TRV with bypass?

Brad_9

I have a bathroom with radiant floor that does not have enough area to adequately heat the room when its very cold out. I'd also like to be able to heat the room up warmer than baseline when in use. I'm thinking a radiator may solve both problems. Can I put the radiator in series with the radiant floor loop? If I do this is there a TRV with a bypass so when the radiant floor is adequate the radiator would be bypassed? Then when I need heat, I could turn up the TRV so the flow would go through the radiator? The delta T on the radiant floor loop runs 1 or 2 degrees F most of the time. Would it matter if I put the radiator on the supply or return from the radiant loop?

Thanks

Brad White_2

I would be reluctant to work those in series

but this depends on the temperature of your RFH circuit. It sounds to me like you have lots of flow, from your statement of a 2-degree delta-T. But my concern is that the radiator could be quite large (assuming the RFH is at a reduced temperature). It may be slow to "pick up" from the baseline, especially when you want it warm for maybe 20 minutes use.

If I can assume you are running the RFH off of a manifold, may I also assume you have higher temperature hot water available?

This is what I did in my bathroom: RFH (of course!) and a hydronic towel warmer (Runtal) off its own circulator zone. No TRV was used (NO bathroom is warm enough when I am buck naked and wet!). I did fit up the towel warmer with 3/8" chrome plated brass tubing and stop cocks for elegant looks, but I do not throttle with these nor do I need to.

For off-season, I have a 6-gallon electric HW heater in series so I can take the edge off without heating the rest of the house, and mostly to have nice dry towels.

Now, you do not need to use a towel warmer, that function is just a bonus, but panel radiators of that type have low mass and rapid response which is what you want. So treat yourself to another zone. Runtal, Burnham and other manufacturers have similar high quality lines of panel radiation. Cast iron radiant is another option but has slower response as you probably know.


Ah, go on! You will not regret it.

And friends and neighbors will be astounded.

Brad_9

One temp

Thanks Brad, I have only one temperature available, which I can vary up to maybe as high as 115*F, more than enough for the rest of the house, I normally run about 100*F. I was planning as large a radiator as I could fit. The problem with another loop is that each loop has a $200 circulator on it (24VDC 10 watt). Also, there isn't really the room to add another loop to the manifold. So my other questions remain.

Larry (from OSHA)

how about

piping in parallel with the radiant floor? I am only a homeowner and have limited knowledge about this, but, if I understand (and please tell me if I'm even close here), if you put a panel rad with a trv in parallel with the radiant loop, wouldn't the panel be self regulating with no need for any bypass? At the low system temp, I wonder if there would be enough output from the panel.

I hope someone will say if this idea has any merit at all, and if not, why. As a homeowner, I'm trying to learn.

Larry

Brad White_2

Larry has a good point

in that if one zone you are only limited to available flow and delta-T (but in a larger sense, aren't we all?. But as he states, the panel would be quite large and deep, maybe a Runtal-style convector?

Even if low temperature, if you could squeeze in another zone (which you stated was impractical, Brad) the lower head would allow for a $60 circulator versus the $200 model.

Brad White_2

I just

re-read your voltage and hence circulator cost (mentioned in my post reply to Larry). You must be living off the grid!

See the Larry post and my added comments and see if that makes sense.

It all gets down to flow, delta-T and radiator size. In the end, an electric heater, but I can hear you say "no" from here. :^)>