Zoning an existing system

[jimmycooker]

Hi,

I have an existing oil fired unzoned central heating system. I have recently moved the boiler outside and want to zone it as shown in the attached jpeg, i.e.

Zone 1: Downstairs
Zone 2: Upstairs
Zone 3: Hot water tank

There is one pipe coming out of the boiler which tee's off upstairs and downstairs.

I have placed a motorised valve on the downstairs flow and want to know if I can just place the remaining two valves as shown, one on the flow into the tank and one just after it on the flow to the rads?

My only concern is that there is a loop arangement, hot water flowing into the hot water tank first, then out to the radiators and back to the boiler?

Is this how unzoned houses are / were piped? If this is the case what piping changes am I likely to need...a separate return from the hot water tank tied into the return line after all upstairs rads?

[jimmycooker]

Is it likely that the system is arranged like this (see attached jpeg)?

[migoplumber]

virtually the same drawing, however neither would work well, you would be outside resetting the boiler every day for an overheat situation.

if i could draw you a pretty pic like them i would, but i cant.

you have to remember that the boiler will always need a flow through it. if all 3 zones shut down, ther would be no flow. boiler on. heat with no where to go. boiler gets and shuts off.
also on drawing didnt see expansion and blow off's but i imagine you know about them and have just tried to simplify.

on boiler flow after 3 m.r.v. put a install a gate valve and join it to the boiler return. or install a proper header circuit. depends on your capabilities!

good luck
shaun

[Bernie2]

Hi!

Agree with Migo don't forget header cistern and vent.
Also by pass valve not on drawing. Check your boiler manual for minimum flow rates through your boiler it may dictate where you can fit the by pass valve.
It may be that you can fit an auto by pass if your using trv's.

[jimmycooker]

I got the first picture of the bord gais website so i assume they know what they're talking about!?

The second pic shows the the hot water tank looped which means if I shut it off all the upstairs rads are off too.

I just wanted to know if this is the way a house would / could have been plumbed.

Do I need to install a bypass in case all three valves fail closed or something? Surely the heating controls switch off power to the boiler when all valves are closed, surely the boiler itself shuts off when the thermostat gets too hot?

[migoplumber]

they are both valid install schematics. maybe the safety and by pass are left off as obviously needed.
the three valves are always closed and only open on a control signal.
the heating controls and thermostat are all safety extras.
generally the boiler overheat stat is a manual reset, requiring somebody to push a button to reset the boiler. not a problem you want to have.

if you are unsure about the system requirements, then it might be better to get a qualified heating engineer in to give you some advice. you can then maybe help him with the work?

good luck
shaun

[Bernie2]

Hi! Jimmy!

This is a bit like an old design we used in the 1970's.

If you look at it though where does the air get out?

Why does the cylinder return go on as the hot flow to the rads?

Why is there no by pass to allow circulation if all the valves close down?

Some oil boilers require a minimum of 40C Return temperature. If the water won't circulate because the valves are closed how will it do that?

An oil boiler runs hot and probably requires a pump over run to cool it after its fired, once again how are you going to do that without a by pass?

If the central heating and hot water are on, there is a chance the radiator return would force water back up the hot water return. Its usual to put the rad return behind the hot water return not in front as shown. You could of course use an injector tee on the rad return.

Incidentally I would check whether Irish standards are accepted as acceptable standards over here.