Heat pump, Good Idea?

[denmendez65]

This is why I like the modern age, dozens of ways to kill a cat. Gas geysers, Heat pumps, 10 geysers in the roof, PV controlled geysers, etc. This is a never ending discussion with each supporting their own install

 

[Tomtomtom]

View attachment 1859013

No issues my side also in the morning

Is that Gemini? That's bizarre units. Outrageous!

 

[Lupus]

If you set your thermostat to 50, you are missing out ~3.5 kWh of capacity in your 150 L thermal battery.

70 is also above the general recommendations, your pressure valve must be working it's damndest. I mean I know the thermostat stops at 70, but it's like your car the rev counter stops at 7000rpm, doesn't mean you need to hit it.

 

[Tomtomtom]

70 is also above the general recommendations, your pressure valve must be working it's damndest. I mean I know the thermostat stops at 70, but it's like your car the rev counter stops at 7000rpm, doesn't mean you need to hit it.

I wondered about that and did a bit of research and didn't find any indication there'd be a problem with the geyser itself. The main issue is safety for the people using the water. But there is a thermostatic mixing valve if you're concerned.

 

[denmendez65]

70 is also above the general recommendations, your pressure valve must be working it's damndest. I mean I know the thermostat stops at 70, but it's like your car the rev counter stops at 7000rpm, doesn't mean you need to hit it.

Only if it sits there. For our use cases, it hits 70 once and gradually loses some 0.5 degrees every hour. So you only hit the rev limiter once a day.

 

[Tomtomtom]

Only if it sits there. For our use cases, it hits 70 once and gradually loses some 0.5 degrees every hour. So you only hit the rev limiter once a day.

Also if we're going with a car analogy... you paid for those revs, use them!

 

[Lupus]

Only if it sits there. For our use cases, it hits 70 once and gradually loses some 0.5 degrees every hour. So you only hit the rev limiter once a day.

Still 70 degrees for an hour. It's still 4 hours before it's down to 68 degrees which is still close to Rev.

 

[Lupus]

I wondered about that and did a bit of research and didn't find any indication there'd be a problem with the geyser itself. The main issue is safety for the people using the water. But there is a thermostatic mixing valve if you're concerned.

Could lead to a burst geyser and insurance are sticklers for that. Though it does have valves to release pressure, which is a bit of water loss.

 

[denmendez65]

Still 70 degrees for an hour. It's still 4 hours before it's down to 68 degrees which is still close to Rev.

Insurance will pay every 5 years if need be for a new geyser. The manufacturer put the setting there so it is within spec. As @Tomtomtom says, we paid for the rev counter and will use all of it.

 

[Tomtomtom]

Could lead to a burst geyser and insurance are sticklers for that. Though it does have valves to release pressure, which is a bit of water loss.

Ok so you forgot to try just raising your temperature setpoint before you dropped $$$ on a pump. These post-hoc rationalisations are not holding water.

I'll accept a 10% shorter lifespan on a R 5k geyser.

 

[DrJohnZoidberg]

70 degrees is too high for hot water for me personally. Have an old person in the house and don't want them burning themselves on water that hot.

Keeping the temp between 50-60C is ideal.

 

[denmendez65]

Could lead to a burst geyser and insurance are sticklers for that. Though it does have valves to release pressure, which is a bit of water loss.

Interesting enough, I only see water dripping from the outlet after a shower or bath. Otherwise it is always dry. According to AI, pressure difference between tap water and 70 degrees is negligible. Issues only arise if the water boils due to thermostat failures. Its AI so take it with a pich of salt but it sounds logical.

What pressure increase will one see between 55 and 70? Cant imagine much or any.

 

[Tomtomtom]

70 degrees is too high for hot water for me personally. Have an old person in the house and don't want them burning themselves on water that hot.

Keeping the temp between 50-60C is ideal.

Thermostatic mixing valve:

PlumbIt

plumbitonline.co.za

Not cheap but answers your concern while preserving that 3-4 kWh capacity.

 

[denmendez65]

70 degrees is too high for hot water for me personally. Have an old person in the house and don't want them burning themselves on water that hot.

Keeping the temp between 50-60C is ideal.

Bathing temp is 39 to 42. So 50/60 would still burn anyone.

 

[DrJohnZoidberg]

Bathing temp is 39 to 42. So 50/60 would still burn anyone.

Yep, but it's not good keeping your geyser at those temps, so easier maintaining a higher temp while not being scalding hot.

 

[Lupus]

Ok so you forgot to try just raising your temperature setpoint before you dropped $$$ on a pump. These post-hoc rationalisations are not holding water.

I'll accept a 10% shorter lifespan on a R 5k geyser.

Nope not forgotten , my dad has his geyser at 70 degrees and for an old person who uses it once a day sure, but not being able to use the hot water for anything without gloves isn't pleasant. 70 degrees is incredibly hot and inefficient way to ensure you have 50 degree showers in the morning .
Right now with the heat pump, if someone goes and showers, it warms it back to 55 degrees in 10 minutes, that 55 degrees will stay till 9pm, where it will raise back to 55 degrees and I get a nice guaranteed hot shower cloudy weather as well.

 

[wingnut771]

Nope not forgotten , my dad has his geyser at 70 degrees and for an old person who uses it once a day sure, but not being able to use the hot water for anything without gloves isn't pleasant. 70 degrees is incredibly hot and inefficient way to ensure you have 50 degree showers in the morning .
Right now with the heat pump, if someone goes and showers, it warms it back to 55 degrees in 10 minutes, that 55 degrees will stay till 9pm, where it will raise back to 55 degrees and I get a nice guaranteed hot shower cloudy weather as well.

Lets see your boob.

 

[Lupus]

Lets see your boob.

I've never had a boob, not even with the old system batteries are charged by 12, even with the geyser once it was warmed the next time it went off was 4pm in the afternoon when generation was under it's demand.

 

[Tomtomtom]

Nope not forgotten , my dad has his geyser at 70 degrees and for an old person who uses it once a day sure, but not being able to use the hot water for anything without gloves isn't pleasant.

Thermostatic mixing valves.

Goes on the outlet of your geyser, mixes the hot water with cold from your supply down to whatever temperature you want. Without sacrificing your geyser's thermal capacity.

 

[wingnut771]

I've never had a boob, not even with the old system batteries are charged by 12, even with the geyser once it was warmed the next time it went off was 4pm in the afternoon when generation was under it's demand.

Now imagine if you had 2 geysers so you didn't have to use power in the early morning to heat the water up but instead, letting the solar production run later into the day. You would be saving 900kWh per month instead of 700.