Oil combi boiler

[jdmorrisn]

Hello all,

I have a couple of questions, but before anyone says leave it to a professional, i am living in Estonia and here is not the same as England (they charge a fortune and install some strange looking cast iron Jäspi boiler and tank and boiler in one location inside the house). I am a fairly confident installer as long as i get everything straight.
Basically I am going to fit an oil boiler on a sealed system and since i have no water storage tank i understand a combi boiler is the best option (a system boiler cant be used on a central heating system without a water tank if i understand correctly?). I am looking at Trianco eurostar combi boiler (i will have it shipped to Eest since they have no such boilers here).

First point is that i only need it for central heating (maybe in future i will connect it to the supply water but its quite difficult to rearrange all the pipework for the moment because of where the boiler will be situated (away from my bathroom) and my priority is heat since i have hot water already - but can i do this? Ie cap the flow and return from the boiler for hot water and only have the heating flow and return connected?

Second; on the boiler schematic drawing it shows a top up bottle and bypass valve between flow and return. Do i really need a top up bottle if i install a filling loop? And is the bypass valve so necessary (I will have only 4 of 12 radiators with trvs/ 1 each room).

Thirdly, how do i calculate how much water will be in the system to see if i need an additional expansion tank (10l is supplied equating to 90litres). i have 12 radiators (3 are small) and maybe 50m piping. And then where exactly do i connect the extra expansion vessel if i need one, just next to the boiler on the flow pipe?

Hope you can help me out will all this, thanks.

 

[Terrywookfit]

Why not email Trianco technical and get an official reply!!

Dont forget that the boiler will always be heating the store thus reducing the efficiency and increasing running costs !!

No reason in theory though why you cant install as proposed !

Just connect mains supply in and put a valve on the outlet, you can then vent and turn off!!
Same in principle as having hot taps turned off!!

 

[jdmorrisn]

Hi Terry,

I will email Trianco, but i thought they may be reluctant to instruct a non certified installer, but i guess what's the worst - i get no answer 8and i thought it would be quicker here).

But maybe you went a little fast for me there.

1. Can a system boiler be installed on a system without a water tank? (system is cheaper than combi)

2. But in practice on a combi i should be able to cap the hot water feed and just have the boiler running for heating? (i will check with Trianco).

3. Dont forget that the boiler will always be heating the store thus reducing the efficiency and increasing running costs !!

- i don't follow - what store? I don't understand this part, sorry.

But thanks.

 

[Terrywookfit]

Yes a system boiler can be used for heating only !!

An oil fired combi has a pre heated store of hot water.

When there is a demand water is pumped from the store to a plate heat exchanger to satisfy the demand!
The burner also fires to replenish the store!
Oil fired boilers are not low water content like gas and also designed to satisfy peak heating demand!
A gas burner can be easily modulated oil can not!!

As an after thought why not just fit a bib tap adjacent to the boiler !
It is then installed as normal!!
I think a system boiler would be the cheaper option though!!

 

[jdmorrisn]

Terry you are the man, but excuse my ignorance and need to clarify 100% (so that the installation goes ok) - If i use a system boiler only for heating, then i do not have to have or need to install a water tank, is this correct? Simply the boiler will pump the water around the radiators and back again and thats it?

Tony.

 

[Terrywookfit]

That is correct!
Fill system via a loop and thats it!!

 

[jdmorrisn]

Thank you very much