Hi,
Recently bought a house with radiant heat on two floors. This is my first winter in the house and I've found the upper floor hardly gets any heat that when there's a call for heat the boiler cycles frequently 2min running then 1min off until the room reaches temp. I tried bleeding the system but just get the same behavior.
The radiant floor loop has a three speed zone pump that runs quietly. I've found enough "custom" design choices in the house that I would like to double check this is the right size pump / speed setting for the amount of heat the house needs.
I can see 1/2" pex runs going into the floor and ceiling but have no info about how long each run is.
Anyone have an idea how to figure out how long each run is?

Thanks,
-G

You can get cheap IR cameras now that attach to your phone and see where the tubing is going that way. I can see all my tubing, even through the walls and in the cement.

You need to describe where the tubing goes and how the fluid loops to and from the boiler. Short cycling like that is not a good thing. Sounds like the boiler is oversized.

Sounds like multiple issues...not getting adequate heat in one or more zones and boiler short cycling. We will need additional information in order to sort this out and provide recommendations. What kind of boiler is being used and what is its Btu/h rating? Do you have a ACCA Manual J8 heat loss analysis of the building? Do you have manifold(s) with flow meters and balance valves? How many circuits does this system have? What is the heated area? What kind of HR emitters are being used (e.g., slab, above-floor or below-floor)? Where are you located?

There are several reasons why a zone may not be adequately heated. The heat loss of the zone may be greater than the heat gain that can be provided by the HR emitter. This could be the result of a bad HR system design (e.g., too large a PEX tube spacing, too long PEX tube circuits, too small a boiler) or the result of maintenance issues (e.g., some blockage of the PEX tube circuit that is causing significant reduction in the circuit flow rate).

There are several reasons why you are experiencing short cycling. The boiler may simply need maintenance or this could be the result of a bad HR design. When low thermal mass heat sources are combined with zoned hydronic radiant distribution systems, it is possible for the heat source to short cycle when only a couple of these zones call for heat. This occurs because the rate of heat produced by the heat source is much greater than the rate of heat used/released by these zones. Low thermal mass heat sources in combination with low volume hydronic circuit and distribution systems cannot absorb this excess heat rate without experiencing a rapid rise in temperature. This causes the heat source to reach its high temperature limit very quickly resulting in very short on times and short cycling. While electric heating elements may tolerate short cycling, gas valves, oil burners, ignition systems, and compressors will have a significantly reduced life expectancy. So you need to sort this out and resolve this short cycling issue quickly. If you know the required parameters, we have free DIY software on our website that can help sort this out for you:

Borst Buffer Tank Design Software

If you are fortunate enough to have PEX tube that has length markings on the tube, you may be able to take the marking difference between the supply and return ends to ascertain the circuit length. Failing that, you would have to fill each circuit with water and then blow out each circuit with air, collect the water to determine its volume in cups and then multiply this volume in cups by 6.52 to determine the length of PEX tube in feet.