Future State Sanity Check

Ekkridon · September 10

Hi all. Homeowner here of a small 100 year old house. Cast iron radiators in most rooms, heavy transfer plate staple up in the kitchen floor, one small stelrad radiator in the basement.

My housemate and I have different comfort needs in the bedrooms and we have a kitchen underfloor that currently runs with the rest of the heating meaning we only have a warm kitchen floor some of the time since the radiators don't run continuously. The design objective of this system was always to zone it off, so the system has a primary loop with an aquastat leading into a buffer tank and then a manifold that can take zone valves with a single grunfos circulator for the secondary distribution loop.

I'm having trouble getting a local contractor (Toronto, Ontario) to quote me either at all on the final zoning step of this work, or they quote an absurd amount. I was just quoted — (price removed due to rules) to supply and install 7 zone valves, one zone controller and one floor thermostat, do all required wiring and reconfiguring. They estimated — (price removed due to rules) in materials - when I know its only about $1500 Canadian for the 7 four wire actuators, one T6 Pro and a Taco Zone Controller. So unless i can find someone i'm likely going to need to do this work myself.

Before i do that I want to sanity check the whole end state design which is what this diagram shows. The primary and secondary loops have no control connection whatsoever - the aquastat just keeps the buffer tank at temperature (for winter I set it to 130 to take advantage of the modcon efficiencies) and the five thermostats just trigger the zone controller and run the grundfos system pump when at least one end switch activates. The new kitchen stat would be a floor model which i am planning to either try to grind out a little grout under a cabinet and then stuff the slab sensor in there.

So

Anything insane about this design overall? One item i considered is whether the taco controller should also trigger the primary loop reheat call just to increase the responsiveness of dumping heat back into the buffer tank - but on slow heating like this I also am not sure if that would matter.
Am I crazy to try to do this myself? (removing existing single t-stat from navien internal control, rewire pump, install and wire taco controller and zone valves, re-add tstats to zone controller). Is there a lot of configuration of the zone controller for a setup like this?
Am I wrong to think that — (price removed due to rules) (Canadian) is overcharging for this work? Anyone know anyone in Toronto that might do this last bit of zoning?

Its a little house - and I know zoning is unusual - but I don't see how else i fix the floor problem - and at night when bedroom comfort is more important the two upstairs bedrooms are isolated from each other, and my housemate and I have temperature preferences about 4-5 degrees from one another. The basement is unfinished and also closed off all the time and the single small rad is just to keep it from freezing.

As always help from the experts - or referral to an expert I can pay! is always appreciated.

Jamie Hall · September 10

Well, please take the prices off — we don't quote those here on the Wall, for a variety of good reasons.

Now — that said, can you do it yourself? Can't really comment on that. It's not all that hard — but it does take time to read and thoroughly understand the instructions for the various gadgets involved and how they are hooked together. Your boiler and buffer tank work together, so the boiler firing should be controlled by the buffer tank temperature. No need for any other control on that. And the zone valves are controlled by the thermostats, and they in turn control the secondary main circulation pump (which with that many zones, should be a delta P controlled pump). You can stick a zone controller in there, and it does make the wiring a little more obvious — but strictly speaking you don't need it.

Ekkridon · September 10

Thanks - blanked out the vendor pricing - left the retail equipment pricing in. I guess the part I was most worried about being a bad idea was that full decoupling of the heating side and the distribution side - I figure it means that the heat call for the buffer tank will be a little slow - but cast iron radiators and underfloor staple up aren't exactly fast either.

I also seem to see lots of strategies for controlling the heat call for a staple up radiant floor too - like just sensing the room air temp (but in my case the floor isn't really the emitter for the air on that floor), slab sensors of course but then they say you can overheat the room - or a combined air and slab sensor so you can kill the heat if the air gets too warm but to the t-call on the slab temperature.

This has all been a lot of learning - and i'd rather not do it myself, but the prices i'm getting do seem to be a little divorced from what I think is the amount of work involved and the cost of the equipment involved - but i could be mistaken on that too.

pecmsg · September 10

pay a qualified contractor what they want. Learn along the way.

Not knowing
Going on the internet
Cutting corners, 90% of the time that costs more, especially in comfort

hot_rod · September 10

We have seen some very nice, code compliant DIYer systems here over the last 30 years! It really comes down to you, not us :)

The buffer temperature is maintained by the ODR settings. Some day the buffer may be 110, other days it ramps to 130.

The way you pipe the buffer is critical to best efficiency.

Your most precious hydronic water is the water you just paid to heat. So that should go direct to load. Not through a buffer, closely spaced tees, around a primary loop, etc, direct to the load. Two and 3 pipe buffer tanks work best.

Use a delta P pump and just plug it into a hot receptacle. Then it can run it's exercise function during off season.

Comfort to most people is judged by air temperature. As much as we try to use floor sensors, occupancy and other internal gains can throw it for a loop. Floor sensing along with air temp limit can work. With a perfectly dialed in ODR the system should run non stop, and not need thermostats :)

Mixing emitters can get tricky CI rads on the same loop with low mass fin tube or panel rads is not always a good idea.

The lower the mass the quicker it will respond to setbacks. Radiant floors, even staple up will flywheel for an hour or more. If you add mass, like tile, you icrease the flywheel.

Be realistic on you room temperature variations. A few degrees okay, don't expect 10- 15° differences.

Future State Sanity Check

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