speed was manual selection, new models have auto selecting 5 speed fans, it was still working when we moved, some 40 years old. Not so good with modulating gas, but no problem with oil.

Oil does not modulate, so to allow different flow rates with a combi boiler inside the boiler there is a water tank, so boiler ends up larger.

I had hot air heating (gas) in my first house, the problem is whole room, well whole house was same temperature, including next to single glazed windows, where with a radiator, as long as not placed under window, it can heat main part of room but allow around the windows to stay cooler, the position of our fan assisted radiator (second house) did not circulate air past the window, but this is some thing to consider.

Using electronic heads in mothers house with a gas modulating boiler worked very well, this house with an oil boiler not so good, but I blame the micro bore more than the TRV heads, and it still works better than with mechanical heads, the idea is by selecting the order in which the rooms heat up, I can reheat each room starting latter than if trying to do all together, but radiators need to be large enough to sink the energy from the boiler, but a 10 minute delay room to room, is enough to speed up reheating of rooms used first. It also means we can turn off rooms not used.

We have now added PV solar panels and a battery, so our oil boiler will now still work with a power cut, how long depends on the sun, but it means less likely to have to light the open fire, after the winter of 1978/9 there is no way I want to rely on the electric supply been there, done that, never again, so heat pump is non starter, at least electric powered, even the idea of a stand by generator the government has changed the tax system, and a diesel generator is now considered as a road vehicle, and has to run on DERV (stands for diesel engined road vehicle) so clearly the government do not want us to use heat pumps. Well I suppose no reason for not being direct drive, but not seen one. The advantage of the heat pump is as long as using fan assisted radiators with condensate drains, it can heat or cool, so if we get global warming we can cool the home as well. However the government is not promoting the reversible versions so clearly nothing to do with global warming. Heat pumps tend to circulate cooler water than oil boilers, so radiators need to be bigger, so again fan assisted radiators seem to be best idea.

My oil boiler uses the conventional system or C Plan, the idea is the boiler has no run on, so can cool by heating the domestic hot water (DHW) to an extent the Y Plan also does this, as default is DHW and most pump will allow water to past through even when not running, to use an S Plan you need a run on system in the boiler. Many combi boilers use a W Plan inside the boiler.

My hot coil for the DHW can not sink the 19 kW from the oil boiler, in summer after 20 minutes the boiler starts to cycle, but some tanks are better than others, so not all hot coils are the same.

Idea with a heat pump is never turn it off, but with any other boiler, we are looking at recovery time, so if this house needs 10 kW of heat to maintain the temperature, one can fit a heat pump with 10 kW output and always keep the house warm, but with an oil we would use double that output at least, and allow rooms or whole house to cool when not using rooms or house, and reheat as an when wanted.

So the heat pump is only going to work with a well insulated house, since yours is not well insulated a heat pump is non starter.