hot water scalding, but house not heating past 15 degrees

[bhm1712]

i have no problem with wiring as im an electrician, mainly production line controls and PLC electronics, but i covered domestic installation also. Its just i have never covered plumbing/ pipe fitting etc.

where can i find this guide to fitting full controls?

 

[bhm1712]

what i cant understand is, i know some people have GDHW and pumped heating with a cylinder stat which turns off a valve and cuts the boiler off, but if you want heating on and the DHW is upto temp, if the boiler is cut off how does the heating warm up?

 

[jackthom]

Untitled

• jackthom
• 19 Dec 2008
• 18

A mid-position valve directs the hot water leaving the boiler/pump to either DHW cylinder only, CH + DHW, or CH only.

A fairly complicated wiring diagram connects the programmer, cylinder thermostat, room thermostat, mid-position valve, boiler and pump so that everything (hopefully) works as intended.

 

[D_Hailsham]

Likely candidates:

1. Cylinder stat faulty.
2. DHW two port motorised zone valve not closing.
3. Three port motorised zone valve not moving to CH only position.
4. Debris in three port motorised zone valve making DHW port stick open.
5. Auto bypass not staying closed.
6. Manual bypass too far open.

Very unlikely candidates if you read the OP carefully.

I have a gravity hot water and pumped heating system

So:
NO cylinder stat
NO zone valve
NO mid pos valve
NO auto bypass
NO manual bypass

The cheapest solution would be to convert to a C-plan.

This still retains gravity HW, but allows HW temperature to be controlled independently of boiler temperature -which can then be set at max for central heating.
Parts needed: Honeywell V4043H valve and L641A cylinder thermostat - cost about £80. Plus wire and time!

The Stelrad Elite Catalogue is very useful for finding out the output of panel radiators.

 

[Softus]

...if you read the OP carefully.

I read it carefully, and nowhere does it say that he doesn't already have a 'C' plan* system.

I've also read your post carefully.

NO cylinder stat

Assumption.

NO zone valve

Assumption.

NO mid pos valve

Assumption.

NO auto bypass

Assumption.

NO manual bypass

Assumption.
_____________________

*According to the Sundial nomenclature, as defined by Honeywell Control Systems Limited, the "'C' plan" designation doesn't contain a hyphen.

 

[bhm1712]

anyone got a wiring diagran for c plan?

 

[bhm1712]

something i dont understand, if the cylinder stat is saying the DHW is at temp and shuts the boiler off to stop it from blowing up, how does the heating carry on working? my boiler has a seperate set of pipes for heating and hot water, one flow for dhw, and one return, one flow for heating (with pump inline) and one return.

surely if there are 2 seperate set of pipes, the 3 way valve pictured here is of no use,

when my room stat is calling for heat it simply turns the pump on, and when it is not calling for heat, it does not turn the boiler off, and nothing blows up....how come it is not the same case for DHW

 

[Softus]

something i dont understand, if the cylinder stat is saying the DHW is at temp and shuts the boiler off to stop it from blowing up, how does the heating carry on working?

Because the cylinder stat doesn't shut the boiler off.

my boiler has a seperate set of pipes for heating and hot water, one flow for dhw, and one return, one flow for heating (with pump inline) and one return.

surely if there are 2 seperate set of pipes, the 3 way valve pictured here is of no use

Correct. No use at all, which is slightly more useful than jackthom.

when my room stat is calling for heat it simply turns the pump on, and when it is not calling for heat, it does not turn the boiler off, and nothing blows up....how come it is not the same case for DHW

Because the DHW primary circuit is not pumped.

 

[D_Hailsham]

anyone got a wiring diagran for c plan?

Here it is with the pipe layout. Note that the valve goes in the return from cylinder to boiler. This is because there is normally a vent pipe in the flow which could get blocked by the valve when closed.

(click on diagrams to enlarge)

View media item 73 View media item 827

 

[D_Hailsham]

something i dont understand, if the cylinder stat is saying the DHW is at temp and shuts the boiler off to stop it from blowing up, how does the heating carry on working? my boiler has a seperate set of pipes for heating and hot water, one flow for dhw, and one return, one flow for heating (with pump inline) and one return.

If you look at the wiring diagram I have just posted, you should be able to answer this question yourself. When the valve is closed, the switch in the valves connects white to orange; the pump and boiler will run. When the valve is open, grey is connected to orange so the boiler runs, but not necessarily the pump - this will depend on the heating timer and thermostat.

when my room stat is calling for heat it simply turns the pump on, and when it is not calling for heat, it does not turn the boiler off, and nothing blows up....how come it is not the same case for DHW

The boiler has its own thermostat, which will shut the boiler down before it blows up! With your existing system, the temperature of your hot water is determined by the boiler thermostat setting.

When you have a C plan, the HW and CH temperatures are determined by the cylinder and room stats. The boiler stat is usually set to max and acts as an overheat stat in case either of the other two fail.

 

[Softus]

If you look at the wiring diagram I have just posted, you should be able to answer this question yourself. When the valve is closed, the switch in the valves connects white to orange; the pump and boiler will run. When the valve is open, grey is connected to orange so the boiler runs, but not necessarily the pump - this will depend on the heating timer and thermostat.

When you have a C plan, the HW and CH temperatures are determined by the cylinder and room stats. The boiler stat is usually set to max and acts as an overheat stat in case either of the other two fail.

Excellent post, IMHO.

 

[ctp]

get an rgi to measure your rooms and calculate your rad sizes ,you can spend as much as u like on controls it will not make your house any warmer if the rads are too small, old stelrads spring to mind.

 

[D_Hailsham]

If you look at the wiring diagram I have just posted, you should be able to answer this question yourself. When the valve is closed, the switch in the valves connects white to orange; the pump and boiler will run. When the valve is open, grey is connected to orange so the boiler runs, but not necessarily the pump - this will depend on the heating timer and thermostat.

When you have a C plan, the HW and CH temperatures are determined by the cylinder and room stats. The boiler stat is usually set to max and acts as an overheat stat in case either of the other two fail.

Excellent post, IMHO.

Are you sure? I'm the person you earlier referred to as: "A steaming great hypocrite".

 

[Softus]

Are you sure?

Quite sure, and I don't know why you're asking, since I'm also sure that you know what a hypocrite is.

 

[D_Hailsham]

Are you sure?

Quite sure, and I don't know why you're asking, since I'm also sure that you know what a hypocrite is.

Yes I do, but you obviously don't. Here are a couple of definitions:

a person who professes beliefs and opinions that he or she does not hold in order to conceal his or her real feelings or motives

Hypocrisy (or the state of being a hypocrite) is the act of preaching a certain belief or way of life, but not, in fact, holding these same virtues oneself.

What I originally wrote, which you took such exception too, is not hypocrisy; so I am not a hypocrite.

I think it's time I added you to my "ignore" list as your contributions rarely help the OP; they just boost your ego.