Fitting a wood stove to a combi boiler
I recently visited a property in Llanberis, North Wales. The customer has a combi boiler connected to radiators throughout the house with the combi boiler supplying instant hot water on demand (as they do of course).
In the kitchen was a newly opened up fireplace – all ready for a multi-fuel stove. The customer wanted to know whether he should just have a stove in the kitchen or whether he should choose a boiler stove and somehow link it to the combi circuit. Fuel is LPG gas (expensive).
Can one link a solid fuel stove to a combi? This question comes up a lot. Yes it is possible, but not without a certain amount of expense and upheaval. The problem is that the combi is a sealed pressurised circuit (water under pressure within the pipes) but solid fuel stoves (with one or two exceptions) are open vented (have an open pipe in the loft as a safety feature in case of boiling).
The suggested method is to add a thermal store to the property (a big store of water – imagine a 6ft tall baked bean can) and connect this to the stove, radiators and solid fuel stove.
The thermal store acts as a buffer between the different devices and connections. The main problems here are cost (thermal store alone £1500 ish), major upheaval (all pipework changed), space loss (where to put new store). Thermal stores can be a great idea in new properties or full property renovations where upheaval is happening anyway.
The options provided to the customer were
a) Add a boiler stove. Add a thermal store. Does everything but expensive and a major upheaval.
b) Add a stove only (without backboiler). Warms the kitchen and that’s all.
c) Add a boiler stove. Disconnect the rads from the combi boiler and connect to stove. Combi does domestic hot water only. Rads only on when stove is on.
d) The third option is the one the customer is going for. Stoves At Home are going to add a boiler stove plus three EXTRA radiators (one heat sink radiator in the bathroom plus one rad in the master bedroom plus one rad in the lounge. This small radiator sytem will exist alongside the existing radiator system. Only a tiny header tank is required in the loft (no cylinder or large cold water cistern). The benefit to the customer is that they have options; on-demand hot water (combi), on demand whole house heating (combi), and “wood burner heats strategic living areas when customer wants to use it and saves on the heating bill”. This does mean that a few rooms have two radiators rather than one.
Something about this last plan appeals to me. The fact that one can choose full on/off luxury if required OR heating just heating a few strategic areas from a simple fire. This might not be suited to all, but for a couple with no kids who tend to just live in a couple of rooms anyway it’s certainly an option – especially if one can get scavenged wood!
To find out more about boiler stoves, combi boilers, thermal stores, wet systems in general you can visit the Stoves with boilers section of this manual.
