Advise on HW control

[Mirez]

Hi all, I've got an old(-ish 1997) back boiler system that heats a tank of hot water by gravity and a pumped central heating system.

At the moment the HW system is on every time the CH system is on and as everything that uses hot water is electrical it heats up daily for no reason at all. I plan on replacing the copper tank with a new version that’s insulated to start with but I'd also like to get better control of the HW.

I've had a look online and frankly ended up more confused then before so can someone give me some basic info on what I need!

I have 5 pipes in total coming to/from the boiler, one is 15mm and is gas in, then I have a large 28mm going up, two 22mm's going up and one 22mm coming in from below. I've traced them up in the loft and the 28 and the lower 22 are the ones to and from the tank and the other 22's are the (retrofitted -fed from above) CH (I find it a bit weird that the pump is pumping down and into the boiler and not up and out but that's another question!)

I'm an electrical engineer so I'm quite happy to do the wiring myself and I'm happy to give the plumbing a go - I just don't quite understand what I need to buy and where it needs to go! I appreciate I could get someone out to do it but I enjoy a good DIY challenge

 

[stem]

That's a bit of a challenge on a forum. It would take all afternoon to type an answer to that. (at the speed I type anyway ) Here's a link to a website that will give you the basic information you require.

I suggest you read it, then if you have a specific question or two, post them on the forum. Click here for plumbing and wiring info.

It's not too hard, I managed to do it 10 years ago.

 

[Mirez]

Thanks Stem, that's really usefull as it shows me exactly what I'm missing - basically one two port valve.

I've discovered the boiler is a GlowWorm 25-2 and whilst the closest match on their website is 45-4 the installers guide looks to be roughly the same unit but nobody panic, I'm assuming nothing as its not the correct literature!, however it actually shows the valve as being fitted in their diagram so I can only assume I had a lazy installer or a tightass homeowner when it was installed.

Either way I'll be installing the new valve and controller soon so hopefully all will be well!

Final question, I has planned to replace the boiler with a new one but given its only 12 years old I thought better of it! Rightly or wrongly?

 

[Hugh Jaleak]

Older system were commonly fitted with the pump on the return, pumping back into the boiler. Some models even had space incorporated within the casing to contain the pump, IIRC my parents old Vulcan Continental was like that.

Fitting a valve to a gravity HW/pumped CH I think is referred to as a 'C' plan. It is imperative though that no valve or restriction is fitted to the flow from the boiler. This must have a clear path from the boiler up to the vent over the F+E tank for safety reasons.

Unusual for a gravity system to be piped in 22mm, but it must work in your case! As long as the valve is fitted in the gravity return it should be ok.

 

[Mirez]

Thankyou! I have no idea on the sizing, especially as the flow is 28 and the return is 22 which surely limits the 28 to 22 anyway?

The flow pipe comes from the boiler, into the loft and T's up and into/over the water tank and down and into the cylinder - its on this run (T to cylinder) that I intend to fit the valve - I'm 99% sure thats the correct place but happy for you to confirm!

Thanks, Mark

 

[Biguns]

Final question, I has planned to replace the boiler with a new one but given its only 12 years old I thought better of it! Rightly or wrongly?

Right!
[/quote]

 

[stem]

The flow pipe comes from the boiler, into the loft and T's up and into/over the water tank and down and into the cylinder - its on this run (T to cylinder) that I intend to fit the valve - I'm 99% sure thats the correct place but happy for you to confirm!

If you are referring to the branch off from the vent pipe to the hot water cylinder, that sounds OK as long as the vent to the cold water tank will not have any obstruction between it and the vent, as Hugh Jaleak stated. Otherwise when the water in boiler expands as it is heated it will have no where to expand to and could cause an explosion.

Here's an example of ice blocking an expansion / vent pipe, OK this example is for a hot water cylinder vent, not a boiler vent, but I'm sure you get the idea. Exploding Hot Water Cylinder

Final question, I has planned to replace the boiler with a new one but given its only 12 years old I thought better of it! Rightly or wrongly?

The age of the boiler is a relialibility issue, it is also a an efficiency issue if you boiler is less than "D" rated I would change it. For really inefficient boilers, the government are offering a scrappage scheme at the moment. so could be a good time to change. You may have to convert it to fully pumped or go for a combi and get rid of the cylinder when you upgrade your boiler, I don't think the new ones have a provision for gravity hot water systems.

 

[Mirez]

If you are referring to the branch off from the vent pipe to the hot water cylinder, that sounds OK as long as the vent to the cold water tank will not have any obstruction between it and the vent

Correct, deffo after the branch! I'm not blocking any pipe from the boiler to the vent pipe. The majority of internet postings seem to suggest the feed as opposed to the return as the better of the two pipes to attach the valve to which suits me as the return would be significantly more awkward to do

Do you consider 12yrs to be old for a boiler then? The local gas chap who serviced it said backboilers can last for 25yrs+ and are generally significantly more reliable then modern ones! Its got a SAP of 79.5% apparently, which I didn't think too bad.

 

[Hugh Jaleak]

Looked after I bet there's plenty more years in it yet! Annual servicing should ensure its efficient and safe for another years use. It'll take you a while to recoup the cost of a new boiler and installation through savings on the gas bill.

General concensus seems to be these HE boilers arent going to last anywhere near as long as the predecessors. So glad I got my new boiler when I did! Personally i'd hang onto it for as long as poss!

 

[Mirez]

That's pretty much my thoughts. In the electronics world nothing is lasting for anywhere near as long as the predecessors did as everything is built down to a stupidly low cost - It seems to be the same with most sectors these days!

 

[stem]

I help maintain a small property owned by a local charity. The property was purchased 15 years ago (ex-grocery store) and it came with a floor standing potterton boiler and 13 radiators that we were told was 30 years old. Since then, over 15 years, it has never needed attention (apart from the usual annual service). Last year in a refurbishment it was taken out at 45 years old replaced with a Vailant Combi. Already it's broken down once.

My mother had a 25 year old Glowworm, also never failed once. So naturally she replaced it with another Glowworm. By the time it was 3 years old it had broken down three times, the last time it filled the house with smoke. You could smell the burning for several days. She's terrified of it now.

Old boilers were a huge slab of cast iron, with a gas valve & burner underneath controlled by a thermostat, and basically that's it. The new boilers especially combi's have many more integral components to go wrong. I suppose that's progress for you. On the positive side they get much more heat out of the energy they consume.

Cars have also become more complicated over the years, I used to service my own, but I've given up on that now. Strangely cars have become more reliable though, so where are boiler manufacturers going wrong?

 

[Mirez]

Well I'd like to thank everyone for their input, I completed the project at the weekend and I'm extreamly pleased with it (and myself as I have no leaks lol)

For the first time I have proper control over the heating! I can now set just the CH to come on and where as before it would take around 10mins to get warm and 30mins to get hot it now gets warm in about 2 minutes and hot in about 15 which is fantastic and its also properly hot now - to the point I've had to turn down most of the radiators!

The final point I've noticed is that where before the boiler would run constantly for about 3 hours before it would start cycling it now starts this in under an hour which is fantastic.

So once again thanks for all the input Much appreciated!

 

[Hugh Jaleak]

You are very welcome. Glad its all gone well.