Thermal store right choice?

[festive]

We currently have an old firebird oil burning boiler and decided to upgrade.

Considering we have a huge amount of surpless firewood here and no gas connection we were advised a cheaper way long term could be a log burner with back boiler condensing boiler (Worcester 18/25 greenstar) and a thermal store.

Plan is to use log burner through most of winter and only use boiler in summer months for hot water.

Any thoughts welcome. My only concern is how much oil will be required in summer months to keep heat store hot just to supply hot water.

Tia

 

[muggles]

Thermal stores are OK but the only real advantage to them over a traditional hot water cylinder is that they can provide you with mains-pressure hot water. This does, of course, require your incoming mains to be up to the job.

A more elegant alternative is a H2 Panel. This will allow you to connect your new boiler (incidentally have a look at Hounsfield -- much much better boilers than WB) to your new solid fuel system and give you great control over both.

As for woodburners, WoodWarm are a great choice...[EDIT] although I now see they no longer do boilers, which is a shame, because theirs were by far the best available

Bear in mind though that this whole setup is going to be very expensive (think £10-15k as a very rough guide without having seen the job) and consider how long the payback period will be before you dive in

 

[dilalio]

My only concern is how much oil will be required in summer months to keep heat store hot just to supply hot water.

Well that will depend on how much hot water you will need won't it?

 

[festive]

Well we are a family of 4 and two bathrooms. We had it working yesterday, only with immersion coil. After few hours to hear i tested, i managed a shower but water ran cold soon after (4mins of hot water). Left me concerned. We will be running a log burner/Boiler to heat it, but concerned the default size of 210litres isn't enough? Anyone?

 

[JohnD]

(4mins of hot water).

how many litres are there in 4 minutes?

had anybody else run a hot tap since you turned on the immersion heater?

 

[festive]

how many litres are there in 4 minutes?

had anybody else run a hot tap since you turned on the immersion heater?

Not sure how to calc as it was mixed as well so not entirely hot of course. Water hadn't been touched and was initially too hot to touch. Reading alot seem to recommend 300/400 litres.. anyway i was assured the Boiler/Log burner with back boiler would both enable a quick recovery on thermal store. However i am concerned a bath would run cold at this rate of loss.

 

[muggles]

Were you running your heating at the time?

 

[Dan Robinson]

Stores do need to be slightly larger than the equivalent cylinder especially if running on solid fuel with a relatively low kw.

 

[JohnD]

Not sure how to calc

fill a bucket. Time it. Calculate litres per minute.

 

[festive]

Were you running your heating at the time?

HEating not plumbed in yet so definately not.

 

[festive]

Stores do need to be slightly larger than the equivalent cylinder especially if running on solid fuel with a relatively low kw.

We have a Worcester 18/25 and when thats not running a beast of a back boiler

PArkray 80b supposedly heats 20 rads

• Nominal output to water = 11.3kW
• Nominal output to room = 5.2kW
• Maximum output to water = 16kW
• Maximum output to room = 8kW

 

[muggles]

We have a Worcester 18/25 and when thats not running a beast of a back boiler

PArkray 80b supposedly heats 20 rads

• Nominal output to water = 11.3kW
• Nominal output to room = 5.2kW
• Maximum output to water = 16kW
• Maximum output to room = 8kW

Unless the room it's in is enormous, you're going to be sweating your tits off in there trying to keep the rest of the house at a sensible temperature with those output figures. I'd also query why they felt an 18-25kW oil boiler was required but you could get away with a maximum 16kW back boiler. Sounds like another badly-specced system all in all, come across them all the time

 

[festive]

Unless the room it's in is enormous, you're going to be sweating your tits off in there trying to keep the rest of the house at a sensible temperature with those output figures. I'd also query why they felt an 18-25kW oil boiler was required but you could get away with a maximum 16kW back boiler. Sounds like another badly-specced system all in all, come across them all the time

Mmm oh ****, i feared this, no the log burner is going in a 4x4m room (dont laugh)
I noticed you haven't queried the thermal store size why is boiler badly spec'd is it over/under.

 

[muggles]

The thermal store probably is a bit undersized, but at the moment that might be the least of your problems. On a very rough back-of-a-fag-packet calculation, your room containing the stove needs 1.2-1.5kW to heat it when it's -3ºC outside. Warmer outside, less heat needed.... Based on your stove appearing to have a 2:1 ratio of heat to water:heat to room, you're only going to get around 3kW to water before the room starts overheating. Push much more than that into there and you'll be throwing open the windows in there just to be able to heat the rest of your house.

I was more suggesting that the entire system is badly specced rather than one boiler specifically, although if you look at the figures, one boiler or the other is wrong. If your house needs the full 18kW minimum output of the oil boiler, the stove boiler is undersized and you'll need to burn oil as well as wood to keep the house warm. If it can be heated satisfactorily with no more than the nominal 11.3kW the stove produces, the oil boiler is oversized and will burn more oil than necessary. I haven't done a heat loss calculation on your house, so I don't know which one is wrong, but one of them definitely is!