what is this thing?

Radiant in-floor heating system. Three electrical boxes… junction box on the right, shut-off in the middle, what’s the thing on the left? Relay? Transformer?
Also… whats that thick section in the condensation tube? Looks like it’s made to hold a filter, but it looks permanent.

Hi Kent,

it looks like the system control transformer, isn’t that a low voltage conductor comming out of the top??



Not a clue with the cover on but I can see high and low voltage wires both going into the box could be transformer, relay or what ever.

I must be getting old or you are extremely fast. I am going to leave this with you got two reports to get out

Yep, I think you’re right, Gerry. Low voltage wire goes to the control box beneath the boiler. I don’t know whether circulation pumps require a relay. If they do, it’s probably located on the pump.

That one Gas tankless hot water heater takes care of 11 zones???:roll:

It uses preheated water from an evacuated-tube solar thermal system with a storage tank that must be 300 gallons. Picture on the right shows the pipes to and from the collectors; hot pipe *from *collectors (with red gauge) on left, cool pipe to collectors (blue gauge) on right with in-line circulation pump (in black housing) installed in it (cooler fluid increases pump lifespan).

Gotcher air vent about 4’ above the pump, gotcher red expansion tank, gotcher control box hung on the wall to the right of the pump. The control box is connected to thermal sensors at the tank and at the collectors, and it’s circuitry switches the pump on and off according to temperature limit settings.

In the storage tank, hot fluid from the collectors circulated through two heat exchange coils and water to preheat the boiler and water heater is circulated through the third coil.

Still must be a very efficient home for the system to serve 6-7 zones (not all 11 will be on at the same time due to diversity) at 6 am, hours after the last sun and usually the coldest part of the day.

wow, i wouldnt know where to begin with that one!!

Bob, the components in bold type in post #6 should be present. Look for leakage, look at the control box display, it should be lit and say something. Hot pipe should feel hot and be insulated. You won’t see inside the tank. I did the draw inspection on this home and that’s how I got the tank interior photo in post #7.

Then you write it up as a specialist inspection, tell the client it’ll save him money if it works and move on.

Hi Kenton,

Based on my Solar hot water system and radiant floor heat system, my guess would be: the left box is for a temperature sensor, most likely on the return side, the large tube in the middle of the condensation tube may be an acid neutralizer.

I actually did a similar draw last week, they had 2-100 gallon tanks in the basement. Their radiant system was a constant “on” system consisting of only one pump and had 10 zones, the temperature control for each room gets adjusted by the valves in the basement to either speed up or slow down the flow through the tubing to provide the desired constant temperature. My system is different but I found this one to be very interseting.



Scott, I believe the temperature sensors at both the collectors and tank are controlled by the control box, but in looking at the system you posted… there are a number of items I don’t recognize.

What’s that big rectangular wall-mounted thing to the left of the left side water heater? Some kind of manifold? It looks like it connects to home heat supply lines.

How come the (red) hot water gauge on the circulation pump slants over to the cold side?

These questions just underline the fact that there are many different kinds of systems and components and unless an inspector has a background in solar HVAC and understands these systems… disclaim them.

Acid neutralizer? I called an HVAC guy last week to ask about the toxicity of condensation (this house had a nasty leak) and he told me condensation is mostly water. Nevertheless, your answer makes sense.

I am not sure what you are looking at for the gauge, I also know one of the tanks is not yet set up. I also do not know what that rectangular thing is either, I wasn’t inspecting the solar part on this Draw, I just noticed the home was using solar when I came up the driveway.

Next time I am there, I will try to get some of the answers.

Something else I found interesting is, the instant hot water heater has an adapter for hooking up a fuel cell. The manufacturer is currently working on a fuel cell, but will not release it until it works for 40,000 hours, it is currently at 8,000 hours.

How did you recognize a hook-up for a fuel cell? I be posting another “What is this thing” picture.

I didn’t recognize it, I wish I could have, I love the idea of fuel cells.

The owner and builder were there and pointed out a lot of the stuff. I plan on going back and asking more questions next time around.