Geyser Heat Pump Water Heater Question

[AMI Contracting]

This was one of our scenarios.
I suggested faulty measuring device, but faulty measurement or location suffice.
Here's what I would ask next.
Is the switch we are relocating high or low pressure (temp)?
If I have my time line correct, unit was installed in Feb. but only recently began to malfunction. That jives with a high pressure sensor (with higher EAT) but not necessarily a low pressure monitor (otherwise I would expect trouble right out of the box).
J

[engineer]

Good thinking - I hadn't thought of the effect of varying EAT, but it makes perfect sense.

However, if the switch to be relocated is pressure, it won't be easy to move!

I suppose it could be a current sensor, but where could such be moved to good effect? Perhaps from a total unit current hot wire to a compressor-only lead, but that would be worth not much more than 10%

My experience with cut-out at significantly below advertised upper temp limit makes sense in the context of my warmer-than-average Florida basement. An experiment may be in order restricting airflow.

[AMI Contracting]

Good thinking - I hadn't thought of the effect of varying EAT, but it makes perfect sense.

However, if the switch to be relocated is pressure, it won't be easy to move!

Good point, pressure is out due to little variation based on location.
Leaving temp sensor.
If we are talking high pressure, I can picture a scenario where thermistor is too close to compressor or cond. fan motor picking up additional heat during long cycles with perhaps higher than average EAT.
It appears we may be left to speculate......
J

[Arch]

Here is where we are as of Saturday. My installer had talked to Geyser as did I.
They are saying that here are Thermistors (sp?) located next to the two relays.
If they are to close to the relays it will cause problems like I am having. They told
to move them about 1/8 inch from the relays. When we opened up the case there
was one of the black round small part with a flat side laying right up against one of
the relays. We moved it out to about 1/8 inch. The other one is not out 1/8 of an inch
but there is some clearance. I do not like to change more than one variable at a
time when I do not know what I am doing. Next we move the other one away from
that relay.

One thing I found interesting was the lock out temp. When this all first started the
lockout happened at 121.6 degrees. Now this last winter I never saw temps above
118 and 119 degrees and the unit ran fine from Febuary till August. With my Water
Furnace helping out the temps have gone up. It has locked out at 121.6 two more
times since we started this project. My installer is going to talk to Geyser again and
see if he can fine out more. Thats what I know at this time.

Take Care
Arch

[Jerry In Maine]

Just installed a Geyser water heater in the basement. It works fine so far, but I had a couple thoughts about its operation during the winter when the basement temps gets ~45*F.

Would there be any benefit to installing a register in the floor above and connecting a flex-duct between it and the Geysers input air filter? The idea would be to get the Geyser some warmer air to breath and hopefully increase its efficiency. The warm air would come from a bedroom and would be ~65*F. We heat with a pellet stove in the living room and stir warm air into outlying rooms via ceiling fans so our bedrooms don't get real warm but the air would be substantially warmer than the temps in the basement. I would also route the Geysers cold exhaust air to the outside via another duct routed to a basement window.

Next question is about installing a tempering tank for the water entering the Geyser. There's a couple things to point out first:

• We get water from 300' deep well, and the water is pretty cold with temps around 46*F.
• Our pellet stove exhaust vent pipe runs through a stairwell going to the attic. This space is closed by a door at the bottom and a hatch at the top. Temps in this space stay around 85*F when the stove is running - which is most of the time during the winter.

My plan was to install 4 each 4" diameter x 8' lengths of PVC pipe in this space. They would be capped with fittings installed so I could connect them in series.with PEX tubing. Water would enter these pipes straight from the well pump and would leave and then enter the Geyser. The intent is for the 4" pipes to hold water in a warm space in order to temper it a bit so the Geyser would feel warmer water than it would if the water came straight from the well. Most of our hot water usage is in the morning, so the cold water would have a good 8 hours to warm and hopefully pick up a couple degrees.

Any thoughts?

thanks

[engineer]

Don't go to crazy ducting the Geyser. Its internal fan is unsuitable for extensive ductwork without a booster blower.

The tempering pipe plan might have some merit, but I wonder if it would rsult in much more than a 5-10 deg increase in EWT to the Geyser - hardly worth the aggravation. I'd also be concerned that the tempering lines could condense water out of ambient air, leading to mold or other problems from uncontrolled water.

[Jerry In Maine]

the duct would be about 10'. nort rosad tech sells a fitting for the back that allows you to connrct the outgoing cool air to you hvac system but doesn't say how long that duct can be.

i wonder what air temp the geyser can handle economically before its no more efficient that than resistance heating with the old electric water heater? geyser manual says its enviroment can be as low as 40* - but i wonder how well it works at/near that temp.

[engineer]

My guess is that capacity and efficiency fall off fairly gradually with lower ambient air temps, down to the point where the evaporator starts to ice. At that point I imagine that efficiency falls off a cliff as the system defrosts itself and activates the resistance element. Depending on coil design and airflow as well as ambient humidity, icing might reasonably be expected as drybulb temp gets down to the 40s; where in the 40s I can't reliably guess.

That phenomenon should be common across any air source HPWH, not just Geyser.

[Jerry In Maine]

If i mount the geyser on a wall mounted shelf at about the same height as the tank it'll be about 4' from the joists of the master bedroom floor where I'd like to install the floor air register. I betting its internal fan could handle that. We heat w/ a pellet stove in the LR - and outlying rooms (like the master BR) might get down to ~65* at night. That's +20* warmer that the basement air during the coldest times of winter.

Cool "exhaust" air will be routed to a basement window in the winter and that's just a couple feet away.

[engineer]

Ejecting Geyser exhaust air would cause replacement air to have to infiltrate from outside. In winter that replacement air would often be even colder than the exhaust air, further increasing the load on the heating system.

During times the Geyser isn't operating, very cold outside air could backflow into the Geyser, freezing its heat exchanger. A damper could prevent that, but if it hung up in the open position, perhaps as a result of icing, you'd be SOL.

I'd reconsider venting the Geyser to the outside in Maine.