Cheaper heating question

[GeoffP]

Not strictly a “period” subject but can I pose a few questions to all you qualified plumbers out there.

Basically, I have a large draughty Georgian farmhouse and I’ve recently installed a large, up to the minute, Combi Boiler for my hot water and partial central heating system but, like most of us, I am concerned about the cost of gas used by trying to heat my house more efficiently (cheaply) in the coming cold months.
Having a good local supply of logs, I have converted most of my rooms to use open log fires with one having a multi-fuel (log) burner but these are not all lit all of the time and the central heating is necessary when it’s cold..

My questions are :-

Can I connect a boiler in my log burner directly into my C/H system (in effect, like another radiator) and heat the water before it goes into the Combi thereby reducing the amount of gas needed to bring it up to temperature?

To make this feasible, I would think that the circulation pump would have to be running at all times when the fire was lit so as not to overheat, so I assume I would have to fit a thermostat to switch on the Combi pump?

I doubt that the temperature would get too high when the system was running but if so, I always have room for more radiators.

I would also think that any venting or pressure problems would be handled by the Combi boiler, any comments on this?

Thanks in anticipation,

Geoff

 

[FamilyWiggs]

Geoff - not a "qualified" plumber, but I have installed my own central heating and plumbed at least 2 houses, so am a reasonably competent "bodger".

My woodburner has a "backboiler" that is connected via a separate loop and a complex manifold into my primary central heating circuit. I inherited the oil boiler (not combi) and backburner, but as far as I have been able to conclude, the backburner circuit joins the manifold from where it flows through the pump, through the booiler, back to the manifold from whence it splts to feed radiator circuits and the primary circuit heats the immersion tank.

The pumpruns whenever the burner is lit - so there is an energy consumption cost here (and these pumps can be quite inefficient, so it is work checking the specs before buying one as they wary considerably.

The system would be vented by whatever means your current system is vented.

During the winter, the boiler rarely fires up when the fire is on.

 

[biffvernon]

...trying to heat my house more efficiently (cheaply) in the coming cold months.
Having a good local supply of logs, I have converted most of my rooms to use open log fires...

Big, big mistake. Most of the heat from your logs will warm the night air. Put a wood-burning stove in each fireplace.

 

[Lime]

Your idea of treating the log burner as a radiator suggests you already know some of the problems you may be facing.

The major problem is ensuring the safe operation of the log boiler and preventing overheating.
Using a log fire to heat water, as with any other solid fuel appliance, is fraught with danger of explosion if anything goes wrong and the boiler is not adequately vented.
If a blockage occurred in the water pipes and/or the boiler overheated for any reason high pressure steam would be created in the system.
To operate safely and avoid any high pressure steam creating an explosion the water in the log boiler needs to be able to vent safely if the pressure rises too much.
Until the fire went out the problem would continue.

The combi boiler works completely differently.
It is not like a conventional gas or oil boiler that is vented to the atmosphere.
The combi works with a sealed water system and is not directly vented to the atmosphere normally.
If a dangerous situation arose within the Combi boiler it's safety systems would cut in and shut off the gas and stop the heat.
Only a small amount of excess heat would be created and the system would remain safe.

However if the log boiler went wrong the Combi boiler would not be able to deal with the high pressure steam from another source that it cannot control.
It would be a very dangerous situation.

Also using a pump to minimise the problem of overheating cannot cope with a power cut.

 

[GeoffP]

Thanks to everyone for the quick replies.

FamilyWiggs: Sounds a bit complicated to me and may be different situation with an oil boiler. Having seen Lime’s later reply, I don’t think I’ll experiment.

Biff: I understand that but there are two reasons why I’ve not put stoves in. Firstly, the cost – anything from £500 upwards and I’ve got eight open fireplaces and am trying to survive on pension. The second reason is my better half who likes to see open fires (she doesn’t have to pay the bills) Actually, I’ve put a tentative bid on an “as new” stove for £100. Not seen it yet but I understand that its good.

Lime: Thanks for the info, I thought there would be problems and I completely understand what you’re saying. Could be very nasty.

Ah Well! So much for my trying to reduce the bills. We’ll have to get the thick blankets out again.

 

[Andrew Bodenham]

GeoffP,

I've looked into this topic, as I was keen to integrate a planned wood-fired range into our existing CH system (which is powered by a very efficient gas boiler). My conclusion was ultimately "no way!" It can be done, technically, but as other posters have suggested the problems of having a manually controlled, potentially eratic heat source in the system are significant. The amount and complexity of additional plumbing and components required could not be justified.

However, you could consider having a separate radiator circuit just for the woodburner, perhaps with rads in room not covered by the main CH, or in those areas which get coldest. This could be a relatively simple open-vented system needing just a header tank and pump. If there were rads from both systems together in a room this would be ok, provided the CH rad was fitted with a TRV - this would effectively reduce demand on the gas boiler when the wood stove was circulating heat. Of course, you may not want to sacrifice more wall space to radiators.

I like the idea of open fires in rooms, but I'd echo comments about the inefficiency of burning wood in an open grate. And remember that those chimmneys are drawing your warm air out of the room all the time - so increasing the overal heating demand for the house. Good for ventilation though! I am also very nervous about leaving open fires unattended, even with spark guards in place, especially with wood which can spit unpredictably.

 

[osprey]

Hello.
Lke Geoff I would like to put in a wood burner but I live in a consevation area and I'm worried about planning as to whether they'd let me install one. There would be a twin wall stainless steel flue seen on the property either out of the roof or on the outside wall.
Has anyone any thoughts on this?
The property is an old converted stable and there is no chimney. I am aware that I may need building regs but it's the planners that concern me and what their opinions would be. I do have an oil combi boiler with a balanced flue but for obvious reasons I want to rely less on oil and Im able to obtain a regular supply of wood


Thanks

 

[Lime]

Perhaps a way of integrating a log burning boiler into an existing central heating system would be to use an ordinary hot water tank as a heat exchanger/store.
The log burner could be plumbed in a conventional way (gravity fed) with pressure valve, header tank, hot water cylinder, heating coil and large pipes.
However the cylinder would be connected up like a radiator in the return pipe to the combi.
The main return pipe to the combi would be intercepted and both ends brought to the tank.
The return coming from the radiators would be connected to the lower part of the tank (where the cold water tank feed is usually connected).
The return to the combi would be connected to the top of the tank where the hot taps are usually fed from.
A vent would be needed here (like on a radiator) to let the air out when required.

An electric thermostat could be fitted to the cylinder side to operate 2 valves.
One valve could be fitted on a bypass pipe running between the top and bottom pipes and set to be open when the tank is cold.
The other fitted directly before the lower connection to the tank set to close when cold.
Thus the tank would be bypassed when cold and less demand made on the combi boiler.
However when the log fired boiler was operating and the tank was hot, only hot water would be fed to the combi boiler and less gas used if any.

A big disadvantage of the hot water tank idea is that the volume of the central heating water would be increased making it more sluggish to heat up.... on the other hand the insulated tank would act like a heat sink .. swings and roundabouts I think.
see
http://www.plumbingpages.com/featurepages/HWNspecials.cfm

There are many other options that *flow* from this idea.
Using two heating coils to accommodate two log burners for instance.
Or using the second heating coil in the return to the combi instead of the whole tank.

I haven't researched it but I expect there are some fancy heat exchangers on the market that may do the job too.

 

[joechip]

Stoves are quite expensive yes but why not install them in the rooms you use the most only. I love open fires but echo the comments of others re dangers and wasted heat so we are going over to multifuel stoves. We also like the look of an open fire as there is nothing quite like it but you can always open the doors to the stove and see the fire anyway and some of the models with large airwashed glass give a very impressive view of the fire. After many trips to the stove showroom we are almost decided on a Charnwood Country 4 for the smaller of the rooms and an Island 1 in bronze for the larger room. Can't wait !

 

[GeoffP]

Thanks again for your replies.

Andrew: The idea of a separate circuit although a bit cumbersome, sounds like something worth looking into. I’ve plenty of room for more radiators but I don’t really fancy the disruption of ripping up floorboards and skirting etc. to put in the new run. I recently did all this when I put the new boiler in.
Re open fires, I don’t use all of them and when they’re not in use I stuff a filled carrier bag up the chimney. This works OK as long as I remember to take it out when I light a fire. I’m also a night owl so I let the fire die right down before going to bed.

Osprey: It sounds as if you want something like the one that was in a French gite I stayed in last year. This was an (open) egg shaped monstrosity that hung from the roof into the middle of the room. Brilliant for heat both downstairs and up if you didn’t mind the looks of it.

Lime: I quite like this idea. Would it be possible to run the C/H piping to a coil (or two) inside the tank? This wouldn’t increase the water volume by much and it would still heat the C/H water up before going into the Combi. I’ve still got three or four good copper tanks waiting to go to the scrapman and I would think that I can buy the separate coils. The site you listed indicates that you can buy twin coiled cylinders but I assume that this is for domestic water heating.
Not being a plumber myself, have you any ideas how I would set up a system?

Joechip: Agreed. I’m already doing this gradually but more pressing jobs are taking up my limited budget. However, I won’t be putting one in the dining room which is only used on Sundays for family dinners. It’s so cosy with about ten of us round the table.

Thanks again,

Geoff

 

[Edwardia]

As a pensioner, you should be able to get some Govt help with heating costs, as well as grants for insulation, boiler or low carbon heating. Have a look on http://www.energysavingtrust.org.uk

Having used logs for heating myself in the past, I have to say that they are not cheap. If you use woodburners you could use pine, but I wouldn't recommend it for open fires as it spits like crazy (the resin in the wood) and can easily scorch rugs and carpet, without a fireguard. I had a gadget which made 'logs' out of paper, so I just Googled and http://www.guardianreaderoffers.co.uk has one for 19.99 They do take several days to dry out, but do burn quite well.

 

[ilikecobwebs]

We inherited a "Gloucester" logburner when we bought our house. It has been functioning now for probably around 30 years. All we've had to do with it is replace the two door glass panels. We burn scrap wood, (ideally wihout paint on), palettes, other people's tree stumps and any branches and twigs from our own garden. Never had to buy a log load in 24 years; just scrounge! Just had the chimney swept after seven years of forgetting, and it was surprisingly clean. The brickmakers for scrap paper have been around for years; we did have one, but lost it. Just recently made some "logs" by compressing scrap paper into a length of plastic tube about 3 inches wide......shoved it out the other end....burned nicely for nigh on 45 minutes. Useful way of getting rid of all that addressed junk-mail that can't go out in the recycling bin.

 

[Anita]

We invested in a hwam woodburner - and absolutely love it. O/H is a joiner and can usually get his hands on offcuts and fairly large "scraps" of wood for free, along with branches/twigs from the garden and nearby. We also do a lot of foraging after the rivers have been high - as there is usually plenty of deadwood washed up on the river banks. Don't know how legal this is, but my argument is that we pay council tax to maintain local parks etc... and by taking away the "spoils" then we are saving local council money from having to do so.

We already have next years wood supply nicely drying out - and all for free!

 

[Edwardia]

Just recently made some "logs" by compressing scrap paper into a length of plastic tube about 3 inches wide......shoved it out the other end....burned nicely for nigh on 45 minutes. Useful way of getting rid of all that addressed junk-mail that can't go out in the recycling bin.

Like this idea, would save shredding junk mail for recycling

 

[yamin]

Nothing to add re back boilers, but my ha'penneth re installing logburners. We have just installed an inherited logburner into an exisiting fireplace space but chimney stack is gone. Man used chimney 'void' and twin walled flue thing that i've seen mentioned here. Sadly its been cold enough to use it already! - we have found that where the open coal fire in the other room would consume 7 to 8 logs in an evening and still not make the room thoroughly warm, the log burner is taking one log every hour and a half and is stonkingly hot! Really fantastic, we're warm as toast! We have partial gas CH and a combi boiler. We plan to heat the whole 'living' area with the log burner and not use the heating at all! Bedrooms no heating and don't like a hot bedroom anyway, bathroom won't be fun but we'll cope, all else can be kept warm downstairs. I spoke to energy consumption at EON the other day and we estimated, based on our consumption last year, number rads etc, that we would be saving £250 per quarter! This DOES NOT include the cost of daily non rad water heating from the combi, which in comparison is not that much with a nice modern boiler like we have. So for the 6 months more or less we'll need heating, we'll save nigh on £500. We have free logs this year, but last year they were £60 per load - at our current consumption there is no question its MUCH cheaper to run this way than using gas - the price rises are really frightening!
In essence then, can you consider just keeping the area around the log burner, i.e your living spaces warm, and just turn off the heating in the other rooms? (We have 5 year old twins, but hey, I remember growing up in a freezing cold draughty house with no heating and I got through!)

Yamin

 

[Edwardia]

Back in 1994, in the first throws of lurve, now husband and moi rented a single skin converted chapel in a village in Kent for £450pcm. It had a logburner in the sitting room and Economy 7 storage heaters. We spent £50 pcm on logs and £475 in the first quarter on electricity trying to keep warm and failing, yet in Summer it was so hot we would drive 15 minsto our local 24hr Tesco to cool down ! Yeah we should have asked questions first but it's easy to be sucked in by a pretty-looking lemon !