Please help me understand my heating system - One Pipe Open Vent System

[JackK]

I am lucky to live in a detached house that has four bedrooms in it - I have an Ideal Mexico 2 boiler with 3 inch steel barrell pipework coming up the external of the house.

I have had a few gas engineers come out to try and replace and they all want to rip out floorboards and generally make a mess and I have done so much research.

I have the following questions

1. I believe I have a one pipe system - Is this correct?
2. Do I have gravity hot water or fully pumped system?
3. Is it possible to have hot water only without central heating? I believe not - If I turn on th eboiler the flow pipe gets hot, some of which goes to the hot water cylinder but the remainder goes to the radiators. Is this correct?

I tried to include a picture of the boiler and pipework - Would be really good to have expert advice from wise forum members on this

My thought was to replace with an Intergas OV HRE 30KW - And I was hoping it would be a like for like swap.

One final point - I replaced a cast iron radiator with a column radiator and a TRV4 valves - It only gets lukewarm - Would the pump speed change how hot the rad gets? There is a 28mm Magnaclean filter on one branch of the return

 

[cross thread]

from your drawing it looks like pumped hot water and heating and a one pipe system .
a column rad won’t work fully on a one pipe system.
your boiler of choice can be fitted and will probably work but not really the best way, upgrade the system will be best .

 

[JackK]

Thank you crosswater - I really cant upgrade all the pipework - I will do that when I have money to do a loft and extension but for now and probably the next ten years I cant keep up with the cost of the house maintenance!

1) Will a new boiler work equally well as the existing Ideal Mexico 2? Is a 30KW Intergas OV the best bang for buck?

2) Why wont a column radiator work but the existing cast iron big radiators do

3) Is what I have "fully pumped" and is there a way to have HW only without central heating? I dont think thats possible

 

[D4dog]

Looks like a one pipe system, but you dont show a vent or header tank, so assume it is closed...there should be an expansion vessel as part of the boiler or on the supply side close to the boiler. Also a pressure release valve and a pressure meter so you can check it, plus a filling loop.

Your hot water supply is seperate...there is a coil in the hot water tank from the boiler, and the tank itself has a seperate cold in and hot out supply which likely has its own much bigger header tank, and is likely gravity fed.

Most systems will have a three port diverter valve so you can have HW, CH or both. Your two port valve (which I suspect either switches to HW when called, or profides either CH or CH and HW) should be relatively simple to upgrade. You do not describec the control system...that would be useful?

30Kw seems a large boiler for a 4 bed house?

 

[JackK]

In the loft there is a cold water storage tank and a F&E expansion tank in the loft as well - Its not sealed system

 

[JackK]

I hope you can see the big fat white flow pipe which then tees into copper for the hot water cylinder

Is my system fully pumped? Partially pumped? Gravity fed?

 

[D4dog]

So HW is gravity fed.

Cannot see why you xannot swap out the valve...I assume it is relatively easy to get to?

 

[JackK]

So HW is gravity fed.

Cannot see why you xannot swap out the valve...I assume it is relatively easy to get to?

Is that how its called? The system is pumped but the HW return is not - I can make modificatoins to the system after the white pipe where the two port valve is

I cannot change the three inch pipework and gave up tryng to get fittings or use a threading machine for that

 

[D4dog]

Ok, so CH control is boiler on or off? Then the valve turns hw on or off. So you have ch or ch+HW..

You could switch to a thre port diverter...but that is pretty serious pipework from the boiler....this a very large older house I assume?

 

[JackK]

Ok, so CH control is boiler on or off? Then the valve turns hw on or off. So you have ch or ch+HW..

You could switch to a thre port diverter...but that is pretty serious pipework from the boiler....this a very large older house I assume?

That’s how I have understood the system. I have to have ch on for hot water to work but I wanted to understand from the forum. Is this a y plan? And is it pumped or gravity or something else

It’s a large older home 1930s. The previous owner must have spent a pretty penny having it put in.

Every engineer says this is commercial pipe work and wants to rip all out and start again

 

[D4dog]

The HW tank coil is part of your "system", the return from that will join the ch system return at some point; this has nothing to do with the HW itself. Hw is simply gravity supply to tank.

 

[D4dog]

Got to say, I agree with your engineers. Ideally, you want a 2 zone heating system (supply goes to two valves, one for upstair and one for down. You then need the upstairs return and downstairs returns to join back as close to boiler as possible), with three way control for HW, CH or both.

TBH, trying to maintain that kind of heating system will turn into a nightmare. Also modern efficient systems are much smaller...move theboiler into the house if possible. Will save you money and heartache going forward.

 

[JackK]

My current boiler which I want to swap out is here

I still dont know if I have a fully pumped system or something else? A lot seems to turn on whether I am fully pumped or not and compliance with regulations etc

 

[D4dog]

Working on a guess...it looks like the supply side splits just after the pump. Do you know what these split into? Upstairs and downstairs rads, or is one to hw tank and one to rads? These look like 28mm...where do they change to old cast iron?

 

[Madrab]

The system is probably pumped CH with gravity HW, certainly going by the size of the HW primary.

Ideally you want someone who is experienced with 1 pipe systems to come and have a look to determine how the system is set up. If it is a 1 pipe and you are not in a position to change to a 2 pipe then it needs careful control and balancing.

Unfortunately you can't just drop a new designer column rad onto the system and expect it to work, in fact you can't just drop any new rad onto the system and expect it to work, it needs an experienced bod to fit as it need to be piped in a specific way/position and then the system needs balanced again.