Looking at options, not sure about terminology

sjh

I have a radiant heating system made up mostly of cast iron radiators along with a few hydronic baseboards, fed by an oil furnace. The oil furnace is in bad shape so it's time to replace it with something else, which is more efficient and less costly to run. The gas company is offering to put in a gas line and a gas furnace. But I would prefer to have an air to water heat pump installed. I can't decide on which option to choose, because a lot of it is confusing. I'm hoping somebody can help me sort through the options.

A lot of people in my area are converting to mini-split heat pumps because of government incentives. But my house is not a wide open space suitable for a heat pump. It would require several of them, all mounted separately, each with their own breakers. That would also mean the vast infrastructure that's been providing heat within the house for 100 years would simply be taking up space. I strongly considered doing it anyway, but there's nothing like radiant heat - it's the best. Replacing that with lukewarm air blowing out of mini splits wouldn't be the same - that type of heat can feel like air conditioning when you're already cold.

I became interested in replacing the oil furnace with an AWHP, once I discovered their existence. Continuing to heat the house with the existing radiant infrastructure, without having to install electric baseboard heaters and mini splits everywhere, while also no longer using fossil fuels, all while (supposedly) saving a huge amount of money, seems appealing.

But upon researching the product category, I find that most of them require you to inject glycol into the water that runs within your radiant infrastructure, which can lead to corrosion and other issues; and even then the max temp might not get high enough for your infrastructure; getting qualified assistance in installing, maintaining, and troubleshooting the system would be a challenge in itself, it's difficult if not impossible to find anybody who works with AWHPs in North America, where AWHPs are a niche product, so I'd probably have to try and do it all myself, and be stuck up the creek if I run into issues. I don't know how successful I'd be installing such a system from beginning to end or even being confident enough to know for sure what to buy.

So I don't know if I can or should go all-in on an AWHP. Maybe it's possible and would work great, but maybe it wouldn't, and I shouldn't take the risk. Instead, I'm considering a hybrid system comprised of a gas furnace along with some sort of heat pump linked to it. If anything goes wrong with either component, there's built-in redundancy.

But I'm a little confused on what I need to buy. Some terms seem to be getting used interchangeably. Notably, AWHP, hydronic boiler, and heat pump water heater. But they're not the same things, are they?

My goal is to have a 'heat pump' providing hot water for the taps, and also to feed the hydronic baseboards/radiators. It would be providing radiant heat via the existing infrastructure, and hot water for personal consumption. So it would be a 'water heater', but it would also I guess be called a boiler? This item, whatever it's called, would be tied into the gas furnace that the gas company will install. Both the gas furnace and the heat pump product would decide amongst themselves which one is running at any given time, according to the ambient temperature determining when each one is more efficient. Ideally, this would cut my heating costs by 40 - 60% compared to oil or resistance electricity or even gas, which are percentages I've seen thrown around in discussions on AWHPs.

Even on the coldest nights, up till I had to shut down the oil furnace, the boiler room in my basement was always comfortably warm or even hot due to all the piping going to and from the living space to the boiler room. A heat pump in there, working in tandem with a gas furnace, would be able to acquire heat from the ambient heat radiating off the hot pipes, so I'm thinking it could become a very efficient system - more efficient than just depending on gas for heat and either a regular gas or a regular electric water heater.

Hopefully that's enough detail for anyone who can provide advice on this. If not, I can provide more details. Any advice is welcome.

hot_rod

To maximize an A2whp you need low temperature heat emitters

Or do some load calculations and see how low you could run the supply to what you have

There are some A2whp capable of 180, dual compressor type, but they are not so common

Crunch the numbers carefully to see which fuel is the most cost effective. Look for hidden fees associated with NG

A NG mod con could be an option, possibly running in condensing mode much of the year

So a heat load first, then a radiator assessment

If course an energy audit would show areas to tighten up the structure. Doing this lowers the load and also required supply temperature also saves fuel dollars

EBEBRATT-Ed

Your location matters and what is the coldest average winter temp? I would forget about mini splits. A heat pump in combination with you boiler is a good idea as you could heat with HPs in the spring and fall.

No matter what anyone tells you as the OA gets colder HP becomes less efficient and have to shut down and defrost when the OA is below 32.

You probably need a dedicated HP water heater (I don't like them either) an expensive throw away appliance IMHO.

But hey, I am old and like the old ways and its JMHO. Others will chime in.

Jamie Hall

Without knowing where you are located, it's a little hard to make any suggestions at all.

However… Air to water heat pumps are a type of heating appliance which replaces — or augments — a fuel (oil or gas) fired boiler or, very rarely, an electric boiler. They are designed to power relatively low temperature emitters, and with a very few exceptions are rally not suited to higher temperature emitters, such as your radiators. As @hot_rod said, one would have to know what emitters you actually had and the design heat load to see what might work.

Then there's another factor in the game: energy costs. In some areas of the country heat pumps will cost less to run than fuel fired heating. In other areas they won't — so again, we need to know where you are.

And last at least for the moment, a heat pump water heater, lite any water heater, is designed to provide domestic hot water and is not usable as a heating source. Like @EBEBRATT-Ed , I don't like them and have had dismal luck with them, but some have found them to be satisfactory.

sjh

Location: southern New Brunswick, climate zone 6. The coldest average temp is -13.6°C in January.

The emitters are old fashioned cast iron radiators + some hydronic baseboards, which are high temp emitters. There's no radiant flooring or anything.

I had an energy assessment done about 4 years ago. The results were not good. The assessor told me "this is the worst I've ever seen". It took until this year before I could get started on renovating the house. After opening up several ceilings and walls, and ripping off some of the exterior siding, it turned out the house was already insulated. I had thought it wasn't, or was only partially insulated, because the house leaks like a sieve. Anyway, we'll be replacing most of the windows, replacing the insulation with better insulation, and insulating the foundation. But the fact that the house was already insulated, and was still "the worst I've ever seen", is a bad sign. The reno is going to cost a fortune.

When the gas company initially came to me with an offer to replace my oil heating with gas, I rejected their offer, partly because of the hidden gas fees that hot_rod mentions. Gas is highly affordable in other parts of Canada and is used to heat most buildings. But in New Brunswick, it's expensive because of unusually high delivery charges. The gas is provided by Liberty.

Liberty Residential Delivery charge: $11.23/GJ
+ Customer charge: $22.50
+ Commodity charge: $13.69/GJ
+ Tax: 15%

1 GJ = 277 kWh. For an example, I used 9401 kWh in February heating only part of the house with electric space heaters. That cost me $1304.07. Electric space heaters are inefficient, but it gives you an idea of the cost to heat this place. I was spending similar amounts to that on oil prior to last year. The oil heated the whole house even with most of the thermostats turned down, because it heated up the pipes that run throughout the house. Unlike electric heat.

SJEnergy residential rate: $.1338/kWh
+ NB Power rate: $.02686/kWh
+ Service charge: $23.44
+ Tax: 15%

With gas, assuming I would have used the equivalent of 9401 kWh, so 33.84 GJ, that would have cost me, based on Liberty's rates, $995.66.

Gas is expensive here. In comparison, gas in Ontario is cheap. Enbridge lists it in m3 instead of GJ. 1 m3 = 0.03789 GJ.

Enbridge residential rates

Gas commodity: $.188148/m3
+ Gas price adjusstment: ($-.002030)/m3
+ Delivery charge: $.0767/m3
+ Monthly charge: $27.91
+ Rate adjustments: ($-.001746)/m3

Based on using 33.84 GJ of gas, which = 893.11 m3.

Burning the same amount of gas that would cost me $995.66 would only cost $307.99 in Ontario. So it's not a slam dunk to switch to gas from oil like it is in some other places. Electricity rates are not worse in New Brunswick than in other parts of the country - the electricity rates are going up by 10% each year but still reasonable, which is why nearly every house and small commercial building I see has mini split heat pumps sprouted on the side now, even though they have a hydronic system already in place - there isn't a lot of forced air HVAC systems in place in the area. Nobody seems to be installing AWHPs here.

Jamie Hall

First — keep the oil heat and your hot water baseboards and radiators. No harm to investigating a new oil boiler (but not a fancy mod/con — you don't need it) when and if you need it, but have the current one cleaned and adjusted properly. As you have discovered, it can keep you warm at a reasonable price. What's not to like?

An air to water heat pump isn't going to do the job. You need the higher temperatures of the fuel fired boiler.

That said, if there are a few rooms or a room or two where you'd like air conditioning, there's also no harm to installing a mini-split for a few rooms, if you have the capital.

sjh

Jamie, oil is not one of the options. It's getting phased out. The whole city used to be on heating oil - that market is getting split up between gas and mini split heat pumps. The oil company wouldn't even clean it last time they were here - they said it was too rusted inside, and they showed me how bad it looks. The cost of heating with oil was very expensive. Even though I never turned most of the thermostats up to room temperature (21 C) except for short periods to check if the motors or certain radiators were working properly, I was routinely spending $10,000 a year on oil bills. I had the thermostats set at only 5 or 10 degrees, just so those parts of the house wouldn't freeze. I want to reduce the cost by half or more, while having the whole house at room temperature all the time, and the choices are gas or electric, but using electricity to heat this house is also very expensive. Heating this house electrically has to be done with some kind of heat pump, or it could end up being $20,000 a year, or even worse, if it's just electric baseboards and space heaters. Or else gas. I don't know for sure what gas is going to cost me, all I can do is make educated guesses based on how much energy this house consumes while I've been here with my heating patterns, and converting that into what gas costs. Somewhat ominously, I notice several buildings around here that had gas put in within the last 10 years, now have mini splits on the side, and have gone so far as to completely cut the gas pipe off where it enters the building from the sidewalk. That tells me they weren't happy with the cost of gas, and I might not be either. Whether I go with gas or heat pumps, I'll get rebates. They're basically going to install gas for free. Heat pumps, I would have to cover most of it, but would get $400 per heat pump as a rebate. If I try to keep using oil by buying a new oil furnace, there's no rebate. I wouldn't consider sticking to oil without having some kind of heat pump or heat pumps also installed, if it could be proven that this would reduce the heating costs significantly.

It looks like I am going to be going on gas because it will provide excellent heat. The mini splits that are going up everywhere supposedly need electric baseboards as backup, or else gas as backup, or oil as backup, because maybe the heat pumps won't work when the temperature is far enough below freezing. Or maybe they will, but with the COP approaching 1.0 in cold temps, it'll probably cost as much as heating with electric baseboards anyway. You can't get insurance if you only install heat pumps because it's not considered a primary heat source.

I'm looking for something to install onto the existing hydronic infrastructure in the basement that will make the entire heating system more efficient and less costly. My idea was to replace the oil furnace with a AWHP, but that's risky because people are telling me it wouldn't work. So my 2nd choice is to get gas and then later, plumb a AWHP in to work with the gas furnace/boiler. My 3rd choice is to have a heat pump water heater added to replace the gas water heater they're going to install. My 4th choice is to install mini splits in 6-8 rooms around the house, along with a few electric heating devices such as baseboards, and they would be providing much of the heat, or all of it at certain times of year, with the gas furnace providing a boost when needed.

Jamie Hall

Well… if the Province is really phasing out oil, either directly or covertly by messing with prices and taxes, your best bet is going to be a gas fired conventional boiler ties into your existing hot water heating system. You can use that for your baseline heat — or all of it — regardless of how cold it is outside.

Yo can also install minisplits for specific rooms for when it is slightly warmer out and their efficiency make it reasonable. They also will supply air conditioning.

At some point you could consider an air to water heat pump, but the current state of the art will not produce anything like warm enough water to heat your house with the existing radiation. You could consider installing a lot more radiation — probably about double what you have now — but that is not going to be cost-effective.

hot_rod

issue 25 takes you through the steps to upgrade a legacy high temperature hydronic system to one compatible with A2whp

If any structure improvements have been made over the years, the load has already been reduced

The correct answer comes from some data collection and number crunching

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_25_NA_Lowering%20water%20temperature%20in%20existing%20hydronic%20heating%20systems.pdf

HVACNUT

There are many good oil fired boiler and operating controls that would significantly lower your fuel bill. But if what you say is happening with fuel oil being phased out, then I agree with @Jamie Hall. The gas fired boiler is the best option for your needs. A 3 pass oil boiler with a gas power burner is simple and reliable. A geo heat pump isn't going to get the radiators hot when you need it. Do they offer incentives for air sealing?

sjh

https://forum.heatinghelp.com/discussion/comment/1862486#Comment_1862486

Yes, the energy audit I took qualified me for several types of incentives including air sealing. There is another program that covers $15,000 for installation of heat pumps but I don't qualify for that one - I only qualify for a $400 rebate per heat pump. I don't believe either program would cover enough of a geothermal installation for most people to consider it, since they cost quite a bit more than the usual options; and if it doesn't solve the issue of my emitters needing high temperatures, then it's probably not a realistic option for me at this time.

This guy installed a AWHP in his house, even though he had high temperature emitters, and he says it's working out great. But he says he has a wood stove that he uses when it's cold. He installed a Nordic ATW65.

ATW65 specs

Bernie_the_Brewer

Here is a website that compares the running costs between different fuels. You may find it useful to see if the awhp idea is even close to feasible: https://siecje.github.io/heatpump-cost/