Multi fuel back boiler taking ages to heat up

Shepherdhouse

I've had a multi fuel stove with back boiler installed and connected to my hot water and central heating. It works 8 radiators and was told the stove was more than enough for this number. It's taking almost 2 hours for the pump to kick in and heat the radiators. I've used just wood and then tried using coal and still takes 2 hours. Is this normal? I've never had one of these systems before and can't find anything online about how long it should take for the heating to kick in.

QrizB

Welcome to the forum.

What model of stove?

2 hours isn't absurdly long, depending on how quickly your fire lights and how much fuel you're using.

My back boiler experience is mostly with Agas and their ilk, but those burn pretty much continuously through the winter months. Heating from cold always takes a while.

matelodave

What, sort of multifuel boiler and what is the rated output of the stove. Is it also heating the hot water tank - if so is the tank gravity fed or pump fed..

Most stoves will take half an hour or more to get up to working temperature without having to heat up a couple of gallons of water in the back boiler as well, The pump shouldn't start running until the boiler is up to temperature otherwise you'll end up with a gunged up flue because the flue temp is too low.

You also need to bear in mind that a good proportion of the heat, probably around 50% is designed to heat the room the boiler is in leaving only around 50% to heat the hot water and central heating.

As said above they aren't really suitable for a quick heat up so you really need to keep it cooking for much longer than you would a gas boiler.

A gas boiler can input something like 25kw -30kw of heat into the heat exchanger (which is likely to be much smaller and much more efficient than a cast iron on in a multifuel boiler) within a couple of minutes.

Whereas a multifuel boiler needs a long time and a fair amount of fuel to get the boiler and chimney/flue up to temperature before it can deliver heat.

Wood has an output of around 4.5kwh a kg and smokeless coal around 5kwh/kg so to get the same sort of output as a gas boiler you need to be stoking it like the Titanic.

QrizB

matelodave said:

Wood has an output of around 4.5kwh a kg and smokeless coal around 5kwh/kg so to get the same sort of output as a gas boiler you need to be stoking it like the Titanic.

30kW soild fuel stove in action:

(sorry!)