Hydronics question

[Thumper2]

Hi , I have read the alberta code , that a water tank can be used for hydronic as long as it is also being used for heating the potable water in the house . A friend of mine has his set up using the bradford white combi 1 water heater , 63,000 btu heater , it has a separate coil inside with 2 extra outlets for the hydronics . My question , I have a new 60 gal 50,000 btu rheem heater and want to add a combi1 heater in series for my hydronics .. ( I know , should have just bought the combi 1 in the first place ,) Anyway , any info , comments , recommendations would be appreciated . thanks in advance

 

[Dana]

You have to be a bit careful when using a standard water heater for space heating that wasn't designed for it for space heating. With too much radiation there could be chronic acidic condensation on the center flue heat exchanger, and it (or the vent stack) could become toast before the end of it's first heating season. It's a lot safer when using condensing water heaters, which are designed to take it (and get an efficiency boost from condensation.) Even with the combi it's important to pay attention to overly cool return water temps.

So, how much radiation are we looking at here?

Have you run a fuel-use based heat load calculation, or a Manual-J or a Hot2000?

What is the point of putting the water heaters in series?

 

[Sponsor]

 

[Thumper2]

You have to be a bit careful when using a standard water heater for space heating that wasn't designed for it for space heating. With too much radiation there could be chronic acidic condensation on the center flue heat exchanger, and it (or the vent stack) could become toast before the end of it's first heating season. It's a lot safer when using condensing water heaters, which are designed to take it (and get an efficiency boost from condensation.) Even with the combi it's important to pay attention to overly cool return water temps.

So, how much radiation are we looking at here?

Have you run a fuel-use based heat load calculation, or a Manual-J or a Hot2000?

What is the point of putting the water heaters in series?

Hi , thanks for the reply , the reason for series , I had just bought the rheem , so , I guess I could sell it and just get the 75 gal combi , but I thought I would get the 50 gal combi , just set the rheem 30 degrees cooler than the combi and have a quicker recovery time , the hydronics exchanger coil with the combi is inside the main tank , indirect water heater in reverse , I'll check with the Bradford white people about concerns of increased acidic condensation, ( thanks . My friend did the combi set up , his flow pattern is 1) combi heats coil loop 2) coil loop circulates to a plate exchanger and back to tank coil, 3) other side of plate exchanger circulates through zones . I am also looking at condensing boilers , the only one I like is the IBC ,

 

[Dana]

You're friend's configuration with the exterior plate type heat exchanger works, but the entering water temp on the return side to the tank needs to stay warm enough to prevent condensation. The temperature will be dependent on flow rates and how much radiation is hanging off the heat exchanger. (It's pretty common to use a hydro-air air handlers with the coils sized to prevent return water cold enough to present a condensation risk.)

So again, how much radiation do you have, and what is your heat load?

You might be able to just do it all with the existing Rheem rather than a combi.

The clear winner would be to use a condensing water heater, assuming there is enough radiation to keep it in condensing range.

The zone-by-zone radiation is also an important consideration for sizing condensing boilers. Too little radiation relative to the minimum firing rate output can cause condensing boilers to short cycle themselves into low efficiency and an early grave. The napkin math on that analysis lives here.

 

[Thumper2]

I've gone through all of uponors manual and completed the heat load calc's . IBC rep says their SL 10 - 85 would be more than adequate for coldest days . I never thought of just taking a loop off the water heater and running that through a plate exchanger ,

 

[Dana]

I've gone through all of uponors manual and completed the heat load calc's .

Don't be coy about it, SHARE the results of the heat load calculations!

Also share how much the radiation will emit (zone by zone, if zoned), at an average water temp (AWT) of 120F (or 50C) .

IBC rep says their SL 10 - 85 would be more than adequate for coldest days . I never thought of just taking a loop off the water heater and running that through a plate exchanger ,

That boiler is big enough to heat 19 out of 20 homes in Alberta. It's not a matter of whether it's going to be adequate on the coldest days, it's a matter of whether the radiation can emit the full minimum output of the boiler at condensing water temperatures. At 95% efficiency the output would be 10,070 BTU/hr. (There are boilers out there that can modulate lower than that.)

Can each zone emit that much heat at an AWT of 50C?

 

[Thumper2]

lol not being coy , sorry working out of town for 2 weeks at a time and don't have the figures with me , but it is 4 zones ,2 low temp , and 2 higher , 1250 sq ft basement slab , 420 sq ft garage slab and another 2 zones of 500 sq ft each of staple up .I did the calcs back in the spring , wish I had a photographic memory lol , I like the IBC because of the firing design , less maintenance I 've been told , but also considering a raypack 80% with the built in recirc pump and bypass to control the return water temp