Oil fired boiler query

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Hi
The bungalow I rent had an old boiler in until two years ago.
A new firebird boiler has been fitted. The hot water tank is separate.
I’ve bern looking at fitting a nest thermostat on it and been sussing out the wiring system.. I think!
Anyway, the pump is wired into a 3 pin round plug and socket on the wall and the boiler on a std 3 pin plug and socket beside it. These go back to a std Drayton controller
This boiler has no divert valve and as far as I can make out , when the pump is off ie hot water selected on the programmer, but when the ch is selected the pump comes on, permanently when the ch light is on
I guess that when it is just hot water and the pump is off the pump itself acts like a diverter valve ? And the water goes to the hot water tank by gravity ?
Is this a efficient way to run the boiler ?
So if the wall stat is turned down the pump is going regardless as long as the programmer has ch selected
I’m wanting to have a nest thermostat wired in but wasn’t sure if the boiler is set

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Sounds like you have a gravity circulation hot water system and pumped central heating. If this is correct, the restrictions of the plumbing will prevent you having the heating on without the hot water being on at the same time. When the boiler is 'on' it will heat the hot water cylinder by natural gravity circulation. When heating is required starting the pump will circulate water around the radiators as well. The room thermostat should start and stop the pump, but sounds as if it may not be connected anymore.

You can install a Nest Heat link on this type of system and wire it up so that when heating is selected the hot water comes on too. Here's a drawing I did for someone else.

Nest with Gravity Fed System.jpg

Ideally you might want to consider converting it to a Y-Plan or S-Plan by adding motorised valves. That would then allow you to have thermostatic control of the hot water, it would save energy by shutting the boiler down when there was no demand, and also provide independent control for the heating and hot water.
 
Thank you Stem for your reply
I’ve been told the system I have is a c plan system with out the tank stat or zone valve.
The original system has been in since the 70’s so a bit out of date.
So the hw side works by the boiler being on but pump off, so does the boiler have some type of internal thermostat? Without a tank stat how does it know when the water is too hot and to switch off ?
The pump is near the boiler but when the boiler kicks in I can hear air whooshing in the pump, which makes a loud rattling noise in the first rad in my son’s room. So much so we can’t turn it on during the night as the noise wakes him up when the boiler kicks in. Hopefully the zone valve will solve that problem or maybe it’ll need an auto bleed valve after the pump perhaps? I tried auto bleed valves on the roads but no success
Thanks for your valuable help
 
I’ve been told the system I have is a c plan system with out the tank stat or zone valve.
I can see why someone may say that, but it's not correct to call it a 'C Plan'. You have a 'gravity hot water system with pumped central heating'. It may be converted to a 'C Plan' by the addition of a hot water cylinder thermostat and motorised valve. But they are the parts that actually make it a 'C Plan'.

does the boiler have some type of internal thermostat?
Yes, otherwise it would actually boil.

Without a tank stat how does it know when the water is too hot and to switch off ?
It doesn't, and that's the problem, the boiler will keep cycling infinitum. Adding a motorised valve that is linked to a cylinder thermostat provides the boiler interlock.

The pump is near the boiler but when the boiler kicks in I can hear air whooshing in the pump, which makes a loud rattling noise in the first rad in my son’s room. So much so we can’t turn it on during the night as the noise wakes him up when the boiler kicks in. Hopefully the zone valve will solve that problem.
Air in the system has nothing to do with a motorised valve it won't change that, and auto bleed valves are not always the answer, usually it's necessary to find out where the air is coming from, it could be poor system design, a fault somewhere, or even gas produced by corrosion, if there is insufficient corrosion inhibitor in the system.

Adding a motorised valve to your system is not just a matter of cutting a pipe and inserting one. Other changes are required including re piping the pump and you may even need a new hot water cylinder if yours is the Primatic type. There will also be a considerable amount of additional wiring required.

Y plan.gif
 
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Thank you Stem
You have been very helpful
I’m definitely going to get it uprated to a s plan system so I can have much more control ability of the system especially the hot water side if it
I think the system is a vented style with a header tank in the loft.
But I think you are possibly correct with what you say about the hot water tank. It’s the original so it possibly wouldn’t cope with having the hot water pumped through it rather than gravity
Cheers for your advice though
It’s appreciated
 
you live in a rented bungalow, get permission first from the landlord before you start doing anything.
 

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