Control for HW in the Cylinder - Gravity Fed System. I need advise please.

Galego · 26-02-2015 1:34pm #1

Hi,
I need a bit of advice. Two question basically.

I have a gravity fed heating system that when the heat is on, heats radiator and hot water cylinder. I don’t seem to have any sort of control in the HW cylinder. So my two questions are:

1- Is it worth for me to spend money and fit some sort of control in the HW cylinder?
2- I heard of two option. A motorized value + thermostat around cylinder or a thermostatic valve (one of those which look like a radiator TRV). Which one would you go for and why? (if any)

Thanks and look forward to some advise.

Dtp1979 · 26-02-2015 1:43pm

Galego wrote: »

Hi,
I need a bit of advice. Two question basically.

I have a gravity fed heating system that when the heat is on, heats radiator and hot water cylinder. I don’t seem to have any sort of control in the HW cylinder. So my two questions are:

1- Is it worth for me to spend money and fit some sort of control in the HW cylinder?
2- I heard of two option. A motorized value + thermostat around cylinder or a thermostatic valve (one of those which look like a radiator TRV). Which one would you go for and why? (if any)

Thanks and look forward to some advise.

What is your heat source ?

Wearb · 26-02-2015 1:45pm

A motorized valve could be controlled (and should for your hot water cylinder) by time and temperature. Unless you have a constant demand for hot water, I would go for the former.

Unless your heat source is a stove or back boiler, in which case you cannot put any sort of restriction on it.

Galego · 26-02-2015 1:54pm

Dtp1979 wrote: »

What is your heat source ?

Sorry I should have mentioned this in my original post.

It is an outdoors boiler. A warmflow kabin pak 21-26k.

Galego · 26-02-2015 1:58pm

Wearb wrote: »

A motorized valve could be controlled (and should for your hot water cylinder) by time and temperature. Unless you have a constant demand for hot water, I would go for the former.

Unless your heat source is a stove or back boiler, in which case you cannot put any sort of restriction on it.

Is it worth the expense?

At the moment the HW in the cylinder is only controlled by the programmable thermostat. But nothing controls the temperature inside the cylinder.

Wearb · 26-02-2015 2:08pm

Galego wrote: »

Is it worth the expense?

At the moment the HW in the cylinder is only controlled by the programmable thermostat. But nothing controls the temperature inside the cylinder.

.

Unless you are doing other work, I would think its not worth it. Of course if you only use your hot water a couple of times a week, then it makes more sense. However, if the system is being drained down or plumber in doing other work anyway or able to do it yourself, then I would do it. First thing though, is to make sure your cylinder and pipework are well insulated.

Not everyone will agree with the above, but that's my opinion anyway.

Galego · 26-02-2015 9:31pm

Wearb wrote: »

.

Unless you are doing other work, I would think its not worth it. Of course if you only use your hot water a couple of times a week, then it makes more sense. However, if the system is being drained down or plumber in doing other work anyway or able to do it yourself, then I would do it. First thing though, is to make sure your cylinder and pipework are well insulated.

Not everyone will agree with the above, but that's my opinion anyway.

Thanks for your advise there.
Last question. Why motorised valve over a thermostatic valve?
I just thought a thermostatic valve would be easier to fit and does pretty much the same job.

Also, a plumber told me yesterday that fitting a thermostatic valve, or motorised valve, when closes should push hot water to radiators quicker which should mean boiler can heat radiators faster (as won't need to heat the water in the cylinder). Does that sound right?

Dtp1979 · 26-02-2015 9:42pm

Galego wrote: »

Thanks for your advise there.
Last question. Why motorised valve over a thermostatic valve?
I just thought a thermostatic valve would be easier to fit and does pretty much the same job.

Also, a plumber told me yesterday that fitting a thermostatic valve, or motorised valve, when closes should push hot water to radiators quicker which should mean boiler can heat radiators faster (as won't need to heat the water in the cylinder). Does that sound right?

A thermostatic valve closes and a motorised valve wired correctly through a cylinder stat will turn off the boiler when the stat reaches 60

Wearb · 26-02-2015 9:45pm

Motorised valve can be controlled with a timer.

When it closes it will allow more water to be pumped to rads. This shouldn't make a big difference if the system was properly sized and designed in the beginning

Galego · 26-02-2015 9:48pm

Dtp1979 wrote: »

A thermostatic valve closes and a motorised valve wired correctly through a cylinder stat will turn off the boiler when the stat reaches 60

Thanks but two questions here.

1- how does it turn off boiler? Would it need a wire to run from the motorised valve all the way to the boiler?
2- if heating is on, but I only want to close off the hw in the cylinder when reaches 60, would a motorised valve turn off the boiler completely so would leave me freezing?

Galego · 26-02-2015 9:54pm

Wearb wrote: »

Motorised valve can be controlled with a timer.

When it closes it will allow more water to be pumped to rads. This shouldn't make a big difference if the system was properly sized and designed in the beginning

Any point to be controlled with a timer? I would have thought the existing programmer already does that?

Also, in theory if the boiler has one less source(cylinder) to pumb hot water this should mean that it is saving fuel. Am I right on that one?

Wearb · 26-02-2015 10:03pm

Galego wrote: »

Any point to be controlled with a timer? I would have thought the existing programmer already does that?

Also, in theory if the boiler has one less source(cylinder) to pumb hot water this should mean that it is saving fuel. Am I right on that one?

For instance, if you only needed hot water every other day or in the evening only, the time could be set to have it heating just before needed and not at all other times.

If you need hot water all the time and have a well insulated setup, it will use very little extra once up to temp. In fact, you may need that little bit of escaped heat in your hot press/airing cupboard.

Dtp1979 · 26-02-2015 10:11pm

Galego wrote: »

Thanks but two questions here.

1- how does it turn off boiler? Would it need a wire to run from the motorised valve all the way to the boiler?
2- if heating is on, but I only want to close off the hw in the cylinder when reaches 60, would a motorised valve turn off the boiler completely so would leave me freezing?

If both heating And hot water are wired through motorised valves the the boiler will not shut off if the heating side is still demanding heat.
This is the ideal way to do it but might not be practical with your current wiring setup

Galego · 26-02-2015 10:13pm

Wearb wrote: »

For instance, if you only needed hot water every other day or in the evening only, the time could be set to have it heating just before needed and not at all other times.

If you need hot water all the time and have a well insulated setup, it will use very little extra once up to temp. In fact, you may need that little bit of escaped heat in your hot press/airing cupboard.

So in my case, is there any real savings in fuel if I have a valve which closes the hw flow going into the cylinder once it reaches 60?
I only have the heat on for 3 hours every evening......as I said this will heat the water in the cylinder for those 3 hours.

If not bothered with the timer would you still prefer the motorised valve over the thermostatic?

Galego · 26-02-2015 10:17pm

Dtp1979 wrote: »

If both heating And hot water are wired through motorised valves the the boiler will not shut off if the heating side is still demanding heat.
This is the ideal way to do it but might not be practical with your current wiring setup

Would you see much savings in fuel if fitted a motorised valve and thermostat in the he cylinder?

I have the heat on an average of 3-4 hours a day during the winter.

Would you see worth doing it?

Dtp1979 · 26-02-2015 10:45pm

Galego wrote: »

Would you see much savings in fuel if fitted a motorised valve and thermostat in the he cylinder?

I have the heat on an average of 3-4 hours a day during the winter.

Would you see worth doing it?

The savings won't be astronomical but you will save yes. As said earlier I'd only do it if other work is being carried out

Wearb · 26-02-2015 11:01pm

Galego wrote: »

So in my case, #is there any real savings in fuel if I have a valve which closes the hw flow going into the cylinder once it reaches 60?
I only have the heat on for 3 hours every evening......as I said this will heat the water in the cylinder for those 3 hours.

If not bothered with the timer would you still prefer the motorised valve over the thermostatic?

There isn't any real difference between fitting a motorized valve controlled by a thermostat without time control, and a thermostatic valve. So in that instance a MV would be a waste of money. Though you should be controlling the amount of time that your cylinder is being heated for.

#Yes there will be a small saving because you cylinder will not be getting above 60 and therefore the heat loss from it will be less.

Galego · 27-02-2015 8:58am

Well I want to do some other work in the system.
I am between to put trvs in all upstairs rooms or zone the upstairs zone - although I don't think i can fully zone it.
Which would you recommend yourself?
The house is around 130sq meters. Upstairs has 4 rooms but not very big.

Upstairs always get 2-3 degrees warmer than downdstaits that is why I would like to do something about it.

Control for HW in the Cylinder - Gravity Fed System. I need advise please.

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