New home; few questions on heating system design and TRV on older rads.

tobilalala

Hi there,

bit of a wall of text sorry about that - useful also for myself if i need to send this to a professional down the way. But thanks for your help / advice upfront.

For context: recently moved to our first home in Toronto/Canada; our first winter in the new home. Not too sure what previous owner/ their HVAC service provider designed; but we see some optimization potential.

Our home as we bought it this past year:
- 3 bedroom / two story semi with finished basement
- ground floor was completely gutted a few years back and is basically one big open space with kitchen, dining & living room sections
- upper floor was partially renovated: new floors, new bathroom. 3 bedrooms located here.
- basement was finished long time ago, however, recently renovated with new tiles and paint. was rented out until we moved in.

Now to the heating/cooling system:
- tankless gas furnace by Navien which heats our water and powers radiator heating system
- ductless mini split heat-pump with 1 outside unit and 3 inside units which cools in summer and heats in winter, installed during the reno.

description per room:
- ground floor (includes a small powder room). renovated in 2020 or so: as mentioned this is essentially one big space with kitchen, dining / living area. has 4 radiators (1 big, 1 med, 2 small) and a heat pump unit. one of the radiators has no TRVs (big rad - has a lockshield valve i believe), others have TRVs. has one mini split which is operated with a remote. Google Nest thermostat which controls basically the entire radiator heating system: either heating or not heating, based on the ground floor temperature.

upper floor:
- Bathroom: renovated 2020 or so. One towel radiator with TRV. unfortunately no heated floor was put in.
- BR1: main bedroom, one large radiator without TRV (see images at bottom). one mini split.
- BR2: smallest bedroom, one large radiator without TRV (see images). window AC unit for summer.
- BR3: 2nd main bedroom, one large radiator without TRV (see images). one mini split.

basement:
- small kitchen area + 3pc bathroom + combined bed/living room: two large radiators with a manual valve to control flow.

Hope the intro covers everything .

Experience this past summer:
- obviously no heating need, mini split ACs are easily able to cool down both ground / upper floors as needed

Experience so far this winter / heating period:
- in general we dont have a problem that it is too cold, it is rather TOO WARM in some areas and TOO COLD in others.

Identified Issue:
Google Nest controls heating and is installed in living area on ground floor: since ground floor is so open and big, it takes the 4 rads quite some time to heat up the room from night time temperature (17-19C).

From my previous homes/apts in Germany, I am used to radiator system for which during heating period (Nov - March) there is ALWAYS a warm/hot flow to all of the rads and each radiator individually decides if it wants to heat or not - based on room temperature and TRV. The flow temperature is based on outside temperature measure.

My understanding of the Google Nest approach in our new home: heat is always OFF, until Nest decides based on my schedule that it should heat to a certain temperature. only then warm water flows to the rads. If rad has a TRV, then rad has capability to heat or not based on surrounding temperature. Not sure how flow temperature is decided, maybe from Nest as it has external temperature reading through external weather data provider?

This general setup causes following issue:
- rooms cannot be controlled individually, for context, we are both working from home a lot and use two of the bedrooms for that. so those should be warm, while ground floor can be cooler.
- ground floor takes long to warm up (like 30-60mins for +1C); maybe rads are too small, but during the time the ground floor is warming, the upstairs bedrooms are literally overheating since the rads are sized too big in this setup and they have no TRV
- basement is obviously cool and suffers from same issue, that rads do not heat unless living room heat is on at the same time- basically we are heating the entire house when really we only need the heat in certain (different) areas throughout the day

Current workaround:
Mini split heat pumps so far work great as a workaround (temperature was not below -3 C though) and this allows us to basically keep temperature in ground floor lower then what we want and heat with heat pump when we need it warmer, since it blows warm air and it is felt immediately (obv still takes few minutes)

Plus, it is actually not that expensive (e.g. we had hydro cost of 3 CAD yesterday on Jan 1 2024, with heat pump running pretty much all day - based on off-peak pricing in Ontario).

However, if we want to rent out the basement, basically the heat would almost never be available in basement, since Nest does not trigger heat since temperature is either set too low or we heat with heat pump which in turn tells Nest it doesn't need to heat because it is already warm enough.

I am investing into a Mysa thermostat to automate also use of the heat pump units - but i still consider this a workaround as main heating system are our rads and our objective is to warm up the house in the morning with rads and then "top-off" with the heat pumps - if that makes sense.

Our considerations to adjust:

- install new rads on upper floor or outfit them with TRVs ( hope i am right that it does not have a TRV and that is just the bleeder ) : based on images, can you tell if TRVs could be retrofitted or should we just replace them entirely?

- not sure if this is possible, but i believe we do not really need the Nest since it is basically just scheduling the offset temperature. I am used to systems where this is programmed directly into the furnace system. and we should have an active heat flow to the rads and the rads decide if they need to pick up the heat or not. I think that for that to work the rads cannot be chained together, but rather there should be a main heating pipe operated by a pump and the rads heat up if TRV opens the line. Not sure how the current setup is, how can i find this out?

Again, sorry for lengthy post. Thanks for not giving up and maybe having some helpful advice. The questions are along the way and hopefully you found them.

Cheers.

Link to rads in upstairs bedrooms:

BR1:
https://ibb.co/72nbQC0
https://ibb.co/CtsP2Hz
BR2:
https://ibb.co/qdyKw8v
https://ibb.co/KXyXQBz
BR3:
https://ibb.co/ydMfhWg
https://ibb.co/0D6sfX8

Big Ed_4

I stopped reading half way through , I spotted your problem ..

In the cold season delete the set back in the Nest program . For comfort in winter you want to maintain the warmth in the home .. Keep the walls warm for when you return . I may be wrong but I am not surprised if your Navien can program for a mild set back, If so run the boiler program rather then the Nest . Cold wether 5*....

Ironman

The Nest is the worst possible choice for a hydronic system and for modulating equipment.

Get rid of it and install a standard thermostat set to 1 CPH and leave it set at one constant temperature. You’ll have better comfort and fuel economy.

Jamie Hall

I second @Ironman 's comment -- and I'll add:

Does the heat pump reach the upper floor rooms? If so, set your ground floor thermostat do a reasonable cool temperature, and use the heat pumps to top up the upstairs if you need it. Or if the heat pump only does downstairs, ... put the thermostat upstairs, and use the heat pump to top up the downstairs as needed.

hot_rod

If you have, or could have all TRVs then you just need a master thermostat somewhere to fire the boiler. TRVs control the heat output as you know.

There are some work arounds where the circulator can call on the boiler when it starts flowing. A flow switch or induction relay, for example. Then the master thermostat would not be needed at all.

Many Euro and Scandinavian systems pull from a district system, where there is always a supply of hot water. A small delta p circulator is powered all the time, it wakes up and provides flow as TRVs start opening.

TRVs may be the very best hydronic controls available. Simple, non electric, proportional temperature controls.