CH newbie help - gravity or pumped?

[tjg]

Hi everyone,

Please can anybody give me a bit of assistance regarding CH.

The timer in my house is not working. It's a Randall 102, and whilst the HW and CH go on/off when rotating the dial manually, the dial does not go round automatically when left to it's own devices.

Therefore I purchased a new programmer. It's a Drayton (Tempus 7 I think, can't remember exactly - I'm at work). There are two jumpers on the back of the new unit, one of which is for gravity/pumped systems.

What I need some advice on is how to tell if my system is gravity fed or pumped? I'm quite prepared to go in search if pumps, etc. but if anyone has some pointers on what to look out for, pipe diameters, possible locations for a pump, etc. then that would be greatly appreciated!

Also, why does the programmer need to know if the system is gravity fed or pumped?

Thanks in advance,

Tony

 

[kevplumb]

pump

zone valve x 2

orrrrr

3 port x 1
failing that none of the above

 

[tjg]

Nice one. I shall get hunting this evening.

 

[Slugbabydotcom]

I would take that one back and simply replace it with the modern equivalent
Danfoss Randall102E5 or 102E7. {Look up GP mini programmers}
No messing about or headaches just a straight swap

 

[chrishutt]

why does the programmer need to know if the system is gravity fed or pumped?

Because if the hot water side of the system is gravity, it is not possible to run central heating (which is always pumped) without hot water. If the system is fully pumped, CH can be selected without HW, therefore there are more programming options available.

 

[tjg]

Thanks for the replies.

I have now investigated the system a bit further. But I am still a bit confused by it.

There are:
- 2 tanks in the loft
- hot water tank in the bathroom cupboard (with tank stat and immersion heater)
- what appears to be a Honeywell 2 port valve on a pipe in the bathroom cupboard
- Grundfos pump found via an access panel in the bathroom
- Potterton Netaheat 10-16 boiler in the kitchen
- Honeywell thermostat downstairs on the wall in the hallway
- TRVs on most radiators

I've read as much as I can about direct/indirect heating, C-plans, S-plans, gravity-fed, fully pumped, etc. But I'm just not able to make sense of the pipework in/out of the hot water tank.

Can anyone please help to explain the setup?

Here is a picture of the tank:

And here is my representation of the pipework:

- the red pipes are ones I observed getting hot, the blues are cold
- boxes "A" and "B" are stop cock things, and "C" is the 2 port valve

Specifically, I find pipe 4 very confusing.

Sorry for the long post, hopefully you can help.

 

[chrishutt]

There appears to be something seriously wrong with the pipework around the cylinder, and above the motorised valve in particular. To work out what is really going on you need to follow the pipes through above and below so we can see the whole picture, so to speak.

 

[ArtfulBodger]

How did you create that schematic?

 

[tjg]

Thanks again for the replies. I've not had chance to follow the pipes up into the loft or round to the rads etc. yet - a job for tomorrow.

It's frustrating because I really want to understand how this is set-up. Everything seems to work ok. I fitted the new programmer (set to gravity), we have HW and CH (all rads get hot, though some more so than others, maybe problem with TRVs or they need balancing?).

I should point out that the house was built as a bungalow in 1966, then was extended upwards in 1972 adding a second floor. I doubt this would be causing too many peculiarities though.

ArtfulBodger - I created the schematic by first of all drawing it out by hand then copying it simply using MS Word's basic drawing utilities.

 

[slippyr4]

surely thank HW cylinder has too many holes. Could (3) in the diagram be an extra tapped outlet for a shower or something?

What's the funny stub of pipe coming up from the primary HE inlet on the cylinder? does that have an air vent cap on it or something? or is it just a dead leg?

 

[tjg]

Too many holes! Based on what I've read, that's what I was thinking too.

There is a shower downstairs, but there is not separate heating device for it. I've not opened the floor upstairs to check the routing of all the pipework, but I'm sure the shower is fed just like the hot taps in the sinks and bath.

What does HE mean? (Heat Exchanger?) I presume you mean pipe 4 on my diagram. The stub is of a smaller diameter than the rest of the pipe (I can't remember exactly where the change in diameter happens), and does have some sort of air vent cap on the top.

 

[slippyr4]

you need to trace the pipes from the pump you discovered, do these go to the HW cylinder? should lead to pipe 4, if you do have a fully pumped system.

There is quite possibly another 2-port valve, just like "C" somewhere else in the system.

 

[chrishutt]

I fitted the new programmer (set to gravity)

It looks like you have a fully pumped system, since the cylinder flow and return circuit looks like 22mm. Programmer might be better set to pumped.

 

[tjg]

Thanks again for the replies. I haven't managed to trace all the routes of the pipes yet (priority for the weekend turned out to be a wasps nest in the loft and a new front door...).

I'll sort out a more accurate diagram as well as it does not show the different pipe diameters (for instance pipe 5 is thinner, as is the "spur" on pipe 4, and also I think the top vertical section of pipe 4 just after it splits horizontally to the right).

I've since found another access panel in a wall in the bedroom. I'm going to open that up for a look tonight.

Thanks again for your help so far, it is appreciated.

 

[meldrew's_mate]

I do like this guy's detail, now that's how to ask a question

Perhaps you have the pump on the return side, the pipes rising from the top primary connection could be the cold fill and the vent. Does one of them go to the bottom of the small header tank just above the shot, and the other loop over the header tank (open ended?). If so the zone valve is for the hot water, and there'll be another somehere else in the system (don't discount under the floorboards ).

By the size of the pipes you should have a fully pumped system, make sure the gate valve (just showing) on pipe 5 is at least 3 turns open as it is only 15mm.

One day I'm going to learn how to post pickies too.