Hot water cylinder coils

ptogher14

Hi all,
I recently had my house plumbed. I installed a 300L hot water cylinder. It has a primary coil and solar coil. At the minute I don't have solar but want to utilise both coils. My plumber reckons these should be plumbed in parallel. I think they should be in series for maximum efficiency. My thinking is by having them in parallel you are reducing the flow rate of them. Thoughts?
By the way I'm not a plumber

ptogher14

ptogher14 wrote: »

Hi all,
I recently had my house plumbed. I installed a 300L hot water cylinder. It has a primary coil and solar coil. At the minute I don't have solar but want to utilise both coils. My plumber reckons these should be plumbed in parallel. I think they should be in series for maximum efficiency. My thinking is by having them in parallel you are reducing the flow rate of them. Thoughts?
By the way I'm not a plumber

I don't think there's much in it but I'd go for plumbing it in series because I'm very lazy and it's easier to plumb also if it's plumbed parallel then the coil sitting at the top of the cylinder will have minimal heat transfer when the cylinder is half heated.

Dtp1979

Ive mine done in parallel.
Stat on top and bottom of cylinder. When top stat reaches 55 it closes top coil. When bottom stat is satisfied it turns off boiler. 250l cylinder heated in about 25 mins maybe less

Dtp1979

Dtp1979 wrote: »

Ive mine done in parallel.
Stat on top and bottom of cylinder. When top stat reaches 55 it closes top coil. When bottom stat is satisfied it turns off boiler. 250l cylinder heated in about 25 mins maybe less

That is a very good way to do it and you can have the benefit of heating the top part of the cylinder like the sink switch on the immersion but bearing in mind your a plumber what are the chances of having that set up repeated correctly by the OP.

ptogher14

gary71 wrote: »

That is a very good way to do it and you can have the benefit of heating the top part of the cylinder like the sink switch on the immersion but bearing in mind your a plumber what are the chances of having that set up repeated correctly by the OP.

I'm a sparks so controlling a MV or 3 port valve with two stats is not an issue. However I'm monitoring the temperature digitally through the boiler so I'm not looking to do that.

The problem I'm having is I'm struggling to heat the hot water tank. It's taking an hour to bring it up from 40 to 50. Boiler output is not a problem. It can heat a 500L buffer tank tank to 75 in a couple of hours. The plumber plumbed the two coils in parallel. I used a different man for the boiler and he reckons they should be in series.

Any research I've done online says parallel may be the way to go but they all talk about identical coils. My two coils are of different outputs.

ptogher14

ptogher14 wrote: »

I'm a sparks so controlling a MV or 3 port valve with two stats is not an issue. However I'm monitoring the temperature digitally through the boiler so I'm not looking to do that.

The problem I'm having is I'm struggling to heat the hot water tank. It's taking an hour to bring it up from 40 to 50. Boiler output is not a problem. It can heat a 500L buffer tank tank to 75 in a couple of hours. The plumber plumbed the two coils in parallel. I used a different man for the boiler and he reckons they should be in series.

Any research I've done online says parallel may be the way to go but they all talk about identical coils. My two coils are of different outputs.

If you have both coils already plumbed and a flow temp of 75c then you have a circulation issue and replumbing it in series isn't the answer also plumbing the coils in parallel can lead to a higher return temperture unless you fit extra controls Like Dtp1979 .

The different sizes of the coils is not a issue.

You can't fit a 3port to a unvented cylinder as there must always be a 2 port wired directly to a cylinder stat for safety reasons.

Dtp1979

Is your balance valve closed too much?

ptogher14

Dtp1979 wrote: »

Is your balance valve closed too much?

I can't see a balancing valve. There's a common return for both manifolds and cylinder and I've no issue heating the house.

Dtp1979

ptogher14 wrote: »

I can't see a balancing valve. There's a common return for both manifolds and cylinder and I've no issue heating the house.

The balance valve is a red wheel valve on the coil return. You might not have one but if u do then make sure it's opened 1 1/2 turns