Wetback fireplace Question

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Beny

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#223073 11-Sep-2017 16:22

For those who have a wetback attached to your fireplace, do you guys turn off the power when burning the fire or do you leave it on? Would it matter if you left it on seeing as the power supposedly only kicks in if the water drops below a certain temperature?

Jase2985

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#1862431 11-Sep-2017 16:32

the power is there as a backup if the temperature is too low.

wellygary

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#1862445 11-Sep-2017 17:01

It also stops your HWC becoming a breeding ground for nasty bugs, leave it on......

http://www.arphs.govt.nz/Portals/0/Health%20Information/Communicable%20Disease/Water%20borne%20illness/Legionellosis/legionellosis.pdf

SATTV

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#1862468 11-Sep-2017 17:52

A friend of mine had a small pot belly stove in a house they rented, they turned off the power in winter as the wetback was far hotter than then electric.

If you fire heats the water sufficiently, turn the power off.

John

I know enough to be dangerous

Rikkitic

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#1862485 11-Sep-2017 18:49

All of the above. We often turn the power off in winter but it isn't really necessary. Summer we have to use it when there is no fire. A big problem for us is no tempering valve due to low pressure. The cylinder has its own thermostat but the wetback sometimes generates steam if we have a fire and the outside temperature isn't cold enough.

Plesse igmore amd axxept applogies in adbance fir anu typos

k1w1k1d

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#1862513 11-Sep-2017 20:08

Our previous log burner had a wetback, but it wasn't overly efficient and wouldn't boil the water. It was referred to as a booster, rather than a proper wetback. Chch clean air rule makers don't want the firebox temperature lowered too much by heating water.

We left the power on and noticed that there was a small reduction in power bills in winter compared to summer. New fire doesn't have a wetback.

If you turn the power off, you will need to turn it back on if you don't use the fire for a day or two.

andrewNZ

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#1862544 11-Sep-2017 21:02

We turn off the electric element for a two reasons, which are due to having an 80's setup.
1) If we don't, we boil the cylinder. That blows pretty much the entire cylinder of water onto the roof., which is a massive waste.
2) Even if we don't boil it, it still gets very hot and has stuffed taps as a result. I've measured 96 degrees at the tap.

Now we have a wee one in the house, I have installed a timer on the cylinder. The timer ensures the hot water is heated to temperature every night. Most winter nights it doesn't turn on because the wetback has done all the heating.

A modern cylinder has relief valves and can never get hot enough to boil.
My advice is to turn it off if it's a problem, otherwise don't worry about it.

Aredwood

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#1862557 11-Sep-2017 21:30

Turn the element off when using the wetback. As wetbacks heat the cylinder "top down", while the element heats the cylinder "bottom up". So if you use alot of hot water while the wetback is running, the incoming cold will be enough to trigger the thermostat and switch on the element. So you will end up using electricity, even though the top of the cylinder is still really hot.

If you want to use a timer. Set it so it turns on after the fire has died down. So the element will only switch on if the fire wasn't lit, or it didn't burn for long enough to fully heat the cylinder.

Also it is illegal to have pressure relief valves on a wetback hot water system. Wetbacks must always be open vented. As they are an uncontrolled heat source. If you have a mains pressure wetback system, there should still be a separate low pressure water circuit for the wetback that must be open vented. So yes even modern wetback systems can still start boiling.

tripper1000

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#1862691 12-Sep-2017 10:19

Aredwood:

If you want to use a timer. Set it so it turns on after the fire has died down. So the element will only switch on if the fire wasn't lit, or it didn't burn for long enough to fully heat the cylinder.

^^^^This solves all the problems. Set the timer to run from midnight until 7am.

1) Health - if your fire doesn't get the cylinder hot enough to kill the bugs, the element finishes the job.

2) Power savings - the fire is given time to get the cylinder as hot as it can and the element makes up any short fall.

3) Environmental - Power after midnight is always from renewables. Power during the day time can come from thermal (fossil fuel) generation.

4) Money savings - if you are on a dual rate (night/day) plan, power between 11pm and 7am is cheaper.

5) The best of both worlds - as Aredwood said, if you don't light the fire, you still have hot water without having to remember to turn the element back on.

My timer has an over-ride switch so if I am expecting higher than normal hot water consumption I can ensure I don't get caught short.

Beny

22 posts

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#1866832 15-Sep-2017 12:52

Aredwood:

Turn the element off when using the wetback. As wetbacks heat the cylinder "top down", while the element heats the cylinder "bottom up". So if you use alot of hot water while the wetback is running, the incoming cold will be enough to trigger the thermostat and switch on the element. So you will end up using electricity, even though the top of the cylinder is still really hot.

If you want to use a timer. Set it so it turns on after the fire has died down. So the element will only switch on if the fire wasn't lit, or it didn't burn for long enough to fully heat the cylinder.

Also it is illegal to have pressure relief valves on a wetback hot water system. Wetbacks must always be open vented. As they are an uncontrolled heat source. If you have a mains pressure wetback system, there should still be a separate low pressure water circuit for the wetback that must be open vented. So yes even modern wetback systems can still start boiling.

Sweet, I just assumed the heated coils coming from the wetback were down the bottom. Ours is a low pressure cylinder.

Rikkitic

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#1866842 15-Sep-2017 13:05

Ours boils all the time. In the summer when the ambient temperature is warmer but we light a fire in the evening, the water often overheats. When we hear it bubbling we have to open some taps to release the steam.

Plesse igmore amd axxept applogies in adbance fir anu typos