Old boiler

[gselectrical]

Hi guys, Started on a re-wire yesterday on a really old stone building. Had a look at the oil boiler today (which controls the heating and hot water) and its ancient. Ive wired up a few new ones but I have very little experience in older boilers.

Basically theres the boiler, a pump next to it, a mechanical programmer and room stat. There is also some sort of stat in the conservartory and one in the attick where the tank is. (these look like normal room stats with the dial, but no numbers) These all run back to junction boxes next to the boiler. There is also a valve under the stairs connected to a switch, wired off the lighting circuit. (This seems to be on all the time)

I need to know how to wire this up. I know how to wire the programmer and room stat but not sure if I need the other stats? Also when do I need the pump next to the boiler running? On heating demand or Hot water? or both?

Any advice much appreciated. Thanks.

 

[Evans Electric]

I am always wary of designing my own heating circuits as there may be hidden pitfalls. If a heating engineer says it a Y plan then I don't mind . If thing is already wired , I presume you have to rewire it, can you copy it, assuming its wired correctly.

See if our heating guy, JL, answers.

Deke

 

[NozSpark]

Oil boilers tend to only have a permament supply..they maintain a set temperature in the boilers water jacket. However when I had one I altered it (2 relays) so it could only fire up when a demend was present.

You then have the programmer, room stats, frost stats & taks stats to control the valves and then the pump.

 

[gselectrical]

Thanks for the replys. It will be quite difficult to copy the previous wiring as it is in such a mess. Seemed to work ok though, tennant said she had control over either the heating or the water. Basically I need to know whether the pump by the boiler pumps the CH or the HW.

Found out what the valve is..apparantly it isolates the CH on half the house.

Also need to know what them 2 stats are for!

Cheers.

 

[Lurch]

If there's no numbers on the dial then I would say they will be frost stats. If there are no other valves then the pump will be for the heating. All you need to do is wire the boiler\pump\roomstat and programmer as gravity with the clock in 10 position and wire the 2 frost stats up in parallel between permanent live and the boiler live. That sounds like the way it's wired in its present state, I'd have the frost stats triggering 2 relays wired across permanent live and HW on\room stat call.

The valve that isolates half the heating, well that's easy enough to wire back in on its own.

 

[Andy™]

Thanks for the replys. It will be quite difficult to copy the previous wiring as it is in such a mess. Seemed to work ok though, tennant said she had control over either the heating or the water. Basically I need to know whether the pump by the boiler pumps the CH or the HW. Found out what the valve is..apparantly it isolates the CH on half the house.

Also need to know what them 2 stats are for!

Cheers.

the whole thing sounds like a standard gravity with frost stat.

the 'hot water' output from programmer will fire boiler. DHW is gravity.

CH from programmer will go via stat and control pump only (the heating would alreay be on by now heating the water)

the frost stats are wired to bypass programmer/stat

 

[paul b b]

Oh strange, i though this was a post about my wife

 

[kme]

However, you need to verify that the DHW is, in fact, a gravity system, and not intended to be pumped. If it should be, and isn`t, the DHW won`t work, at a minimum, and the boiler could have a poody about it............

Some of the "bespoke"/"self designed" systems can be an absolute PITA to suss out.

n.b. If you definitely only have 1no. 2 port valve; gravity DHW is certainly likely.

If its 3 port, all bets are off.

n.b. IF you can, trace the pipework, and do yourself a drawing, as you might with wiring - they`re very similar........

 

[gselectrical]

Oh strange, i though this was a post about my wife

lol. Pretty sure theres only one valve so Ill wire it up as suggested by Lurch today. Thanks for the replys. J

 

[gselectrical]

[quote name='Andy

 

[kme]

For a gravity system, you cannot have CH without DHW. Only available in the fully pumped systems.

n.b. DHW - fire boiler.

CH - as above & pump.

with stats in relevant positions, of course......

 

[Andy™]

n.b. If you definitely only have 1no. 2 port valve; gravity DHW is certainly likely.

gravity systems dont have valves, unless zoned, which is unlikely

 

[Andy™]

How can I wire it so that the CH and HW can be controlled seperatly. Above, it looks like the hot water would have to be on in order for the boiler to run?Thanks. J

you cant. you either have DHW or DHW & CH. there is no CH on its own

 

[gselectrical]

[quote name='Andy

 

[Andy™]

the programmer has 2 outputs - one for DHW, one for CH. the output for DHW goes to boiler only. the output for CH goes to pump only

 

[ProDave]

Oil boilers tend to only have a permament supply..they maintain a set temperature in the boilers water jacket. However when I had one I altered it (2 relays) so it could only fire up when a demend was present.

No they don't.

An oil boiler works just like a gas boiler, you power it and it fires up when heating or hot water is demanded. Otherwise it's idle and goes cold.

You are probably thinking of an oil combi boiler. Yes those do maintain a jacket of hot water. I think they do that as the design of oil boilers can't fire up and instantly heat the water like a combi gas boiler can.

 

[gselectrical]

Rite got it now. Sorry it took so long....long day!

 

[NozSpark]

No they don't.An oil boiler works just like a gas boiler, you power it and it fires up when heating or hot water is demanded. Otherwise it's idle and goes cold.

You are probably thinking of an oil combi boiler. Yes those do maintain a jacket of hot water. I think they do that as the design of oil boilers can't fire up and instantly heat the water like a combi gas boiler can.

Mine did... until I modified it - It had 2 pumps DHW & CH and no valves. It was a replacement (different location) for a 4 pipe system fed from a Parkray coal hopper fed fire.... it was gravity DHW but it wouldn't convect!!

Also it fired up just as quick as my combi in my new house!!

 

[Lurch]

Ok, cheers. How can I wire it so that when programmer has water "on", Heating "off" the CH pump doesnt run? I have a 3-core flex to the boiler and a 3-core flex to the CH pump. When all connected will it not backfeed on HW demand causing the CH pump to run? Sorry if im not understanding this as quickly as I should be!! J

Download the wiring diagrams from the Honeywell site and keep a copy in the van. If you pop in some of the plumbers merchants you might find some of the pocket guides from Honeywell\Drayton with all the wiring types in.

In fact, Drayton have an app for the phone (works with old phones as well, not just an iphone\smartphone app) with all the manuals on for all their equipment and faultfinding guides\wiring diagrams for heating systems.

http://www.draytoncontrols.co.uk/content.aspx?id=3016

http://www.draytoncontrols.co.uk/WorkArea/DownloadAsset.aspx?id=3012

If you wire it as a gravity system, it will work as a gravity system. When the programmer is in HW on\CH off then the boiler gets power and the pump doesn;t, so it doesn;t run.

The Drayton catalogue has wiring info for all their kit and some nice pictures of heating types and associated wiring.

http://www.draytoncontrols.co.uk/WorkArea/DownloadAsset.aspx?id=3082