Home heating - radiators

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sxz

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# 144034 5-May-2014 15:50

My wife and I are considering home heating. We have an open fire place (not used) so are probably going for a flued gas burner to fill the hole and keep the mantle looking good.

As we are moving to gas, we will probably also put in an infinity water heater, and remove the old low pressure hot water cylinder.

At the same time I would love to install a hot water radiator (like you had in school) in the hallway by the bedrooms. I see you can get them on Trademe fairly cheap. I presume the cost is simply: Plumbing hot & return water to the water heater + getting a controller/thermostat. One question I have is do I need a special infinity water heater that has a seperate chamber to deal with the recycled/closed radiator water system?

Can anyone shed any light/advice on having a single radiator installed? Is there something I have overlooked that would make this expensive? I understand that as we will have gas hot water that this will be a fairly efficient form of heating.

Cheers guys,

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# 1037105 5-May-2014 16:01

There are HEAPS of heating discussions, you can find many of them here as background.

I wouldn't go gas these days. Unless you do heating, hot water, and cooking it's pretty expensive. You have to consider the changing price of power though, and gas, and the daily charges.

Getting rid of my fireplace and heater made my house HEAPS warmer. Sure when the fire was lit that one room was boiling hot, but other times it let a draft through and was really cold.

A radiator system for one radiator sounds expensive, I'd think you should do every room or don't bother. A heat pump is probably going to be better value long term. My wife's family and most of the UK has them, they can be a bit problematic but they are very effective.

Of course before you look at heating you need good insulation otherwise it'll get expensive.

Sidestep

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# 1037107 5-May-2014 16:05

I'm not sure how efficient it'd be heating water with an instant water heater, then using that hot water to heat through a basic radiator. We use a "Marshall" wood fired boiler and ring main to feed a bunch of "Myson" wall mounted, fan forced, thermo controlled radiators. It's really only efficient because the initial water heating's pretty much free.

mattwnz

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# 1037189 5-May-2014 17:25

If you are moving to gas, you may want to consider the Escea gas fires which recirculate heat around different rooms in the house. Hot water radiators are pretty expensive to setup in NZ. Not sure about the quality of the ones on trademe. I have seem some setup on a hot water cylinder linked to a wetback on a wood burner.

Consumer has just done a home heating article. I believe it rated heat pumps as one of the cheapest ways to heat a house.

sxz

681 posts

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# 1038547 7-May-2014 19:18

Thanks guys, those responses have been really helpful. I've been reading lots of reviews and have seen:
1) Infinity heaters can be slow to provide hot water
2) Infinity heaters can be affected by running a hot tap elsewhere in the house.

Have you found this common?

The reason I want to go to infinity heaters is to give us good pressure, free up the hot water cupboard, and of course, save money. No point doing that if the showers run cold when someone washes the dishes!

Looking at the infinity heaters I see some have 3 hot water outputs and 2 cold water inputs. The picture in my mind would be one dedicated stream to our only shower, fed from the cold mains. One dedicated stream to go to the rest of the hot water in the house. Finally, if it's cheap enough, I would love to feed one stream to a radiator and have that recycle into the final cold input into the heater, so in my mind it should be quite efficient to run, because once its going it only needs to keep the water warm. That one radiator will be in the hallway by the bathroom, so there shouldn't needs to be much pluming. I would have thought just a tap (possibly on a timer) to turn it on and off - should be no more than a few hundred bucks?

Thoughts?

kiwigander

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# 1038639 7-May-2014 21:50

How will that recycling bit work?

I see the point of having a closed loop so the infinity heater only has to add enough heat to the water stream to replace what's being lost at the radiator and through the pipes. But what moves the water? My LPG-fired instantaneous water heater relies on mains pressure to push cold water through its manifold. Once the water's heated up and been through the radiator I don't see how it can be fed back into the infinity heater.

We've got two radiators running off a wetback in our woodfire, but that is not a simple arrangement. There's a circulating pump under the house (under the woodfire) and it's all kept topped up by a reservoir up in the loft which itself is kept topped up by a ballcock. You might be able to do something similar with an instantaneous gas fired water heater if there's one that offers a dedicated circuit and is compatible with a low pressure water system. "Might" is the key word.

Regs

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# 1038654 7-May-2014 22:04

timmmay:
I wouldn't go gas these days. Unless you do heating, hot water, and cooking it's pretty expensive. You have to consider the changing price of power though, and gas, and the daily charges.

if you went for a heatpump central heating system instead of a gas central heating system you could be paying an extra $4000-$8000. It would take 10 years at daily charge of $1.10 to get to $4000.

heatpumps are also more efficient, but reticulated gas is also 5 times cheaper per kwh, so that either evens the running cost or spins it in favour of gas.

a gas central heating system can heat the entire house in 5 minutes, a heatpump system takes a bit longer.

lots of valid reasons to consider gas, don't write it off. especially not by looking at the daily charge without considering all the other factors...!

Jase2985

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# 1038719 8-May-2014 06:01

the only think with gas is it doesnt cool in the summer

timmmay

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# 1038724 8-May-2014 07:01

Regs: if you went for a heatpump central heating system instead of a gas central heating system you could be paying an extra $4000-$8000. It would take 10 years at daily charge of $1.10 to get to $4000.

heatpumps are also more efficient, but reticulated gas is also 5 times cheaper per kwh, so that either evens the running cost or spins it in favour of gas.

a gas central heating system can heat the entire house in 5 minutes, a heatpump system takes a bit longer.

lots of valid reasons to consider gas, don't write it off. especially not by looking at the daily charge without considering all the other factors...!

Agree gas central heating is viable, but probably not the way the OP is doing it. Get someone in to do it properly.

From Brivis gas central heating: "With a correctly sized, Warm Air designed system, you can expect preheat times of around half an hour to raise the temperature by 6 degrees Celsius (depending on the level of insulation and heat loss).". So not that 5 minutes you said. A heat pump can have a room significantly warmer in 5-10 minutes, and probably up to heat in 10-20 minutes depending on the heat pump and room size.

I'm not sure that it matters how long it takes to heat a room. Everything works on timers these days, and can come on whenever you want, so efficiency and cost is more important IMHO.

It looks like gas central heating would cost around $12,000 to do properly. A heat pump based system would probably cost 30-50% more, maybe even more than that, with the advantage it would cool the house in summer if required. Expected life is probably 7-10 years before you'd have to replace the outdoor unit. A single heat pump would be $4K, two would probably be $7-8K. I have two in my house, it works well, not ducted.

Sidestep

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# 1038759 8-May-2014 08:59

sxz: Thanks guys, those responses have been really helpful. I've been reading lots of reviews and have seen:
1) Infinity heaters can be slow to provide hot water
2) Infinity heaters can be affected by running a hot tap elsewhere in the house.

Have you found this common?

The key to taking advantage of tankless hot water units is to correctly size your unit to your anticipated demand, and keep the hot water run to a minimum.
Then hot water's almost instant, and taps can be turned on & off without affecting your shower flow/heat.

We've replaced 2 hot water tanks in outbuildings with 'Paloma Wallman' 24 litre units mounted on external walls close to where the hot water's required.
‘24’ means 24 litres per minute at 25 degree temperature rise (that's shower temp) - 44Kw output. They have programmable remote controllers to adjust heat on the fly.

One has a main controller panel (in the shower) and a sub panel (in the kitchen) for extra convenience. The controller works by adjusting internal mixing of cold and heated water through a range of flows.

The hot water was used in large amounts infrequently. One is on a disability washroom and one on a guest cabin, keeping permanent tanks full of hot water heated was wasteful.
24- 26 liter flow should be enough for a house, I've also seen these units sequentially 'stacked' or manifolded together for situations where larger flows are required.

Internall they're pretty basic. The heat exchanger that converts your gas/lpg into hot water is basically a copper coil over a burner – not too high tech.
Transporting that hot water via a pump powered circuit, and the radiator itself as a heat exchanger would be lossy.

ghettomaster

285 posts

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# 1038762 8-May-2014 09:12

I'm no expert, but with regards to hot water heating and infinity systems, someone once told me it takes more energy to heat water instantly than it does to maintain heat. Also, as has already been mentioned, you do lose pressure if you're running two showers, for example, but that lower pressure is often still better than the old low-pressure water tanks running one shower in my experience.

If the OP wants to go gas and recover the space from the hot water cupboard, an outside gas hot water cylinder might be something to consider.

timmmay

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# 1038772 8-May-2014 09:33

I put my hot water cylinder in my ceiling. Works fine.

timbosan

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# 1038787 8-May-2014 09:44

I can give you a real world example of moving to continuous gas hot water, as I did this about 3 years ago when renovations when carried out on the house. The reasons where quite similar to yours - regaining space and not running out of hot water.

There is no gas on my side of the street so I have gas bottles (2 of the big 45L ones) and only have hot water (i.e. not gas heating and no gas oven). I am more than pleased by the results, although you do need to keep an eye on the bottles if you have them - once we ran out totally and now have a small (BBQ size) gas bottle as a backup.

As for the gas central heating, I got a quote for this just last month, and it integrates with the existing Rinnai hot water system. It is rated at 20Kw (I think) heating, but as pointed out there is no facility for cooling. To install in a 3 bed bungalow the quote came in at just over $9K. Compare this to a 11Kw central heat pump system with 5 outlets that gives heating and cooling. Depends on which you want the most.

EDIT - This is the system (A Rinnai iHeat). Its not a radiator system like you are after, but uses the hot water to warm the air via a transfer unit, and then distributes that around the house via outlets in the floor or roof.

Let me know if you want more info, or I can post some pics if that would help.

Regs

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# 1040402 8-May-2014 22:10

timmmay:
Regs: if you went for a heatpump central heating system instead of a gas central heating system you could be paying an extra $4000-$8000. It would take 10 years at daily charge of $1.10 to get to $4000.

heatpumps are also more efficient, but reticulated gas is also 5 times cheaper per kwh, so that either evens the running cost or spins it in favour of gas.

a gas central heating system can heat the entire house in 5 minutes, a heatpump system takes a bit longer.

lots of valid reasons to consider gas, don't write it off. especially not by looking at the daily charge without considering all the other factors...!

Agree gas central heating is viable, but probably not the way the OP is doing it. Get someone in to do it properly.

From Brivis gas central heating: "With a correctly sized, Warm Air designed system, you can expect preheat times of around half an hour to raise the temperature by 6 degrees Celsius (depending on the level of insulation and heat loss).". So not that 5 minutes you said. A heat pump can have a room significantly warmer in 5-10 minutes, and probably up to heat in 10-20 minutes depending on the heat pump and room size.

I'm not sure that it matters how long it takes to heat a room. Everything works on timers these days, and can come on whenever you want, so efficiency and cost is more important IMHO.

It looks like gas central heating would cost around $12,000 to do properly. A heat pump based system would probably cost 30-50% more, maybe even more than that, with the advantage it would cool the house in summer if required. Expected life is probably 7-10 years before you'd have to replace the outdoor unit. A single heat pump would be $4K, two would probably be $7-8K. I have two in my house, it works well, not ducted.

My brivis with 10 outlets cost $8k and I've heard recent quotes in similar range. 5 minutes is from experience, not reading 'safe' specs off a website, and that's the entire house, not one or two rooms (i.e one or two heatpumps).

Cooling can be a bonus, or a burden. I didn't want high summer bills, so having no cooling option saves a few dollars!

Regs

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# 1040405 8-May-2014 22:15

ghettomaster: I'm no expert, but with regards to hot water heating and infinity systems, someone once told me it takes more energy to heat water instantly than it does to maintain heat. Also, as has already been mentioned, you do lose pressure if you're running two showers, for example, but that lower pressure is often still better than the old low-pressure water tanks running one shower in my experience.

If the OP wants to go gas and recover the space from the hot water cupboard, an outside gas hot water cylinder might be something to consider.

You generally choose the infinity systems for precise temperature control at the outlet (e.g. set temp to 37 and fill the bath for kids without worrying about testing it), and for the continuous supply (i.e. never running put of hot water). I believe heatpump systems (gas or elec) are better for cost saving (although somewhat offset by the high cost of installation).

Aredwood

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# 1040447 8-May-2014 23:32

If you want to run radiators. Get a proper boiler that is designed for that. Infinities (and im referring to the actual Rinnai brand and not all instantaneous gas water heaters) Are good at what they are designed for. But they are not designed for running radiators. Yes they will work but will be very inefficient doing so. They need cold water on their inlet for good efficiency. Also most radiators cant handle mains pressure meaning to run them off an infinity. And use the same infinity for hot water you will need a separate heat exchanger.

Im guessing that the 4 pipe connection "infinities" you are referring to are actually European combi boilers. They are a central heating boiler with a second inbuilt heat exchanger that is used for heating the hot water.

And why do you want to install a heater in the hallway? Even if it achieves perfect temp regulation of the hallway the temp regulation of the bedrooms will be poor. You don't sleep, read books, watch TV ect in the hallway. So why would you install a heater there yet not install heaters in the bedrooms and lounge?

My recommendation - decide on a form of heating and use it throughout the whole house. And if you get a central heating system, Please don't stick the thermostat in the hallway. That is the worst place for them. If you do the temperature tends to cycle alot. - The rooms will keep going hot, cold, hot, cold, instead of staying on a steady temp.

My own house - 300L mains pressure hot water cylinder, Solar panels, radiator central heating, spa pool, homemade 3 way heat exchanger to transfer heat between the mains pressure potable water / closed circuit central heating water / spa water. And my main heat source is a home made waste oil fired boiler. It cost me a bit in both time and material costs to build it and install it. But running costs are almost nothing for almost unlimited mains pressure hot water, almost whole house heating. And the spa is more enjoyable knowing the electricity meter is madly spinning away to keep it hot. Currently only have radiators in the bedrooms. Will soon add radiators to the open plan lounge/kitchen/dining room and to the garage (because I can).

Alot of doing that is a hobby. But it helps that Im a Plumber / Gasfitter by trade.

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