Electric DHW and Heat from small(est) footprint? –
Homeowner just trying to make good decisions here and looking for some insights from those with a lot more knowledge this area.
Short story – I am looking for an electric DHW and heat solution that takes up the smallest footprint… but still environmentally justifiable. Suggestions?
Longer story – Live in a 1905 rowhouse in DC. Major renovation a few years ago, which included hydronic radiant floors, closed-cell foam on all exterior walls/roof, and all new doors and windows. 3 stories, but the overall footprint is so small, we just have no storage. Clawing back half of my mechanical room to use as storage has a considerable value. Looking for what I could use to replace my stand alone (aged) gas boiler and gas DHW tank. Would also like to add in solar, so want to get the whole house to be all electric. Was looking at the Eco SANCO2 system, which looks to deliver both, but some online stories of problems and lack of support has me concerned. Exploring whether there are better options. House modeled to only need 9,000btu of heat in winter… so the smallest of units on that side should work. Thanks in advance. I just do not know enough of the industry to make sure I am looking at all the possible options. Suggestions?
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Replies
Smallest footprint is probably a wall-mount gas combination boiler. Google that phrase to get an idea of what I'm talking about. Getting as small as 9K may be a challenge.
If all-electric is important you may want to look into Chiltrix. Slightly less experimental that SANCO, although their implementation of DHW is kludgy. It can provide cooling as well, and they have heads as small as 3K BTU. One for each floor would be perfect.
At such low load, there is probably no ROI in any fancy equipment.
A standard resistance tank with a side arm or plate HX to feed the hydronic setup is probably the lowest cost electric option.
If you want to stay with gas, you can look at an HTP RGH20 with a plate HX for heat.
The SANCO2 would definitely work in your case but does require careful setup. To get good efficiency out of these, you need a large tank and have to be careful to feed it the lowest possible return water from your hydronic loop and not to over pump the loop.
>At such low load, there is probably no ROI in any fancy equipment.
And if you're using resistance to heat the tank there's no point in the complexity of hydronic, just use electric baseboard heat.
Electric resistance heat is far less green than gas fired heat. The reason is that most of the electric supply is sourced by natural gas fired power plants, or coal, in your region (and nearly everywhere in the US, actually). If you use electric resistance, you have all the losses in terms of energy conversion at the power plant, then the losses in the power lines bringing the electricity to you. If you have a gas fired heater, that burns the gas directly, you don't have all of those losses so you actually use much less fuel for the same amount of heat output.
All electric only helps in terms of emissions when using a heat pump, which is MOVING heat, not MAKING heat. This is where the efficiency gains come from. Electric resistance offers none of that.
In your region (I used to do a lot of contract work around DC/Baltimore), air conditioning is your primary concern anyway most of the year. Minisplits are great for that, and can provide some bonus heat when needed. Minisplits are also a form of heat pump, so they have that efficiency gain you're looking for if you want to go all electric. I would seriously consider minisplits as your primary heating and cooling equipment, and maybe a small gas-fired boiler to run your hydronic system when you want or need it. This way you're running on the electric minsplits most of the time, and you're only firing that boiler during unusually cold weather.
For a water heater, a heat pump water heater is your best option if you want to go all electric. A gas water heater is much cheaper though, and probably can be found in smaller sizes too if you're short on space, which I imagine is probably the case in a row house. Row houses in Baltimore are all of about 14 feet wide, and DC is probably similar.
Bill
Since it was 95F in Washington today I'm assuming you have air conditioning, otherwise you wouldn't be asking about heat! Tell us about your air conditioning system.
Thanks for the replies. Yes, this is a case of if I knew then what I know now, I’d be mini-splits…. So we went with hydronic radiant flooring to get rid of massive old boilers that really limited room set-up. When we were 75% down that path, we realized that what we really needed was a full gut back to brick. Put in a nice AC system, a ton smaller than what was in and a high seer rating. Actually finding an ac contractor who didn’t just want to drop in the same replacement was hard. I ended up getting the house modeled separately, just so I had something to compare bids. Most had no such modeling… despite new windows and doors and closed cell. There is no question that a highly insulated home with radiant flooring is a waste. It is not on much.
So where I am is where I am. I am looking to add solar and want to get away from gas in the house. Ideally one tank of some sort to manage both. I looked at a combi system a few years ago and the ROI made no sense in the world for a nice gas fired system. Hoping an all electric offered better options.
The thing about gas is that you can get a lot of heat, 100K BTU or 200K BTU is no problem. So you can have tankless appliances, which are compact. Electric can't deliver those kinds of loads, either with resistance or heat pump, so you need to have a tank so you can save up hot water for when you need it. It's the tank that takes up room.
If you are able to upgrade your electric service to 400 amps it would be hard to find any heater that take up less space in the room than a tankless electric.
Seems like two heaters would be the smart move one for heating and a second for domestic.
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