Central Heating system in old house - help needed!

[harry]

In these days, that would be a very foolish move. You might need that fire in emergency.

[Tim Lamb]

That's interesting. A quick google gets lots of hits on Potterton boiler spares but I assume these are likely to be 22mm or less.

Quite!

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[Dave Liquorice]

Then express your self clearly: SV - Service Valve.

[Dave Liquorice]

Ninth word mean anything to you?

[Dave Liquorice]

Danfoss and Honeywell have them, seem to be listed in relation to cylinder controls. A quick look indicates that temp range might be a problem, but as I came across these things when looking at how to configure the thermal store here I'm reasonably sure that >80C ones will be available.

As I said the plumbing is still important, the legs to from the heat dump rad still need to be short so the difference between 28 and 22 won't be great. The flow I'd plumb to the top of the rad and the return from the bottom to "encourage" circulation.

[Tim Lamb]

OK.

Sound advice. There is space for a tall job at the head of the bath so this may not be the issue I had envisaged. The simplest back boiler for my existing log burner is 10,000BTU or a bit under 3kW. I guess these figures are optimistic max. values so 2kW may be a more realistic output.

The idea is to fit a thermal store in addition to our existing cistern. Feed the lower section by gravity from the log burner and the top from the gas pumped CH system.

Water for a new underfloor heating system would be drawn by a plate heat exchanger. Whether this could also be used to aid the gas set up has not yet been considered. 2kW does not sound very much but the heated area is open plan and the stove should still push out several kW radiant and convection.

The job has been deferred to the autumn, time and impending visitors. The heating season onset will provide a powerful deadline!

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[Dave Liquorice]

On our store (300l and over 5' high) the wood burner is connected bottom to about a foot below the top. The oil boiler from above the solar coil to the top. CH comes from the same level as the lower boiler connection to about half way. DHW a few inches above the CH top connection to the top.

Wouldn't the UFH be fed off the normal CH loop via a thermostatic mixer valve (cold side T'd from the UFH return) set to around 40 C?

Or "it's too late to start messing about with the heating now"... B-)

[argosgold]

Very true. What I don't need is the hassle of dealing with many different interconnected heating systems. My plan is to replace the open fireplace with back boiler to a more efficient (though not, admittedly, connected to the Central Heating) multi-fuel stove.

As we have a small house, a modest-sized stove would be able to take the chill off the whole house, or heat the living area.

Not, I think, a foolish move, but one which I have decided on. And need advice on the connections of various devices to Central heating in order to have an understanding of how things may proceed.

[Dave Liquorice]

If done properly it's not complicated and "just works". From your description of what you currently have it's a mess.

Personally with the Aga available as well as the gas boiler I'd look very hard at boiler on the new stove and thermal store to buffer the heat. And probably solar thermal as well, to provide heat for DHW in the summer when you probably don't want the Aga on. An MCS acredited solar thermal system will attract a RHPP now and, when they come in, RHI payments.

[Tim Lamb]

I have plenty of height and no plans for solar. Our roof is N/S so not ideal.

Currently, the original part of the house is heated by wall hung radiators and gas boiler. It could be re-jigged as you say but underfloor heating does not readily suit short periods of on time. We do not currently run the gas boiler overnight or for the mid part of the day. There will be 3 possibly 4 outlets from the manifold each on a separate room stat. I don't know how balancing would be achieved from a single pump. I intend to involve Polypipe in the design so will wait for their comments.

That excuse only works once:-)

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[robgraham]

ne point: its not a well designed system.

I was looking for a way back into discussing the OP's heating system again. One of the things that hasn't been picked up on is that the Aga and the oil boiler both heat the DHW - and no one has queried how that is configured at the moment-, is this part of the really horrible idea of change over valves ?

Why when the Dunsley Neutraliser has been around for a loooong time, would anyone dream up such a system. It is worth noting that the Dunsley is in effect a miniature heat store in that all sources of heat can be blended in it.

Rob

[Dave Liquorice]

I read it that the Rayburn heated one cylinder and HW supply. The oil boiler the other cylinder and another HW supply. ie two independant HW supplies.

Most plumbers haven't a clue about solid fuel systems but rather admitting they don't bodge something together. Something that sort of works but is over complicated with valves, stats and manual change overs etc.

[Dave Liquorice]

Ah but when you have the thermal store it's the store temperature that determines when the boiler fires not when the CH/HW demands heat.

It would probably be best to have a seperate zone, inc pump, for UFH. That can tickle away slowly taking heat from the store. The stove (I think you are putting in a stove with boiler, too many similar threads...) might be able to keep up with that low steady demand, if it doesn't and the store temp drops too low the boiler fires and heats it back up.

Take a look at:

In the evening, when the stove is on, you can see heating demand from the barn being fully provided from the store 3 times. The store temp plots are bit out, IIRC upper and bottom sensors are in pockets, the others are just pushed into holes in the tank insulation, a WIP...

Oh... you do have a problem. B-)

[argosgold]

I'd be looking at Solar (amongst other options) but for the fact that the property is a listed building and I'd be unlikely to get planning consent for the installation of solar panels on the roof.

I guess that I'm looking for is something simple that can't bite me on the bum with plumbers callouts a few years down the line that can give reliable, controllable heat without any knock on effect on the rest of the house's systems.

I hear what you're all saying about the use and worth of back boilers, however.