gravity HW / pumped CH?

[Steve]

I'm planning some improvements to my Grandad's central heating as part of his utility room improvements. He currently has a simple floorstanding gas boiler with a seperate pump and programmer. I want to replace the programmer but want to know what sort of system he has.

Going to upstairs is an un-pumped pair of pipes at 22-25mm. I suspect these go to the cylinder, but I see no other pipes that go upstairs, so is it possible these pipes also feed the rads? There is a pumped pair that go to the downstairs rads.

The programmer is an old Honeywell with a small display and three sliders to select the mode, and on/twice/once/off for CH and HW. And there is a cable from this to the pump and to the boiler. There appears to be no other valves and controls, apart from a roomstat.

Should there be a cylinder stat? Or is there some other way that the system regulates the cylinder temp? Is it possible the upstairs rads are on the same circuit as the cylinder, unpumped?

Any advice would be appreciated so I can understand this better, and perhaps buy them a new programmer. The thermostat is more modern and doesnt need replacing.

Thanks.

 

[bengasman]

No disrespect, but if you have to ask these questions, I doubt you will be doing your granddad a favour by tinkering with his system as it is a lot easier to do harm than it is to do good.
Leave it as it is, or pay a pro to improve it.

 

[mickyg]

why do you want to replace the programmer? I find most old people only know how to use a mechanical programmer.

 

[bengasman]

why do you want to replace the programmer? I find most old people only know how to use a mechanical programmer.

You youngsters just don't have respect for your elders anymore these days.
When I were young...........

 

[Steve]

because they are having the room decorated and it looks awful - all yellowed and old. I found a funky looking programmer with two "channels" - but the wiring diagrams dont give one for a room stat and no cylinder stat. And it seems bizarre that there's no cylinder stat?

 

[D_Hailsham]

I found a funky looking programmer

Make and model no?

Will you granddad understand and appreciate a "funky looking programmer"? K.I.S.S.

 

[JohnD]

Where are your photos?

For anyone over 60, I recommend the Invensys/ACL/Drayton electro-mechanical SM2 programmer

http://www.draytoncontrols.co.uk/product.aspx?id=1249

I fitted one for my old mum. She couldn't cope with the ACL Lifestyle digital one. It plugged straight onto the same backplate

p.s. fit a Cylinder Stat. They will send you the diagram for a Gravity HW circuit if you ask nicely, it is not provided with the programmer as this does not meet current standards.

Do you want to buy a Tapstat?

 

[Steve]

Do you want to buy a Tapstat?

A what now?

My grandad has a sat nav and a computer. Though he's forever asking for my help with them I wasnt thinking anything too complex, just something more modern that does the simple 2-channel switching job.

 

[JohnD]

http://www.draytoncontrols.co.uk/search.aspx?search=tapstat&page=1

 

[Steve]

Thanks John, but what does this actually do? Just turn off the hot water from the boiler? In which case what does the boiler then do? First thought is "overheat", but clearly there has to be some regulation in the boiler. I guess the problem is I dont fully understand how gravity systems work - the water flow muct be very slow, no?

 

[JohnD]

with a gravity system, the boiler runs continually, subject only to the timer and the boiler stat.

so if the boiler stat is 80C, it will keep itself, and the gravity pipes, at that temp, and the cylinder will eventually reach (almost) the same temp. this is scalding and wasteful. the tapstat allows you to control the cylinder temp, by shutting off the gravity flow when cylinder reaches the preset temp.

btw insulate those pipes including under the floor. they are probably 28mm which is a less-common size of Climaflex. I got mine at a large builders merchant (not a shed). Gravity HW pipeswaste a lot of heat as they are big, and hot for a long time (especially with no cyl stat)

yes, gravity flow is very slow. I recently added a HW circuit pump and motor valve to my old mum's system, anmd got some flak here for an untidy job A 3-port valve would be more usual. You will have to puzzle out what those upstairs pipes do. It might be a bit hard for you to modernise this system, but I am sure you can make it more energy-efficient. You can give it a clean, too, and maybe add a Magnaclean.

I am just a householder.

 

[Steve]

thanks for that John, much appreciated. I can see the benefit now of a cyinder stat. Another problem here is that the whole system is very old - when the boiler was changed to gas (20-25 years ago!) thats all that was changed, the rads are old, and cylinder is old. So theres probably not much point fitting new things to an old cylinder, better to wait till they replace everything. I'm not sure they want to change things, to be honest, though I would like to. Was just after some suggestions.

Their current boiler is a glowworm i think.

 

[JohnD]

insulate all the pipes and the cylinder to save money and get more useful heat (£20-£50 probably)

bale the mud out of the F&E and sponge it clean (£nil)

give the system a clean with Sentinel X400 (£15)

after rinsing, refill using X100 inhibitor (£15)

Ask what to do if there is fungus in the F&E

consider adding TRVs if you are going to fit then yourself (£10 each ish) during a drain-down

If they can afford it, fit a Magnaclean on a vertical 22mm pumped return pipe and I guarantee you will be amazed and delighted to see how much black sediment it collects (£100)

A clean system is always worth having and will improve efficiency, save wear on moving parts, and may prevent an expensive blockage.

 

[mogget]

If this programmer is a Honeywell ST699, it's still available

http://www.screwfix.com/prods/86588...afeed-_-Plumbing-_-Honeywell ST699 Programmer

along with its matching room stat

http://www.screwfix.com/prods/26159...ng-Controls/Honeywell-T6360B-Room-Thermostat#

 

[JohnD]

Honeywell ST699 is very simple and easy to use

I have one myself

Is your grandad's stained with dirt, or with cigarette smoke?