I have a customer who is turning a hydronic system into an upper/lower flat configuration and has asked for ideas on how to meter usage seperately.
Anyone have any thoughts on how one might do this?
Pictures in my minds eye include water metering or zone timing......
Thanks,
Joe

I was thinking of timing of thermostat calls too (as long as it can't be reset by the occupants.)

Water metering may introduce unacceptable head loss / flow restrictions.

Zone timing should be easy - you've probably heard me sing the praises of Readington LCD hourmeters. Put one on the thermostat call signal. You would have to figure the math to translate zone calls into btuh flow. Delta-T of supply and return water is easy, flow less so. Should be able to reach an approximation acceptable to all parties.

If equitable charges are of concern, the occupants of the upper flat may have a built-in disadvantage -- heat loss from the top. If time of day electricity charges apply and the heat pump is multi-stage, there will be added complexity, such as: who caused aux. heat to turn on last night? Otherwise usage (quantity) is a function of flow rate, length of time, and ∆T. Web Energy Logger? Perhaps simpler, heat is included.

Regards,

Masoud

Posted By Masoud on 15 Dec 2010 09:09 PM
If equitable charges are of concern, the occupants of the upper flat may have a built-in disadvantage...

but possibly a nicer view. 

Posted By Masoud on 15 Dec 2010 09:09 PM
If equitable charges are of concern, the occupants of the upper flat may have a built-in disadvantage -- heat loss from the top.

Regards,

Masoud

But in return they would have someone heating the space below them. I bet it would be close to a wash.

Doc,

I yield to your professional opinion, as I'm not privy to Manual J calcs. However, I think the 2nd Law of thermodynamics works against the people living upstairs. I'm assuming the hydronic heating coils are in the floors of each flat. Thus, the upper unit's floor will be warmer than the heated space below. I understand that if the space below were not heated, the situation would have been worse for the people living above.


Regards,

Masoud

I usually only do an envelop calculation, so I look at the whole house for reason of simplification. Only for radiant heat, I do a room by room. Just sized a 2 story new built house room by room, with equal floors. R-19 walls, R-40 roof. Heatloss was similar between the floors. Can change with different solar gain, and different r-values.

Sure, hydronic loops are in each floor, the upper unit will have a higher heatloss due to the roof, but it will also have heatgain from below from the heated apartment below. Much less than forced air systems, but still much better than unconditioned space.

System has gas boiler and cast radiators. Need to read op hours of each stat I'm thinking.......
Inexpensive timers anyone?
j

Readington LCD hourmeters - about $30

Posted By geome on 15 Dec 2010 08:47 AM
I was thinking of timing of thermostat calls too (as long as it can't be reset by the occupants.)

That doesn't even come CLOSE to measuring the fuel used by the separate units unless you could somehow verify (the un-verifiable and not-a-constant) differences in heat losses to the two distinctly different units.  To be suitable for trade (as in being legally allowed to charge on the basis of the readings) the measurements of the actual heat used has to be far more accurate than you'll get with timing the heat calls from thermostats, even from nearly-identical units.

The mass of the boiler, and how it's controlled affects how much heat is abandoned in the boiler at the end of a burn. With a non-heat-purging high-mass cast-iron boiler that that can be a significant fraction of the total. In instances where there are overlapping calls for heat from each flat, how do you apportion the fuel used during those periods?

Very accurate flow meters and good temperature measurements at the beginning and end of each flat's radiation loops to determine the delta-T is the only way to get a true handle on how many BTUs went into each apartment. Then you might be able split the fuel costs based on the ratio.  In the end I doubt it'll be cost effective to measure it well enough to truly work though.

Posted By Dana1 on 20 Dec 2010 03:29 PM
To be suitable for trade (as in being legally allowed to charge on the basis of the readings) the measurements of the actual heat used has to be far more accurate than you'll get with timing the heat calls from thermostats, even from nearly-identical units.

I hear what your saying, but if the tenants agree in the lease as to the basis of allocation, I don't see a problem - but I am not a legal expert (thank goodness.)    As someone mentioned elsewhere on this same topic, the cost to install monitoring equipment would ultimately be recouped from the tenants.