Heat Zone Flow Metering

x2hv11

I have a rental properties in which I want to meter the amount of heat used by each apartment (All apartments are zoned separately). I was thinking of putting either a BTU flow meter or a regular flow meter on each zone. Some of these flow meters are extremely expensive. Does anyone have any suggestions on a reasonably priced flow meter or maybe another way to meter heat used for each zone. My goal is to bill each tenant for heat. System: Central oil boiler with each apartment zoned.

Jamie Hall

There are any number of flow meters available -- you'd want a totalizing one. Prices vary all over the map for them.

However, that will only measure total flow -- neither energy actually delivered nor power at any given time. For that you need to be able to measure the flow and both the inlet and return temperatures for each apartment, recorded simultaneously. From that you can determine the power at any moment and the total energy. There may be such equipment -- in fact I'm rather sure there is -- but it may also be rather expensive.

Then there is also a slight can of worms involved here. You will need to alter your lease terms to indicate that you are charging for heat and also the method used -- and any meters will have to be calibrated and checked and sealed.

jad3675

When they do this in Europe, they have a rather inexpensive and elegant solution. A caloric meter that attaches to the radiator. They're installed at the beginning of the season, then removed and read at the end of the season. They're single use.
They look something like this:

Jamie Hall

Interesting. They have quite the product line. It appears that you might need one for each radiator... and I dare say importing and calibration for use might not come cheap.

NoelAnderson

How about just wiring a timer to each of the zone valves or pumps and then divide the total bill up by the time each apartment ran.

Jamie Hall

NoelAnderson said:

How about just wiring a timer to each of the zone valves or pumps and then divide the total bill up by the time each apartment ran.

Much the simplest approach -- but it doesn't actually measure energy delivered, since for that you need to have the supply and return temperatures and the flow rate. While the supply temperature would, presumably, be the same, neither the return temperature nor flow rate can be assumed to be (and probably aren't).

This is perhaps the most important point I have to make here: if you are putting this forward as a way to measure energy or fuel used, then you absolutely have to do that, and not bill on the basis of some surrogate measure such as operating time. Simply put, while your tenants may accept the surrogate basis at the moment, in the event of a billing dispute you would have no defensible basis on which to bill. This could result, in the best case, in simply a disagreement which you might have to take to arbitration -- but in the; worst case could involve you in litigation. Which you don't want.