Heat Pump Hydronics and Hot Water System – Installation
Hello,
I recently did an interior remodel on my 1978, 1600 sqf home. I am in Zone 6a in California (Sierra Mountains). During the demolition, I installed Warmboard-R with Schluter membrane and fast set. Tile throughout the ground and first floor. Everything was tested at the manifold for pressure and terminates there.
I chose Arctic Heat for the heat pump, expansion tank, buffer tank etc., supplying both warm/cool floors and hot water prep for an existing heat pump water heater (possible fan coils at a later date).
My challenge is getting a contractor to perform the install of the heat pump equipment when it arrives. Some folks are not accepting new clients until February 2023 and the rest say the job is too small.
–My question is, would I be able to perform the install myself?–
I have experience with electric (breakers, conduit etc) and have installed a leg from the sub panel to the outside and into a shed.
My biggest concern is knowing the correct placement of the equipment, pipe angles and so on.
While there is technical support from Arctic Heat, I don’t think they are going to be able to advise me on placement etc
EDIT: Stem wall foundation with perimeter wall vents. The heat pump would sit right behind the back of the garage, enter the wall there to connect to the rest of the equipment. Sub-panel located in garage too, so fairly easy conduit run with outside shut off to the heat pump.
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Replies
Does your jurisdiction allow DIY installation of HVAC equipment? Mine doesn't.
Will Arctic help you with the design? Things like what size pipe, what size wire, what other components are needed, what valves and shutoffs you need. If you have a roadmap and you know how to do basic plumbing and electrical it's not that hard.
I can do it myself without penalty from the Town. As far as pipe sizing, breakers, wire guage etc., I think I am good but the placement, length of run etc is lacking for me.
The Artic manual is fairly good and provides several system diagrams that should give you a good idea of how things should be layed 0ut. That said, there are a number of components that those diagrams don't show and you need to think about and plan for including isolation valves, system flush points, air/water/dirt separators, auto fill valves, etc. Wiring can be tricky and is very custom for these systems too depending on how much control you're looking to exercise over individual zones.
After you get through all of the planning you'll need to be comfortable with assembly of everything and have the right tools to do the job. Think soldering of large diameter copper pipe (guessing you'll have 1.25in headers).
I'd say if you take your time to plan, find high quality components, and take your time with the assembly the job is doable albeit probably harder and more time consuming than you're imagining.
It is those pieces that are absent from the Arctic Heat manual that I am worried about. It is 1 1/4 inch pipe for some of the build.
I'm of the view that any project is doable if you put the effort into it. Hydronics is not too bad but there is some learning.
The key to pulling any of these projects off is to simplify the design as much as possible. You see on the internet these big walls of copper and pumps, you don't want this.
For example, reduce the number of zones. For a single story structure, you want the whole setup on a single zone. If you want a bit of individual zone control, say the bathroom to be hotter, you can increase the flowrate in that area, no need for a dedicated thermostat.
Reduce the number of pumps. A simple air to water setup needs only two pumps, one from the heat pump to the buffer tank, one from the buffer tank to your zone manifold.
Most systems you see have a lot of copper. This takes a lot of time+skill and cost. Stick to Pex or Pert pipe. Might not look as neat but much easier to build, plus if you need to make changes it is easy to cut and splice.
Lot of hydronics has way oversized pipes. This might be left over from the days of gravity feed systems. For example, in colder climate than you and a larger place and all the main hydronic plumbing is with 3/4" pex.
Common rocky hydronic mistake is putting pumps in the wrong location. It is very hard to suck water up hill, it should be pumped up hill. This means inlet of your pumps should be near the bottom of your system and preferably a short direct connection to your buffer or expansion tank.
Keep the domestic hot water separate from the air to water. A standard HPWH is much cheaper, simpler and in your warm climate most likely more efficient.
There is an article on this site that might be interesting read:
https://www.greenbuildingadvisor.com/article/air-to-water-heat-pump-retrofit
P.S. You can reduce the pumping loses a fair bit by using swept elbows such as the Sioux Chief 642X3. These are also great for DHW plumbing as they are less likely to erode and crack.
A lot of good info in that article. Tying into our earlier discussion about heat pumps, the Nordic he used is a split system, where refrigerant runs through the wall and all the water stays in the house, no glycol required.
The three-pipe configuration for the buffer tank ties back to a conversation we had a few weeks ago about buffer tanks. It looks like the ideal solution, bypass the buffer when the circulator is running but have it available when it isn't. I wonder if there should be a check valve at the top entry into the tank, so that the circulator can only pull water from the heat exchanger and not the buffer tank.
I don't think a check valve on the buffer tank will work. The extra pressure drop there might mean that when the zone pump is running with the heat pump off, it will pull cold water through the heat pump from the bottom of the buffer tank.
Having written that, there definitely should be check valve on the heat pump circulator (probably the built in IFC is good enough) to add a bit of restriction to prevent this.
So on my heat pump (Chiltrix) the circulator runs even when the heat pump is off, that's how it knows the buffer tank temperature so it knows when to kick on again. It runs at about 2 gpm when the heat pump is off. When the heat pump is on its circulator runs at variable rate, up to about 7 GPM, depending on conditions.
Inside there is another circulator which is activated by the zone valves, I have it set at constant pressure so it produces about 1.5 GPM for each zone valve that is open, there are four total. So the circulator in the heat pump is pushing between two and seven GPM depending on conditions, the circulator on the zones is pushing between zero and six GPM depending on conditions. The difference between them is either going into or coming out of the top of the buffer tank. The return from to the heat pump comes from the bottom of the tank, and the return from the zones goes into the bottom of the tank. The difference in their flows is exactly equal to the flow into the top of the tank.
I was thinking check valve because I didn't want the buffer tank short-circuiting the loop but I don't think the pumps would let that happen. The danger I could see is a scenario where the heat pump is at its limit, it's running full out and the flow is choked down a bit to keep the temperature up. If all zones are on the zone circulator would be pulling cold water from the buffer tank, so colder water is circulating than if the buffer weren't being used. I haven't lived with this unit in really cold weather so I don't know if this scenario really happens.
If I remember correctly, your setup has a small buffer tank. In that case it doesn't matter much what the heat pump is doing but in case of a larger buffer tank, you want to use a remote sensor and disable the heat pump circulator once the target temperature is reached. Without this, that 2GPM will quickly mix even a larger tank which you don't want.
I think with your setup, as is is pretty good. As soon as any of your zones start dumping cold water into the buffer tank, it will be pumped to the heat pump by the 2gpm idle flow rate which should cause it to ramp up. Eventually the heat pump circulator flow will match your zone flow rate at which point there won't be any more flow through the tank. In case all the zones finish calling for heat, the heat pump will run until the buffer tank is fully up to temperature ready for the next call.
Yep, 17 gallons.
I think you're right about how it will work.
DC, do you have any threads or info on your system?
I don't have a dedicated thread. I only commissioned the system in April, I'm waiting until I've got a full year of operation at which point I'd like to write a comprehensive review. I've already made a few modifications.
Thanks...with the addition of fan coils for cooling coming later, the Arctic design is set in stone and from what I can tell it is a good one. I will have more than two thermostats and while downstairs is one big zone, upstairs will have the area split up. I plan to use pex anywhere possible.
The Arctic heat pump is way more efficient than my heat pump water heater, so using it to preheat at a lower than desired temperature was a good working solution from Arctic and the numbers tie out.
"Arctic heat pump is way more efficient " I would definitely question this. On paper an indirect off a modcon should be more efficient but in reality it runs at the efficiency of a standard power vented tank. This comes from me measuring the summer time gas usage. Big issue is the return water temperature tends to be too hot (especially when making up for standby losses) and all the heat in the volume of the plumbing external to the tank is wasted each time the heater off. Both of these will also be an issue with your air to water setup.
A heat pump providing lower temperature water with the need of an external tank to bring it up to full temperature, I don't see it. I would love to know for sure, would be great if you get a chance once you are up and running and do some data logging on your setup.
Will do so...in my case, the most efficient period for hot water will be summer as the garage is colder than outside, so with the Arctic Heat outside and hot water heater in the garage I cannot see how it would not perform more efficiently.
Do you cool the house in the summer? If so, a heat pump water heater is contributing to the cooling of the house and taking load off of the AC. It also provided dehumidification.
Can I use Pex-AL-Pex to connect the HP, boiler, buffer, valves etc?
The boiler is a 1 1/4 NPT fitting but I think the rest is all 1 inch.
Thanks for all the helpful advice so far.
You can. You can also use oxygen barrier PEX, which I find easier to work with.