Do they make a short hybrid water heater to fit 5 block tall crawlspace or just get 38 gallon elec?

[MidtoupperMichigan]

Have a cottage we moved to a new 5 block tall foundation just put in and crawlspace is 5 blocks tall. I like the efficiency of the hybrid water heaters but they look to be taller than any other water heaters out there. This will be in northern Michigan so its not going to be too warm in crawlspace for the hybrid to pull heat out of the air so I am thinking of just going with a Rheem 38 gallon short 31.5" tall electric dual 3800 element water heater even though I have natural gas, I feel its going to be simple and easy and I can shut if off at the main breaker when the cottage is not in use which will be multiple weeks in the winter and maybe a couple in spring and couple in fall when no one is at the cottage. Cottage is small 662 sq ft cottage 2 bed 1 bath. Will have shower/tub and bathroom sink and washer and dishwasher and kitchen sink but most often it will be 2-4 people using the cottage at a time. The Rheem is sold at Home Depot for around $400 or so but is rated at "approx" $296 a year which is relatively low for an electric model especially since i plan to turn it off when not in use. I have considered putting it on the main level of the 1 story cottage so its less water line distance and a bit warmer but I suppose I will need to be heating the crawlspace area anyway for the water pipes that will be running down there and sewer pipes.

 

[Michael Young]

Install a tankless water heater. The new Rinnai Sensei is AWESOME!!

 

[Sponsor]

 

[Dana]

What are you using to heat / cool this place?

Are the crawlspace walls insulated (to the code-min R15 continuous insulation)?

Is the crawlspace vented to the outdoors?

The Rheem hybrids are set up for ducting, so it doesn't really need it's own large room. An insulated conditioned crawl space could be included as part of the minimum "room volume" if it's not vented to the outdoors. In a house that size both the intake and exhaust from the water heater could terminate in an unvented insulated crawlspace- it has way more than the 700 cubic feet minimum volume requirement, and would work without actively heating the crawlspace as long as there isn't insulation in the floor joists, and the foundation walls are insulated.

 

[MidtoupperMichigan]

Install a tankless water heater. The new Rinnai Sensei is AWESOME!!

I was thinking of installing a tankless on demand water heater but the guy that does the winterization for me up there said they get too much build up and then I hear they have shorter life spans. He says the water I have has too much mineral build up issues for a tankless. I also hear they need to be cleaned out for this reason too? I love the idea of the size and efficiency and I do have natural gas up there too. Are they easy to drain for winterizing the cottage?

 

[MidtoupperMichigan]

What are you using to heat / cool this place?

Are the crawlspace walls insulated (to the code-min R15 continuous insulation)?

Is the crawlspace vented to the outdoors?

The Rheem hybrids are set up for ducting, so it doesn't really need it's own large room. An insulated conditioned crawl space could be included as part of the minimum "room volume" if it's not vented to the outdoors. In a house that size both the intake and exhaust from the water heater could terminate in an unvented insulated crawlspace- it has way more than the 700 cubic feet minimum volume requirement, and would work without actively heating the crawlspace as long as there isn't insulation in the floor joists, and the foundation walls are insulated.

Block walls are not insulated but I am considering putting up foam board if that is a good way to do that? Crawlspace is currently not finished as I have areas to finish covering from where the steel beams lifted and set the cottage down on the new foundation so it could be vented but I am leaning toward not having it vented. I am leaning toward insulating it well and no vents. The crawlspace did not require a sump pump crock as we are high out of the ground and does not have a drain. I was not aware the Rheem can be ducted. Biggest issue I have is the crawlspace for a hybrid is only 5 blocks tall which I estimate at 9"x5 blocks is only 45" tall. That is why I was looking at getting a short 31.5" electric 2 element 38 gallon.

 

[Dana]

I was thinking of installing a tankless on demand water heater but the guy that does the winterization for me up there said they get too much build up and then I hear they have shorter life spans. He says the water I have has too much mineral build up issues for a tankless. I also hear they need to be cleaned out for this reason too? I love the idea of the size and efficiency and I do have natural gas up there too. Are they easy to drain for winterizing the cottage?

Even if you had soft enough water to not lime up, in your location you're likely to end up freezing & destroying the heat exchanger on some windy night during a Polar Vortex cold snap.

 

[MidtoupperMichigan]

Even if you had soft enough water to not lime up, in your location you're likely to end up freezing & destroying the heat exchanger on some windy night during a Polar Vortex cold snap.

So heat exchanger between the heat pump and the tank on a hybrid or a on demand water heater? And so do you think for my situation, that a basic short conventional electric water heater is a reasonable solution?

 

[Dana]

Block walls are not insulated but I am considering putting up foam board if that is a good way to do that? Crawlspace is currently not finished as I have areas to finish covering from where the steel beams lifted and set the cottage down on the new foundation so it could be vented but I am leaning toward not having it vented. I am leaning toward insulating it well and no vents. The crawlspace did not require a sump pump crock as we are high out of the ground and does not have a drain. I was not aware the Rheem can be ducted. Biggest issue I have is the crawlspace for a hybrid is only 5 blocks tall which I estimate at 9"x5 blocks is only 45" tall. That is why I was looking at getting a short 31.5" electric 2 element 38 gallon.

There are multiple threads on this site on how to insulated basement walls that would be relevant to short crawlspaces (= hobbit-basement).

A Rheem hybrid water heater would have to live on the first floor, but could fit into a tiny <10 square foot utility closet if ducted. Read the manual- they're not huge from a footprint perspective, only tall. According to the dimensions in the brochure, the 50 gallon version could be ducted taking up only 27" x 36" (~7 square feet) of total floor space.

 

[MidtoupperMichigan]

Great points! I am also wondering if the hybrid will just eat up the heat from my furnace heat in the room?

 

[Dana]

Great points! I am also wondering if the hybrid will just eat up the heat from my furnace heat in the room?

2/3 of the heat going into the water comes from the room. If it's a furnace heating the house, it's coming from the furnace, if it's a heat pump heating the room it's coming from the heat pump, and if it's sunshine heating the room it's coming from sunshine. So the cost of that 2/3 heat will vary.

A cold climate heat pump uses about half the electricity of resistance space heat when it's 0F outside, and only a quarter as much when it's 40F out.

Residential retail propane in MI has been averaging about $1.75/gallon recently, and has a source-fuel energy of about 91,600 BTU/gallon. At 80% efficiency it's delivering only 0.8 x 91600= 73,280 BTU/gallon. Normalizing to $/MMTU (million BTU), that's 1,000,000/73,280=13.65 gallons/MMBTU, x $1.75/gallon= ~$24/MMBTU.

Residential retail electricity in MI has been running about 16 cents/kwh. In a resistance heater like an electric baseboard it delivers 3412 BTU/kwh. Normalizing to $/MMBTU that's 1,000,000/3412= 293 kwh/MMBTU, x $0.16/kwh= $47/MMBTU.

When it's 0F outside a cold climate heat put would be half that, or roughly the same as 80% propane.

When it's 40F outside it would only run half the cost of 80% propane.

The average winter temp in Petosky is about 25F, a temp at which a cold climate heat pump is using about 1/3 the amount of electricity as a resistance heater, so even in winter the cost of heating with a cold climate heat pump is cheaper than an 80% gas burner, and the 2/3 fraction of the heat pump water heater is proportionally cheaper. During the shoulder seasons it's about half the cost and in the summer the 2/3 fraction is essentially "free", since it's taking it's heat from dehumidification & cooling loads.

 

[MidtoupperMichigan]

Thank you. Thank you. I also happen to have natural gas there from DTE and dont have to use propane but still I will look over the great information you have provided! My comparison is going to be to a "$296 estimated yearly energy cost" Rheem 38 gallon dual 3800 element electric heater that will fit in my short 45" crawlspace.

 

[Dana]

Thank you. Thank you. I also happen to have natural gas there from DTE and dont have to use propane but still I will look over the great information you have provided! My comparison is going to be to a "$296 estimated yearly energy cost" Rheem 38 gallon dual 3800 element electric heater that will fit in my short 45" crawlspace.

The "$296 estimated yearly energy cost" on energy guide labeling is based on 12 cent electricity, not 16 cents.

Natural gas is almost always going to be cheaper heat than a cold climate heat pump @16 cents/kwh electricity. Heat pumps are often competitive @ 10 cent/kwh electric rates, even more so in warmer climates than yours.

Take a look at your natural gas rate structures (and connection charges, which are sometimes daunting). If you have a high monthly base charge fo the gas grid and you're not actively using it propane or heat pumps can sometimes be cheaper than gas.

 

[MidtoupperMichigan]

Thank you. Great points again. I will look at a bill from another cottage nearby.

 

[wwhitney]

As to the titular question, are there currently any commercially available options for a lowboy heat pump water heater?

I can imagine (1) a unit with the heat pump on the side of the tank, or (2) a unit designed for horizontal installation, or (3) a heat pump in a separate unit that can be put next to the tank?

Thanks,
Wayne

 

[Dana]

As to the titular question, are there currently any commercially available options for a lowboy heat pump water heater?

I can imagine (1) a unit with the heat pump on the side of the tank, or (2) a unit designed for horizontal installation, or (3) a heat pump in a separate unit that can be put next to the tank?

Thanks,
Wayne

There used to be options for retrofitting a hydronic heat pump to an existing electric tank of any size/shape, but those companies have all gone bust. SFAIK nobody makes a lowboy heat pump water heater.

Getting Into Hot Water — Part 2 - GreenBuildingAdvisor

In my last blog, I discussed the basics of our domestic hot water (DHW) load, and looked briefly at adding a solar hot water system to satisfy most of that load. What I decided to do first was to try a heat-pump water heater (HPWH), partly because it was a much simpler and less costly...

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Sanden's SAN-43SSAQA tank is only 38" tall, but the compressor unit has to be outdoors, which presents a serious freeze risk for the plumbing between the compressor & tank in midtouppermichigan's location. They can still make hot water when it's -20F outside, but if the power goes down for any amount of time...

But a Sanden would work great in Berkeley, if you don't mind spending 4 grand on a water heater.

 

[JDHAA]

Be careful about shutting off water heaters supplied with groundwater (pumps): my brother in law nearly died of Legionnaire's Disease when he shut off the water heater at his camp before the tank had fully warmed up. When he came back a week later, turned it on, and showered, he inhaled a ton of Legionnella bacteria - it turns out it's quite common in groundwater, and it had reproduced in the warm water while he was gone. He was in intensive care for six weeks and still has some cognitive problems.